diff --git a/card.js b/card.js
index 28718f7..867d405 100644
--- a/card.js
+++ b/card.js
@@ -20,7 +20,7 @@
     EventDispatcher.call(self);
 
     var path = H5P.getPath(image.path, id);
-    var width, height, margin, $card, $wrapper, removedState, flippedState;
+    var width, height, $card, $wrapper, removedState, flippedState;
 
     alt = alt || 'Missing description'; // Default for old games
 
@@ -91,7 +91,7 @@
     /**
      * Remove.
      */
-    self.remove = function (announce) {
+    self.remove = function () {
       $card.addClass('h5p-matched');
       removedState = true;
     };
@@ -137,7 +137,7 @@
                   '</div>' +
                 '</div></li>')
         .appendTo($container)
-        .on('keydown', function (event) {
+        .on('keydown', function (event) {
           switch (event.which) {
             case 13: // Enter
             case 32: // Space
diff --git a/memory-game.js b/memory-game.js
index 7c61076..1557e18 100644
--- a/memory-game.js
+++ b/memory-game.js
@@ -154,7 +154,7 @@ H5P.MemoryGame = (function (EventDispatcher, $) {
      * Shuffle the cards and restart the game!
      * @private
      */
-    var resetGame = function () {
+    var resetGame = function () {
 
       // Reset cards
       removed = 0;
@@ -197,7 +197,7 @@ H5P.MemoryGame = (function (EventDispatcher, $) {
       buttonElement.innerHTML = label;
       buttonElement.setAttribute('role', 'button');
       buttonElement.tabIndex = 0;
-      buttonElement.addEventListener('click', function (event) {
+      buttonElement.addEventListener('click', function () {
         action.apply(buttonElement);
       }, false);
       buttonElement.addEventListener('keypress', function (event) {
@@ -437,7 +437,7 @@ H5P.MemoryGame = (function (EventDispatcher, $) {
 
         $bottom = $('<div/>', {
           tabindex: '-1',
-          appendTo: $container
+          appendTo: $container
         });
         $taskComplete = $('<div/>', {
           'class': 'h5p-memory-complete h5p-memory-hidden-read',
@@ -467,10 +467,10 @@ H5P.MemoryGame = (function (EventDispatcher, $) {
 
     /**
      * Will try to scale the game so that it fits within its container.
-     * Puts the cards into a grid layout to make it as square as possible – 
+     * Puts the cards into a grid layout to make it as square as possible –
      * which improves the playability on multiple devices.
      *
-     * @private
+     * @private
      */
     var scaleGameSize = function () {
 
@@ -538,7 +538,7 @@ H5P.MemoryGame = (function (EventDispatcher, $) {
   /**
    * Determine color contrast level compared to white(#fff)
    *
-   * @private
+   * @private
    * @param {string} color hex code
    * @return {number} From 1 to Infinity.
    */
diff --git a/popup.js b/popup.js
index 3f07631..07c3f64 100644
--- a/popup.js
+++ b/popup.js
@@ -18,7 +18,7 @@
     var $top = $popup.find('.h5p-memory-top');
 
     // Hook up the close button
-    $popup.find('.h5p-memory-close').on('click', function () {
+    $popup.find('.h5p-memory-close').on('click', function () {
       self.close(true);
     }).on('keypress', function (event) {
       if (event.which === 13 || event.which === 32) {
diff --git a/upgrades.js b/upgrades.js
index 42c39bd..ce870bc 100644
--- a/upgrades.js
+++ b/upgrades.js
@@ -1,6 +1,6 @@
 var H5PUpgrades = H5PUpgrades || {};
 
-H5PUpgrades['H5P.MemoryGame'] = (function ($) {
+H5PUpgrades['H5P.MemoryGame'] = (function () {
   return {
     1: {
       /**
@@ -42,4 +42,4 @@ H5PUpgrades['H5P.MemoryGame'] = (function ($) {
       }
     }
   };
-})(H5P.jQuery);
+})();