diff --git a/Gruntfile.js b/Gruntfile.js
index 76f5f62c..2b39f8b0 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -99,20 +99,16 @@ module.exports = function(grunt) {
            * Keys will be used as directives for the compiler
            * values can be strings or arrays.
            * If no value is required use null
-           *
-           * The directive 'externs' is treated as a special case
-           * allowing a grunt file syntax (<config:...>, *)
-           *
-           * Following are some directive samples...
            */
-           //compilation_level: 'ADVANCED_OPTIMIZATIONS',
+          //compilation_level: 'ADVANCED_OPTIMIZATIONS',
           compilation_level: 'SIMPLE_OPTIMIZATIONS',
-          //externs: ['path/to/file.js', '/source/**/*.js'],
+          externs: ['piskel-closure-externs.js'],
           define: ["'goog.DEBUG=false'"],
           warning_level: 'verbose',
           jscomp_off: ['checkTypes', 'fileoverviewTags'],
           summary_detail_level: 1,
-          output_wrapper: '"(function(){%output%}).call(this);"'
+          language_in: 'ECMASCRIPT3'
+          //output_wrapper: '"(function(){%output%}).call(this);"'
         },
         execOpts: { // [OPTIONAL] Set exec method options
            /**
@@ -138,6 +134,10 @@ module.exports = function(grunt) {
         //src: 'path/to/file.js',
         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'
         ]
@@ -171,13 +171,13 @@ module.exports = function(grunt) {
   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', 'compile']);
+  grunt.registerTask('default', ['leadingIndent:jsFiles', 'leadingIndent:cssFiles', 'jshint', 'concat', 'compile', 'uglify']);
 
   // Start webserver
   grunt.registerTask('serve', ['connect:serve']);
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/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