diff --git a/app/assets/javascripts/base.js b/app/assets/javascripts/base.js index 235a6e39..b7263d48 100644 --- a/app/assets/javascripts/base.js +++ b/app/assets/javascripts/base.js @@ -8,20 +8,18 @@ window.CodeOcean = { } }; -$(function() { - var ANIMATION_DURATION = 500; +var ANIMATION_DURATION = 500; - $.isController = function(name) { - return $('.container[data-controller="' + name + '"]').isPresent(); - }; +$.isController = function(name) { + return $('.container[data-controller="' + name + '"]').isPresent(); +}; - $.fn.isPresent = function() { - return this.length > 0; - }; +$.fn.isPresent = function() { + return this.length > 0; +}; - $.fn.scrollTo = function(selector) { - $(this).animate({ - scrollTop: $(selector).offset().top - $(this).offset().top + $(this).scrollTop() - }, ANIMATION_DURATION); - }; -}); +$.fn.scrollTo = function(selector) { + $(this).animate({ + scrollTop: $(selector).offset().top - $(this).offset().top + $(this).scrollTop() + }, ANIMATION_DURATION); +}; diff --git a/app/assets/javascripts/bootstrap-dropdown-submenu.js b/app/assets/javascripts/bootstrap-dropdown-submenu.js index aed16bbb..10809c02 100644 --- a/app/assets/javascripts/bootstrap-dropdown-submenu.js +++ b/app/assets/javascripts/bootstrap-dropdown-submenu.js @@ -14,7 +14,7 @@ $(document).on('turbolinks:load', function() { var menu = $(this).parent().find("ul"); var menupos = menu.offset(); - var newPos; + var newPos = 0.0; if ((menupos.left + menu.width()) + 30 > $(window).width()) { newPos = -menu.width(); } else { diff --git a/app/assets/javascripts/editor/editor.js.erb b/app/assets/javascripts/editor/editor.js.erb index 6bb6dc27..42f082f1 100644 --- a/app/assets/javascripts/editor/editor.js.erb +++ b/app/assets/javascripts/editor/editor.js.erb @@ -33,6 +33,7 @@ var CodeOceanEditor = { <% @config ||= CodeOcean::Config.new(:code_ocean).read(erb: false) %> sendEvents: <%= @config['codeocean_events'] ? @config['codeocean_events']['enabled'] : false %>, eventURL: "<%= @config['codeocean_events'] ? events_path : '' %>", + fileTypeURL: "<%= file_types_path %>", configureEditors: function () { @@ -43,7 +44,7 @@ configureEditors: function () { confirmDestroy: function (event) { event.preventDefault(); - if (confirm($(this).data('message-confirm'))) { + if (confirm($(event.target).data('message-confirm'))) { this.destroyFile(); } }, @@ -63,7 +64,7 @@ configureEditors: function () { if ($('#output-' + index).isPresent()) { return $('#output-' + index); } else { - var element = $('
').attr('id', 'output-' + index);
+      var element = $('
').attr('id', 'output-' + index);
       $('#output').append(element);
       return element;
     }
@@ -79,13 +80,13 @@ configureEditors: function () {
     }
   },
 
-  getPanelClass: function (result) {
+  getCardClass: function (result) {
     if (result.stderr && !result.score) {
-      return 'panel-danger';
+      return 'card bg-danger text-white';
     } else if (result.score < 1) {
-      return 'panel-warning';
+      return 'card bg-warning';
     } else {
-      return 'panel-success';
+      return 'card bg-success text-white';
     }
   },
 
@@ -107,11 +108,22 @@ configureEditors: function () {
     progress_bar.css('width', percentage + '%');
   },
 
+  // The event ready.jstree is fired too early and thus doesn't work.
+  selectFileInJsTree: function(filetree, file_id) {
+    if (!filetree.hasClass('jstree-loading')) {
+      filetree.jstree("deselect_all");
+      filetree.jstree().select_node(file_id);
+    } else {
+      setTimeout(this.selectFileInJsTree.bind(null, filetree, file_id), 250);
+    }
+  },
+
   showFirstFile: function() {
     var frame = $('.frame[data-role="main_file"]').isPresent() ? $('.frame[data-role="main_file"]') : $('.frame').first();
     var file_id = frame.find('.editor').data('file-id');
     this.setActiveFile(frame.data('filename'), file_id);
-    $('#files').jstree().select_node(file_id);
+    var filetree = $('#files');
+    this.selectFileInJsTree(filetree, file_id);
     this.showFrame(frame);
     this.toggleButtonStates();
   },
@@ -124,11 +136,11 @@ configureEditors: function () {
 
   getProgressBarClass: function (percentage) {
     if (percentage < this.ADEQUATE_PERCENTAGE) {
-      return 'progress-bar progress-bar-striped progress-bar-danger';
+      return 'progress-bar progress-bar-striped bg-danger';
     } else if (percentage < this.SUCCESSFULL_PERCENTAGE) {
-      return 'progress-bar progress-bar-striped progress-bar-warning';
+      return 'progress-bar progress-bar-striped bg-warning';
     } else {
-      return 'progress-bar progress-bar-striped progress-bar-success';
+      return 'progress-bar progress-bar-striped bg-success';
     }
   },
 
@@ -158,7 +170,7 @@ configureEditors: function () {
         category: 'editor_paste',
         data: pasteObject.text,
         exercise_id: $('#editor').data('exercise-id'),
-        file_id: $(this).data('file-id')
+        file_id: $(event.target).data('file-id')
       });
     }
   },
@@ -266,6 +278,21 @@ configureEditors: function () {
     this.initializeRequestForComments()
   },
 
+  updateEditorModeToFileTypeID: function (editor, fileTypeID) {
+    var newMode = 'ace/mode/text'
+
+    $.ajax(this.fileTypeURL + '/' + fileTypeID, {
+      dataType: 'json'
+    }).done(function (data) {
+        if (data['editor_mode'] !== null) {
+          newMode = data['editor_mode'];
+        }
+    }).fail(_.noop)
+      .always(function () {
+        ace.edit(editor).session.setMode(newMode);
+    });
+  },
+
   initializeFileTree: function () {
     $('#files').jstree($('#files').data('entries'));
     $('#files').on('click', 'li.jstree-leaf', function (event) {
@@ -296,8 +323,8 @@ configureEditors: function () {
 
   handleSideBarToggle: function() {
     $('#sidebar').toggleClass('sidebar-col').toggleClass('sidebar-col-collapsed');
-    $('#sidebar-collapsed').toggleClass('hidden');
-    $('#sidebar-uncollapsed').toggleClass('hidden');
+    $('#sidebar-collapsed').toggleClass('d-none');
+    $('#sidebar-uncollapsed').toggleClass('d-none');
   },
 
   initializeRegexes: function () {
@@ -369,17 +396,17 @@ configureEditors: function () {
     return Modernizr.websockets;
   },
 
-  populatePanel: function (panel, result, index) {
-    panel.removeClass('panel-default').addClass(this.getPanelClass(result));
-    panel.find('.panel-title .filename').text(result.filename);
-    panel.find('.panel-title .number').text(index + 1);
-    panel.find('.row .col-sm-9').eq(0).find('.number').eq(0).text(result.passed);
-    panel.find('.row .col-sm-9').eq(0).find('.number').eq(1).text(result.count);
-    panel.find('.row .col-sm-9').eq(1).find('.number').eq(0).text(parseFloat((result.score * result.weight).toFixed(2)));
-    panel.find('.row .col-sm-9').eq(1).find('.number').eq(1).text(result.weight);
-    panel.find('.row .col-sm-9').eq(2).html(result.message);
-    if (result.error_messages) panel.find('.row .col-sm-9').eq(3).text(result.error_messages.join(' '));
-    //panel.find('.row .col-sm-9').eq(4).find('a').attr('href', '#output-' + index);
+  populateCard: function (card, result, index) {
+    card.addClass(this.getCardClass(result));
+    card.find('.card-title .filename').text(result.filename);
+    card.find('.card-title .number').text(index + 1);
+    card.find('.row .col-sm-9').eq(0).find('.number').eq(0).text(result.passed);
+    card.find('.row .col-sm-9').eq(0).find('.number').eq(1).text(result.count);
+    card.find('.row .col-sm-9').eq(1).find('.number').eq(0).text(parseFloat((result.score * result.weight).toFixed(2)));
+    card.find('.row .col-sm-9').eq(1).find('.number').eq(1).text(result.weight);
+    card.find('.row .col-sm-9').eq(2).html(result.message);
+    if (result.error_messages) card.find('.row .col-sm-9').eq(3).text(result.error_messages.join(' '));
+    //card.find('.row .col-sm-9').eq(4).find('a').attr('href', '#output-' + index);
   },
 
   publishCodeOceanEvent: function (payload) {
@@ -556,14 +583,14 @@ configureEditors: function () {
   },
 
   showOutputBar: function() {
-    $('#output_sidebar_collapsed').addClass('hidden');
-    $('#output_sidebar_uncollapsed').removeClass('hidden');
+    $('#output_sidebar_collapsed').addClass('d-none');
+    $('#output_sidebar_uncollapsed').removeClass('d-none');
     $('#output_sidebar').removeClass('output-col-collapsed').addClass('output-col');
   },
 
   hideOutputBar: function() {
-    $('#output_sidebar_collapsed').removeClass('hidden');
-    $('#output_sidebar_uncollapsed').addClass('hidden');
+    $('#output_sidebar_collapsed').removeClass('d-none');
+    $('#output_sidebar_uncollapsed').addClass('d-none');
     $('#output_sidebar').removeClass('output-col').addClass('output-col-collapsed');
   },
 
@@ -572,12 +599,12 @@ configureEditors: function () {
   },
 
   initializeDescriptionToggle: function() {
-    $('#exercise-headline').on('click', this.toggleDescriptionPanel.bind(this));
-    $('a#toggle').on('click', this.toggleDescriptionPanel.bind(this));
+    $('#exercise-headline').on('click', this.toggleDescriptionCard.bind(this));
+    $('a#toggle').on('click', this.toggleDescriptionCard.bind(this));
   },
 
-  toggleDescriptionPanel: function() {
-    $('#description-panel').toggleClass('description-panel-collapsed').toggleClass('description-panel');
+  toggleDescriptionCard: function() {
+    $('#description-card').toggleClass('description-card-collapsed').toggleClass('description-card');
     $('#description-symbol').toggleClass('fa-chevron-down').toggleClass('fa-chevron-right');
     var toggle = $('a#toggle');
     toggle.text(toggle.text() == toggle.data('hide') ? toggle.data('show') : toggle.data('hide'));
diff --git a/app/assets/javascripts/editor/evaluation.js b/app/assets/javascripts/editor/evaluation.js
index feced0eb..23e18bf0 100644
--- a/app/assets/javascripts/editor/evaluation.js
+++ b/app/assets/javascripts/editor/evaluation.js
@@ -9,7 +9,7 @@ CodeOceanEditorEvaluation = {
     this.clearScoringOutput();
     this.createSubmission('#assess', null, function (response) {
       this.showSpinner($('#assess'));
-      $('#score_div').removeClass('hidden');
+      $('#score_div').removeClass('d-none');
       var url = response.score_url;
       this.initializeSocketForScoring(url);
     }.bind(this));
@@ -26,9 +26,9 @@ CodeOceanEditorEvaluation = {
 
   printScoringResult: function (result, index) {
     $('#results').show();
-    var panel = $('#dummies').children().first().clone();
-    this.populatePanel(panel, result, index);
-    $('#results ul').first().append(panel);
+    var card = $('#dummies').children().first().clone();
+    this.populateCard(card, result, index);
+    $('#results ul').first().append(card);
   },
 
   printScoringResults: function (response) {
@@ -60,7 +60,7 @@ CodeOceanEditorEvaluation = {
   renderHint: function (object) {
     var hint = object.data || object.hint;
     if (hint) {
-      $('#hint .panel-body').text(hint);
+      $('#hint .card-body').text(hint);
       $('#hint').fadeIn();
     }
   },
diff --git a/app/assets/javascripts/editor/participantsupport.js b/app/assets/javascripts/editor/participantsupport.js
index a826cbf0..f0329256 100644
--- a/app/assets/javascripts/editor/participantsupport.js
+++ b/app/assets/javascripts/editor/participantsupport.js
@@ -1,12 +1,12 @@
 CodeOceanEditorFlowr = {
   isFlowrEnabled: true,
-  flowrResultHtml: '
',
+  flowrResultHtml: '
',
 
   handleStderrOutputForFlowr: function () {
     if (!this.isFlowrEnabled) return;
 
     var flowrUrl = $('#flowrHint').data('url');
-    var flowrHintBody = $('#flowrHint .panel-body');
+    var flowrHintBody = $('#flowrHint .card-body');
     var queryParameters = {
       query: this.flowrOutputBuffer
     };
@@ -19,8 +19,8 @@ CodeOceanEditorFlowr = {
         var resultTile = $(collapsibleTileHtml);
 
         resultTile.find('h4 > a').text(question.title + ' | Found via ' + question.source);
-        resultTile.find('.panel-body').html(question.body);
-        resultTile.find('.panel-body').append('Open this question');
+        resultTile.find('.card-body').html(question.body);
+        resultTile.find('.card-body').append('Open this question');
 
         flowrHintBody.append(resultTile);
       });
diff --git a/app/assets/javascripts/editor/prompt.js b/app/assets/javascripts/editor/prompt.js
index 1cbdfc8f..e767ba43 100644
--- a/app/assets/javascripts/editor/prompt.js
+++ b/app/assets/javascripts/editor/prompt.js
@@ -2,19 +2,19 @@ CodeOceanEditorPrompt = {
     prompt: '#prompt',
 
     showPrompt: function(msg) {
-        var label = $('#prompt .input-group-addon');
+        var label = $('#prompt .input-group-text');
         var prompt = $(this.prompt);
         label.text(msg.data || label.data('prompt'));
-        if (prompt.isPresent() && prompt.hasClass('hidden')) {
-            prompt.removeClass('hidden');
+        if (prompt.isPresent() && prompt.hasClass('d-none')) {
+            prompt.removeClass('d-none');
         }
         $('#prompt input').focus();
     },
 
     hidePrompt: function() {
         var prompt = $(this.prompt);
-        if (prompt.isPresent() && !prompt.hasClass('hidden')) {
-            prompt.addClass('hidden');
+        if (prompt.isPresent() && !prompt.hasClass('d-none')) {
+            prompt.addClass('d-none');
         }
     },
 
diff --git a/app/assets/javascripts/editor/submissions.js b/app/assets/javascripts/editor/submissions.js
index 30f63a75..6c4fd96a 100644
--- a/app/assets/javascripts/editor/submissions.js
+++ b/app/assets/javascripts/editor/submissions.js
@@ -155,7 +155,7 @@ CodeOceanEditorSubmissions = {
     $('#stop').data('url', submission.stop_url);
     this.running = true;
     this.showSpinner($('#run'));
-    $('#score_div').addClass('hidden');
+    $('#score_div').addClass('d-none');
     this.toggleButtonStates();
     var url = submission.run_url.replace(this.FILENAME_URL_PLACEHOLDER, this.active_file.filename.replace(/#$/,'')); // remove # if it is the last character, this is not part of the filename and just an anchor
     this.initializeSocketForRunning(url);
@@ -175,7 +175,7 @@ CodeOceanEditorSubmissions = {
     if ($('#test').is(':visible')) {
       this.createSubmission('#test', null, function(response) {
         this.showSpinner($('#test'));
-        $('#score_div').addClass('hidden');
+        $('#score_div').addClass('d-none');
         var url = response.test_url.replace(this.FILENAME_URL_PLACEHOLDER, this.active_file.filename.replace(/#$/,'')); // remove # if it is the last character, this is not part of the filename and just an anchor
         this.initializeSocketForTesting(url);
       }.bind(this));
diff --git a/app/assets/javascripts/editor/turtle.js b/app/assets/javascripts/editor/turtle.js
index bc5552eb..1bf80b32 100644
--- a/app/assets/javascripts/editor/turtle.js
+++ b/app/assets/javascripts/editor/turtle.js
@@ -38,10 +38,10 @@ CodeOceanEditorTurtle = {
 
   showCanvas: function () {
     if ($('#turtlediv').isPresent()
-        && this.turtlecanvas.hasClass('hidden')) {
+        && this.turtlecanvas.hasClass('d-none')) {
       // initialize two-column layout
       $('#output-col1').addClass('col-lg-7 col-md-7 two-column');
-      this.turtlecanvas.removeClass('hidden');
+      this.turtlecanvas.removeClass('d-none');
     }
   }
 
diff --git a/app/assets/javascripts/exercises.js.erb b/app/assets/javascripts/exercises.js.erb
index e964eebc..71167533 100644
--- a/app/assets/javascripts/exercises.js.erb
+++ b/app/assets/javascripts/exercises.js.erb
@@ -66,10 +66,9 @@ $(document).on('turbolinks:load', function() {
     $('#files').append(html);
     $('#files li:last select[name*="file_type_id"]').val(getSelectedExecutionEnvironment().file_type_id);
     $('#files li:last select').chosen(window.CodeOcean.CHOSEN_OPTIONS);
+    $('#files li:last select').remove();
+    $('#files li:last>div:last').removeClass('in').addClass('show')
     $('body, html').scrollTo('#add-file');
-    // if we collapse the file forms by default, we need to click on the new element in order to open it.
-    // however, this crashes for more files (if we add several ones by clicking the add button more often), since the elements are probably not correctly added to the files list.
-    //$('#files li:last>div:first>a>div').click();
 
     // initialize the ace editor for the new textarea.
     // pass the correct index and the last ace editor under the node files. this is the last one, since we just added it.
@@ -93,7 +92,7 @@ $(document).on('turbolinks:load', function() {
 
   var deleteFile = function(event) {
     event.preventDefault();
-    var fileUrl = $(this).data('file-url');
+    var fileUrl = $(event.target).data('file-url');
 
     if (confirm('<%= I18n.t('shared.confirm_destroy') %>')) {
       var jqxhr = $.ajax({
@@ -139,9 +138,9 @@ $(document).on('turbolinks:load', function() {
   var enableBatchUpdate = function() {
     $('thead .batch a').on('click', function(event) {
       event.preventDefault();
-      if (!$(this).data('toggled')) {
-        $(this).data('toggled', true);
-        $(this).text($(this).data('text'));
+      if (!$(event.target).data('toggled')) {
+        $(event.target).data('toggled', true);
+        $(event.target).text($(event.target).data('text'));
         buildCheckboxes();
       } else {
         performBatchUpdate();
@@ -199,7 +198,7 @@ $(document).on('turbolinks:load', function() {
   var observeFileRoleChanges = function() {
     $(document).on('change', 'select[name$="[role]"]', function() {
       var is_test_file = $(this).val() === 'teacher_defined_test';
-      var parent = $(this).parents('.panel');
+      var parent = $(this).parents('.card');
       var fields = parent.find('.test-related-fields');
       if (is_test_file) {
         fields.slideDown();
@@ -262,17 +261,13 @@ $(document).on('turbolinks:load', function() {
       jqxhr.fail(ajaxError);
   }
 
-  if ($.isController('exercises')) {
+  if ($.isController('exercises') || $.isController('submissions')) {
       // ignore tags table since it is in the dom before other tables
     if ($('table:not(#tags-table)').isPresent()) {
       enableBatchUpdate();
     } else if ($('.edit_exercise, .new_exercise').isPresent()) {
       execution_environments = $('form').data('execution-environments');
       file_types = $('form').data('file-types');
-      // new MarkdownEditor('#exercise_instructions');
-      // new MarkdownEditor('#exercise_description')
-      // todo: add an ace editor for each file
-      new PagedownEditor('#exercise_description');
 
       enableInlineFileCreation();
       inferFileAttributes();
diff --git a/app/assets/javascripts/forms.js b/app/assets/javascripts/forms.js
index 6bee8d0d..b74840bb 100644
--- a/app/assets/javascripts/forms.js
+++ b/app/assets/javascripts/forms.js
@@ -14,11 +14,11 @@ $(document).on('turbolinks:load', function() {
       var alternative_input = parent.find('.alternative-input');
 
       if (alternative_input.attr('disabled')) {
-        $(this).text($(this).data('text-toggled'));
+        $(this).text($(event.target).data('text-toggled'));
         original_input.attr('disabled', true).hide();
         alternative_input.attr('disabled', false).show();
       } else {
-        $(this).text($(this).data('text-initial'));
+        $(this).text($(event.target).data('text-initial'));
         alternative_input.attr('disabled', true).hide();
         original_input.attr('disabled', false).show();
       }
@@ -26,5 +26,27 @@ $(document).on('turbolinks:load', function() {
   });
 
   window.CodeOcean.CHOSEN_OPTIONS = CHOSEN_OPTIONS;
-  $('select:visible').chosen(CHOSEN_OPTIONS);
+  chosen_inputs = $('select').filter(function(){
+    return !$(this).parents('ul').is('#dummies');
+  });
+
+  // enable chosen hook when editing an exercise to update ace code highlighting
+  if ($.isController('exercises') && $('.edit_exercise, .new_exercise').isPresent()) {
+      chosen_inputs.filter(function(){
+          return $(this).attr('id').includes('file_type_id');
+      }).on('change chosen:ready', function(event, parameter) {
+          // Set ACE editor mode (for code highlighting) on change of file type and after initialization
+          editorInstance = $(event.target).closest('.card-body').find('.editor')[0];
+          selectedFileType = event.target.value;
+          CodeOceanEditor.updateEditorModeToFileTypeID(editorInstance, selectedFileType);
+      })
+  }
+
+  chosen_inputs.chosen(CHOSEN_OPTIONS);
+});
+
+// Remove some elements before going back to an older site. Otherwise, they might not work.
+$(document).on('turbolinks:before-cache', function() {
+    $('.chosen-container').remove();
+    $('#wmd-button-row-description').remove();
 });
diff --git a/app/assets/javascripts/markdown_ace_editor.js b/app/assets/javascripts/markdown_ace_editor.js
index 42e566fe..bd9845f3 100644
--- a/app/assets/javascripts/markdown_ace_editor.js
+++ b/app/assets/javascripts/markdown_ace_editor.js
@@ -9,7 +9,7 @@
         });
         editor.setShowPrintMargin(false);
         var session = editor.getSession();
-        session.setMode('markdown');
+        session.setMode('ace/mode/markdown');
         session.setUseWrapMode(true);
         session.setValue($(selector).val());
     };
diff --git a/app/assets/javascripts/pagedown.js b/app/assets/javascripts/pagedown.js
deleted file mode 100644
index b48c2ae6..00000000
--- a/app/assets/javascripts/pagedown.js
+++ /dev/null
@@ -1,10 +0,0 @@
-(function() {
-    var ACE_FILES_PATH = '/assets/ace/';
-
-    window.PagedownEditor = function(selector) {
-        var converter = Markdown.getSanitizingConverter();
-        var editor    = new Markdown.Editor( converter );
-
-        editor.run();
-    };
-})();
\ No newline at end of file
diff --git a/app/assets/javascripts/pagedown/markdown.editor.js.erb b/app/assets/javascripts/pagedown/markdown.editor.js.erb
new file mode 100644
index 00000000..4f5ecb6d
--- /dev/null
+++ b/app/assets/javascripts/pagedown/markdown.editor.js.erb
@@ -0,0 +1,2131 @@
+// needs Markdown.Converter.js at the moment
+
+(function () {
+
+    var util = {},
+        position = {},
+        ui = {},
+        doc = window.document,
+        re = window.RegExp,
+        nav = window.navigator,
+        SETTINGS = { lineLength: 72 },
+
+        // Used to work around some browser bugs where we can't use feature testing.
+        uaSniffed = {
+            isIE: /msie/.test(nav.userAgent.toLowerCase()),
+            isIE_5or6: /msie 6/.test(nav.userAgent.toLowerCase()) || /msie 5/.test(nav.userAgent.toLowerCase()),
+            isOpera: /opera/.test(nav.userAgent.toLowerCase())
+        };
+
+
+    // -------------------------------------------------------------------
+    //  YOUR CHANGES GO HERE
+    //
+    // I've tried to localize the things you are likely to change to
+    // this area.
+    // -------------------------------------------------------------------
+
+    // The text that appears on the upper part of the dialog box when
+    // entering links.
+    var linkDialogTitle = "<%= I18n.t('components.markdown_editor.insert_link.dialog_title', default: 'Insert link') %>";
+    var linkInputLabel = "<%= I18n.t('components.markdown_editor.insert_link.input_label', default: 'Link URL') %>";
+    var linkInputPlaceholder = "http://example.com/ \"optional title\"";
+    var linkInputHelp = "<%= I18n.t('components.markdown_editor.insert_link.input_help', default: 'Enter URL to point link to and optional title to display when mouse is placed over the link') %>";
+
+    var imageDialogTitle = "<%= I18n.t('components.markdown_editor.insert_image.dialog_title', default: 'Insert image') %>";
+    var imageInputLabel = "<%= I18n.t('components.markdown_editor.insert_image.input_label', default: 'Image URL') %>";
+    var imageInputPlaceholder = "http://example.com/images/diagram.jpg \"optional title\"";
+    var imageInputHelp = "<%= I18n.t('components.markdown_editor.insert_link.input_help', default: 'Enter URL where image is located and optional title to display when mouse is placed over the image') %>";
+
+    var defaultHelpHoverTitle = "Markdown Editing Help";
+
+    // -------------------------------------------------------------------
+    //  END OF YOUR CHANGES
+    // -------------------------------------------------------------------
+
+    // help, if given, should have a property "handler", the click handler for the help button,
+    // and can have an optional property "title" for the button's tooltip (defaults to "Markdown Editing Help").
+    // If help isn't given, not help button is created.
+    //
+    // The constructed editor object has the methods:
+    // - getConverter() returns the markdown converter object that was passed to the constructor
+    // - run() actually starts the editor; should be called after all necessary plugins are registered. Calling this more than once is a no-op.
+    // - refreshPreview() forces the preview to be updated. This method is only available after run() was called.
+    Markdown.Editor = function (markdownConverter, idPostfix, help) {
+
+        idPostfix = idPostfix || "";
+
+        var hooks = this.hooks = new Markdown.HookCollection();
+        hooks.addNoop("onPreviewRefresh");       // called with no arguments after the preview has been refreshed
+        hooks.addNoop("postBlockquoteCreation"); // called with the user's selection *after* the blockquote was created; should return the actual to-be-inserted text
+        hooks.addFalse("insertImageDialog");
+        /* called with one parameter: a callback to be called with the URL of the image. If the application creates
+         * its own image insertion dialog, this hook should return true, and the callback should be called with the chosen
+         * image url (or null if the user cancelled). If this hook returns false, the default dialog will be used.
+         */
+
+        this.getConverter = function () {
+            return markdownConverter;
+        }
+
+        var that = this,
+            cards;
+
+        this.run = function () {
+            if (cards)
+                return; // already initialized
+
+            cards = new CardCollection(idPostfix);
+            var commandManager = new CommandManager(hooks);
+            var previewManager = new PreviewManager(markdownConverter, cards, function () {
+                hooks.onPreviewRefresh();
+            });
+            var undoManager, uiManager;
+
+            if (!/\?noundo/.test(doc.location.href)) {
+                undoManager = new UndoManager(function () {
+                    previewManager.refresh();
+                    if (uiManager) // not available on the first call
+                        uiManager.setUndoRedoButtonStates();
+                }, cards);
+                this.textOperation = function (f) {
+                    undoManager.setCommandMode();
+                    f();
+                    that.refreshPreview();
+                }
+            }
+
+            uiManager = new UIManager(idPostfix, cards, undoManager, previewManager, commandManager, help);
+            uiManager.setUndoRedoButtonStates();
+
+            var forceRefresh = that.refreshPreview = function () {
+                previewManager.refresh(true);
+            };
+
+            forceRefresh();
+        };
+
+    };
+
+    // before: contains all the text in the input box BEFORE the selection.
+    // after: contains all the text in the input box AFTER the selection.
+    function Chunks() { }
+
+    // startRegex: a regular expression to find the start tag
+    // endRegex: a regular expresssion to find the end tag
+    Chunks.prototype.findTags = function (startRegex, endRegex) {
+
+        var chunkObj = this;
+        var regex;
+
+        if (startRegex) {
+
+            regex = util.extendRegExp(startRegex, "", "$");
+
+            this.before = this.before.replace(regex,
+                function (match) {
+                    chunkObj.startTag = chunkObj.startTag + match;
+                    return "";
+                });
+
+            regex = util.extendRegExp(startRegex, "^", "");
+
+            this.selection = this.selection.replace(regex,
+                function (match) {
+                    chunkObj.startTag = chunkObj.startTag + match;
+                    return "";
+                });
+        }
+
+        if (endRegex) {
+
+            regex = util.extendRegExp(endRegex, "", "$");
+
+            this.selection = this.selection.replace(regex,
+                function (match) {
+                    chunkObj.endTag = match + chunkObj.endTag;
+                    return "";
+                });
+
+            regex = util.extendRegExp(endRegex, "^", "");
+
+            this.after = this.after.replace(regex,
+                function (match) {
+                    chunkObj.endTag = match + chunkObj.endTag;
+                    return "";
+                });
+        }
+    };
+
+    // If remove is false, the whitespace is transferred
+    // to the before/after regions.
+    //
+    // If remove is true, the whitespace disappears.
+    Chunks.prototype.trimWhitespace = function (remove) {
+        var beforeReplacer, afterReplacer, that = this;
+        if (remove) {
+            beforeReplacer = afterReplacer = "";
+        } else {
+            beforeReplacer = function (s) {
+                that.before += s;
+                return "";
+            };
+            afterReplacer = function (s) { that.after = s + that.after; return ""; }
+        }
+
+        this.selection = this.selection.replace(/^(\s*)/, beforeReplacer).replace(/(\s*)$/, afterReplacer);
+    };
+
+
+    Chunks.prototype.skipLines = function (nLinesBefore, nLinesAfter, findExtraNewlines) {
+
+        if (nLinesBefore === undefined) {
+            nLinesBefore = 1;
+        }
+
+        if (nLinesAfter === undefined) {
+            nLinesAfter = 1;
+        }
+
+        nLinesBefore++;
+        nLinesAfter++;
+
+        var regexText;
+        var replacementText;
+
+        // chrome bug ... documented at: http://meta.stackoverflow.com/questions/63307/blockquote-glitch-in-editor-in-chrome-6-and-7/65985#65985
+        if (navigator.userAgent.match(/Chrome/)) {
+            "X".match(/()./);
+        }
+
+        this.selection = this.selection.replace(/(^\n*)/, "");
+
+        this.startTag = this.startTag + re.$1;
+
+        this.selection = this.selection.replace(/(\n*$)/, "");
+        this.endTag = this.endTag + re.$1;
+        this.startTag = this.startTag.replace(/(^\n*)/, "");
+        this.before = this.before + re.$1;
+        this.endTag = this.endTag.replace(/(\n*$)/, "");
+        this.after = this.after + re.$1;
+
+        if (this.before) {
+
+            regexText = replacementText = "";
+
+            while (nLinesBefore--) {
+                regexText += "\\n?";
+                replacementText += "\n";
+            }
+
+            if (findExtraNewlines) {
+                regexText = "\\n*";
+            }
+            this.before = this.before.replace(new re(regexText + "$", ""), replacementText);
+        }
+
+        if (this.after) {
+
+            regexText = replacementText = "";
+
+            while (nLinesAfter--) {
+                regexText += "\\n?";
+                replacementText += "\n";
+            }
+            if (findExtraNewlines) {
+                regexText = "\\n*";
+            }
+
+            this.after = this.after.replace(new re(regexText, ""), replacementText);
+        }
+    };
+
+    // end of Chunks
+
+    // A collection of the important regions on the page.
+    // Cached so we don't have to keep traversing the DOM.
+    // Also holds ieCachedRange and ieCachedScrollTop, where necessary; working around
+    // this issue:
+    // Internet explorer has problems with CSS sprite buttons that use HTML
+    // lists.  When you click on the background image "button", IE will
+    // select the non-existent link text and discard the selection in the
+    // textarea.  The solution to this is to cache the textarea selection
+    // on the button's mousedown event and set a flag.  In the part of the
+    // code where we need to grab the selection, we check for the flag
+    // and, if it's set, use the cached area instead of querying the
+    // textarea.
+    //
+    // This ONLY affects Internet Explorer (tested on versions 6, 7
+    // and 8) and ONLY on button clicks.  Keyboard shortcuts work
+    // normally since the focus never leaves the textarea.
+    function CardCollection(postfix) {
+        this.buttonBar = doc.getElementById("wmd-button-bar" + postfix);
+        this.preview = doc.getElementById("wmd-preview" + postfix);
+        this.input = doc.getElementById("wmd-input" + postfix);
+    }
+    // Returns true if the DOM element is visible, false if it's hidden.
+    // Checks if display is anything other than none.
+    util.isVisible = function (elem) {
+
+        if (window.getComputedStyle) {
+            // Most browsers
+            return window.getComputedStyle(elem, null).getPropertyValue("display") !== "none";
+        }
+        else if (elem.currentStyle) {
+            // IE
+            return elem.currentStyle["display"] !== "none";
+        }
+    };
+
+
+    // Adds a listener callback to a DOM element which is fired on a specified
+    // event.
+    util.addEvent = function (elem, event, listener) {
+        if (elem.attachEvent) {
+            // IE only.  The "on" is mandatory.
+            elem.attachEvent("on" + event, listener);
+        }
+        else {
+            // Other browsers.
+            elem.addEventListener(event, listener, false);
+        }
+    };
+
+
+    // Removes a listener callback from a DOM element which is fired on a specified
+    // event.
+    util.removeEvent = function (elem, event, listener) {
+        if (elem.detachEvent) {
+            // IE only.  The "on" is mandatory.
+            elem.detachEvent("on" + event, listener);
+        }
+        else {
+            // Other browsers.
+            elem.removeEventListener(event, listener, false);
+        }
+    };
+
+    // Converts \r\n and \r to \n.
+    util.fixEolChars = function (text) {
+        text = text.replace(/\r\n/g, "\n");
+        text = text.replace(/\r/g, "\n");
+        return text;
+    };
+
+    // Extends a regular expression.  Returns a new RegExp
+    // using pre + regex + post as the expression.
+    // Used in a few functions where we have a base
+    // expression and we want to pre- or append some
+    // conditions to it (e.g. adding "$" to the end).
+    // The flags are unchanged.
+    //
+    // regex is a RegExp, pre and post are strings.
+    util.extendRegExp = function (regex, pre, post) {
+
+        if (pre === null || pre === undefined) {
+            pre = "";
+        }
+        if (post === null || post === undefined) {
+            post = "";
+        }
+
+        var pattern = regex.toString();
+        var flags;
+
+        // Replace the flags with empty space and store them.
+        pattern = pattern.replace(/\/([gim]*)$/, function (wholeMatch, flagsPart) {
+            flags = flagsPart;
+            return "";
+        });
+
+        // Remove the slash delimiters on the regular expression.
+        pattern = pattern.replace(/(^\/|\/$)/g, "");
+        pattern = pre + pattern + post;
+
+        return new re(pattern, flags);
+    };
+
+    // UNFINISHED
+    // The assignment in the while loop makes jslint cranky.
+    // I'll change it to a better loop later.
+    position.getTop = function (elem, isInner) {
+        var result = elem.offsetTop;
+        if (!isInner) {
+            while (elem = elem.offsetParent) {
+                result += elem.offsetTop;
+            }
+        }
+        return result;
+    };
+
+    position.getHeight = function (elem) {
+        return elem.offsetHeight || elem.scrollHeight;
+    };
+
+    position.getWidth = function (elem) {
+        return elem.offsetWidth || elem.scrollWidth;
+    };
+
+    position.getPageSize = function () {
+
+        var scrollWidth, scrollHeight;
+        var innerWidth, innerHeight;
+
+        // It's not very clear which blocks work with which browsers.
+        if (self.innerHeight && self.scrollMaxY) {
+            scrollWidth = doc.body.scrollWidth;
+            scrollHeight = self.innerHeight + self.scrollMaxY;
+        }
+        else if (doc.body.scrollHeight > doc.body.offsetHeight) {
+            scrollWidth = doc.body.scrollWidth;
+            scrollHeight = doc.body.scrollHeight;
+        }
+        else {
+            scrollWidth = doc.body.offsetWidth;
+            scrollHeight = doc.body.offsetHeight;
+        }
+
+        if (self.innerHeight) {
+            // Non-IE browser
+            innerWidth = self.innerWidth;
+            innerHeight = self.innerHeight;
+        }
+        else if (doc.documentElement && doc.documentElement.clientHeight) {
+            // Some versions of IE (IE 6 w/ a DOCTYPE declaration)
+            innerWidth = doc.documentElement.clientWidth;
+            innerHeight = doc.documentElement.clientHeight;
+        }
+        else if (doc.body) {
+            // Other versions of IE
+            innerWidth = doc.body.clientWidth;
+            innerHeight = doc.body.clientHeight;
+        }
+
+        var maxWidth = Math.max(scrollWidth, innerWidth);
+        var maxHeight = Math.max(scrollHeight, innerHeight);
+        return [maxWidth, maxHeight, innerWidth, innerHeight];
+    };
+
+    // Handles pushing and popping TextareaStates for undo/redo commands.
+    // I should rename the stack variables to list.
+    function UndoManager(callback, cards) {
+
+        var undoObj = this;
+        var undoStack = []; // A stack of undo states
+        var stackPtr = 0; // The index of the current state
+        var mode = "none";
+        var lastState; // The last state
+        var timer; // The setTimeout handle for cancelling the timer
+        var inputStateObj;
+
+        // Set the mode for later logic steps.
+        var setMode = function (newMode, noSave) {
+            if (mode != newMode) {
+                mode = newMode;
+                if (!noSave) {
+                    saveState();
+                }
+            }
+
+            if (!uaSniffed.isIE || mode != "moving") {
+                timer = setTimeout(refreshState, 1);
+            }
+            else {
+                inputStateObj = null;
+            }
+        };
+
+        var refreshState = function (isInitialState) {
+            inputStateObj = new TextareaState(cards, isInitialState);
+            timer = undefined;
+        };
+
+        this.setCommandMode = function () {
+            mode = "command";
+            saveState();
+            timer = setTimeout(refreshState, 0);
+        };
+
+        this.canUndo = function () {
+            return stackPtr > 1;
+        };
+
+        this.canRedo = function () {
+            if (undoStack[stackPtr + 1]) {
+                return true;
+            }
+            return false;
+        };
+
+        // Removes the last state and restores it.
+        this.undo = function () {
+
+            if (undoObj.canUndo()) {
+                if (lastState) {
+                    // What about setting state -1 to null or checking for undefined?
+                    lastState.restore();
+                    lastState = null;
+                }
+                else {
+                    undoStack[stackPtr] = new TextareaState(cards);
+                    undoStack[--stackPtr].restore();
+
+                    if (callback) {
+                        callback();
+                    }
+                }
+            }
+
+            mode = "none";
+            cards.input.focus();
+            refreshState();
+        };
+
+        // Redo an action.
+        this.redo = function () {
+
+            if (undoObj.canRedo()) {
+
+                undoStack[++stackPtr].restore();
+
+                if (callback) {
+                    callback();
+                }
+            }
+
+            mode = "none";
+            cards.input.focus();
+            refreshState();
+        };
+
+        // Push the input area state to the stack.
+        var saveState = function () {
+            var currState = inputStateObj || new TextareaState(cards);
+
+            if (!currState) {
+                return false;
+            }
+            if (mode == "moving") {
+                if (!lastState) {
+                    lastState = currState;
+                }
+                return;
+            }
+            if (lastState) {
+                if (undoStack[stackPtr - 1].text != lastState.text) {
+                    undoStack[stackPtr++] = lastState;
+                }
+                lastState = null;
+            }
+            undoStack[stackPtr++] = currState;
+            undoStack[stackPtr + 1] = null;
+            if (callback) {
+                callback();
+            }
+        };
+
+        var handleCtrlYZ = function (event) {
+
+            var handled = false;
+
+            if (event.ctrlKey || event.metaKey) {
+
+                // IE and Opera do not support charCode.
+                var keyCode = event.charCode || event.keyCode;
+                var keyCodeChar = String.fromCharCode(keyCode);
+
+                switch (keyCodeChar) {
+
+                    case "y":
+                        undoObj.redo();
+                        handled = true;
+                        break;
+
+                    case "z":
+                        if (!event.shiftKey) {
+                            undoObj.undo();
+                        }
+                        else {
+                            undoObj.redo();
+                        }
+                        handled = true;
+                        break;
+                }
+            }
+
+            if (handled) {
+                if (event.preventDefault) {
+                    event.preventDefault();
+                }
+                if (window.event) {
+                    window.event.returnValue = false;
+                }
+            }
+        };
+
+        // Set the mode depending on what is going on in the input area.
+        var handleModeChange = function (event) {
+
+            if (!event.ctrlKey && !event.metaKey) {
+
+                var keyCode = event.keyCode;
+
+                if ((keyCode >= 33 && keyCode <= 40) || (keyCode >= 63232 && keyCode <= 63235)) {
+                    // 33 - 40: page up/dn and arrow keys
+                    // 63232 - 63235: page up/dn and arrow keys on safari
+                    setMode("moving");
+                }
+                else if (keyCode == 8 || keyCode == 46 || keyCode == 127) {
+                    // 8: backspace
+                    // 46: delete
+                    // 127: delete
+                    setMode("deleting");
+                }
+                else if (keyCode == 13) {
+                    // 13: Enter
+                    setMode("newlines");
+                }
+                else if (keyCode == 27) {
+                    // 27: escape
+                    setMode("escape");
+                }
+                else if ((keyCode < 16 || keyCode > 20) && keyCode != 91) {
+                    // 16-20 are shift, etc.
+                    // 91: left window key
+                    // I think this might be a little messed up since there are
+                    // a lot of nonprinting keys above 20.
+                    setMode("typing");
+                }
+            }
+        };
+
+        var setEventHandlers = function () {
+            util.addEvent(cards.input, "keypress", function (event) {
+                // keyCode 89: y
+                // keyCode 90: z
+                if ((event.ctrlKey || event.metaKey) && (event.keyCode == 89 || event.keyCode == 90)) {
+                    event.preventDefault();
+                }
+            });
+
+            var handlePaste = function () {
+                if (uaSniffed.isIE || (inputStateObj && inputStateObj.text != cards.input.value)) {
+                    if (timer == undefined) {
+                        mode = "paste";
+                        saveState();
+                        refreshState();
+                    }
+                }
+            };
+
+            util.addEvent(cards.input, "keydown", handleCtrlYZ);
+            util.addEvent(cards.input, "keydown", handleModeChange);
+            util.addEvent(cards.input, "mousedown", function () {
+                setMode("moving");
+            });
+
+            cards.input.onpaste = handlePaste;
+            cards.input.ondrop = handlePaste;
+        };
+
+        var init = function () {
+            setEventHandlers();
+            refreshState(true);
+            saveState();
+        };
+
+        init();
+    }
+
+    // end of UndoManager
+
+    // The input textarea state/contents.
+    // This is used to implement undo/redo by the undo manager.
+    function TextareaState(cards, isInitialState) {
+
+        // Aliases
+        var stateObj = this;
+        var inputArea = cards.input;
+        this.init = function () {
+            if (!util.isVisible(inputArea)) {
+                return;
+            }
+            if (!isInitialState && doc.activeElement && doc.activeElement !== inputArea) { // this happens when tabbing out of the input box
+                return;
+            }
+
+            this.setInputAreaSelectionStartEnd();
+            this.scrollTop = inputArea.scrollTop;
+            if (!this.text && inputArea.selectionStart || inputArea.selectionStart === 0) {
+                this.text = inputArea.value;
+            }
+
+        };
+
+        // Sets the selected text in the input box after we've performed an
+        // operation.
+        this.setInputAreaSelection = function () {
+
+            if (!util.isVisible(inputArea)) {
+                return;
+            }
+
+            if (inputArea.selectionStart !== undefined && !uaSniffed.isOpera) {
+
+                inputArea.focus();
+                inputArea.selectionStart = stateObj.start;
+                inputArea.selectionEnd = stateObj.end;
+                inputArea.scrollTop = stateObj.scrollTop;
+            }
+            else if (doc.selection) {
+
+                if (doc.activeElement && doc.activeElement !== inputArea) {
+                    return;
+                }
+
+                inputArea.focus();
+                var range = inputArea.createTextRange();
+                range.moveStart("character", -inputArea.value.length);
+                range.moveEnd("character", -inputArea.value.length);
+                range.moveEnd("character", stateObj.end);
+                range.moveStart("character", stateObj.start);
+                range.select();
+            }
+        };
+
+        this.setInputAreaSelectionStartEnd = function () {
+
+            if (!cards.ieCachedRange && (inputArea.selectionStart || inputArea.selectionStart === 0)) {
+
+                stateObj.start = inputArea.selectionStart;
+                stateObj.end = inputArea.selectionEnd;
+            }
+            else if (doc.selection) {
+
+                stateObj.text = util.fixEolChars(inputArea.value);
+
+                // IE loses the selection in the textarea when buttons are
+                // clicked.  On IE we cache the selection. Here, if something is cached,
+                // we take it.
+                var range = cards.ieCachedRange || doc.selection.createRange();
+
+                var fixedRange = util.fixEolChars(range.text);
+                var marker = "\x07";
+                var markedRange = marker + fixedRange + marker;
+                range.text = markedRange;
+                var inputText = util.fixEolChars(inputArea.value);
+
+                range.moveStart("character", -markedRange.length);
+                range.text = fixedRange;
+
+                stateObj.start = inputText.indexOf(marker);
+                stateObj.end = inputText.lastIndexOf(marker) - marker.length;
+
+                var len = stateObj.text.length - util.fixEolChars(inputArea.value).length;
+
+                if (len) {
+                    range.moveStart("character", -fixedRange.length);
+                    while (len--) {
+                        fixedRange += "\n";
+                        stateObj.end += 1;
+                    }
+                    range.text = fixedRange;
+                }
+
+                if (cards.ieCachedRange)
+                    stateObj.scrollTop = cards.ieCachedScrollTop; // this is set alongside with ieCachedRange
+
+                cards.ieCachedRange = null;
+
+                this.setInputAreaSelection();
+            }
+        };
+
+        // Restore this state into the input area.
+        this.restore = function () {
+
+            if (stateObj.text != undefined && stateObj.text != inputArea.value) {
+                inputArea.value = stateObj.text;
+            }
+            this.setInputAreaSelection();
+            inputArea.scrollTop = stateObj.scrollTop;
+        };
+
+        // Gets a collection of HTML chunks from the inptut textarea.
+        this.getChunks = function () {
+
+            var chunk = new Chunks();
+            chunk.before = util.fixEolChars(stateObj.text.substring(0, stateObj.start));
+            chunk.startTag = "";
+            chunk.selection = util.fixEolChars(stateObj.text.substring(stateObj.start, stateObj.end));
+            chunk.endTag = "";
+            chunk.after = util.fixEolChars(stateObj.text.substring(stateObj.end));
+            chunk.scrollTop = stateObj.scrollTop;
+
+            return chunk;
+        };
+
+        // Sets the TextareaState properties given a chunk of markdown.
+        this.setChunks = function (chunk) {
+
+            chunk.before = chunk.before + chunk.startTag;
+            chunk.after = chunk.endTag + chunk.after;
+
+            this.start = chunk.before.length;
+            this.end = chunk.before.length + chunk.selection.length;
+            this.text = chunk.before + chunk.selection + chunk.after;
+            this.scrollTop = chunk.scrollTop;
+        };
+        this.init();
+    }
+    function PreviewManager(converter, cards, previewRefreshCallback) {
+
+        var managerObj = this;
+        var timeout;
+        var elapsedTime;
+        var oldInputText;
+        var maxDelay = 3000;
+        var startType = "delayed"; // The other legal value is "manual"
+
+        // Adds event listeners to elements
+        var setupEvents = function (inputElem, listener) {
+
+            util.addEvent(inputElem, "input", listener);
+            inputElem.onpaste = listener;
+            inputElem.ondrop = listener;
+
+            util.addEvent(inputElem, "keypress", listener);
+            util.addEvent(inputElem, "keydown", listener);
+        };
+
+        var getDocScrollTop = function () {
+
+            var result = 0;
+
+            if (window.innerHeight) {
+                result = window.pageYOffset;
+            }
+            else
+            if (doc.documentElement && doc.documentElement.scrollTop) {
+                result = doc.documentElement.scrollTop;
+            }
+            else
+            if (doc.body) {
+                result = doc.body.scrollTop;
+            }
+
+            return result;
+        };
+
+        var makePreviewHtml = function () {
+
+            // If there is no registered preview card
+            // there is nothing to do.
+            if (!cards.preview)
+                return;
+
+
+            var text = cards.input.value;
+            if (text && text == oldInputText) {
+                return; // Input text hasn't changed.
+            }
+            else {
+                oldInputText = text;
+            }
+
+            var prevTime = new Date().getTime();
+
+            text = converter.makeHtml(text);
+
+            // Calculate the processing time of the HTML creation.
+            // It's used as the delay time in the event listener.
+            var currTime = new Date().getTime();
+            elapsedTime = currTime - prevTime;
+
+            pushPreviewHtml(text);
+        };
+
+        // setTimeout is already used.  Used as an event listener.
+        var applyTimeout = function () {
+
+            if (timeout) {
+                clearTimeout(timeout);
+                timeout = undefined;
+            }
+
+            if (startType !== "manual") {
+
+                var delay = 0;
+
+                if (startType === "delayed") {
+                    delay = elapsedTime;
+                }
+
+                if (delay > maxDelay) {
+                    delay = maxDelay;
+                }
+                timeout = setTimeout(makePreviewHtml, delay);
+            }
+        };
+
+        var getScaleFactor = function (card) {
+            if (card.scrollHeight <= card.clientHeight) {
+                return 1;
+            }
+            return card.scrollTop / (card.scrollHeight - card.clientHeight);
+        };
+
+        var setCardScrollTops = function () {
+            if (cards.preview) {
+                cards.preview.scrollTop = (cards.preview.scrollHeight - cards.preview.clientHeight) * getScaleFactor(cards.preview);
+            }
+        };
+
+        this.refresh = function (requiresRefresh) {
+
+            if (requiresRefresh) {
+                oldInputText = "";
+                makePreviewHtml();
+            }
+            else {
+                applyTimeout();
+            }
+        };
+
+        this.processingTime = function () {
+            return elapsedTime;
+        };
+
+        var isFirstTimeFilled = true;
+
+        // IE doesn't let you use innerHTML if the element is contained somewhere in a table
+        // (which is the case for inline editing) -- in that case, detach the element, set the
+        // value, and reattach. Yes, that *is* ridiculous.
+        var ieSafePreviewSet = function (text) {
+            var preview = cards.preview;
+            var parent = preview.parentNode;
+            var sibling = preview.nextSibling;
+            parent.removeChild(preview);
+            preview.innerHTML = text;
+            if (!sibling)
+                parent.appendChild(preview);
+            else
+                parent.insertBefore(preview, sibling);
+        };
+
+        var nonSuckyBrowserPreviewSet = function (text) {
+            cards.preview.innerHTML = text;
+        };
+
+        var previewSetter;
+
+        var previewSet = function (text) {
+            if (previewSetter)
+                return previewSetter(text);
+
+            try {
+                nonSuckyBrowserPreviewSet(text);
+                previewSetter = nonSuckyBrowserPreviewSet;
+            } catch (e) {
+                previewSetter = ieSafePreviewSet;
+                previewSetter(text);
+            }
+        };
+
+        var pushPreviewHtml = function (text) {
+
+            var emptyTop = position.getTop(cards.input) - getDocScrollTop();
+
+            if (cards.preview) {
+                previewSet(text);
+                previewRefreshCallback();
+            }
+
+            setCardScrollTops();
+
+            if (isFirstTimeFilled) {
+                isFirstTimeFilled = false;
+                return;
+            }
+
+            var fullTop = position.getTop(cards.input) - getDocScrollTop();
+
+            if (uaSniffed.isIE) {
+                setTimeout(function () {
+                    window.scrollBy(0, fullTop - emptyTop);
+                }, 0);
+            }
+            else {
+                window.scrollBy(0, fullTop - emptyTop);
+            }
+        };
+
+        var init = function () {
+
+            setupEvents(cards.input, applyTimeout);
+            makePreviewHtml();
+
+            if (cards.preview) {
+                cards.preview.scrollTop = 0;
+            }
+        };
+
+        init();
+    }
+    // This simulates a modal dialog box and asks for the URL when you
+    // click the hyperlink or image buttons.
+    //
+    // text: The html for the input box.
+    // defaultInputText: The default value that appears in the input box.
+    // callback: The function which is executed when the prompt is dismissed, either via OK or Cancel.
+    //      It receives a single argument; either the entered text (if OK was chosen) or null (if Cancel
+    //      was chosen).
+    ui.prompt = function (title, inputLabel, inputPlaceholder, inputHelp, callback) {
+
+        // These variables need to be declared at this level since they are used
+        // in multiple functions.
+        var dialog;         // The dialog box.
+        var input;         // The text box where you enter the hyperlink.
+
+
+        if (inputPlaceholder === undefined) {
+            inputPlaceholder = "";
+        }
+
+        // Used as a keydown event handler. Esc dismisses the prompt.
+        // Key code 27 is ESC.
+        var checkEscape = function (key) {
+            var code = (key.charCode || key.keyCode);
+            if (code === 27) {
+                close(true);
+            }
+        };
+
+        // Dismisses the hyperlink input box.
+        // isCancel is true if we don't care about the input text.
+        // isCancel is false if we are going to keep the text.
+        var close = function (isCancel) {
+            util.removeEvent(doc.body, "keydown", checkEscape);
+            var text = input.value;
+
+            if (isCancel) {
+                text = null;
+            }
+            else {
+                // Fixes common pasting errors.
+                text = text.replace(/^http:\/\/(https?|ftp):\/\//, '$1://');
+                if (!/^(?:https?|ftp):\/\//.test(text))
+                    text = 'http://' + text;
+            }
+
+            $(dialog).modal('hide');
+
+            callback(text);
+            return false;
+        };
+
+
+
+        // Create the text input box form/window.
+        var createDialog = function () {
+            // 
+
+            // The main dialog box.
+            dialog = doc.createElement("div");
+            dialog.className = "modal fade";
+            dialog.style.display = "none";
+
+            var dialogContainer = doc.createElement("div");
+            dialogContainer.className = "modal-dialog";
+            dialog.appendChild(dialogContainer);
+
+            var dialogContent = doc.createElement("div");
+            dialogContent.className = "modal-content";
+            dialogContainer.appendChild(dialogContent);
+
+            // The header.
+            var header = doc.createElement("div");
+            header.className = "modal-header";
+            header.innerHTML = '
'+title+'
 ';
+            dialogContent.appendChild(header);
+
+            // The body.
+            var body = doc.createElement("div");
+            body.className = "modal-body";
+            dialogContent.appendChild(body);
+
+            // The footer.
+            var footer = doc.createElement("div");
+            footer.className = "modal-footer";
+            dialogContent.appendChild(footer);
+
+            // The web form container for the text box and buttons.
+            var form = doc.createElement("form");
+            form.onsubmit = function () { return close(false); };
+            body.appendChild(form);
+
+            // The input text box
+            var formGroup = doc.createElement("div");
+            formGroup.className = "form-group";
+            form.appendChild(formGroup);
+
+            var label = doc.createElement("label");
+            label.htmlFor = "url-" + new Date().getTime();
+            label.innerHTML = inputLabel;
+            formGroup.appendChild(label);
+
+            input = doc.createElement("input");
+            input.id = label.htmlFor;
+            input.type = "text";
+            input.className = "form-control";
+            input.placeholder = inputPlaceholder;
+            formGroup.appendChild(input);
+
+            var helpBlock = doc.createElement("span");
+            helpBlock.className = "help-block form-text";
+            helpBlock.innerHTML = inputHelp || '';
+            formGroup.appendChild(helpBlock);
+
+            // The ok button
+            var okButton = doc.createElement("button");
+            okButton.className = "btn btn-primary";
+            okButton.type = "button";
+            okButton.onclick = function () { return close(false); };
+            okButton.innerHTML = "OK";
+
+            // The cancel button
+            var cancelButton = doc.createElement("button");
+            cancelButton.className = "btn btn-secondary";
+            cancelButton.type = "button";
+            cancelButton.onclick = function () { return close(true); };
+            cancelButton.innerHTML = "Cancel";
+
+            footer.appendChild(okButton);
+            footer.appendChild(cancelButton);
+
+            util.addEvent(doc.body, "keydown", checkEscape);
+
+            doc.body.appendChild(dialog);
+
+        };
+
+        // Why is this in a zero-length timeout?
+        // Is it working around a browser bug?
+        setTimeout(function () {
+
+            createDialog();
+
+            var defTextLen = 0;
+            if (input.selectionStart !== undefined) {
+                input.selectionStart = 0;
+                input.selectionEnd = defTextLen;
+            }
+            else if (input.createTextRange) {
+                var range = input.createTextRange();
+                range.collapse(false);
+                range.moveStart("character", -defTextLen);
+                range.moveEnd("character", defTextLen);
+                range.select();
+            }
+
+            $(dialog).on('shown', function () {
+                input.focus();
+            });
+
+            $(dialog).on('hidden', function () {
+                dialog.parentNode.removeChild(dialog);
+            });
+
+            $(dialog).modal()
+
+        }, 0);
+    };
+
+    function UIManager(postfix, cards, undoManager, previewManager, commandManager, helpOptions) {
+
+        var inputBox = cards.input,
+            buttons = {}; // buttons.undo, buttons.link, etc. The actual DOM elements.
+
+        makeSpritedButtonRow();
+
+        var keyEvent = "keydown";
+        if (uaSniffed.isOpera) {
+            keyEvent = "keypress";
+        }
+
+        util.addEvent(inputBox, keyEvent, function (key) {
+
+            // Check to see if we have a button key and, if so execute the callback.
+            if ((key.ctrlKey || key.metaKey) && !key.altKey && !key.shiftKey) {
+
+                var keyCode = key.charCode || key.keyCode;
+                var keyCodeStr = String.fromCharCode(keyCode).toLowerCase();
+
+                switch (keyCodeStr) {
+                    case "b":
+                        doClick(buttons.bold);
+                        break;
+                    case "i":
+                        doClick(buttons.italic);
+                        break;
+                    case "l":
+                        doClick(buttons.link);
+                        break;
+                    case "q":
+                        doClick(buttons.quote);
+                        break;
+                    case "k":
+                        doClick(buttons.code);
+                        break;
+                    case "g":
+                        doClick(buttons.image);
+                        break;
+                    case "o":
+                        doClick(buttons.olist);
+                        break;
+                    case "u":
+                        doClick(buttons.ulist);
+                        break;
+                    case "h":
+                        doClick(buttons.heading);
+                        break;
+                    case "r":
+                        doClick(buttons.hr);
+                        break;
+                    case "y":
+                        doClick(buttons.redo);
+                        break;
+                    case "z":
+                        if (key.shiftKey) {
+                            doClick(buttons.redo);
+                        }
+                        else {
+                            doClick(buttons.undo);
+                        }
+                        break;
+                    default:
+                        return;
+                }
+
+
+                if (key.preventDefault) {
+                    key.preventDefault();
+                }
+
+                if (window.event) {
+                    window.event.returnValue = false;
+                }
+            }
+        });
+
+        // Auto-indent on shift-enter
+        util.addEvent(inputBox, "keyup", function (key) {
+            if (key.shiftKey && !key.ctrlKey && !key.metaKey) {
+                var keyCode = key.charCode || key.keyCode;
+                // Character 13 is Enter
+                if (keyCode === 13) {
+                    var fakeButton = {};
+                    fakeButton.textOp = bindCommand("doAutoindent");
+                    doClick(fakeButton);
+                }
+            }
+        });
+
+        // special handler because IE clears the context of the textbox on ESC
+        if (uaSniffed.isIE) {
+            util.addEvent(inputBox, "keydown", function (key) {
+                var code = key.keyCode;
+                if (code === 27) {
+                    return false;
+                }
+            });
+        }
+
+
+        // Perform the button's action.
+        function doClick(button) {
+
+            inputBox.focus();
+
+            if (button.textOp) {
+
+                if (undoManager) {
+                    undoManager.setCommandMode();
+                }
+
+                var state = new TextareaState(cards);
+
+                if (!state) {
+                    return;
+                }
+
+                var chunks = state.getChunks();
+
+                // Some commands launch a "modal" prompt dialog.  Javascript
+                // can't really make a modal dialog box and the WMD code
+                // will continue to execute while the dialog is displayed.
+                // This prevents the dialog pattern I'm used to and means
+                // I can't do something like this:
+                //
+                // var link = CreateLinkDialog();
+                // makeMarkdownLink(link);
+                //
+                // Instead of this straightforward method of handling a
+                // dialog I have to pass any code which would execute
+                // after the dialog is dismissed (e.g. link creation)
+                // in a function parameter.
+                //
+                // Yes this is awkward and I think it sucks, but there's
+                // no real workaround.  Only the image and link code
+                // create dialogs and require the function pointers.
+                var fixupInputArea = function () {
+
+                    inputBox.focus();
+
+                    if (chunks) {
+                        state.setChunks(chunks);
+                    }
+
+                    state.restore();
+                    previewManager.refresh();
+                };
+
+                var noCleanup = button.textOp(chunks, fixupInputArea);
+
+                if (!noCleanup) {
+                    fixupInputArea();
+                }
+
+            }
+
+            if (button.execute) {
+                button.execute(undoManager);
+            }
+        }
+        function setupButton(button, isEnabled) {
+
+            if (isEnabled) {
+                button.disabled = false;
+
+                if (!button.isHelp) {
+                    button.onclick = function () {
+                        if (this.onmouseout) {
+                            this.onmouseout();
+                        }
+                        doClick(this);
+                        return false;
+                    }
+                }
+            }
+            else {
+                button.disabled = true;
+            }
+        }
+
+        function bindCommand(method) {
+            if (typeof method === "string")
+                method = commandManager[method];
+            return function () { method.apply(commandManager, arguments); }
+        }
+
+        function makeSpritedButtonRow() {
+
+            var buttonBar = cards.buttonBar;
+            var buttonRow = document.createElement("div");
+            buttonRow.id = "wmd-button-row" + postfix;
+            buttonRow.className = 'btn-toolbar';
+            buttonRow = buttonBar.appendChild(buttonRow);
+
+            var makeButton = function (id, title, iconClass, textOp, group) {
+                var button = document.createElement("button");
+                button.className = "btn btn-secondary btn-sm";
+                var buttonImage = document.createElement("i");
+                buttonImage.className = iconClass;
+                button.appendChild(buttonImage);
+                button.id = id + postfix;
+                button.title = title;
+                button.setAttribute("data-toggle", "tooltip");
+                button.setAttribute("data-placement", "top");
+                if (textOp)
+                    button.textOp = textOp;
+                setupButton(button, true);
+                if (group) {
+                    group.appendChild(button);
+                } else {
+                    buttonRow.appendChild(button);
+                }
+                return button;
+            };
+            var makeGroup = function (num) {
+                var group = document.createElement("div");
+                group.className = "m-1 btn-group wmd-button-group" + num;
+                group.id = "wmd-button-group" + num + postfix;
+                buttonRow.appendChild(group);
+                return group
+            };
+
+            var group1 = makeGroup(1);
+            buttons.bold = makeButton("wmd-bold-button", "<%= I18n.t('components.markdown_editor.bold.button_title', default: 'Bold (Ctrl+B)') %>", "m-1 fa fa-bold", bindCommand("doBold"), group1);
+            buttons.italic = makeButton("wmd-italic-button", "<%= I18n.t('components.markdown_editor.italic.button_title', default: 'Italic (Ctrl+I)') %>", "m-1 fa fa-italic", bindCommand("doItalic"), group1);
+
+            var group2 = makeGroup(2);
+            buttons.link = makeButton("wmd-link-button", "<%= I18n.t('components.markdown_editor.insert_link.button_title', default: 'Link (Ctrl+L)') %>", "m-1 fa fa-link", bindCommand(function (chunk, postProcessing) {
+                return this.doLinkOrImage(chunk, postProcessing, false);
+            }), group2);
+            buttons.image = makeButton("wmd-image-button", "<%= I18n.t('components.markdown_editor.insert_image.button_title', default: 'Image (Ctrl+G)') %>", "m-1 fa fa-picture-o", bindCommand(function (chunk, postProcessing) {
+                return this.doLinkOrImage(chunk, postProcessing, true);
+            }), group2);
+            buttons.quote = makeButton("wmd-quote-button", "<%= I18n.t('components.markdown_editor.blockquoute.button_title', default: 'Blockquote (Ctrl+Q)') %>", "m-1 fa fa-quote-left", bindCommand("doBlockquote"), group2);
+            buttons.code = makeButton("wmd-code-button", "<%= I18n.t('components.markdown_editor.code_sample.button_title', default: 'Code Sample (Ctrl+K)') %>", "m-1 fa fa-code", bindCommand("doCode"), group2);
+
+            var group3 = makeGroup(3);
+            buttons.ulist = makeButton("wmd-ulist-button", "<%= I18n.t('components.markdown_editor.bulleted_list.button_title', default: 'Bulleted List (Ctrl+U)') %>", "m-1 fa fa-list-ul", bindCommand(function (chunk, postProcessing) {
+                this.doList(chunk, postProcessing, false);
+            }), group3);
+            buttons.olist = makeButton("wmd-olist-button", "<%= I18n.t('components.markdown_editor.numbered_list.button_title', default: 'Numbered List (Ctrl+O)') %>", "m-1 fa fa-list-ol", bindCommand(function (chunk, postProcessing) {
+                this.doList(chunk, postProcessing, true);
+            }), group3);
+            buttons.heading = makeButton("wmd-heading-button", "<%= I18n.t('components.markdown_editor.heading.button_title', default: 'Heading (Ctrl+H)') %>", "m-1 fa fa-font", bindCommand("doHeading"), group3);
+
+            var group4 = makeGroup(4);
+            buttons.undo = makeButton("wmd-undo-button", "<%= I18n.t('components.markdown_editor.undo.button_title', default: 'Undo (Ctrl+Z)') %>", "m-1 fa fa-undo", null, group4);
+            buttons.undo.execute = function (manager) { if (manager) manager.undo(); };
+
+            var redoTitle = /win/.test(nav.platform.toLowerCase()) ?
+                "<%= I18n.t('components.markdown_editor.redo.button_title.win', default: 'Redo (Ctrl+Y)') %>" :
+                "<%= I18n.t('components.markdown_editor.redo.button_title.other', default: 'Redo (Ctrl+Shift+Z)') %>"; // mac and other non-Windows platforms
+
+            buttons.redo = makeButton("wmd-redo-button", redoTitle, "m-1 fa fa-repeat", null, group4);
+            buttons.redo.execute = function (manager) { if (manager) manager.redo(); };
+
+            if (helpOptions) {
+                var group5 = makeGroup(5);
+                group5.className = group5.className + " ml-auto";
+                var helpButton = document.createElement("button");
+                var helpButtonImage = document.createElement("i");
+                helpButtonImage.className = "m-1 fa fa-info";
+                helpButton.appendChild(helpButtonImage);
+                helpButton.className = "btn btn-info btn-sm";
+                helpButton.id = "wmd-help-button" + postfix;
+                helpButton.isHelp = true;
+                helpButton.setAttribute("data-toggle", "tooltip");
+                helpButton.setAttribute("data-placement", "top");
+                helpButton.title = helpOptions.title || defaultHelpHoverTitle;
+                helpButton.onclick = helpOptions.handler;
+
+                setupButton(helpButton, true);
+                group5.appendChild(helpButton);
+                buttons.help = helpButton;
+            }
+
+            setUndoRedoButtonStates();
+        }
+
+        function setUndoRedoButtonStates() {
+            if (undoManager) {
+                setupButton(buttons.undo, undoManager.canUndo());
+                setupButton(buttons.redo, undoManager.canRedo());
+            }
+        }
+        this.setUndoRedoButtonStates = setUndoRedoButtonStates;
+
+    }
+
+    function CommandManager(pluginHooks) {
+        this.hooks = pluginHooks;
+    }
+
+    var commandProto = CommandManager.prototype;
+
+    // The markdown symbols - 4 spaces = code, > = blockquote, etc.
+    commandProto.prefixes = "(?:\\s{4,}|\\s*>|\\s*-\\s+|\\s*\\d+\\.|=|\\+|-|_|\\*|#|\\s*\\[[^\n]]+\\]:)";
+
+    // Remove markdown symbols from the chunk selection.
+    commandProto.unwrap = function (chunk) {
+        var txt = new re("([^\\n])\\n(?!(\\n|" + this.prefixes + "))", "g");
+        chunk.selection = chunk.selection.replace(txt, "$1 $2");
+    };
+
+    commandProto.wrap = function (chunk, len) {
+        this.unwrap(chunk);
+        var regex = new re("(.{1," + len + "})( +|$\\n?)", "gm"),
+            that = this;
+
+        chunk.selection = chunk.selection.replace(regex, function (line, marked) {
+            if (new re("^" + that.prefixes, "").test(line)) {
+                return line;
+            }
+            return marked + "\n";
+        });
+
+        chunk.selection = chunk.selection.replace(/\s+$/, "");
+    };
+
+    commandProto.doBold = function (chunk, postProcessing) {
+        return this.doBorI(chunk, postProcessing, 2, "strong text");
+    };
+
+    commandProto.doItalic = function (chunk, postProcessing) {
+        return this.doBorI(chunk, postProcessing, 1, "emphasized text");
+    };
+
+    // chunk: The selected region that will be enclosed with */**
+    // nStars: 1 for italics, 2 for bold
+    // insertText: If you just click the button without highlighting text, this gets inserted
+    commandProto.doBorI = function (chunk, postProcessing, nStars, insertText) {
+
+        // Get rid of whitespace and fixup newlines.
+        chunk.trimWhitespace();
+        chunk.selection = chunk.selection.replace(/\n{2,}/g, "\n");
+
+        // Look for stars before and after.  Is the chunk already marked up?
+        // note that these regex matches cannot fail
+        var starsBefore = /(\**$)/.exec(chunk.before)[0];
+        var starsAfter = /(^\**)/.exec(chunk.after)[0];
+
+        var prevStars = Math.min(starsBefore.length, starsAfter.length);
+
+        // Remove stars if we have to since the button acts as a toggle.
+        if ((prevStars >= nStars) && (prevStars != 2 || nStars != 1)) {
+            chunk.before = chunk.before.replace(re("[*]{" + nStars + "}$", ""), "");
+            chunk.after = chunk.after.replace(re("^[*]{" + nStars + "}", ""), "");
+        }
+        else if (!chunk.selection && starsAfter) {
+            // It's not really clear why this code is necessary.  It just moves
+            // some arbitrary stuff around.
+            chunk.after = chunk.after.replace(/^([*_]*)/, "");
+            chunk.before = chunk.before.replace(/(\s?)$/, "");
+            var whitespace = re.$1;
+            chunk.before = chunk.before + starsAfter + whitespace;
+        }
+        else {
+
+            // In most cases, if you don't have any selected text and click the button
+            // you'll get a selected, marked up region with the default text inserted.
+            if (!chunk.selection && !starsAfter) {
+                chunk.selection = insertText;
+            }
+
+            // Add the true markup.
+            var markup = nStars <= 1 ? "*" : "**"; // shouldn't the test be = ?
+            chunk.before = chunk.before + markup;
+            chunk.after = markup + chunk.after;
+        }
+
+
+    };
+
+    commandProto.stripLinkDefs = function (text, defsToAdd) {
+
+        text = text.replace(/^[ ]{0,3}\[(\d+)\]:[ \t]*\n?[ \t]*?[ \t]*\n?[ \t]*(?:(\n*)["(](.+?)[")][ \t]*)?(?:\n+|$)/gm,
+            function (totalMatch, id, link, newlines, title) {
+                defsToAdd[id] = totalMatch.replace(/\s*$/, "");
+                if (newlines) {
+                    // Strip the title and return that separately.
+                    defsToAdd[id] = totalMatch.replace(/["(](.+?)[")]$/, "");
+                    return newlines + title;
+                }
+                return "";
+            });
+
+        return text;
+    };
+
+    commandProto.addLinkDef = function (chunk, linkDef) {
+
+        var refNumber = 0; // The current reference number
+        var defsToAdd = {}; //
+        // Start with a clean slate by removing all previous link definitions.
+        chunk.before = this.stripLinkDefs(chunk.before, defsToAdd);
+        chunk.selection = this.stripLinkDefs(chunk.selection, defsToAdd);
+        chunk.after = this.stripLinkDefs(chunk.after, defsToAdd);
+
+        var defs = "";
+        var regex = /(\[)((?:\[[^\]]*\]|[^\[\]])*)(\][ ]?(?:\n[ ]*)?\[)(\d+)(\])/g;
+
+        var addDefNumber = function (def) {
+            refNumber++;
+            def = def.replace(/^[ ]{0,3}\[(\d+)\]:/, "  [" + refNumber + "]:");
+            defs += "\n" + def;
+        };
+
+        // note that
+        // a) the recursive call to getLink cannot go infinite, because by definition
+        //    of regex, inner is always a proper substring of wholeMatch, and
+        // b) more than one level of nesting is neither supported by the regex
+        //    nor making a lot of sense (the only use case for nesting is a linked image)
+        var getLink = function (wholeMatch, before, inner, afterInner, id, end) {
+            inner = inner.replace(regex, getLink);
+            if (defsToAdd[id]) {
+                addDefNumber(defsToAdd[id]);
+                return before + inner + afterInner + refNumber + end;
+            }
+            return wholeMatch;
+        };
+
+        chunk.before = chunk.before.replace(regex, getLink);
+
+        if (linkDef) {
+            addDefNumber(linkDef);
+        }
+        else {
+            chunk.selection = chunk.selection.replace(regex, getLink);
+        }
+
+        var refOut = refNumber;
+
+        chunk.after = chunk.after.replace(regex, getLink);
+
+        if (chunk.after) {
+            chunk.after = chunk.after.replace(/\n*$/, "");
+        }
+        if (!chunk.after) {
+            chunk.selection = chunk.selection.replace(/\n*$/, "");
+        }
+
+        chunk.after += "\n\n" + defs;
+
+        return refOut;
+    };
+
+    // takes the line as entered into the add link/as image dialog and makes
+    // sure the URL and the optinal title are "nice".
+    function properlyEncoded(linkdef) {
+        return linkdef.replace(/^\s*(.*?)(?:\s+"(.+)")?\s*$/, function (wholematch, link, title) {
+            link = link.replace(/\?.*$/, function (querypart) {
+                return querypart.replace(/\+/g, " "); // in the query string, a plus and a space are identical
+            });
+            link = decodeURIComponent(link); // unencode first, to prevent double encoding
+            link = encodeURI(link).replace(/'/g, '%27').replace(/\(/g, '%28').replace(/\)/g, '%29');
+            link = link.replace(/\?.*$/, function (querypart) {
+                return querypart.replace(/\+/g, "%2b"); // since we replaced plus with spaces in the query part, all pluses that now appear where originally encoded
+            });
+            if (title) {
+                title = title.trim ? title.trim() : title.replace(/^\s*/, "").replace(/\s*$/, "");
+                title = $.trim(title).replace(/"/g, "quot;").replace(/\(/g, "(").replace(/\)/g, ")").replace(//g, ">");
+            }
+            return title ? link + ' "' + title + '"' : link;
+        });
+    }
+
+    commandProto.doLinkOrImage = function (chunk, postProcessing, isImage) {
+
+        chunk.trimWhitespace();
+        chunk.findTags(/\s*!?\[/, /\][ ]?(?:\n[ ]*)?(\[.*?\])?/);
+        var background;
+
+        if (chunk.endTag.length > 1 && chunk.startTag.length > 0) {
+
+            chunk.startTag = chunk.startTag.replace(/!?\[/, "");
+            chunk.endTag = "";
+            this.addLinkDef(chunk, null);
+
+        }
+        else {
+
+            // We're moving start and end tag back into the selection, since (as we're in the else block) we're not
+            // *removing* a link, but *adding* one, so whatever findTags() found is now back to being part of the
+            // link text. linkEnteredCallback takes care of escaping any brackets.
+            chunk.selection = chunk.startTag + chunk.selection + chunk.endTag;
+            chunk.startTag = chunk.endTag = "";
+
+            if (/\n\n/.test(chunk.selection)) {
+                this.addLinkDef(chunk, null);
+                return;
+            }
+            var that = this;
+            // The function to be executed when you enter a link and press OK or Cancel.
+            // Marks up the link and adds the ref.
+            var linkEnteredCallback = function (link) {
+
+                if (link !== null) {
+                    // (                          $1
+                    //     [^\\]                  anything that's not a backslash
+                    //     (?:\\\\)*              an even number (this includes zero) of backslashes
+                    // )
+                    // (?=                        followed by
+                    //     [[\]]                  an opening or closing bracket
+                    // )
+                    //
+                    // In other words, a non-escaped bracket. These have to be escaped now to make sure they
+                    // don't count as the end of the link or similar.
+                    // Note that the actual bracket has to be a lookahead, because (in case of to subsequent brackets),
+                    // the bracket in one match may be the "not a backslash" character in the next match, so it
+                    // should not be consumed by the first match.
+                    // The "prepend a space and finally remove it" steps makes sure there is a "not a backslash" at the
+                    // start of the string, so this also works if the selection begins with a bracket. We cannot solve
+                    // this by anchoring with ^, because in the case that the selection starts with two brackets, this
+                    // would mean a zero-width match at the start. Since zero-width matches advance the string position,
+                    // the first bracket could then not act as the "not a backslash" for the second.
+                    chunk.selection = (" " + chunk.selection).replace(/([^\\](?:\\\\)*)(?=[[\]])/g, "$1\\").substr(1);
+
+                    var linkDef = " [999]: " + properlyEncoded(link);
+
+                    var num = that.addLinkDef(chunk, linkDef);
+                    chunk.startTag = isImage ? "![" : "[";
+                    chunk.endTag = "][" + num + "]";
+
+                    if (!chunk.selection) {
+                        if (isImage) {
+                            chunk.selection = "enter image description here";
+                        }
+                        else {
+                            chunk.selection = "enter link description here";
+                        }
+                    }
+                }
+                postProcessing();
+            };
+
+
+            if (isImage) {
+                if (!this.hooks.insertImageDialog(linkEnteredCallback))
+                    ui.prompt(imageDialogTitle, imageInputLabel, imageInputPlaceholder, imageInputHelp, linkEnteredCallback);
+            }
+            else {
+                ui.prompt(linkDialogTitle, linkInputLabel, linkInputPlaceholder, linkInputHelp, linkEnteredCallback);
+            }
+            return true;
+        }
+    };
+
+    // When making a list, hitting shift-enter will put your cursor on the next line
+    // at the current indent level.
+    commandProto.doAutoindent = function (chunk, postProcessing) {
+
+        var commandMgr = this,
+            fakeSelection = false;
+
+        chunk.before = chunk.before.replace(/(\n|^)[ ]{0,3}([*+-]|\d+[.])[ \t]*\n$/, "\n\n");
+        chunk.before = chunk.before.replace(/(\n|^)[ ]{0,3}>[ \t]*\n$/, "\n\n");
+        chunk.before = chunk.before.replace(/(\n|^)[ \t]+\n$/, "\n\n");
+
+        // There's no selection, end the cursor wasn't at the end of the line:
+        // The user wants to split the current list item / code line / blockquote line
+        // (for the latter it doesn't really matter) in two. Temporarily select the
+        // (rest of the) line to achieve this.
+        if (!chunk.selection && !/^[ \t]*(?:\n|$)/.test(chunk.after)) {
+            chunk.after = chunk.after.replace(/^[^\n]*/, function (wholeMatch) {
+                chunk.selection = wholeMatch;
+                return "";
+            });
+            fakeSelection = true;
+        }
+
+        if (/(\n|^)[ ]{0,3}([*+-]|\d+[.])[ \t]+.*\n$/.test(chunk.before)) {
+            if (commandMgr.doList) {
+                commandMgr.doList(chunk);
+            }
+        }
+        if (/(\n|^)[ ]{0,3}>[ \t]+.*\n$/.test(chunk.before)) {
+            if (commandMgr.doBlockquote) {
+                commandMgr.doBlockquote(chunk);
+            }
+        }
+        if (/(\n|^)(\t|[ ]{4,}).*\n$/.test(chunk.before)) {
+            if (commandMgr.doCode) {
+                commandMgr.doCode(chunk);
+            }
+        }
+
+        if (fakeSelection) {
+            chunk.after = chunk.selection + chunk.after;
+            chunk.selection = "";
+        }
+    };
+
+    commandProto.doBlockquote = function (chunk, postProcessing) {
+
+        chunk.selection = chunk.selection.replace(/^(\n*)([^\r]+?)(\n*)$/,
+            function (totalMatch, newlinesBefore, text, newlinesAfter) {
+                chunk.before += newlinesBefore;
+                chunk.after = newlinesAfter + chunk.after;
+                return text;
+            });
+
+        chunk.before = chunk.before.replace(/(>[ \t]*)$/,
+            function (totalMatch, blankLine) {
+                chunk.selection = blankLine + chunk.selection;
+                return "";
+            });
+
+        chunk.selection = chunk.selection.replace(/^(\s|>)+$/, "");
+        chunk.selection = chunk.selection || "Blockquote";
+
+        // The original code uses a regular expression to find out how much of the
+        // text *directly before* the selection already was a blockquote:
+
+        /*
+        if (chunk.before) {
+        chunk.before = chunk.before.replace(/\n?$/, "\n");
+        }
+        chunk.before = chunk.before.replace(/(((\n|^)(\n[ \t]*)*>(.+\n)*.*)+(\n[ \t]*)*$)/,
+        function (totalMatch) {
+        chunk.startTag = totalMatch;
+        return "";
+        });
+        */
+
+        // This comes down to:
+        // Go backwards as many lines a possible, such that each line
+        //  a) starts with ">", or
+        //  b) is almost empty, except for whitespace, or
+        //  c) is preceeded by an unbroken chain of non-empty lines
+        //     leading up to a line that starts with ">" and at least one more character
+        // and in addition
+        //  d) at least one line fulfills a)
+        //
+        // Since this is essentially a backwards-moving regex, it's susceptible to
+        // catastrophic backtracking and can cause the browser to hang;
+        // see e.g. http://meta.stackoverflow.com/questions/9807.
+        //
+        // Hence we replaced this by a simple state machine that just goes through the
+        // lines and checks for a), b), and c).
+
+        var match = "",
+            leftOver = "",
+            line;
+        if (chunk.before) {
+            var lines = chunk.before.replace(/\n$/, "").split("\n");
+            var inChain = false;
+            for (var i = 0; i < lines.length; i++) {
+                var good = false;
+                line = lines[i];
+                inChain = inChain && line.length > 0; // c) any non-empty line continues the chain
+                if (/^>/.test(line)) {                // a)
+                    good = true;
+                    if (!inChain && line.length > 1)  // c) any line that starts with ">" and has at least one more character starts the chain
+                        inChain = true;
+                } else if (/^[ \t]*$/.test(line)) {   // b)
+                    good = true;
+                } else {
+                    good = inChain;                   // c) the line is not empty and does not start with ">", so it matches if and only if we're in the chain
+                }
+                if (good) {
+                    match += line + "\n";
+                } else {
+                    leftOver += match + line;
+                    match = "\n";
+                }
+            }
+            if (!/(^|\n)>/.test(match)) {             // d)
+                leftOver += match;
+                match = "";
+            }
+        }
+
+        chunk.startTag = match;
+        chunk.before = leftOver;
+
+        // end of change
+
+        if (chunk.after) {
+            chunk.after = chunk.after.replace(/^\n?/, "\n");
+        }
+
+        chunk.after = chunk.after.replace(/^(((\n|^)(\n[ \t]*)*>(.+\n)*.*)+(\n[ \t]*)*)/,
+            function (totalMatch) {
+                chunk.endTag = totalMatch;
+                return "";
+            }
+        );
+
+        var replaceBlanksInTags = function (useBracket) {
+
+            var replacement = useBracket ? "> " : "";
+
+            if (chunk.startTag) {
+                chunk.startTag = chunk.startTag.replace(/\n((>|\s)*)\n$/,
+                    function (totalMatch, markdown) {
+                        return "\n" + markdown.replace(/^[ ]{0,3}>?[ \t]*$/gm, replacement) + "\n";
+                    });
+            }
+            if (chunk.endTag) {
+                chunk.endTag = chunk.endTag.replace(/^\n((>|\s)*)\n/,
+                    function (totalMatch, markdown) {
+                        return "\n" + markdown.replace(/^[ ]{0,3}>?[ \t]*$/gm, replacement) + "\n";
+                    });
+            }
+        };
+
+        if (/^(?![ ]{0,3}>)/m.test(chunk.selection)) {
+            this.wrap(chunk, SETTINGS.lineLength - 2);
+            chunk.selection = chunk.selection.replace(/^/gm, "> ");
+            replaceBlanksInTags(true);
+            chunk.skipLines();
+        } else {
+            chunk.selection = chunk.selection.replace(/^[ ]{0,3}> ?/gm, "");
+            this.unwrap(chunk);
+            replaceBlanksInTags(false);
+
+            if (!/^(\n|^)[ ]{0,3}>/.test(chunk.selection) && chunk.startTag) {
+                chunk.startTag = chunk.startTag.replace(/\n{0,2}$/, "\n\n");
+            }
+
+            if (!/(\n|^)[ ]{0,3}>.*$/.test(chunk.selection) && chunk.endTag) {
+                chunk.endTag = chunk.endTag.replace(/^\n{0,2}/, "\n\n");
+            }
+        }
+
+        chunk.selection = this.hooks.postBlockquoteCreation(chunk.selection);
+
+        if (!/\n/.test(chunk.selection)) {
+            chunk.selection = chunk.selection.replace(/^(> *)/,
+                function (wholeMatch, blanks) {
+                    chunk.startTag += blanks;
+                    return "";
+                });
+        }
+    };
+
+    commandProto.doCode = function (chunk, postProcessing) {
+
+        var hasTextBefore = /\S[ ]*$/.test(chunk.before);
+        var hasTextAfter = /^[ ]*\S/.test(chunk.after);
+
+        // Use 'four space' markdown if the selection is on its own
+        // line or is multiline.
+        if ((!hasTextAfter && !hasTextBefore) || /\n/.test(chunk.selection)) {
+
+            chunk.before = chunk.before.replace(/[ ]{4}$/,
+                function (totalMatch) {
+                    chunk.selection = totalMatch + chunk.selection;
+                    return "";
+                });
+
+            var nLinesBack = 1;
+            var nLinesForward = 1;
+
+            if (/(\n|^)(\t|[ ]{4,}).*\n$/.test(chunk.before)) {
+                nLinesBack = 0;
+            }
+            if (/^\n(\t|[ ]{4,})/.test(chunk.after)) {
+                nLinesForward = 0;
+            }
+
+            chunk.skipLines(nLinesBack, nLinesForward);
+
+            if (!chunk.selection) {
+                chunk.startTag = "    ";
+                chunk.selection = "enter code here";
+            }
+            else {
+                if (/^[ ]{0,3}\S/m.test(chunk.selection)) {
+                    if (/\n/.test(chunk.selection))
+                        chunk.selection = chunk.selection.replace(/^/gm, "    ");
+                    else // if it's not multiline, do not select the four added spaces; this is more consistent with the doList behavior
+                        chunk.before += "    ";
+                }
+                else {
+                    chunk.selection = chunk.selection.replace(/^[ ]{4}/gm, "");
+                }
+            }
+        }
+        else {
+            // Use backticks (`) to delimit the code block.
+
+            chunk.trimWhitespace();
+            chunk.findTags(/`/, /`/);
+
+            if (!chunk.startTag && !chunk.endTag) {
+                chunk.startTag = chunk.endTag = "`";
+                if (!chunk.selection) {
+                    chunk.selection = "enter code here";
+                }
+            }
+            else if (chunk.endTag && !chunk.startTag) {
+                chunk.before += chunk.endTag;
+                chunk.endTag = "";
+            }
+            else {
+                chunk.startTag = chunk.endTag = "";
+            }
+        }
+    };
+
+    commandProto.doList = function (chunk, postProcessing, isNumberedList) {
+
+        // These are identical except at the very beginning and end.
+        // Should probably use the regex extension function to make this clearer.
+        var previousItemsRegex = /(\n|^)(([ ]{0,3}([*+-]|\d+[.])[ \t]+.*)(\n.+|\n{2,}([*+-].*|\d+[.])[ \t]+.*|\n{2,}[ \t]+\S.*)*)\n*$/;
+        var nextItemsRegex = /^\n*(([ ]{0,3}([*+-]|\d+[.])[ \t]+.*)(\n.+|\n{2,}([*+-].*|\d+[.])[ \t]+.*|\n{2,}[ \t]+\S.*)*)\n*/;
+
+        // The default bullet is a dash but others are possible.
+        // This has nothing to do with the particular HTML bullet,
+        // it's just a markdown bullet.
+        var bullet = "-";
+
+        // The number in a numbered list.
+        var num = 1;
+
+        // Get the item prefix - e.g. " 1. " for a numbered list, " - " for a bulleted list.
+        var getItemPrefix = function () {
+            var prefix;
+            if (isNumberedList) {
+                prefix = " " + num + ". ";
+                num++;
+            }
+            else {
+                prefix = " " + bullet + " ";
+            }
+            return prefix;
+        };
+
+        // Fixes the prefixes of the other list items.
+        var getPrefixedItem = function (itemText) {
+
+            // The numbering flag is unset when called by autoindent.
+            if (isNumberedList === undefined) {
+                isNumberedList = /^\s*\d/.test(itemText);
+            }
+
+            // Renumber/bullet the list element.
+            itemText = itemText.replace(/^[ ]{0,3}([*+-]|\d+[.])\s/gm,
+                function (_) {
+                    return getItemPrefix();
+                });
+
+            return itemText;
+        };
+
+        chunk.findTags(/(\n|^)*[ ]{0,3}([*+-]|\d+[.])\s+/, null);
+
+        if (chunk.before && !/\n$/.test(chunk.before) && !/^\n/.test(chunk.startTag)) {
+            chunk.before += chunk.startTag;
+            chunk.startTag = "";
+        }
+
+        if (chunk.startTag) {
+
+            var hasDigits = /\d+[.]/.test(chunk.startTag);
+            chunk.startTag = "";
+            chunk.selection = chunk.selection.replace(/\n[ ]{4}/g, "\n");
+            this.unwrap(chunk);
+            chunk.skipLines();
+
+            if (hasDigits) {
+                // Have to renumber the bullet points if this is a numbered list.
+                chunk.after = chunk.after.replace(nextItemsRegex, getPrefixedItem);
+            }
+            if (isNumberedList == hasDigits) {
+                return;
+            }
+        }
+
+        var nLinesUp = 1;
+
+        chunk.before = chunk.before.replace(previousItemsRegex,
+            function (itemText) {
+                if (/^\s*([*+-])/.test(itemText)) {
+                    bullet = re.$1;
+                }
+                nLinesUp = /[^\n]\n\n[^\n]/.test(itemText) ? 1 : 0;
+                return getPrefixedItem(itemText);
+            });
+
+        if (!chunk.selection) {
+            chunk.selection = "List item";
+        }
+
+        var prefix = getItemPrefix();
+
+        var nLinesDown = 1;
+
+        chunk.after = chunk.after.replace(nextItemsRegex,
+            function (itemText) {
+                nLinesDown = /[^\n]\n\n[^\n]/.test(itemText) ? 1 : 0;
+                return getPrefixedItem(itemText);
+            });
+
+        chunk.trimWhitespace(true);
+        chunk.skipLines(nLinesUp, nLinesDown, true);
+        chunk.startTag = prefix;
+        var spaces = prefix.replace(/./g, " ");
+        this.wrap(chunk, SETTINGS.lineLength - spaces.length);
+        chunk.selection = chunk.selection.replace(/\n/g, "\n" + spaces);
+
+    };
+
+    commandProto.doHeading = function (chunk, postProcessing) {
+
+        // Remove leading/trailing whitespace and reduce internal spaces to single spaces.
+        chunk.selection = chunk.selection.replace(/\s+/g, " ");
+        chunk.selection = chunk.selection.replace(/(^\s+|\s+$)/g, "");
+
+        // If we clicked the button with no selected text, we just
+        // make a level 2 hash header around some default text.
+        if (!chunk.selection) {
+            chunk.startTag = "## ";
+            chunk.selection = "Heading";
+            chunk.endTag = "";
+            return;
+        }
+
+        var headerLevel = 0;     // The existing header level of the selected text.
+
+        // Remove any existing hash heading markdown and save the header level.
+        chunk.findTags(/#+[ ]*/, /[ ]*#+/);
+        if (/#+/.test(chunk.startTag)) {
+            headerLevel = re.lastMatch.length;
+        }
+        chunk.startTag = chunk.endTag = "";
+
+        // Try to get the current header level by looking for - and = in the line
+        // below the selection.
+        chunk.findTags(null, /\s?(-+|=+)/);
+        if (/=+/.test(chunk.endTag)) {
+            headerLevel = 1;
+        }
+        if (/-+/.test(chunk.endTag)) {
+            headerLevel = 2;
+        }
+
+        // Skip to the next line so we can create the header markdown.
+        chunk.startTag = chunk.endTag = "";
+        chunk.skipLines(1, 1);
+
+        // We make a level 2 header if there is no current header.
+        // If there is a header level, we substract one from the header level.
+        // If it's already a level 1 header, it's removed.
+        var headerLevelToCreate = headerLevel == 0 ? 2 : headerLevel - 1;
+
+        if (headerLevelToCreate > 0) {
+
+            // The button only creates level 1 and 2 underline headers.
+            // Why not have it iterate over hash header levels?  Wouldn't that be easier and cleaner?
+            var headerChar = headerLevelToCreate >= 2 ? "-" : "=";
+            var len = chunk.selection.length;
+            if (len > SETTINGS.lineLength) {
+                len = SETTINGS.lineLength;
+            }
+            chunk.endTag = "\n";
+            while (len--) {
+                chunk.endTag += headerChar;
+            }
+        }
+    };
+
+    commandProto.doHorizontalRule = function (chunk, postProcessing) {
+        chunk.startTag = "----------\n";
+        chunk.selection = "";
+        chunk.skipLines(2, 1, true);
+    }
+
+
+})();
diff --git a/app/assets/javascripts/pagedown/pagedown.js.erb b/app/assets/javascripts/pagedown/pagedown.js.erb
new file mode 100644
index 00000000..cada3497
--- /dev/null
+++ b/app/assets/javascripts/pagedown/pagedown.js.erb
@@ -0,0 +1,43 @@
+//= require markdown.converter
+//  markdown.editor is slightly adjusted to work with Bootstrap 4.
+//  Taken from https://github.com/hughevans/pagedown-bootstrap-rails, V2.1.4
+//= require markdown.editor
+//= require markdown.sanitizer
+//= require markdown.extra
+
+renderPagedown = function() {
+    $(".wmd-output").each(function (i) {
+        const converter = new Markdown.Converter();
+        const content = $(this).html();
+        return $(this).html(converter.makeHtml(content));
+    })
+};
+
+createPagedownEditor = function( selector, context ) {
+    if (context == null) { context = 'body'; }
+    return $(selector, context).each(function(i, input) {
+        if ($(input).data('is_rendered')) {
+            return;
+        }
+        const attr = $(input).attr('id').split('wmd-input')[1];
+        const converter = new Markdown.Converter();
+        Markdown.Extra.init(converter);
+        const help = {
+            handler() {
+                window.open('http://daringfireball.net/projects/markdown/syntax');
+                return false;
+            },
+            title: "<%= I18n.t('components.markdown_editor.help', default: 'Markdown Editing Help') %>"
+        };
+
+        const editor = new Markdown.Editor(converter, attr, help);
+        editor.run();
+        $('[data-toggle="tooltip"]').tooltip();
+        return $(input).data('is_rendered', true);
+    });
+};
+
+$(document).on('turbolinks:load', function() {
+    renderPagedown();
+    return createPagedownEditor('.wmd-input');
+});
diff --git a/app/assets/javascripts/sortable.js b/app/assets/javascripts/sortable.js
index c9a767c8..fd9a5070 100644
--- a/app/assets/javascripts/sortable.js
+++ b/app/assets/javascripts/sortable.js
@@ -1,4 +1,4 @@
-$(document).ready(function(){
+$(document).on('turbolinks:load', function(){
   (function vendorTableSorter(){
     /*
       SortTable
diff --git a/app/assets/javascripts/statistics_activity_history.js b/app/assets/javascripts/statistics_activity_history.js
index dbad1841..c4f03e5b 100644
--- a/app/assets/javascripts/statistics_activity_history.js
+++ b/app/assets/javascripts/statistics_activity_history.js
@@ -49,7 +49,7 @@ $(document).on('turbolinks:load', function() {
 
       var refreshData = function (callback) {
         var params = new URLSearchParams(window.location.search.slice(1));
-        var jqxhr = $.ajax(prefix + '-activity-history.json', {
+        var jqxhr = $.ajax('/statistics/graphs/' + prefix + '-activity-history.json', {
           dataType: 'json',
           data: {from: params.get('from'), to: params.get('to'), interval: params.get('interval')},
           method: 'GET'
diff --git a/app/assets/javascripts/statistics_graphs.js b/app/assets/javascripts/statistics_graphs.js
index 5ad7597f..8caabe1a 100644
--- a/app/assets/javascripts/statistics_graphs.js
+++ b/app/assets/javascripts/statistics_graphs.js
@@ -101,7 +101,7 @@ $(document).on('turbolinks:load', function() {
       });
     }
 
-    manageGraph('user-activity', 'graphs/user-activity', 10);
-    manageGraph('rfc-activity', 'graphs/rfc-activity', 30);
+    manageGraph('user-activity', '/statistics/graphs/user-activity', 10);
+    manageGraph('rfc-activity', '/statistics/graphs/rfc-activity', 30);
   }
 });
diff --git a/app/assets/javascripts/submission_statistics.js b/app/assets/javascripts/submission_statistics.js
index 1adbf404..7cef0e02 100644
--- a/app/assets/javascripts/submission_statistics.js
+++ b/app/assets/javascripts/submission_statistics.js
@@ -5,30 +5,40 @@ $(document).on('turbolinks:load', function() {
 
   var currentSubmission = 0;
   var active_file = undefined;
-  var fileTrees = []
+  var fileTrees = [];
   var editor = undefined;
-  var fileTypeById = {}
+  var fileTypeById = {};
 
   var showActiveFile = function() {
     var session = editor.getSession();
-    var fileType = fileTypeById[active_file.file_type_id]
+    var fileType = fileTypeById[active_file.file_type_id];
     session.setMode(fileType.editor_mode);
     session.setTabSize(fileType.indent_size);
     session.setValue(active_file.content);
     session.setUseSoftTabs(true);
     session.setUseWrapMode(true);
 
+    // The event ready.jstree is fired too early and thus doesn't work.
+    var selectFileInJsTree = function() {
+      if (!filetree.hasClass('jstree-loading')) {
+        filetree.jstree("deselect_all");
+        filetree.jstree().select_node(active_file.file_id);
+      } else {
+        setTimeout(selectFileInJsTree, 250);
+      }
+    };
+
+    filetree = $(fileTrees[currentSubmission]);
+    selectFileInJsTree();
+    // Finally change jstree element to prevent flickering
     showFileTree(currentSubmission);
-    filetree = $(fileTrees[currentSubmission])
-    filetree.jstree("deselect_all");
-    filetree.jstree().select_node(active_file.file_id);
   };
 
   var initializeFileTree = function() {
     $('.files').each(function(index, element) {
       fileTree = $(element).jstree($(element).data('entries'));
       fileTree.on('click', 'li.jstree-leaf', function() {
-        var id = parseInt($(this).attr('id'))
+        var id = parseInt($(this).attr('id'));
         _.each(files[currentSubmission], function(file) {
           if (file.file_id === id) {
             active_file = file;
@@ -42,8 +52,8 @@ $(document).on('turbolinks:load', function() {
 
   var showFileTree = function(index) {
     $('.files').hide();
-    $(fileTrees[index].context).show();
-  }
+    $(fileTrees[index]).show();
+  };
 
   if ($.isController('exercises') && $('#timeline').isPresent()) {
 
@@ -85,7 +95,7 @@ $(document).on('turbolinks:load', function() {
         if (file.name === active_file.name) {
           fileIndex = index;
         }
-      })
+      });
       active_file = currentFiles[fileIndex];
       showActiveFile();
     });
@@ -94,10 +104,10 @@ $(document).on('turbolinks:load', function() {
       clearInterval(playInterval);
       playInterval = undefined;
       playButton.find('span.fa').removeClass('fa-pause').addClass('fa-play')
-    }
+    };
 
     playButton.on('click', function(event) {
-      if (playInterval == undefined) {
+      if (playInterval === undefined) {
         playInterval = setInterval(function() {
           if ($.isController('exercises') && $('#timeline').isPresent() && slider.val() < submissions.length - 1) {
             slider.val(parseInt(slider.val()) + 1);
@@ -112,7 +122,7 @@ $(document).on('turbolinks:load', function() {
       }
     });
 
-    active_file = files[0][0]
+    active_file = files[0][0];
     initializeFileTree();
     showActiveFile();
   }
diff --git a/app/assets/stylesheets/base.css.scss b/app/assets/stylesheets/base.css.scss
index 127b36ca..96087248 100644
--- a/app/assets/stylesheets/base.css.scss
+++ b/app/assets/stylesheets/base.css.scss
@@ -28,6 +28,7 @@ span.caret {
   .progress-bar {
     line-height: initial;
     min-width: 2em;
+    color: white;
   }
 }
 
@@ -35,7 +36,7 @@ span.caret {
   margin-top: 0.5em;
 }
 
-.badge {
+.badge-pill {
   font-size: 100%;
 }
 
diff --git a/app/assets/stylesheets/bootstrap-dropdown-submenu.css.scss b/app/assets/stylesheets/bootstrap-dropdown-submenu.css.scss
index d0855298..ceb88020 100644
--- a/app/assets/stylesheets/bootstrap-dropdown-submenu.css.scss
+++ b/app/assets/stylesheets/bootstrap-dropdown-submenu.css.scss
@@ -3,10 +3,14 @@
 }
 
 .dropdown-submenu > .dropdown-menu {
-  top: 0;
+  top: -0.2em;
   left: 100%;
 }
 
+.dropdown-submenu.open > ul.dropdown-menu  {
+  display: block;
+}
+
 .dropdown-submenu > a:after {
   display: block;
   content: " ";
@@ -25,11 +29,11 @@
   border-left-color: #ffffff;
 }
 
-.dropdown-submenu.pull-left {
+.dropdown-submenu.float-left {
   float: none;
 }
 
-.dropdown-submenu.pull-left > .dropdown-menu {
+.dropdown-submenu.float-left > .dropdown-menu {
   left: -100%;
   margin-left: 10px;
   -webkit-border-radius: 6px 0 6px 6px;
diff --git a/app/assets/stylesheets/editor.css.scss b/app/assets/stylesheets/editor.css.scss
index dad17193..1b591fc8 100644
--- a/app/assets/stylesheets/editor.css.scss
+++ b/app/assets/stylesheets/editor.css.scss
@@ -144,7 +144,8 @@ button i.fa-spin {
   min-height: 1px;
   padding-left: 15px;
   padding-right: 15px;
-  box-sizing: border-box
+  box-sizing: border-box;
+  margin-left: auto;
 }
 
 .output-col-collapsed {
@@ -155,7 +156,8 @@ button i.fa-spin {
   min-height: 1px;
   padding-left: 15px;
   padding-right: 15px;
-  box-sizing: border-box
+  box-sizing: border-box;
+  margin-left: auto;
 }
 
 .enforce-top-margin {
@@ -166,14 +168,14 @@ button i.fa-spin {
   margin-right: 10px !important;
 }
 
-.description-panel-collapsed {
+.description-card-collapsed {
   -webkit-transition: width 2s;
   transition: width 2s;
   height: 0px;
   visibility: hidden;
 }
 
-.description-panel {
+.description-card {
   height: auto;
   -webkit-transition: height 2s;
   transition: height 2s;
diff --git a/app/assets/stylesheets/exercise_collections.scss b/app/assets/stylesheets/exercise_collections.scss
index 79141988..1b3c6c76 100644
--- a/app/assets/stylesheets/exercise_collections.scss
+++ b/app/assets/stylesheets/exercise_collections.scss
@@ -57,10 +57,6 @@ rect.value-bar {
   }
 }
 
-.table-responsive#exercise-list {
-  max-height: 512px;
-}
-
 .exercise-id-tooltip {
   position: absolute;
   display: none;
diff --git a/app/assets/stylesheets/exercises.css.scss b/app/assets/stylesheets/exercises.css.scss
index 817fdeac..6790776a 100644
--- a/app/assets/stylesheets/exercises.css.scss
+++ b/app/assets/stylesheets/exercises.css.scss
@@ -35,11 +35,19 @@ input[type='file'] {
     margin: 10px 0 10px 0;
   }
 
-  .lead.description-panel-collapsed {
+  .lead.description-card-collapsed {
     margin: 0;
   }
 }
 
+[data-toggle="collapse"] .fa:before {
+  content: "\f139";
+}
+
+[data-toggle="collapse"].collapsed .fa:before {
+  content: "\f13a";
+}
+
 // Graph Settings
 
 .axis path {
diff --git a/app/assets/stylesheets/request-for-comments.css.scss b/app/assets/stylesheets/request-for-comments.css.scss
index 77b0810b..09209c2d 100644
--- a/app/assets/stylesheets/request-for-comments.css.scss
+++ b/app/assets/stylesheets/request-for-comments.css.scss
@@ -127,7 +127,7 @@
   background-color:#f9f9f9
 }
 
-.ace_tooltip {
+:not(.allow_ace_tooltip) > .ace_tooltip {
   display: none !important;
 }
 
diff --git a/app/assets/stylesheets/statistics.css.scss b/app/assets/stylesheets/statistics.css.scss
index 4dee2b34..e636e9b0 100644
--- a/app/assets/stylesheets/statistics.css.scss
+++ b/app/assets/stylesheets/statistics.css.scss
@@ -76,8 +76,8 @@ tr.highlight {
   grid-gap: 10px;
 
   > a {
-    color: #fff;
-    text-decoration: none;
+    color: #fff !important;
+    text-decoration: none !important;
 
     > div {
       border: 2px solid #0055ba;
diff --git a/app/controllers/file_types_controller.rb b/app/controllers/file_types_controller.rb
index 8f29b72b..d450df3d 100644
--- a/app/controllers/file_types_controller.rb
+++ b/app/controllers/file_types_controller.rb
@@ -38,7 +38,7 @@ class FileTypesController < ApplicationController
   end
 
   def set_editor_modes
-    @editor_modes = Dir.glob('vendor/assets/javascripts/ace/mode-*.js').map do |filename|
+    @editor_modes = Dir.glob('vendor/assets/javascripts/ace/mode-*.js').sort.map do |filename|
       name = filename.gsub(/\w+\/|mode-|.js$/, '')
       [name, "ace/mode/#{name}"]
     end
diff --git a/app/helpers/pagedown_form_builder.rb b/app/helpers/pagedown_form_builder.rb
new file mode 100644
index 00000000..d38407f2
--- /dev/null
+++ b/app/helpers/pagedown_form_builder.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+class PagedownFormBuilder < ActionView::Helpers::FormBuilder
+  def pagedown(method, args)
+    # Adopt simple form builder to work with form_for
+    @attribute_name = method
+    @input_html_options = args[:input_html]
+
+    @template.capture do
+      @template.concat wmd_button_bar
+      @template.concat wmd_textarea
+      @template.concat wmd_preview if show_wmd_preview?
+    end
+  end
+
+  private
+
+  def wmd_button_bar
+    @template.content_tag :div, nil, id: "wmd-button-bar-#{base_id}"
+  end
+
+  def wmd_textarea
+    @template.text_area @object_name, @attribute_name,
+                       **@input_html_options,
+                       class: 'form-control wmd-input',
+                       id: "wmd-input-#{base_id}"
+  end
+
+  def wmd_preview
+    @template.content_tag :div, nil,
+                         class: 'wmd-preview',
+                         id: "wmd-preview-#{base_id}"
+  end
+
+  def show_wmd_preview?
+    @input_html_options[:preview].present?
+  end
+
+  def base_id
+    options[:pagedown_id_suffix] || @attribute_name
+  end
+end
diff --git a/app/models/error_template.rb b/app/models/error_template.rb
index 4265a736..83c2f360 100644
--- a/app/models/error_template.rb
+++ b/app/models/error_template.rb
@@ -3,6 +3,6 @@ class ErrorTemplate < ApplicationRecord
   has_and_belongs_to_many :error_template_attributes
 
   def to_s
-    "#{id} [#{name}]"
+    name
   end
 end
diff --git a/app/models/error_template_attribute.rb b/app/models/error_template_attribute.rb
index 0a228958..42661132 100644
--- a/app/models/error_template_attribute.rb
+++ b/app/models/error_template_attribute.rb
@@ -2,6 +2,6 @@ class ErrorTemplateAttribute < ApplicationRecord
   has_and_belongs_to_many :error_template
 
   def to_s
-    "#{id} [#{key}]"
+    key
   end
 end
diff --git a/app/views/application/_breadcrumbs.html.slim b/app/views/application/_breadcrumbs.html.slim
index 151e33e8..7899ae0e 100644
--- a/app/views/application/_breadcrumbs.html.slim
+++ b/app/views/application/_breadcrumbs.html.slim
@@ -3,17 +3,17 @@
     - if model = Kernel.const_get(controller_path.classify) rescue nil
       - object = model.find_by(id: params[:id])
       - if model.try(:nested_resource?)
-        li = model.model_name.human(count: 2)
+        li.breadcrumb-item = model.model_name.human(count: 2)
         - if object
-          li = object
+          li.breadcrumb-item = object
       - else
-        li = link_to(model.model_name.human(count: 2), send(:"#{model.model_name.collection}_path"))
+        li.breadcrumb-item = link_to(model.model_name.human(count: 2), send(:"#{model.model_name.collection}_path"))
         - if object
-          li = link_to(object, send(:"#{model.model_name.singular}_path", object))
-      li.active
+          li.breadcrumb-item = link_to(object, send(:"#{model.model_name.singular}_path", object))
+      li.breadcrumb-item.active
         - if I18n.translation_present?("shared.#{params[:action]}")
           = t("shared.#{params[:action]}")
         - else
           = t("#{controller_name}.index.#{params[:action]}")
     - else
-      li.active = t("breadcrumbs.#{controller_name}.#{params[:action]}")
+      li.breadcrumb-item.active = t("breadcrumbs.#{controller_name}.#{params[:action]}")
diff --git a/app/views/application/_flash.html.slim b/app/views/application/_flash.html.slim
index a1f7191c..4a78c032 100644
--- a/app/views/application/_flash.html.slim
+++ b/app/views/application/_flash.html.slim
@@ -1,6 +1,7 @@
 #flash-container
   #flash.container.fixed_error_messages data-message-failure=t('shared.message_failure')
     - %w[alert danger info notice success warning].each do |severity|
-      div.alert.flash class="alert-#{{'alert' => 'warning', 'notice' => 'success'}.fetch(severity, severity)}"
-        p id="flash-#{severity}" = flash[severity]
-        span.fa.fa-times
+      div.alert.flash class="alert-#{{'alert' => 'warning', 'notice' => 'success'}.fetch(severity, severity)} alert-dismissible fade show"
+        p.mb-0 id="flash-#{severity}" = flash[severity]
+        button type="button" class="close" data-dismiss="alert" aria-label="Close"
+          span.text-white aria-hidden="true" ×
diff --git a/app/views/application/_locale_selector.html.slim b/app/views/application/_locale_selector.html.slim
index b6dbbfbf..b278ab5a 100644
--- a/app/views/application/_locale_selector.html.slim
+++ b/app/views/application/_locale_selector.html.slim
@@ -1,7 +1,7 @@
-li.dropdown
-  a.dropdown-toggle data-toggle='dropdown' href='#'
+li.nav-item.dropdown
+  a.nav-link.dropdown-toggle.mx-3 data-toggle='dropdown' href='#'
     = t("locales.#{I18n.locale}")
     span.caret
-  ul.dropdown-menu role='menu'
+  ul.dropdown-menu.p-0.mt-1 role='menu'
     - I18n.available_locales.sort_by { |locale| t("locales.#{locale}") }.each do |locale|
-      li = link_to(t("locales.#{locale}"), url_for(params.permit!.merge(locale: locale)))
+      li = link_to(t("locales.#{locale}"), url_for(params.permit!.merge(locale: locale)), class: 'dropdown-item')
diff --git a/app/views/application/_navigation.html.slim b/app/views/application/_navigation.html.slim
index 168a747f..006de33b 100644
--- a/app/views/application/_navigation.html.slim
+++ b/app/views/application/_navigation.html.slim
@@ -1,14 +1,14 @@
 - if current_user.try(:internal_user?)
   ul.nav.navbar-nav
-    li.dropdown
-      a.dropdown-toggle data-toggle='dropdown' href='#'
+    li.nav-item.dropdown
+      a.nav-link.dropdown-toggle.mx-3 data-toggle='dropdown' href='#'
         = t('shared.administration')
         span.caret
-      ul.dropdown-menu role='menu'
+      ul.dropdown-menu.p-0.mt-1 role='menu'
         - if current_user.admin?
-          li = link_to(t('breadcrumbs.dashboard.show'), admin_dashboard_path, 'data-turbolinks' => "false")
-          li = link_to(t('breadcrumbs.statistics.show'), statistics_path)
-          li.divider
+          li = link_to(t('breadcrumbs.dashboard.show'), admin_dashboard_path, class: 'dropdown-item', 'data-turbolinks' => "false")
+          li = link_to(t('breadcrumbs.statistics.show'), statistics_path, class: 'dropdown-item')
+          li.dropdown-divider role='separator'
         = render('navigation_submenu', title: t('activerecord.models.exercise.other'),
                 models: [Exercise, ExerciseCollection, ProxyExercise, Tag, Submission], link: exercises_path, cached: true)
         = render('navigation_submenu', title: t('navigation.sections.users'), models: [InternalUser, ExternalUser],
diff --git a/app/views/application/_navigation_collection_link.html.slim b/app/views/application/_navigation_collection_link.html.slim
index 412ea0bd..fc45dd4a 100644
--- a/app/views/application/_navigation_collection_link.html.slim
+++ b/app/views/application/_navigation_collection_link.html.slim
@@ -1,2 +1,2 @@
 - if policy(model).index?
-  li = link_to(model.model_name.human(count: 2), send(:"#{model.model_name.collection}_path"))
+  li = link_to(model.model_name.human(count: 2), send(:"#{model.model_name.collection}_path"), class: 'dropdown-item')
diff --git a/app/views/application/_navigation_submenu.html.slim b/app/views/application/_navigation_submenu.html.slim
index 23daf814..047955d7 100644
--- a/app/views/application/_navigation_submenu.html.slim
+++ b/app/views/application/_navigation_submenu.html.slim
@@ -1,6 +1,6 @@
-li.dropdown.dropdown-submenu
+li.dropdown-submenu
   - link = link.nil? ? "#" : link
-  a href=link class="dropdown-toggle" data-toggle="dropdown" = title
-  ul class="dropdown-menu"
+  a.dropdown-item.dropdown-toggle href=link data-toggle="dropdown" = title
+  ul.dropdown-menu.p-0
     - models.each do |model|
       = render('navigation_collection_link', model: model, cached: true)
diff --git a/app/views/application/_session.html.slim b/app/views/application/_session.html.slim
index 38e58588..db401908 100644
--- a/app/views/application/_session.html.slim
+++ b/app/views/application/_session.html.slim
@@ -1,19 +1,19 @@
 - if current_user
-  li.dropdown
-    a.dropdown-toggle data-toggle='dropdown' href='#'
+  li.nav-item.dropdown
+    a.nav-link.dropdown-toggle data-toggle='dropdown' href='#'
       i.fa.fa-user
       = current_user
       span.caret
-    ul.dropdown-menu role='menu'
+    ul.dropdown-menu.p-0.mt-1 role='menu'
       - if current_user.internal_user?
-        li = link_to(t('consumers.show.link'), current_user.consumer) if current_user.consumer
-        li = link_to(t('internal_users.show.link'), current_user)
-        li = link_to(t('request_for_comments.index.all'), request_for_comments_path)
-        li = link_to(t('request_for_comments.index.get_my_rfc_activity'), my_rfc_activity_path)
-      li = link_to(t('request_for_comments.index.get_my_comment_requests'), my_request_for_comments_path)
+        li = link_to(t('consumers.show.link'), current_user.consumer, class: 'dropdown-item') if current_user.consumer
+        li = link_to(t('internal_users.show.link'), current_user, class: 'dropdown-item')
+        li = link_to(t('request_for_comments.index.all'), request_for_comments_path, class: 'dropdown-item')
+        li = link_to(t('request_for_comments.index.get_my_rfc_activity'), my_rfc_activity_path, class: 'dropdown-item')
+      li = link_to(t('request_for_comments.index.get_my_comment_requests'), my_request_for_comments_path, class: 'dropdown-item')
       - if current_user.internal_user?
-        li = link_to(t('sessions.destroy.link'), sign_out_path, method: :delete)
+        li = link_to(t('sessions.destroy.link'), sign_out_path, method: :delete, class: 'dropdown-item')
 - else
-  li = link_to(sign_in_path) do
+  li.nav-item = link_to(sign_in_path, class: 'nav-link') do
     i.fa.fa-sign-in
     = t('sessions.new.link')
diff --git a/app/views/code_harbor_links/index.html.slim b/app/views/code_harbor_links/index.html.slim
index 953985c4..ca4a81d4 100644
--- a/app/views/code_harbor_links/index.html.slim
+++ b/app/views/code_harbor_links/index.html.slim
@@ -9,7 +9,7 @@ h1 = CodeHarborLink.model_name.human(count: 2)
     tbody
       - @code_harbor_links.each do |code_harbor_link|
         tr
-          td = code_harbor_link.oauth2token
+          td = link_to(code_harbor_link.oauth2token, code_harbor_link)
           td = link_to(t('shared.show'), code_harbor_link)
           td = link_to(t('shared.edit'), edit_code_harbor_link_path(code_harbor_link))
           td = link_to(t('shared.destroy'), code_harbor_link, data: {confirm: t('shared.confirm_destroy')}, method: :delete)
diff --git a/app/views/code_ocean/files/_form.html.slim b/app/views/code_ocean/files/_form.html.slim
index 46c5b2c2..a00912c0 100644
--- a/app/views/code_ocean/files/_form.html.slim
+++ b/app/views/code_ocean/files/_form.html.slim
@@ -12,5 +12,5 @@
     = f.label(:file_template_id, t('activerecord.attributes.file.file_template_id'))
     = f.collection_select(:file_template_id, FileTemplate.all.order(:name), :id, :name, {:include_blank => true}, class: 'form-control')
   = f.hidden_field(:context_id)
-  .hidden#noTemplateLabel data-text=t('file_template.no_template_label')
+  .d-none#noTemplateLabel data-text=t('file_template.no_template_label')
   .actions = render('shared/submit_button', f: f, object: CodeOcean::File.new)
diff --git a/app/views/consumers/index.html.slim b/app/views/consumers/index.html.slim
index c05581ed..b707c1f0 100644
--- a/app/views/consumers/index.html.slim
+++ b/app/views/consumers/index.html.slim
@@ -9,7 +9,7 @@ h1 = Consumer.model_name.human(count: 2)
     tbody
       - @consumers.each do |consumer|
         tr
-          td = consumer.name
+          td = link_to(consumer.name, consumer)
           td = link_to(t('shared.show'), consumer)
           td = link_to(t('shared.edit'), edit_consumer_path(consumer))
           td = link_to(t('shared.destroy'), consumer, data: {confirm: t('shared.confirm_destroy')}, method: :delete)
diff --git a/app/views/error_template_attributes/_form.html.slim b/app/views/error_template_attributes/_form.html.slim
index 4fc28b02..72160cfd 100644
--- a/app/views/error_template_attributes/_form.html.slim
+++ b/app/views/error_template_attributes/_form.html.slim
@@ -9,8 +9,9 @@
   .form-group
     = f.label(:regex)
     = f.text_field(:regex, class: 'form-control', required: true)
-    .help-block == t('error_templates.hints.signature')
-  .form-group
-    = f.check_box(:important)
+    .help-block.form-text == t('error_templates.hints.signature')
+  .form-check.form-group
+    label.form-check-label
+    = f.check_box(:important, class: 'form-check-input')
     = t('activerecord.attributes.error_template_attribute.important')
   .actions = render('shared/submit_button', f: f, object: @error_template_attribute)
diff --git a/app/views/error_template_attributes/index.html.slim b/app/views/error_template_attributes/index.html.slim
index 81d5cac9..268b1547 100644
--- a/app/views/error_template_attributes/index.html.slim
+++ b/app/views/error_template_attributes/index.html.slim
@@ -17,9 +17,10 @@ h1 = ErrorTemplateAttribute.model_name.human(count: 2)
               span class="fa fa-star" aria-hidden="true"
             - else
               span class="fa fa-star-o" aria-hidden="true"
-          td = error_template_attribute.key
+          td = link_to(error_template_attribute.key, error_template_attribute)
           td = error_template_attribute.description
-          td = error_template_attribute.regex
+          td
+            code = error_template_attribute.regex
           td = link_to(t('shared.show'), error_template_attribute)
           td = link_to(t('shared.edit'), edit_error_template_attribute_path(error_template_attribute))
           td = link_to(t('shared.destroy'), error_template_attribute, data: {confirm: t('shared.confirm_destroy')}, method: :delete)
diff --git a/app/views/error_template_attributes/show.html.slim b/app/views/error_template_attributes/show.html.slim
index 2bdd01ca..5d6ef58b 100644
--- a/app/views/error_template_attributes/show.html.slim
+++ b/app/views/error_template_attributes/show.html.slim
@@ -2,7 +2,10 @@ h1
   = @error_template_attribute
   = render('shared/edit_button', object: @error_template_attribute)
 
-- [:key, :description, :regex, :important].each do |attribute|
+- [:key, :description].each do |attribute|
   = row(label: "error_template_attribute.#{attribute}", value: @error_template_attribute.send(attribute))
+= row(label: "error_template_attribute.key") do
+  code = @error_template_attribute.key
+= row(label: "error_template_attribute.important", value: @error_template_attribute.important)
 
 // todo: used by
diff --git a/app/views/error_templates/_form.html.slim b/app/views/error_templates/_form.html.slim
index d9716ce3..f912ec7b 100644
--- a/app/views/error_templates/_form.html.slim
+++ b/app/views/error_templates/_form.html.slim
@@ -9,12 +9,12 @@
   .form-group
     = f.label(:signature)
     = f.text_field(:signature, class: 'form-control')
-    .help-block == t('error_templates.hints.signature')
+    .help-block.form-text == t('error_templates.hints.signature')
   .form-group
     = f.label(:description)
     = f.text_field(:description, class: 'form-control')
   .form-group
     = f.label(:hint)
     = f.text_field(:hint, class: 'form-control')
-    .help-block == t('error_templates.hints.hint_templates')
+    .help-block.form-text == t('error_templates.hints.hint_templates')
   .actions = render('shared/submit_button', f: f, object: @error_template)
diff --git a/app/views/error_templates/index.html.slim b/app/views/error_templates/index.html.slim
index f44b3f67..1f532a86 100644
--- a/app/views/error_templates/index.html.slim
+++ b/app/views/error_templates/index.html.slim
@@ -11,7 +11,7 @@ h1 = ErrorTemplate.model_name.human(count: 2)
     tbody
       - @error_templates.each do |error_template|
         tr
-          td = error_template.name
+          td = link_to(error_template.name, error_template)
           td = error_template.description
           td = link_to(error_template.execution_environment)
           td = link_to(t('shared.show'), error_template)
diff --git a/app/views/error_templates/show.html.slim b/app/views/error_templates/show.html.slim
index 9936ef7f..ae6ea2a4 100644
--- a/app/views/error_templates/show.html.slim
+++ b/app/views/error_templates/show.html.slim
@@ -4,10 +4,12 @@ h1
 
 = row(label: 'error_template.name', value: @error_template.name)
 = row(label: 'exercise.execution_environment', value: link_to(@error_template.execution_environment))
-- [:signature, :description, :hint].each do |attribute|
+= row(label: "error_template.signature") do
+  code = @error_template.signature
+- [:description, :hint].each do |attribute|
   = row(label: "error_template.#{attribute}", value: @error_template.send(attribute))
 
-h3
+h2.mt-4
   = t 'error_templates.attributes'
 
 .table-responsive
@@ -27,9 +29,10 @@ h3
               span class="fa fa-star" aria-hidden="true"
             - else
               span class="fa fa-star-o" aria-hidden="true"
-          td = attribute.key
+          td = link_to(attribute.key, attribute)
           td = attribute.description
-          td = attribute.regex
+          td
+            code = attribute.regex
           td = link_to(t('shared.show'), attribute)
           td = link_to(t('shared.destroy'), attribute_error_template_url(:error_template_attribute_id => attribute.id), :method => :delete)
 
@@ -37,4 +40,4 @@ h3
   = collection_select({}, :error_template_attribute_id,
           ErrorTemplateAttribute.where.not(id: @error_template.error_template_attributes.select(:id).to_a).order('important DESC', :key),
           :id, :key, {include_blank: false}, class: '')
-  button.btn.btn-default = t('error_templates.add_attribute')
+  button.btn.btn-outline-primary = t('error_templates.add_attribute')
diff --git a/app/views/execution_environments/_form.html.slim b/app/views/execution_environments/_form.html.slim
index e1b02c0a..13ee252e 100644
--- a/app/views/execution_environments/_form.html.slim
+++ b/app/views/execution_environments/_form.html.slim
@@ -12,17 +12,17 @@
     a.toggle-input data={text_initial: t('shared.new'), text_toggled: t('shared.back')} href='#' = t('shared.new')
     .original-input = f.select(:docker_image, @docker_images, {}, class: 'form-control')
     = f.text_field(:docker_image, class: 'alternative-input form-control', disabled: true)
-    .help-block == t('.hints.docker_image')
+    .help-block.form-text == t('.hints.docker_image')
   .form-group
     = f.label(:exposed_ports)
     = f.text_field(:exposed_ports, class: 'form-control', placeholder: '3000, 4000')
-    .help-block == t('.hints.exposed_ports')
+    .help-block.form-text == t('.hints.exposed_ports')
   .form-group
     = f.label(:memory_limit)
     = f.number_field(:memory_limit, class: 'form-control', min: DockerClient::MINIMUM_MEMORY_LIMIT, value: f.object.memory_limit || DockerClient::DEFAULT_MEMORY_LIMIT)
-  .checkbox
-    label
-      = f.check_box(:network_enabled)
+  .form-check.mb-3
+    label.form-check-label
+      = f.check_box(:network_enabled, class: 'form-check-input')
       = t('activerecord.attributes.execution_environment.network_enabled')
   .form-group
     = f.label(:permitted_execution_time)
@@ -33,11 +33,11 @@
   .form-group
     = f.label(:run_command)
     = f.text_field(:run_command, class: 'form-control', placeholder: 'command %{filename}', required: true)
-    .help-block == t('.hints.command')
+    .help-block.form-text == t('.hints.command')
   .form-group
     = f.label(:test_command)
     = f.text_field(:test_command, class: 'form-control', placeholder: 'command %{filename}')
-    .help-block == t('.hints.command')
+    .help-block.form-text == t('.hints.command')
   .form-group
     = f.label(:testing_framework)
     = f.select(:testing_framework, @testing_framework_adapters, {include_blank: true}, class: 'form-control')
diff --git a/app/views/execution_environments/index.html.slim b/app/views/execution_environments/index.html.slim
index dc30898f..20e99620 100644
--- a/app/views/execution_environments/index.html.slim
+++ b/app/views/execution_environments/index.html.slim
@@ -15,7 +15,7 @@ h1 = ExecutionEnvironment.model_name.human(count: 2)
     tbody
       - @execution_environments.each do |execution_environment|
         tr
-          td = execution_environment.name
+          td = link_to(execution_environment.name, execution_environment)
           td = link_to(execution_environment.author, execution_environment.author)
           td = execution_environment.pool_size
           td = execution_environment.memory_limit
diff --git a/app/views/execution_environments/show.html.slim b/app/views/execution_environments/show.html.slim
index da9fd9c8..6d917a61 100644
--- a/app/views/execution_environments/show.html.slim
+++ b/app/views/execution_environments/show.html.slim
@@ -5,7 +5,10 @@ h1
 = row(label: 'execution_environment.name', value: @execution_environment.name)
 = row(label: 'execution_environment.user', value: link_to(@execution_environment.author, @execution_environment.author))
 = row(label: 'execution_environment.file_type', value: @execution_environment.file_type.present? ? link_to(@execution_environment.file_type, @execution_environment.file_type) : nil)
-- [:docker_image, :exposed_ports, :memory_limit, :network_enabled, :permitted_execution_time, :pool_size, :run_command, :test_command].each do |attribute|
+- [:docker_image, :exposed_ports, :memory_limit, :network_enabled, :permitted_execution_time, :pool_size].each do |attribute|
   = row(label: "execution_environment.#{attribute}", value: @execution_environment.send(attribute))
+- [:run_command, :test_command].each do |attribute|
+  = row(label: "execution_environment.#{attribute}") do
+    code = @execution_environment.send(attribute)
 = row(label: 'execution_environment.testing_framework', value: @testing_framework_adapter.try(:framework_name))
 = row(label: 'execution_environment.help', value: render_markdown(@execution_environment.help))
diff --git a/app/views/exercise_collections/_add_exercise_modal.slim b/app/views/exercise_collections/_add_exercise_modal.slim
index 62080f4f..e0880b58 100644
--- a/app/views/exercise_collections/_add_exercise_modal.slim
+++ b/app/views/exercise_collections/_add_exercise_modal.slim
@@ -2,7 +2,8 @@
 
 form#exercise-selection
   .form-group
-    span.label = t('activerecord.attributes.exercise_collections.exercises')
+    span.badge = t('activerecord.attributes.exercise_collections.exercises')
+    .mb-2
     = collection_select({}, :exercise_ids, exercises, :id, :title, {}, {id: 'add-exercise-list', class: 'form-control', multiple: true})
 
 button.btn.btn-primary#add-exercises = t('exercise_collections.form.add_exercises')
diff --git a/app/views/exercise_collections/_form.html.slim b/app/views/exercise_collections/_form.html.slim
index 6b09206e..07fc874f 100644
--- a/app/views/exercise_collections/_form.html.slim
+++ b/app/views/exercise_collections/_form.html.slim
@@ -3,9 +3,10 @@
   .form-group
     = f.label(t('activerecord.attributes.exercise_collections.name'))
     = f.text_field(:name, class: 'form-control', required: true)
-  .form-group
-    = f.label(t('activerecord.attributes.exercise_collections.use_anomaly_detection'))
-    = f.check_box(:use_anomaly_detection, {class: 'form-control'})
+  .form-check.form-group
+    label.form-check-label
+      = f.check_box(:use_anomaly_detection, class: 'form-check-input')
+      = t('activerecord.attributes.exercise_collections.use_anomaly_detection')
   .form-group
     = f.label(t('activerecord.attributes.exercise_collections.user'))
     = f.collection_select(:user_id, InternalUser.order(:name), :id, :name, {}, {class: 'form-control'})
@@ -26,10 +27,10 @@
             td = link_to(t('shared.show'), item.exercise, 'data-turbolinks' => "false")
             td
               a.remove-exercise href='#' = t('shared.destroy')
-  .hidden
+  .d-none
     = f.collection_select(:exercise_ids, Exercise.all, :id, :title, {}, {id: 'exercise-select', class: 'form-control', multiple: true})
   .exercise-actions
-    button.btn.btn-primary type='button' data-toggle='modal' data-target='#add-exercise-modal' = t('exercise_collections.form.add_exercises')
+    button.btn.btn-outline-primary type='button' data-toggle='modal' data-target='#add-exercise-modal' = t('exercise_collections.form.add_exercises')
     button.btn.btn-secondary#sort-button type='button' = t('exercise_collections.form.sort_by_title')
 
   .actions = render('shared/submit_button', f: f, object: @exercise_collection)
diff --git a/app/views/exercise_collections/show.html.slim b/app/views/exercise_collections/show.html.slim
index 83789df3..4fa6a8ac 100644
--- a/app/views/exercise_collections/show.html.slim
+++ b/app/views/exercise_collections/show.html.slim
@@ -7,7 +7,7 @@ h1
 = row(label: 'exercise_collections.use_anomaly_detection', value: @exercise_collection.use_anomaly_detection)
 = row(label: 'exercise_collections.updated_at', value: @exercise_collection.updated_at)
 
-h4 = t('activerecord.attributes.exercise_collections.exercises')
+h4.mt-4 = t('activerecord.attributes.exercise_collections.exercises')
 .table-responsive#exercise-list
   table.table
     thead
@@ -24,5 +24,5 @@ h4 = t('activerecord.attributes.exercise_collections.exercises')
           td = exercise_collection_item.position
           td = link_to(exercise.title, exercise)
           td = link_to_if(exercise.execution_environment && policy(exercise.execution_environment).show?, exercise.execution_environment, exercise.execution_environment)
-          td = exercise.user.name
+          td = link_to_if(exercise.user && policy(exercise.user).show?, exercise.user.name, exercise.user)
           td = link_to(t('shared.statistics'), statistics_exercise_path(exercise), 'data-turbolinks' => "false")
diff --git a/app/views/exercise_collections/statistics.html.slim b/app/views/exercise_collections/statistics.html.slim
index 60c49a01..74c9f49d 100644
--- a/app/views/exercise_collections/statistics.html.slim
+++ b/app/views/exercise_collections/statistics.html.slim
@@ -6,7 +6,7 @@ h1 = @exercise_collection
 = row(label: 'exercises.statistics.average_worktime', value: @exercise_collection.average_working_time.round(3).to_s + 's')
 
 #graph
-  #data.hidden(data-working-times=ActiveSupport::JSON.encode(@exercise_collection.collection_statistics) data-average-working-time=@exercise_collection.average_working_time)
+  #data.d-none(data-working-times=ActiveSupport::JSON.encode(@exercise_collection.collection_statistics) data-average-working-time=@exercise_collection.average_working_time)
   #legend
     - {time: t('exercises.statistics.average_worktime'),
         min: 'min. anomaly threshold',
diff --git a/app/views/exercises/_code_field.html.slim b/app/views/exercises/_code_field.html.slim
index bb2a806f..8fd19eec 100644
--- a/app/views/exercises/_code_field.html.slim
+++ b/app/views/exercises/_code_field.html.slim
@@ -3,5 +3,5 @@
   |  
   a.toggle-input data={text_initial: t('shared.upload_file'), text_toggled: t('shared.back')} href='#' = t('shared.upload_file')
   = form.text_area(attribute, class: 'code-field form-control', rows: 16, style: "display:none;")
-  = form.file_field(attribute, class: 'alternative-input form-control', disabled: true)
+  = form.file_field(attribute, class: 'alternative-input form-control-file', disabled: true)
   = render partial: 'editor_edit', locals: { exercise: @exercise }
diff --git a/app/views/exercises/_editor.html.slim b/app/views/exercises/_editor.html.slim
index f741cb56..44fc0aec 100644
--- a/app/views/exercises/_editor.html.slim
+++ b/app/views/exercises/_editor.html.slim
@@ -6,8 +6,7 @@
 - hide_rfc_button = @hide_rfc_button || false
 #editor.row data-exercise-id=@exercise.id data-message-depleted=t('exercises.editor.depleted') data-message-timeout=t('exercises.editor.timeout',  permitted_execution_time: @exercise.execution_environment.permitted_execution_time) data-errors-url=execution_environment_errors_path(exercise.execution_environment) data-submissions-url=submissions_path data-user-id=@current_user.id data-user-external-id=external_user_external_id data-working-times-url=working_times_exercise_path(@exercise) data-intervention-save-url=intervention_exercise_path(@exercise) data-rfc-interventions=show_rfc_interventions data-break-interventions=show_break_interventions data-course_token=@course_token data-search-save-url=search_exercise_path(@exercise)
   div id="sidebar" class=(@exercise.hide_file_tree ? 'sidebar-col-collapsed' : 'sidebar-col') = render('editor_file_tree', exercise: @exercise, files: @files)
-  div id='output_sidebar' class='output-col-collapsed' = render('exercises/editor_output', external_user_id: external_user_id, consumer_id: consumer_id )
-  div id='frames' class='editor-col'
+  div.editor-col.col.p-0 id='frames'
     #editor-buttons.btn-group.enforce-bottom-margin
       = render('editor_button', disabled: true, icon: 'fa fa-ban', id: 'dummy', label: t('exercises.editor.dummy'))
       = render('editor_button', icon: 'fa fa-desktop', id: 'render', label: t('exercises.editor.render'))
@@ -24,6 +23,7 @@
       = t('exercises.editor.lastsaved')
       span
       button style="display:none" id="autosave"
+  div id='output_sidebar' class='output-col-collapsed' = render('exercises/editor_output', external_user_id: external_user_id, consumer_id: consumer_id )
 
 
 = render('shared/modal', id: 'comment-modal', title: t('exercises.implement.comment.request'), template: 'exercises/_request_comment_dialogcontent')
diff --git a/app/views/exercises/_editor_button.html.slim b/app/views/exercises/_editor_button.html.slim
index ae69529e..7dd492d1 100644
--- a/app/views/exercises/_editor_button.html.slim
+++ b/app/views/exercises/_editor_button.html.slim
@@ -1,4 +1,4 @@
-button.btn class=local_assigns.fetch(:classes, 'btn-primary btn-sm') *local_assigns.fetch(:data, {}) disabled=local_assigns.fetch(:disabled, false) id=id title=local_assigns[:title] type='button'
+button.btn class=local_assigns.fetch(:classes, 'btn-primary btn-lg') *local_assigns.fetch(:data, {}) disabled=local_assigns.fetch(:disabled, false) id=id title=local_assigns[:title] type='button'
   i.fa.fa-circle-o-notch.fa-spin
-  i class=icon
+  i class=(label.present? ? icon : "#{icon} m-0")
   = label
diff --git a/app/views/exercises/_editor_edit.html.slim b/app/views/exercises/_editor_edit.html.slim
index 83f27d68..18ea0109 100644
--- a/app/views/exercises/_editor_edit.html.slim
+++ b/app/views/exercises/_editor_edit.html.slim
@@ -1,5 +1,5 @@
-#editor-edit.panel-group.row.original-input data-exercise-id=@exercise.id
+#editor-edit.original-input data-exercise-id=@exercise.id
   #frames
     .edit-frame
-      .editor-content.hidden
-      .editor
\ No newline at end of file
+      .editor-content.d-none
+      .editor.allow_ace_tooltip
\ No newline at end of file
diff --git a/app/views/exercises/_editor_file_tree.html.slim b/app/views/exercises/_editor_file_tree.html.slim
index c51dd855..32612828 100644
--- a/app/views/exercises/_editor_file_tree.html.slim
+++ b/app/views/exercises/_editor_file_tree.html.slim
@@ -1,18 +1,18 @@
-div id='sidebar-collapsed' class=(@exercise.hide_file_tree ? '' : 'hidden')
-  = render('editor_button', classes: 'btn-block btn-primary btn-sm', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-plus-square', id: 'sidebar-collapse-collapsed', label:'', title:t('exercises.editor.expand_action_sidebar'))
+div id='sidebar-collapsed' class=(@exercise.hide_file_tree ? '' : 'd-none')
+  = render('editor_button', classes: 'btn-block btn-primary btn', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-plus-square', id: 'sidebar-collapse-collapsed', label:'', title:t('exercises.editor.expand_action_sidebar'))
 
   - if @exercise.allow_file_creation and not @exercise.hide_file_tree?
-    = render('editor_button', classes: 'btn-block btn-primary btn-sm enforce-top-margin', data: {:'data-cause' => 'file', :'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-plus', id: 'create-file-collapsed', label:'', title: t('exercises.editor.create_file'))
+    = render('editor_button', classes: 'btn-block btn-primary btn enforce-top-margin', data: {:'data-cause' => 'file', :'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-plus', id: 'create-file-collapsed', label:'', title: t('exercises.editor.create_file'))
 
-  = render('editor_button', classes: 'btn-block btn-primary btn-sm enforce-top-margin', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-download', id: 'download-collapsed', label:'', title: t('exercises.editor.download'))
-  = render('editor_button', classes: 'btn-block btn-primary btn-sm enforce-top-margin', data: {:'data-message-confirm' => t('exercises.editor.confirm_start_over'), :'data-url' => reload_exercise_path(@exercise), :'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-history', id: 'start-over-collapsed', label:'', title: t('exercises.editor.start_over'))
-  - if !@course_token.blank?
-    = render('editor_button', classes: 'btn-block btn-primary btn-sm enforce-top-margin', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-search', id: 'sidebar-search-collapsed', label: '', title: t('search.search_in_forum'))
+  = render('editor_button', classes: 'btn-block btn-primary btn enforce-top-margin', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-download', id: 'download-collapsed', label:'', title: t('exercises.editor.download'))
+  = render('editor_button', classes: 'btn-block btn-primary btn enforce-top-margin', data: {:'data-message-confirm' => t('exercises.editor.confirm_start_over'), :'data-url' => reload_exercise_path(@exercise), :'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-history', id: 'start-over-collapsed', label:'', title: t('exercises.editor.start_over'))
+  //- if !@course_token.blank?
+    = render('editor_button', classes: 'btn-block btn-primary btn enforce-top-margin', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'right'}, icon: 'fa fa-search', id: 'sidebar-search-collapsed', label: '', title: t('search.search_in_forum'))
 
-div id='sidebar-uncollapsed' class=(@exercise.hide_file_tree ? 'hidden' : '')
-  = render('editor_button', classes: 'btn-block btn-primary btn-sm', icon: 'fa fa-minus-square', id: 'sidebar-collapse', label: t('exercises.editor.collapse_action_sidebar'))
+div id='sidebar-uncollapsed' class=(@exercise.hide_file_tree ? 'd-none' : '')
+  = render('editor_button', classes: 'btn-block btn-primary btn', icon: 'fa fa-minus-square', id: 'sidebar-collapse', label: t('exercises.editor.collapse_action_sidebar'))
 
-  div class=(@exercise.hide_file_tree ? 'hidden' : '')
+  div class=(@exercise.hide_file_tree ? 'd-none' : '')
     hr
 
     #files data-entries=FileTree.new(files).to_js_tree
@@ -20,11 +20,11 @@ div id='sidebar-uncollapsed' class=(@exercise.hide_file_tree ? 'hidden' : '')
     hr
 
   - if @exercise.allow_file_creation and not @exercise.hide_file_tree?
-    = render('editor_button', classes: 'btn-block btn-primary btn-sm', data: {:'data-cause' => 'file'}, icon: 'fa fa-plus', id: 'create-file', label: t('exercises.editor.create_file'))
-    = render('editor_button', classes: 'btn-block btn-warning btn-sm', data: {:'data-cause' => 'file', :'data-message-confirm' => t('shared.confirm_destroy')}, icon: 'fa fa-times', id: 'destroy-file', label: t('exercises.editor.destroy_file'))
+    = render('editor_button', classes: 'btn-block btn-primary btn', data: {:'data-cause' => 'file'}, icon: 'fa fa-plus', id: 'create-file', label: t('exercises.editor.create_file'))
+    = render('editor_button', classes: 'btn-block btn-warning btn', data: {:'data-cause' => 'file', :'data-message-confirm' => t('shared.confirm_destroy')}, icon: 'fa fa-times', id: 'destroy-file', label: t('exercises.editor.destroy_file'))
 
-  = render('editor_button', classes: 'btn-block btn-primary btn-sm enforce-top-margin', icon: 'fa fa-download', id: 'download', label: t('exercises.editor.download'))
-  = render('editor_button', classes: 'btn-block btn-primary btn-sm', data: {:'data-message-confirm' => t('exercises.editor.confirm_start_over'), :'data-url' => reload_exercise_path(@exercise)}, icon: 'fa fa-history', id: 'start-over', label: t('exercises.editor.start_over'))
+  = render('editor_button', classes: 'btn-block btn-primary btn enforce-top-margin', icon: 'fa fa-download', id: 'download', label: t('exercises.editor.download'))
+  = render('editor_button', classes: 'btn-block btn-primary btn', data: {:'data-message-confirm' => t('exercises.editor.confirm_start_over'), :'data-url' => reload_exercise_path(@exercise)}, icon: 'fa fa-history', id: 'start-over', label: t('exercises.editor.start_over'))
 
   //- if !@course_token.blank?
       .input-group.enforce-top-margin
diff --git a/app/views/exercises/_editor_frame.html.slim b/app/views/exercises/_editor_frame.html.slim
index eff1541c..8d79ed43 100644
--- a/app/views/exercises/_editor_frame.html.slim
+++ b/app/views/exercises/_editor_frame.html.slim
@@ -11,5 +11,5 @@
       - else
         = link_to(file.native_file.file.name_with_extension, file.native_file.url)
   - else
-    .editor-content.hidden data-file-id=file.ancestor_id = file.content
+    .editor-content.d-none data-file-id=file.ancestor_id = file.content
     .editor data-file-id=file.ancestor_id data-indent-size=file.file_type.indent_size data-mode=file.file_type.editor_mode data-read-only=file.read_only data-allow-auto-completion=exercise.allow_auto_completion.to_s data-id=file.id
\ No newline at end of file
diff --git a/app/views/exercises/_editor_output.html.slim b/app/views/exercises/_editor_output.html.slim
index 2c760ec5..661b3eff 100644
--- a/app/views/exercises/_editor_output.html.slim
+++ b/app/views/exercises/_editor_output.html.slim
@@ -1,58 +1,61 @@
 div id='output_sidebar_collapsed'
-  = render('editor_button', classes: 'btn-block btn-primary btn-sm', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'left'}, title: t('exercises.editor.expand_output_sidebar'), icon: 'fa fa-plus-square', id: 'toggle-sidebar-output-collapsed', label: '')
-div id='output_sidebar_uncollapsed' class='hidden col-sm-12 enforce-bottom-margin' data-message-no-output=t('exercises.implement.no_output')
+  = render('editor_button', classes: 'btn-block btn-primary btn', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'left'}, title: t('exercises.editor.expand_output_sidebar'), icon: 'fa fa-plus-square', id: 'toggle-sidebar-output-collapsed', label: '')
+div.h-100 id='output_sidebar_uncollapsed' class='d-none col-sm-12 enforce-bottom-margin' data-message-no-output=t('exercises.implement.no_output')
   .row
-    = render('editor_button', classes: 'btn-block btn-primary btn-sm', icon: 'fa fa-minus-square', id: 'toggle-sidebar-output', label: t('exercises.editor.collapse_output_sidebar'))
+    = render('editor_button', classes: 'btn-block btn-primary btn', icon: 'fa fa-minus-square', id: 'toggle-sidebar-output', label: t('exercises.editor.collapse_output_sidebar'))
 
-  div.enforce-big-top-margin.hidden id='score_div'
-    #results
-      h2 = t('exercises.implement.results')
-      p.test-count == t('exercises.implement.test_count', count: 0)
-      ul.list-unstyled
-      ul#dummies.hidden.list-unstyled
-        li.panel.panel-default
-          .panel-heading
-            h3.panel-title == t('exercises.implement.file', filename: '', number: 0)
-          .panel-body
-            = row(label: 'exercises.implement.passed_tests', value: t('shared.out_of', maximum_value: 0, value: 0).html_safe)
-            = row(label: 'activerecord.attributes.submission.score', value: t('shared.out_of', maximum_value: 0, value: 0).html_safe)
-            = row(label: 'exercises.implement.feedback')
-            = row(label: 'exercises.implement.error_messages')
-            /= row(label: 'exercises.implement.output', value: link_to(t('shared.show'), '#'))
-    #score data-maximum-score=@exercise.maximum_score data-score=@submission.try(:score)
-      h4
-        span == "#{t('activerecord.attributes.submission.score')}: "
-        span.score
-      .progress
-        .progress-bar role='progressbar'
+  div.position-absolute.d-flex.mb-1.w-100 style="overflow: scroll; left: 0; bottom: 0; height: calc(100% - 3rem);"
+    div.w-100
+      div.enforce-big-top-margin.d-none id='score_div'
+        #results
+          h2 = t('exercises.implement.results')
+          p.test-count == t('exercises.implement.test_count', count: 0)
+          ul.list-unstyled
+          ul#dummies.d-none.list-unstyled
+            li.card.mt-2
+              .card-header
+                h3.card-title.m-0 == t('exercises.implement.file', filename: '', number: 0)
+              .card-body.bg-white.text-dark
+                = row(label: 'exercises.implement.passed_tests', value: t('shared.out_of', maximum_value: 0, value: 0).html_safe)
+                = row(label: 'activerecord.attributes.submission.score', value: t('shared.out_of', maximum_value: 0, value: 0).html_safe)
+                = row(label: 'exercises.implement.feedback')
+                = row(label: 'exercises.implement.error_messages')
+                /= row(label: 'exercises.implement.output', value: link_to(t('shared.show'), '#'))
+        #score data-maximum-score=@exercise.maximum_score data-score=@submission.try(:score)
+          h4
+            span == "#{t('activerecord.attributes.submission.score')}: "
+            span.score
+          .progress
+            .progress-bar role='progressbar'
 
-    br
-    - if lti_outcome_service?(@exercise.id, external_user_id, consumer_id)
-      p.text-center = render('editor_button', classes: 'btn-lg btn-success', data: {:'data-url' => submit_exercise_path(@exercise)}, icon: 'fa fa-send', id: 'submit', label: t('exercises.editor.submit'))
-    - else
-      p.text-center = render('editor_button', classes: 'btn-lg btn-warning-outline', data: {:'data-placement' => 'bottom', :'data-tooltip' => true}, icon: 'fa fa-clock-o', id: 'submit_outdated', label: t('exercises.editor.exercise_deadline_passed'), title: t('exercises.editor.tooltips.exercise_deadline_passed'))
-    hr
+        br
+        - if lti_outcome_service?(@exercise.id, external_user_id, consumer_id)
+          p.text-center = render('editor_button', classes: 'btn-lg btn-success', data: {:'data-url' => submit_exercise_path(@exercise)}, icon: 'fa fa-send', id: 'submit', label: t('exercises.editor.submit'))
+        - else
+          p.text-center = render('editor_button', classes: 'btn-lg btn-outline-warning disabled', data: {:'data-placement' => 'bottom', :'data-tooltip' => true}, icon: 'fa fa-clock-o', id: 'submit_outdated', label: t('exercises.editor.exercise_deadline_passed'), title: t('exercises.editor.tooltips.exercise_deadline_passed'))
+        hr
 
-  div.enforce-big-top-margin
-    #turtlediv
-      canvas#turtlecanvas.hidden width=400 height=400
-  div.enforce-big-top-margin
-    #hint
-      .panel.panel-warning
-        .panel-heading = t('exercises.implement.hint')
-        .panel-body
-  div.enforce-big-top-margin
-    #prompt.input-group.hidden
-      span.input-group-addon data-prompt=t('exercises.editor.input') = t('exercises.editor.input')
-      input#prompt-input.form-control type='text'
-      span.input-group-btn
-        button#prompt-submit.btn.btn-primary type="button" = t('exercises.editor.send')
-    #error-hints
-      .heading = t('exercises.implement.error_hints.heading')
-      ul.body
-    #output
-      pre = t('exercises.implement.no_output_yet')
-    - if CodeOcean::Config.new(:code_ocean).read[:flowr][:enabled]
-      #flowrHint.panel.panel-info data-url=CodeOcean::Config.new(:code_ocean).read[:flowr][:url] role='tab'
-        .panel-heading = 'Gain more insights here'
-        .panel-body
+      div.enforce-big-top-margin
+        #turtlediv
+          canvas#turtlecanvas.d-none width=400 height=400
+      div.enforce-big-top-margin
+        #hint
+          .card.bg-warning
+            .card-header = t('exercises.implement.hint')
+            .card-body
+      div.enforce-big-top-margin
+        #prompt.input-group.d-none
+          div.input-group-prepend
+            span.input-group-text data-prompt=t('exercises.editor.input') = t('exercises.editor.input')
+          input#prompt-input.form-control type='text'
+          span.input-group-btn
+            button#prompt-submit.btn.btn-primary type="button" = t('exercises.editor.send')
+        #error-hints
+          .heading = t('exercises.implement.error_hints.heading')
+          ul.body
+        #output.mt-2
+          pre = t('exercises.implement.no_output_yet')
+        - if CodeOcean::Config.new(:code_ocean).read[:flowr][:enabled]
+          #flowrHint.card.card.text-white.bg-info data-url=CodeOcean::Config.new(:code_ocean).read[:flowr][:url] role='tab'
+            .card-header = 'Gain more insights here'
+            .card-body
diff --git a/app/views/exercises/_file_form.html.slim b/app/views/exercises/_file_form.html.slim
index 57f43d43..d85751fc 100644
--- a/app/views/exercises/_file_form.html.slim
+++ b/app/views/exercises/_file_form.html.slim
@@ -1,41 +1,42 @@
 - id = f.object.id
 
-li.panel.panel-default
-  .panel-heading role="tab" id="heading"
-    a.file-heading data-toggle="collapse" href="#collapse#{id}"
+li.card.mt-2
+  .card-header role="tab" id="heading"
+    a.file-heading.collapsed data-toggle="collapse" href="#collapse#{id}"
       div.clearfix role="button"
+        i class="fa" aria-hidden="true"
         span = f.object.name
-  .panel-collapse.collapse class=('in' if f.object.name.nil?) id="collapse#{id}" role="tabpanel"
-    .panel-body
+  .card-collapse.collapse class=('in' if f.object.name.nil?) id="collapse#{id}" role="tabpanel"
+    .card-body
       - if policy(f.object).destroy?
         .clearfix
-          .btn.btn-warning.btn-sm.pull-right.delete-file data-file-url=code_ocean_file_path(id) = t('shared.destroy')
+          .btn.btn-warning.btn-sm.float-right.delete-file data-file-url=code_ocean_file_path(id) = t('shared.destroy')
       .form-group
         = f.label(:name, t('activerecord.attributes.file.name'))
         = f.text_field(:name, class: 'form-control')
       .form-group
         = f.label(:path, t('activerecord.attributes.file.path'))
         = f.text_field(:path, class: 'form-control')
-        .help-block = t('.hints.path')
+        .help-block.form-text = t('.hints.path')
       .form-group
         = f.label(:file_type_id, t('activerecord.attributes.file.file_type_id'))
         = f.collection_select(:file_type_id, @file_types, :id, :name, {}, class: 'form-control')
       .form-group
         = f.label(:role, t('activerecord.attributes.file.role'))
         = f.select(:role, CodeOcean::File::TEACHER_DEFINED_ROLES.map { |role| [t("files.roles.#{role}"), role] }, {include_blank: true}, class: 'form-control')
-      .checkbox
-        label
-          = f.check_box(:hidden)
+      .form-check
+        label.form-check-label
+          = f.check_box(:hidden, class: 'form-check-input')
           = t('activerecord.attributes.file.hidden')
-      .checkbox
-        label
-          = f.check_box(:read_only)
+      .form-check.mb-3
+        label.form-check-label
+          = f.check_box(:read_only, class: 'form-check-input')
           = t('activerecord.attributes.file.read_only')
       .test-related-fields style="display: #{f.object.teacher_defined_test? ? 'initial' : 'none'};"
         .form-group
           = f.label(:name, t('activerecord.attributes.file.feedback_message'))
           = f.text_area(:feedback_message, class: 'form-control', maxlength: 255)
-          .help-block = t('.hints.feedback_message')
+          .help-block.form-text = t('.hints.feedback_message')
         .form-group
           = f.label(:role, t('activerecord.attributes.file.weight'))
           = f.number_field(:weight, class: 'form-control', min: 1, step: 'any')
diff --git a/app/views/exercises/_form.html.slim b/app/views/exercises/_form.html.slim
index 646c359a..b6d0980b 100644
--- a/app/views/exercises/_form.html.slim
+++ b/app/views/exercises/_form.html.slim
@@ -1,14 +1,14 @@
 - execution_environments = ExecutionEnvironment.where('file_type_id IS NOT NULL').select(:file_type_id, :id)
 - file_types = FileType.where('file_extension IS NOT NULL').select(:file_extension, :id)
 
-= form_for(@exercise, data: {execution_environments: execution_environments, file_types: file_types}, multipart: true) do |f|
+= form_for(@exercise, data: {execution_environments: execution_environments, file_types: file_types}, multipart: true, builder: PagedownFormBuilder) do |f|
   = render('shared/form_errors', object: @exercise)
   .form-group
     = f.label(:title)
     = f.text_field(:title, class: 'form-control', required: true)
   .form-group
     = f.label(:description)
-    = f.pagedown_editor :description
+    = f.pagedown :description, input_html: { preview: true, rows: 10 }
   .form-group
     = f.label(:execution_environment_id)
     = f.collection_select(:execution_environment_id, @execution_environments, :id, :name, {}, class: 'form-control')
@@ -16,34 +16,34 @@
     = f.label(:instructions)
     = f.hidden_field(:instructions)
     .form-control.markdown
-  .checkbox
-    label
-      = f.check_box(:public)
+  .form-check
+    label.form-check-label
+      = f.check_box(:public, class: 'form-check-input')
       = t('activerecord.attributes.exercise.public')
-  .checkbox
-    label
-      = f.check_box(:hide_file_tree)
+  .form-check
+    label.form-check-label
+      = f.check_box(:hide_file_tree, class: 'form-check-input')
       = t('activerecord.attributes.exercise.hide_file_tree')
-  .checkbox
-    label
-      = f.check_box(:allow_file_creation)
+  .form-check
+    label.form-check-label
+      = f.check_box(:allow_file_creation, class: 'form-check-input')
       = t('activerecord.attributes.exercise.allow_file_creation')
-  .checkbox
-    label
-      = f.check_box(:allow_auto_completion)
+  .form-check.mb-3
+    label.form-check-label
+      = f.check_box(:allow_auto_completion, class: 'form-check-input')
       = t('activerecord.attributes.exercise.allow_auto_completion')
   .form-group
     = f.label(t('activerecord.attributes.exercise.difficulty'))
-    = f.number_field :expected_difficulty, in: 1..10, step: 1
+    = f.number_field :expected_difficulty, in: 1..10, step: 1, class: 'form-control'
 
   h2 = t('exercises.form.tags')
-  ul.list-unstyled.panel-group
-    li.panel.panel-default
-      .panel-heading role="tab" id="heading"
+  ul.list-unstyled.card-group
+    li.card
+      .card-header role="tab" id="heading"
         a.file-heading data-toggle="collapse" href="#tag-collapse"
           div.clearfix role="button"
             span = t('exercises.form.click_to_collapse')
-      .panel-collapse.collapse id="tag-collapse" role="tabpanel"
+      .card-collapse.collapse id="tag-collapse" role="tabpanel"
         .table-responsive
           table.table#tags-table
             thead
@@ -55,15 +55,15 @@
                 tr
                   td = b.check_box
                   td = b.object.tag.name
-                  td = number_field "tag_factors[#{b.object.tag.id}]", :factor, :value => b.object.factor, in: 1..10, step: 1
+                  td = number_field "tag_factors[#{b.object.tag.id}]", :factor, :value => b.object.factor, in: 1..10, step: 1, class: 'form-control-sm'
 
   h2 = t('activerecord.attributes.exercise.files')
-  ul#files.list-unstyled.panel-group
+  ul#files.list-unstyled
     = f.fields_for :files do |files_form|
       = render('file_form', f: files_form)
 
-  a#add-file.btn.btn-default.btn-sm.pull-right href='#' = t('.add_file')
-  ul#dummies.hidden = f.fields_for(:files, CodeOcean::File.new, child_index: 'index') do |files_form|
+  a#add-file.btn.btn-secondary.btn-sm.float-right href='#' = t('.add_file')
+  ul#dummies.d-none = f.fields_for(:files, CodeOcean::File.new, child_index: 'index') do |files_form|
     = render('file_form', f: files_form)
 
   .actions = render('shared/submit_button', f: f, object: @exercise)
\ No newline at end of file
diff --git a/app/views/exercises/_request_comment_dialogcontent.html.slim b/app/views/exercises/_request_comment_dialogcontent.html.slim
index 8fb71781..70405ea0 100644
--- a/app/views/exercises/_request_comment_dialogcontent.html.slim
+++ b/app/views/exercises/_request_comment_dialogcontent.html.slim
@@ -2,7 +2,7 @@ h5#rfc_intervention_text style='display: none;' = t('exercises.implement.rfc_int
 h5 = t('exercises.implement.comment.question')
 
 
-textarea.form-control#question(style='resize:none;')
+textarea.form-control.flex-grow-1#question(style='resize:none;')
 p = ''
 / data-cause='requestComments' is not used here right now, we pass the button #requestComments (not askForCommentsButton) as initiator of the action. 
 / But if we use this button, it will work since the correct cause is supplied
diff --git a/app/views/exercises/external_users/statistics.html.slim b/app/views/exercises/external_users/statistics.html.slim
index 5d91716a..e89627ed 100644
--- a/app/views/exercises/external_users/statistics.html.slim
+++ b/app/views/exercises/external_users/statistics.html.slim
@@ -10,21 +10,21 @@ h1 = "#{@exercise} (external user #{@external_user})"
       - file_types.add(ActiveSupport::JSON.encode(file.file_type))
     - all_files.push(submission.files)
 
-  .hidden#data data-submissions=ActiveSupport::JSON.encode(@submissions) data-files=ActiveSupport::JSON.encode(all_files) data-file-types=ActiveSupport::JSON.encode(file_types)
+  .d-none#data data-submissions=ActiveSupport::JSON.encode(@submissions) data-files=ActiveSupport::JSON.encode(all_files) data-file-types=ActiveSupport::JSON.encode(file_types)
 
   #stats-editor.row
     - index = 0
     - all_files.each do |files|
-      .files class=(@exercise.hide_file_tree ? 'hidden col-sm-3' : 'col-sm-3') data-index=index data-entries=FileTree.new(files).to_js_tree
+      .files class=(@exercise.hide_file_tree ? 'd-none col-sm-3' : 'col-sm-3') data-index=index data-entries=FileTree.new(files).to_js_tree
       - index += 1
     div class=(@exercise.hide_file_tree ? 'col-sm-12' : 'col-sm-9')
       #current-file.editor
 
   .flex-container
-    button.btn.btn-default id='play-button'
+    button.btn.btn-secondary id='play-button'
       span.fa.fa-play
     #submissions-slider.flex-item
-      input type='range' orient='horizontal' list='datapoints' min=0 max=@submissions.length-1 value=0
+      input type='range' orient='horizontal' list='datapoints' min=0 max=@submissions.length-1 value=0 style="width: 100%"
       datalist#datapoints
         - index=0
         - @submissions.each do |submission|
@@ -59,7 +59,7 @@ h1 = "#{@exercise} (external user #{@external_user})"
                 td =
                 td = @working_times_until[index] if index > 0
     p = t('.addendum')
-    .hidden#wtimes data-working_times=ActiveSupport::JSON.encode(@working_times_until);
+    .d-none#wtimes data-working_times=ActiveSupport::JSON.encode(@working_times_until);
     div#progress_chart.col-lg-12
       .graph-functions-2
 
diff --git a/app/views/exercises/feedback.html.slim b/app/views/exercises/feedback.html.slim
index 508b1478..5090d0e2 100644
--- a/app/views/exercises/feedback.html.slim
+++ b/app/views/exercises/feedback.html.slim
@@ -8,17 +8,17 @@ h1 = link_to(@exercise, exercise_path(@exercise))
   - if @feedbacks.nil? or @feedbacks.size == 0
     .no-feedback = t('user_exercise_feedback.no_feedback')
 
-  ul.list-unstyled.panel-group
+  ul.list-unstyled
     - @feedbacks.each do |feedback|
-      li.panel.panel-default
-        .panel-heading role="tab" id="heading"
+      li.card.mt-2
+        .card-header role="tab" id="heading"
           div.clearfix.feedback-header
             span.username = link_to(feedback.user.name, statistics_external_user_exercise_path(id: @exercise.id, external_user_id: feedback.user.id))
             - if feedback.anomaly_notification
               i class="fa fa-envelope-o" data-placement="top" data-toggle="tooltip" data-container="body" title=feedback.anomaly_notification.reason
             span.date = feedback.created_at
-        .panel-collapse role="tabpanel"
-          .panel-body.feedback
+        .card-collapse role="tabpanel"
+          .card-body.feedback
             .text = feedback.feedback_text
             .difficulty = "#{t('user_exercise_feedback.difficulty')} #{feedback.difficulty}" if feedback.difficulty
             .worktime = "#{t('user_exercise_feedback.working_time')} #{feedback.user_estimated_worktime}" if feedback.user_estimated_worktime
diff --git a/app/views/exercises/implement.html.slim b/app/views/exercises/implement.html.slim
index a243bd91..f90a838d 100644
--- a/app/views/exercises/implement.html.slim
+++ b/app/views/exercises/implement.html.slim
@@ -2,13 +2,13 @@
   #editor-column.col-md-12
     .exercise.clearfix
       div
-        span.badge.pull-right.score
+        span.badge.badge-pill.float-right.score
 
         h1 id="exercise-headline"
           i class="fa fa-chevron-down" id="description-symbol"
           = @exercise.title
 
-      #description-panel.lead.description-panel
+      #description-card.lead.description-card
         = render_markdown(@exercise.description)
 
       a#toggle href="#" data-show=t('shared.show') data-hide=t('shared.hide') = t('shared.hide')
diff --git a/app/views/exercises/index.html.slim b/app/views/exercises/index.html.slim
index 25cd13e0..35da19cb 100644
--- a/app/views/exercises/index.html.slim
+++ b/app/views/exercises/index.html.slim
@@ -9,45 +9,43 @@ h1 = Exercise.model_name.human(count: 2)
     = f.search_field(:title_cont, class: 'form-control', placeholder: t('activerecord.attributes.exercise.title'))
 
 .table-responsive
-  table.table
+  table.table.mt-4
     thead
       tr
-        th = sort_link(@search, :title, t('activerecord.attributes.exercise.title'))
-        th = sort_link(@search, :execution_environment_id, t('activerecord.attributes.exercise.execution_environment'))
-        th = t('.test_files')
-        th = t('activerecord.attributes.exercise.maximum_score')
-        th = t('activerecord.attributes.exercise.tags')
-        th = t('activerecord.attributes.exercise.difficulty')
-        th
+        th.p-1 = sort_link(@search, :title, t('activerecord.attributes.exercise.title'))
+        th.p-1 = sort_link(@search, :execution_environment_id, t('activerecord.attributes.exercise.execution_environment'))
+        th.p-1 = t('.test_files')
+        th.p-1 = t('activerecord.attributes.exercise.maximum_score')
+        th.p-1 = t('activerecord.attributes.exercise.tags')
+        th.p-1 = t('activerecord.attributes.exercise.difficulty')
+        th.p-1
           = t('activerecord.attributes.exercise.public')
           - if policy(Exercise).batch_update?
             br
             span.batch = link_to(t('shared.batch_update'), '#', 'data-text' => t('shared.update', model: t('activerecord.models.exercise.other')))
-        th colspan=6 = t('shared.actions')
+        th.p-1 colspan=6 = t('shared.actions')
     tbody
       - @exercises.each do |exercise|
         tr data-id=exercise.id
-          td = exercise.title
-          td = link_to_if(exercise.execution_environment && policy(exercise.execution_environment).show?, exercise.execution_environment, exercise.execution_environment)
-          td = exercise.files.teacher_defined_tests.count
-          td = exercise.maximum_score
-          td = exercise.exercise_tags.count
-          td = exercise.expected_difficulty
-          td.public data-value=exercise.public? = symbol_for(exercise.public?)
-          td = link_to(t('shared.edit'), edit_exercise_path(exercise)) if policy(exercise).edit?
-          td = link_to(t('.implement'), implement_exercise_path(exercise)) if policy(exercise).implement?
-          td = link_to(t('shared.statistics'), statistics_exercise_path(exercise), 'data-turbolinks' => "false") if policy(exercise).statistics?
+          td.p-1.pt-2 = link_to(exercise.title, exercise, 'data-turbolinks' => "false") if policy(exercise).show?
+          td.p-1.pt-2 = link_to_if(exercise.execution_environment && policy(exercise.execution_environment).show?, exercise.execution_environment, exercise.execution_environment)
+          td.p-1.pt-2 = exercise.files.teacher_defined_tests.count
+          td.p-1.pt-2 = exercise.maximum_score
+          td.p-1.pt-2 = exercise.exercise_tags.count
+          td.p-1.pt-2 = exercise.expected_difficulty
+          td.p-1.pt-2.public data-value=exercise.public? = symbol_for(exercise.public?)
+          td.p-1.pt-2 = link_to(t('shared.edit'), edit_exercise_path(exercise)) if policy(exercise).edit?
+          td.p-1.pt-2 = link_to(t('.implement'), implement_exercise_path(exercise)) if policy(exercise).implement?
+          td.p-1.pt-2 = link_to(t('shared.statistics'), statistics_exercise_path(exercise), 'data-turbolinks' => "false") if policy(exercise).statistics?
 
-          td
+          td.p-1
             .btn-group
-              button.btn.btn-primary-outline.btn-xs.dropdown-toggle data-toggle="dropdown" type="button" = t('shared.actions_button')
-              span.caret
-              span.sr-only Toggle Dropdown
-              ul.dropdown-menu.pull-right role="menu"
-                li = link_to(t('shared.show'), exercise, 'data-turbolinks' => "false") if policy(exercise).show?
-                li = link_to(t('activerecord.models.user_exercise_feedback.other'), feedback_exercise_path(exercise)) if policy(exercise).feedback?
-                li = link_to(t('shared.destroy'), exercise, data: {confirm: t('shared.confirm_destroy')}, method: :delete) if policy(exercise).destroy?
-                li = link_to(t('.clone'), clone_exercise_path(exercise), data: {confirm: t('shared.confirm_destroy')}, method: :post) if policy(exercise).clone?
+              button.btn.btn-outline-primary.btn-sm.dropdown-toggle data-toggle="dropdown" type="button" = t('shared.actions_button')
+              ul.dropdown-menu.float-right role="menu"
+                li = link_to(t('shared.show'), exercise, 'data-turbolinks' => "false", class: 'dropdown-item') if policy(exercise).show?
+                li = link_to(t('activerecord.models.user_exercise_feedback.other'), feedback_exercise_path(exercise), class: 'dropdown-item') if policy(exercise).feedback?
+                li = link_to(t('shared.destroy'), exercise, data: {confirm: t('shared.confirm_destroy')}, method: :delete, class: 'dropdown-item') if policy(exercise).destroy?
+                li = link_to(t('.clone'), clone_exercise_path(exercise), data: {confirm: t('shared.confirm_destroy')}, method: :post, class: 'dropdown-item') if policy(exercise).clone?
 
 = render('shared/pagination', collection: @exercises)
 p = render('shared/new_button', model: Exercise)
diff --git a/app/views/exercises/show.html.slim b/app/views/exercises/show.html.slim
index 29994548..20307202 100644
--- a/app/views/exercises/show.html.slim
+++ b/app/views/exercises/show.html.slim
@@ -12,7 +12,7 @@ h1
 
 = row(label: 'exercise.title', value: @exercise.title)
 = row(label: 'exercise.user', value: link_to_if(policy(@exercise.author).show?, @exercise.author, @exercise.author))
-= row(label: 'exercise.description', value: render_markdown(@exercise.description))
+= row(label: 'exercise.description', value: render_markdown(@exercise.description), class: 'm-0')
 = row(label: 'exercise.execution_environment', value: link_to_if(policy(@exercise.execution_environment).show?, @exercise.execution_environment, @exercise.execution_environment))
 /= row(label: 'exercise.instructions', value: render_markdown(@exercise.instructions))
 = row(label: 'exercise.maximum_score', value: @exercise.maximum_score)
@@ -20,24 +20,23 @@ h1
 = row(label: 'exercise.hide_file_tree', value: @exercise.hide_file_tree?)
 = row(label: 'exercise.allow_file_creation', value: @exercise.allow_file_creation?)
 = row(label: 'exercise.allow_auto_completion', value: @exercise.allow_auto_completion?)
-= row(label: 'exercise.embedding_parameters') do
-  = content_tag(:input, nil, class: 'form-control', readonly: true, value: embedding_parameters(@exercise))
 = row(label: 'exercise.difficulty', value: @exercise.expected_difficulty)
 = row(label: 'exercise.tags', value: @exercise.exercise_tags.map{|et| "#{et.tag.name} (#{et.factor})"}.sort.join(", "))
+= row(label: 'exercise.embedding_parameters', class: 'mb-4') do
+  = content_tag(:input, nil, class: 'form-control mb-4', readonly: true, value: embedding_parameters(@exercise))
 
-h2 = t('activerecord.attributes.exercise.files')
+h2.mt-4 = t('activerecord.attributes.exercise.files')
 
-ul.list-unstyled.panel-group#files
+ul.list-unstyled#files
   - @exercise.files.each do |file|
-    li.panel.panel-default
-      .panel-heading role="tab" id="heading"
-        a.file-heading data-toggle="collapse" data-parent="#files" href=".collapse#{file.id}"
+    li.card.mt-2
+      .card-header role="tab" id="heading"
+        a.file-heading.collapsed data-toggle="collapse" data-parent="#files" href=".collapse#{file.id}"
           div.clearfix role="button"
+            i class="fa" aria-hidden="true"
             span = file.name_with_extension
-            // probably set an icon here that shows that the rows can be collapsed
-            //span.pull-right.collapse.in class="collapse#{file.id}" ☼
-      .panel-collapse.collapse class="collapse#{file.id}" role="tabpanel"
-        .panel-body
+      .card-collapse.collapse class="collapse#{file.id}" role="tabpanel"
+        .card-body
           - if policy(file).destroy?
-            .clearfix = link_to(t('shared.destroy'), file, class:'btn btn-warning btn-sm pull-right', data: {confirm: t('shared.confirm_destroy')}, method: :delete)
+            .clearfix = link_to(t('shared.destroy'), file, class:'btn btn-warning btn-sm float-right', data: {confirm: t('shared.confirm_destroy')}, method: :delete)
           = render('shared/file', file: file)
diff --git a/app/views/exercises/statistics.html.slim b/app/views/exercises/statistics.html.slim
index 09611491..b19b04dc 100644
--- a/app/views/exercises/statistics.html.slim
+++ b/app/views/exercises/statistics.html.slim
@@ -32,7 +32,7 @@ h1 = @exercise
       -working_time = @exercise.average_working_time_for(user.id) or 0
       -working_time_array.push working_time
     hr
-    .hidden#data data-working-time=ActiveSupport::JSON.encode(working_time_array)
+    .d-none#data data-working-time=ActiveSupport::JSON.encode(working_time_array)
     .graph-functions
     div#chart_1
     hr
diff --git a/app/views/external_users/show.html.slim b/app/views/external_users/show.html.slim
index f0028745..33e2dd6b 100644
--- a/app/views/external_users/show.html.slim
+++ b/app/views/external_users/show.html.slim
@@ -4,9 +4,9 @@ h1 = @user.name
 //= row(label: 'external_user.email', value: @user.email)
 = row(label: 'external_user.consumer', value: link_to(@user.consumer, @user.consumer))
 
-h4 = link_to(t('.exercise_statistics'), statistics_external_user_path(@user))
+h4.mt-4 = link_to(t('.exercise_statistics'), statistics_external_user_path(@user))
 
-h4 = t('.tag_statistics')
+h4.mt-4 = t('.tag_statistics')
 #loading
   .spinner
   = t('.loading_tag_statistics')
diff --git a/app/views/file_templates/index.html.slim b/app/views/file_templates/index.html.slim
index 3022ea53..ba7c3eb7 100644
--- a/app/views/file_templates/index.html.slim
+++ b/app/views/file_templates/index.html.slim
@@ -10,7 +10,7 @@ h1 = FileTemplate.model_name.human(count: 2)
     tbody
       - @file_templates.each do |file_template|
         tr
-          td = file_template.name
+          td = link_to(file_template.name, file_template)
           td = link_to(file_template.file_type, file_type_path(file_template.file_type))
           td = link_to(t('shared.show'), file_template)
           td = link_to(t('shared.edit'), edit_file_template_path(file_template))
diff --git a/app/views/file_types/_form.html.slim b/app/views/file_types/_form.html.slim
index d36f54cf..e234a457 100644
--- a/app/views/file_types/_form.html.slim
+++ b/app/views/file_types/_form.html.slim
@@ -12,16 +12,16 @@
   .form-group
     = f.label(:indent_size)
     = f.number_field(:indent_size, class: 'form-control', placeholder: 2, required: true)
-  .checkbox
-    label
-      = f.check_box(:binary)
+  .form-check
+    label.form-check-label
+      = f.check_box(:binary, class: 'form-check-input')
       = t('activerecord.attributes.file_type.binary')
-  .checkbox
-    label
-      = f.check_box(:executable)
+  .form-check
+    label.form-check-label
+      = f.check_box(:executable, class: 'form-check-input')
       = t('activerecord.attributes.file_type.executable')
-  .checkbox
-    label
-      = f.check_box(:renderable)
+  .form-check.mb-3
+    label.form-check-label
+      = f.check_box(:renderable, class: 'form-check-input')
       = t('activerecord.attributes.file_type.renderable')
   .actions = render('shared/submit_button', f: f, object: @file_type)
diff --git a/app/views/file_types/index.html.slim b/app/views/file_types/index.html.slim
index a8a4d294..95f1394f 100644
--- a/app/views/file_types/index.html.slim
+++ b/app/views/file_types/index.html.slim
@@ -11,7 +11,7 @@ h1 = FileType.model_name.human(count: 2)
     tbody
       - @file_types.each do |file_type|
         tr
-          td = file_type.name
+          td = link_to(file_type.name, file_type)
           td = link_to(file_type.author, file_type.author)
           td = file_type.file_extension
           td = link_to(t('shared.show'), file_type)
diff --git a/app/views/file_types/show.json.jbuilder b/app/views/file_types/show.json.jbuilder
new file mode 100644
index 00000000..0842614e
--- /dev/null
+++ b/app/views/file_types/show.json.jbuilder
@@ -0,0 +1 @@
+json.extract! @file_type, :id, :name, :editor_mode, :file_extension, :executable, :renderable, :binary
diff --git a/app/views/hints/_form.html.slim b/app/views/hints/_form.html.slim
index 09814d96..21ab6bc1 100644
--- a/app/views/hints/_form.html.slim
+++ b/app/views/hints/_form.html.slim
@@ -3,15 +3,15 @@
   .form-group
     = f.label(:name)
     = f.text_field(:name, class: 'form-control', required: true)
-  .form
+  .form-group
     = f.label(:locale)
     = f.select(:locale, I18n.available_locales.map { |locale| [t("locales.#{locale}"), locale] }, {}, class: 'form-control')
   .form-group
     = f.label(:message)
     = f.text_field(:message, class: 'form-control', placeholder: "'$2' has no method '$1'.", required: true)
-    .help-block = t('.hints.message')
+    .help-block.form-text = t('.hints.message')
   .form-group
     = f.label(:regular_expression)
     = f.text_field(:regular_expression, class: 'form-control', placeholder: 'undefined method (\w+) for (\w+)', required: true)
-    .help-block = t('.hints.regular_expression')
+    .help-block.form-text = t('.hints.regular_expression')
   .actions = render('shared/submit_button', f: f, object: @hint)
diff --git a/app/views/internal_users/_form.html.slim b/app/views/internal_users/_form.html.slim
index f7f89299..4a6ff45c 100644
--- a/app/views/internal_users/_form.html.slim
+++ b/app/views/internal_users/_form.html.slim
@@ -5,7 +5,7 @@
     = f.collection_select(:consumer_id, Consumer.all.sort_by(&:name), :id, :name, {}, class: 'form-control')
   .form-group
     = f.label(:email)
-    = f.text_field(:email, class: 'form-control', required: true)
+    = f.email_field(:email, class: 'form-control', required: true)
   .form-group
     = f.label(:name)
     = f.text_field(:name, class: 'form-control', required: true)
diff --git a/app/views/internal_users/activate.html.slim b/app/views/internal_users/activate.html.slim
index cd52abca..25795ed6 100644
--- a/app/views/internal_users/activate.html.slim
+++ b/app/views/internal_users/activate.html.slim
@@ -9,4 +9,4 @@ h1 = t('.headline')
     = f.label(:password_confirmation)
     = f.password_field(:password_confirmation, class: 'form-control', required: true)
   = f.hidden_field(:activation_token)
-  .actions = submit_tag(t('.submit'), class: 'btn btn-default')
+  .actions = submit_tag(t('.submit'), class: 'btn btn-primary')
diff --git a/app/views/internal_users/forgot_password.html.slim b/app/views/internal_users/forgot_password.html.slim
index 8ccb884a..ca10fdac 100644
--- a/app/views/internal_users/forgot_password.html.slim
+++ b/app/views/internal_users/forgot_password.html.slim
@@ -3,5 +3,5 @@ h1 = t('.headline')
 = form_tag do
   .form-group
     = label_tag(:email, t('activerecord.attributes.internal_user.email'))
-    = text_field_tag(:email, params[:email], autofocus: true, class: 'form-control', required: true)
-  .actions = submit_tag(t('.submit'), class: 'btn btn-default')
+    = email_field_tag(:email, params[:email], autofocus: true, class: 'form-control', required: true)
+  .actions = submit_tag(t('.submit'), class: 'btn btn-primary')
diff --git a/app/views/internal_users/index.html.slim b/app/views/internal_users/index.html.slim
index c4b6c1a0..29f07649 100644
--- a/app/views/internal_users/index.html.slim
+++ b/app/views/internal_users/index.html.slim
@@ -12,7 +12,7 @@ h1 = InternalUser.model_name.human(count: 2)
     = f.select(:role_eq, User::ROLES.map { |role| [t("users.roles.#{role}"), role] }, {}, class: 'form-control', prompt: t('activerecord.attributes.internal_user.role'))
 
 .table-responsive
-  table.table
+  table.table.mt-4
     thead
       tr
         th = t('activerecord.attributes.internal_user.name')
diff --git a/app/views/internal_users/reset_password.html.slim b/app/views/internal_users/reset_password.html.slim
index a743ef46..857121c2 100644
--- a/app/views/internal_users/reset_password.html.slim
+++ b/app/views/internal_users/reset_password.html.slim
@@ -9,4 +9,4 @@ h1 = t('.headline')
     = f.label(:password_confirmation)
     = f.password_field(:password_confirmation, class: 'form-control', required: true)
   = f.hidden_field(:reset_password_token)
-  .actions = submit_tag(t('.submit'), class: 'btn btn-default')
+  .actions = submit_tag(t('.submit'), class: 'btn btn-primary')
diff --git a/app/views/layouts/application.html.slim b/app/views/layouts/application.html.slim
index becb0200..9a5f8de6 100644
--- a/app/views/layouts/application.html.slim
+++ b/app/views/layouts/application.html.slim
@@ -13,22 +13,18 @@ html lang='en'
     = yield(:head)
     = csrf_meta_tags
   body
-    nav.navbar.navbar-default role='navigation'
+    nav.navbar.navbar-dark.bg-dark.navbar-expand-md.mb-4 role='navigation'
       .container
-        .navbar-header
-          button.navbar-toggle data-target='#navbar-collapse' data-toggle='collapse' type='button'
-            span.sr-only Toggle navigation
-            span.icon-bar
-            span.icon-bar
-            span.icon-bar
-          .navbar-brand
-            i.fa.fa-code
-            = application_name
+        button.navbar-toggler data-target='#navbar-collapse' data-toggle='collapse' type='button' aria-expanded='false' aria-label='Toggle navigation'
+          span.navbar-toggler-icon.sr-only
+        .navbar-brand
+          i.fa.fa-code
+          = application_name
         #navbar-collapse.collapse.navbar-collapse
           = render('navigation', cached: true)
-          ul.nav.navbar-nav.navbar-right
+          ul.nav.navbar-nav.ml-auto
             = render('locale_selector', cached: true)
-            li = link_to(t('shared.help.link'), '#modal-help', data: {toggle: 'modal'})
+            li.nav-item.mr-3 = link_to(t('shared.help.link'), '#modal-help', data: {toggle: 'modal'}, class: 'nav-link')
             = render('session')
     .container data-controller=controller_name
       = render('flash')
diff --git a/app/views/proxy_exercises/_form.html.slim b/app/views/proxy_exercises/_form.html.slim
index bd57bf06..601ef950 100644
--- a/app/views/proxy_exercises/_form.html.slim
+++ b/app/views/proxy_exercises/_form.html.slim
@@ -1,11 +1,11 @@
-= form_for(@proxy_exercise, multipart: true) do |f|
+= form_for(@proxy_exercise, multipart: true, builder: PagedownFormBuilder) do |f|
   = render('shared/form_errors', object: @proxy_exercise)
   .form-group
     = f.label(:title)
     = f.text_field(:title, class: 'form-control', required: true)
   .form-group
     = f.label(:description)
-    = f.pagedown_editor :description
+    = f.pagedown :description, input_html: { preview: true, rows: 10 }
 
   h3 Exercises
   .table-responsive
diff --git a/app/views/proxy_exercises/index.html.slim b/app/views/proxy_exercises/index.html.slim
index 85ef3890..a2e7e460 100644
--- a/app/views/proxy_exercises/index.html.slim
+++ b/app/views/proxy_exercises/index.html.slim
@@ -6,30 +6,30 @@ h1 = ProxyExercise.model_name.human(count: 2)
     = f.search_field(:title_cont, class: 'form-control', placeholder: t('activerecord.attributes.proxy_exercise.title'))
 
 .table-responsive
-  table.table
+  table.table.mt-4
     thead
       tr
-        th = sort_link(@search, :title, t('activerecord.attributes.proxy_exercise.title'))
-        th = t('activerecord.attributes.exercise.token')
-        th = t('activerecord.attributes.proxy_exercise.files_count')
-        th colspan=6 = t('shared.actions')
+        th.p-1 = sort_link(@search, :title, t('activerecord.attributes.proxy_exercise.title'))
+        th.p-1 = t('activerecord.attributes.exercise.token')
+        th.p-1 = t('activerecord.attributes.proxy_exercise.files_count')
+        th.p-1 colspan=6 = t('shared.actions')
     tbody
       - @proxy_exercises.each do |proxy_exercise|
         tr data-id=proxy_exercise.id
-          td = link_to(proxy_exercise.title,proxy_exercise)
-          td = proxy_exercise.token
-          td = proxy_exercise.count_files
-          td = link_to(t('shared.edit'), edit_proxy_exercise_path(proxy_exercise)) if policy(proxy_exercise).edit?
+          td.p-1.pt-2 = link_to(proxy_exercise.title,proxy_exercise)
+          td.p-1.pt-2 = proxy_exercise.token
+          td.p-1.pt-2 = proxy_exercise.count_files
+          td.p-1.pt-2 = link_to(t('shared.edit'), edit_proxy_exercise_path(proxy_exercise)) if policy(proxy_exercise).edit?
 
-          td
+          td.p-1
             .btn-group
-              button.btn.btn-primary-outline.btn-xs.dropdown-toggle data-toggle="dropdown" type="button" = t('shared.actions_button')
+              button.btn.btn-outline-primary.btn-sm.dropdown-toggle data-toggle="dropdown" type="button" = t('shared.actions_button')
               span.caret
               span.sr-only Toggle Dropdown
-              ul.dropdown-menu.pull-right role="menu"
-                li = link_to(t('shared.show'), proxy_exercise, 'data-turbolinks' => "false") if policy(proxy_exercise).show?
-                li = link_to(t('shared.destroy'), proxy_exercise, data: {confirm: t('shared.confirm_destroy')}, method: :delete) if policy(proxy_exercise).destroy?
-                li = link_to(t('.clone'), clone_proxy_exercise_path(proxy_exercise), data: {confirm: t('shared.confirm_destroy')}, method: :post) if policy(proxy_exercise).clone?
+              ul.dropdown-menu.float-right role="menu"
+                li = link_to(t('shared.show'), proxy_exercise, 'data-turbolinks' => "false", class: 'dropdown-item') if policy(proxy_exercise).show?
+                li = link_to(t('shared.destroy'), proxy_exercise, data: {confirm: t('shared.confirm_destroy')}, method: :delete, class: 'dropdown-item') if policy(proxy_exercise).destroy?
+                li = link_to(t('.clone'), clone_proxy_exercise_path(proxy_exercise), data: {confirm: t('shared.confirm_destroy')}, method: :post, class: 'dropdown-item') if policy(proxy_exercise).clone?
 
 = render('shared/pagination', collection: @proxy_exercises)
 p = render('shared/new_button', model: ProxyExercise)
diff --git a/app/views/proxy_exercises/show.html.slim b/app/views/proxy_exercises/show.html.slim
index dee0a7a0..3b05e830 100644
--- a/app/views/proxy_exercises/show.html.slim
+++ b/app/views/proxy_exercises/show.html.slim
@@ -14,7 +14,8 @@ h1
 = row(label: 'proxy_exercise.files_count', value: @exercises.count)
 = row(label: 'exercise.description', value: @proxy_exercise.description)
 = row(label: 'exercise.token', value: @proxy_exercise.token)
-h3 Exercises
+
+h2.mt-4 Exercises
 .table-responsive
   table.table
     thead
diff --git a/app/views/request_for_comments/_admin_menu.html.slim b/app/views/request_for_comments/_admin_menu.html.slim
index 3f71b2ed..cfdfccf1 100644
--- a/app/views/request_for_comments/_admin_menu.html.slim
+++ b/app/views/request_for_comments/_admin_menu.html.slim
@@ -1,9 +1,8 @@
-br
-h4 Admin Menu
-h5
-  ul
-    li = link_to "User's current status of this exercise", statistics_external_user_exercise_path(id: @request_for_comment.exercise_id, external_user_id: @request_for_comment.user_id)
-    li = link_to "All exercises of this user", statistics_external_user_path(id: @request_for_comment.user_id)
-  ul
-    li = link_to "Implement the exercise yourself", implement_exercise_path(id: @request_for_comment.exercise_id)
-    li = link_to "Show the exercise", exercise_path(id: @request_for_comment.exercise_id)
+hr
+h5.mt-4 Admin Menu
+ul.text
+  li = link_to "User's current status of this exercise", statistics_external_user_exercise_path(id: @request_for_comment.exercise_id, external_user_id: @request_for_comment.user_id)
+  li = link_to "All exercises of this user", statistics_external_user_path(id: @request_for_comment.user_id)
+ul.text
+  li = link_to "Implement the exercise yourself", implement_exercise_path(id: @request_for_comment.exercise_id)
+  li = link_to "Show the exercise", exercise_path(id: @request_for_comment.exercise_id)
diff --git a/app/views/request_for_comments/_mark_as_solved.html.slim b/app/views/request_for_comments/_mark_as_solved.html.slim
index b3df57fd..cac16d06 100644
--- a/app/views/request_for_comments/_mark_as_solved.html.slim
+++ b/app/views/request_for_comments/_mark_as_solved.html.slim
@@ -4,4 +4,4 @@ button.btn.btn-primary#mark-as-solved-button = t('request_for_comments.mark_as_s
   p = t('request_for_comments.write_a_thank_you_node')
   textarea#thank-you-note
   button.btn.btn-primary#send-thank-you-note = t('request_for_comments.send_thank_you_note')
-  button.btn.btn-default#cancel-thank-you-note = t('request_for_comments.cancel_thank_you_note')
+  button.btn.btn-secondary#cancel-thank-you-note = t('request_for_comments.cancel_thank_you_note')
diff --git a/app/views/request_for_comments/index.html.slim b/app/views/request_for_comments/index.html.slim
index d253f0ab..eb222e31 100644
--- a/app/views/request_for_comments/index.html.slim
+++ b/app/views/request_for_comments/index.html.slim
@@ -9,7 +9,7 @@ h1 = RequestForComment.model_name.human(count: 2)
     = f.select(:solved_not_eq,  [[t('request_for_comments.show_all'), 2], [t('request_for_comments.show_unsolved'), 1], [t('request_for_comments.show_solved'), 0]])
 
 .table-responsive
-  table.table.sortable
+  table.table.sortable.mt-4
     thead
       tr
         th
@@ -39,7 +39,7 @@ h1 = RequestForComment.model_name.human(count: 2)
           - else
             td = '-'
           td = request_for_comment.comments_count
-          td = request_for_comment.user.displayname
+          td = link_to_if(request_for_comment.user && policy(request_for_comment.user).show?, request_for_comment.user.displayname, request_for_comment.user)
           td = t('shared.time.before', time: distance_of_time_in_words_to_now(request_for_comment.created_at))
           td = t('shared.time.before', time: distance_of_time_in_words_to_now(request_for_comment.last_comment.nil? ? request_for_comment.updated_at : request_for_comment.last_comment))
 
diff --git a/app/views/request_for_comments/show.html.erb b/app/views/request_for_comments/show.html.erb
index 5f6a53f5..2bc57dc8 100644
--- a/app/views/request_for_comments/show.html.erb
+++ b/app/views/request_for_comments/show.html.erb
@@ -25,7 +25,7 @@
     
 
     

-      

+      

         <%= t('activerecord.attributes.request_for_comments.question')%>
       

       

@@ -42,7 +42,7 @@
       

         <% output_runs = testruns.select { |run| run.cause == 'run' } %>
         <% if output_runs.size > 0 %>
-          
<%= t('request_for_comments.runtime_output') %>

+          
<%= t('request_for_comments.runtime_output') %>