diff --git a/.gitignore b/.gitignore
index b785b0e8..1bdbebc0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,4 +13,7 @@ npm-debug.log
 *.stackdump
 
 # builds
-build
\ No newline at end of file
+build
+
+# Closure compiler generated JS binary.
+closure_compiled_binary.js
\ No newline at end of file
diff --git a/Gruntfile.js b/Gruntfile.js
index 497085a8..0b3f3320 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -11,7 +11,6 @@
  */
 
 module.exports = function(grunt) {
-
   var piskelScripts = require('./piskel-script-list.js').scripts;
   var getGhostConfig = function (delay) {
     return {
@@ -84,6 +83,61 @@ module.exports = function(grunt) {
           'build/piskel-packaged-min.js' : ['build/piskel-packaged.js']
         }
       }
+    },
+    closureCompiler:  {
+      options: {
+        // [REQUIRED] Path to closure compiler
+        compilerFile: 'closure_compiler_20130823.jar',
+
+        // [OPTIONAL] set to true if you want to check if files were modified
+        // before starting compilation (can save some time in large sourcebases)
+        //checkModified: true,
+
+        // [OPTIONAL] Set Closure Compiler Directives here
+        compilerOpts: {
+          /**
+           * Keys will be used as directives for the compiler
+           * values can be strings or arrays.
+           * If no value is required use null
+           */
+          //compilation_level: 'ADVANCED_OPTIMIZATIONS',
+          compilation_level: 'SIMPLE_OPTIMIZATIONS',
+          externs: ['piskel-closure-externs.js'],
+          // Inject some constants in JS code, could we use that for appengine wiring ?
+          //define: ["'goog.DEBUG=false'"],
+          warning_level: 'verbose',
+          jscomp_off: ['checkTypes', 'fileoverviewTags'],
+          summary_detail_level: 1,
+          language_in: 'ECMASCRIPT3'
+          //output_wrapper: '"(function(){%output%}).call(this);"'
+        },
+        execOpts: { // [OPTIONAL] Set exec method options
+          maxBuffer: 999999 * 1024
+        }
+
+      },
+      compile: {
+
+        /**
+         *[OPTIONAL] Here you can add new or override previous option of the Closure Compiler Directives.
+         * IMPORTANT! The feature is enabled as a temporary solution to [#738](https://github.com/gruntjs/grunt/issues/738).
+         * As soon as issue will be fixed this feature will be removed.
+         */
+        TEMPcompilerOpts: {
+        },
+        src: [
+          'js/**/*.js',
+          //'!js/lib/**/*.js',
+          '!js/lib/bootstrap/**/*.js',
+          '!js/lib/jsColor_1_4_0/**/*.js',
+          '!js/lib/gif/**/*.js',
+          'piskel-boot.js',
+          'piskel-script-list.js'
+        ],
+
+        // This generated JS binary is currently not used and even excluded from source control using .gitignore.
+        dest: 'closure_compiled_binary.js'
+      }
     }
   });
 
@@ -99,6 +153,7 @@ module.exports = function(grunt) {
   grunt.loadNpmTasks('grunt-contrib-jshint');
   grunt.loadNpmTasks('grunt-contrib-concat');
   grunt.loadNpmTasks('grunt-contrib-uglify');
+  grunt.loadNpmTasks('grunt-closure-tools');
   grunt.loadNpmTasks('grunt-ghost');
   grunt.loadNpmTasks('grunt-leading-indent');
 
@@ -106,15 +161,17 @@ module.exports = function(grunt) {
   grunt.registerTask('lint', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint']);
 
   // Validate & Test 
-  grunt.registerTask('test', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint', 'connect:test', 'ghost:default']);
+  grunt.registerTask('test', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint', 'compile', 'connect:test', 'ghost:default']);
 
   // Validate & Test (faster version) will NOT work on travis !!
-  grunt.registerTask('precommit', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint', 'connect:test', 'ghost:local']);
+  grunt.registerTask('precommit', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint', 'compile', 'connect:test', 'ghost:local']);
+
+  // Compile JS code (eg verify JSDoc annotation and types, no actual minified code generated).
+  grunt.registerTask('compile', ['closureCompiler:compile']);
 
   // Validate & Build
-  grunt.registerTask('default', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint', 'concat', 'uglify']);
+  grunt.registerTask('default', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint', 'concat', 'compile', 'uglify']);
 
   // Start webserver
   grunt.registerTask('serve', ['connect:serve']);
-
 };
diff --git a/closure_compiler_20130823.jar b/closure_compiler_20130823.jar
new file mode 100644
index 00000000..fc290866
Binary files /dev/null and b/closure_compiler_20130823.jar differ
diff --git a/js/Events.js b/js/Events.js
index 06e2dda2..d7f8d25b 100644
--- a/js/Events.js
+++ b/js/Events.js
@@ -1,5 +1,5 @@
 // TODO(grosbouddha): put under pskl namespace.
-Events = {
+var Events = {
   
   TOOL_SELECTED : "TOOL_SELECTED",
   TOOL_RELEASED : "TOOL_RELEASED",
diff --git a/js/drawingtools/BaseTool.js b/js/drawingtools/BaseTool.js
index f1d77ad0..0b3d365e 100644
--- a/js/drawingtools/BaseTool.js
+++ b/js/drawingtools/BaseTool.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.BaseTool
  *
  * @require pskl.utils
diff --git a/js/drawingtools/Circle.js b/js/drawingtools/Circle.js
index a665dc96..784a90c2 100644
--- a/js/drawingtools/Circle.js
+++ b/js/drawingtools/Circle.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.Circle
  *
  * @require pskl.utils
diff --git a/js/drawingtools/ColorPicker.js b/js/drawingtools/ColorPicker.js
index 9c5d72c6..8bbedf0d 100644
--- a/js/drawingtools/ColorPicker.js
+++ b/js/drawingtools/ColorPicker.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.ColorPicker
  *
  * @require pskl.utils
diff --git a/js/drawingtools/Eraser.js b/js/drawingtools/Eraser.js
index fd3cb7e3..c66a4220 100644
--- a/js/drawingtools/Eraser.js
+++ b/js/drawingtools/Eraser.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.Eraser
  *
  * @require Constants
diff --git a/js/drawingtools/Move.js b/js/drawingtools/Move.js
index e561b91a..a800f481 100644
--- a/js/drawingtools/Move.js
+++ b/js/drawingtools/Move.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.Move
  *
  * @require pskl.utils
diff --git a/js/drawingtools/PaintBucket.js b/js/drawingtools/PaintBucket.js
index 428596e0..cb0ffa66 100644
--- a/js/drawingtools/PaintBucket.js
+++ b/js/drawingtools/PaintBucket.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.PaintBucket
  *
  * @require pskl.utils
diff --git a/js/drawingtools/Rectangle.js b/js/drawingtools/Rectangle.js
index 532afd35..6d555508 100644
--- a/js/drawingtools/Rectangle.js
+++ b/js/drawingtools/Rectangle.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.Rectangle
  *
  * @require pskl.utils
diff --git a/js/drawingtools/SimplePen.js b/js/drawingtools/SimplePen.js
index 1f7d482a..a5dbbb0e 100644
--- a/js/drawingtools/SimplePen.js
+++ b/js/drawingtools/SimplePen.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.SimplePen
  *
  * @require pskl.utils
diff --git a/js/drawingtools/Stroke.js b/js/drawingtools/Stroke.js
index e97bc144..6952c1bc 100644
--- a/js/drawingtools/Stroke.js
+++ b/js/drawingtools/Stroke.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.Stroke
  *
  * @require pskl.utils
diff --git a/js/drawingtools/selectiontools/BaseSelect.js b/js/drawingtools/selectiontools/BaseSelect.js
index 334171dc..13c761ac 100644
--- a/js/drawingtools/selectiontools/BaseSelect.js
+++ b/js/drawingtools/selectiontools/BaseSelect.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.BaseSelect
  *
  * @require pskl.utils
diff --git a/js/drawingtools/selectiontools/RectangleSelect.js b/js/drawingtools/selectiontools/RectangleSelect.js
index 810d814b..9789c427 100644
--- a/js/drawingtools/selectiontools/RectangleSelect.js
+++ b/js/drawingtools/selectiontools/RectangleSelect.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.RectangleSelect
  *
  * @require pskl.utils
diff --git a/js/drawingtools/selectiontools/ShapeSelect.js b/js/drawingtools/selectiontools/ShapeSelect.js
index 6d931850..ffe3a628 100644
--- a/js/drawingtools/selectiontools/ShapeSelect.js
+++ b/js/drawingtools/selectiontools/ShapeSelect.js
@@ -1,4 +1,4 @@
-/*
+/**
  * @provide pskl.drawingtools.ShapeSelect
  *
  * @require pskl.utils
diff --git a/js/utils/PixelUtils.js b/js/utils/PixelUtils.js
index 94e1fcb5..0966d5a3 100644
--- a/js/utils/PixelUtils.js
+++ b/js/utils/PixelUtils.js
@@ -44,7 +44,7 @@
         x0 : Math.min(x0, x1), 
         y0 : Math.min(y0, y1),
         x1 : Math.max(x0, x1), 
-        y1 : Math.max(y0, y1),
+        y1 : Math.max(y0, y1)
       };
     },
 
@@ -172,6 +172,6 @@
         widthBoundDpi = Math.floor(width / pictureWidth);
 
       return Math.min(heightBoundDpi, widthBoundDpi);
-    },
+    }
   };
 })();
\ No newline at end of file
diff --git a/js/utils/core.js b/js/utils/core.js
index 58fc39fd..46ccaaed 100644
--- a/js/utils/core.js
+++ b/js/utils/core.js
@@ -24,7 +24,7 @@ if (typeof Function.prototype.bind !== "function") {
   };
 }
 
-/*
+/**
  * @provide pskl.utils
  *
  * @require Constants
diff --git a/package.json b/package.json
index 857b51aa..cfc74920 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,7 @@
     "grunt-contrib-jshint": "0.5.4",
     "grunt-contrib-uglify": "0.2.2",
     "grunt-ghost": "1.0.12",
-    "grunt-leading-indent" : "0.1.0"
+    "grunt-leading-indent": "0.1.0",
+    "grunt-closure-tools": "~0.8.3"
   }
 }
diff --git a/piskel-boot.js b/piskel-boot.js
index 2ac97da7..1c8da006 100644
--- a/piskel-boot.js
+++ b/piskel-boot.js
@@ -11,14 +11,14 @@
     window.exports = {};
     var scriptIndex = 0;
     window.loadNextScript = function () {
-      if (scriptIndex == exports.scripts.length) {
+      if (scriptIndex == window.exports.scripts.length) {
         pskl.app.init();
         // cleanup
         delete window.exports;
         delete window.loadDebugScripts;
         delete window.done;
       } else {
-        loadScript(exports.scripts[scriptIndex], "loadNextScript()");
+        loadScript(window.exports.scripts[scriptIndex], "loadNextScript()");
         scriptIndex ++;
       }
     };
diff --git a/piskel-closure-externs.js b/piskel-closure-externs.js
new file mode 100644
index 00000000..b5f3d789
--- /dev/null
+++ b/piskel-closure-externs.js
@@ -0,0 +1,17 @@
+/**
+ * @fileoverview Externs for Piskel
+ *
+ * @externs
+ */
+
+// Piskel externs.
+var exports;
+var $;
+var console;
+var pskl; 
+
+// Piskel libs externs.
+var define;
+var jQuery;
+var getComputedStyle;
+var URL;
\ No newline at end of file