diff --git a/.gitignore b/.gitignore
index 9d68abca..780fe156 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,9 @@ npm-debug.log
 build/*.js
 build/*.css
 
+# diffs
+diff.txt
+
 # Closure compiler generated JS binary.
 build/closure/closure_compiled_binary.js
 
diff --git a/src/css/tools.css b/src/css/tools.css
index 3b0dbcf2..6f38e313 100644
--- a/src/css/tools.css
+++ b/src/css/tools.css
@@ -130,7 +130,7 @@
 }
 
 .tool-rectangle-select .drawing-canvas-container:hover {
-  cursor: url(../img/icons/select.png) 15 15, pointer;
+  cursor: crosshair;
 }
 
 .tool-shape-select .drawing-canvas-container:hover {
diff --git a/src/js/Events.js b/src/js/Events.js
index 07d75b09..97d84028 100644
--- a/src/js/Events.js
+++ b/src/js/Events.js
@@ -32,6 +32,7 @@ var Events = {
    * Number of frames, content of frames, color used for the palette may have changed.
    */
   PISKEL_RESET: "PISKEL_RESET",
+  PISKEL_SAVE_STATE: "PISKEL_SAVE_STATE",
 
   PISKEL_SAVED: "PISKEL_SAVED",
 
diff --git a/src/js/app.js b/src/js/app.js
index 07885727..28225379 100644
--- a/src/js/app.js
+++ b/src/js/app.js
@@ -30,7 +30,10 @@
 
       piskel.addLayer(layer);
 
-      this.piskelController = new pskl.controller.PiskelController(piskel);
+      this.corePiskelController = new pskl.controller.piskel.PiskelController(piskel);
+      this.corePiskelController.init();
+
+      this.piskelController = new pskl.controller.piskel.PublicPiskelController(this.corePiskelController);
       this.piskelController.init();
 
       this.paletteController = new pskl.controller.PaletteController();
@@ -69,7 +72,7 @@
       this.selectionManager = new pskl.selection.SelectionManager(this.piskelController);
       this.selectionManager.init();
 
-      this.historyService = new pskl.service.HistoryService(this.piskelController);
+      this.historyService = new pskl.service.HistoryService(this.corePiskelController);
       this.historyService.init();
 
       this.notificationController = new pskl.controller.NotificationController();
diff --git a/src/js/controller/DrawingController.js b/src/js/controller/DrawingController.js
index 1cb9dd7f..8bfe9f08 100644
--- a/src/js/controller/DrawingController.js
+++ b/src/js/controller/DrawingController.js
@@ -157,8 +157,8 @@
         // Warning : do not call setCurrentButton here
         // mousemove do not have the correct mouse button information on all browsers
         this.currentToolBehavior.moveToolAt(
-          coords.x,
-          coords.y,
+          coords.x | 0,
+          coords.y | 0,
           this.getCurrentColor_(event),
           currentFrame,
           this.overlayFrame,
@@ -175,6 +175,7 @@
           event
         );
       }
+      $.publish(Events.CURSOR_MOVED, [coords.x, coords.y]);
       this.previousMousemoveTime = currentTime;
     }
   };
diff --git a/src/js/controller/LayersListController.js b/src/js/controller/LayersListController.js
index b3e2a76f..27246926 100644
--- a/src/js/controller/LayersListController.js
+++ b/src/js/controller/LayersListController.js
@@ -44,15 +44,15 @@
       this.piskelController.setCurrentLayerIndex(parseInt(index, 10));
     } else if (el.classList.contains('edit-icon')) {
       index = el.parentNode.dataset.layerIndex;
-      var layer = this.piskelController.getLayerByIndex(parseInt(index, 10));
-      this.renameLayer_(layer);
+      this.renameLayerAt_(index);
     }
   };
 
-  ns.LayersListController.prototype.renameLayer_ = function (layer) {
-    var newName = window.prompt("Please enter the layer name", layer.getName());
-    if (newName) {
-      layer.setName(newName);
+  ns.LayersListController.prototype.renameLayerAt_ = function (index) {
+    var layer = this.piskelController.getLayerAt(index);
+    var name = window.prompt("Please enter the layer name", layer.getName());
+    if (name) {
+      this.piskelController.renameLayerAt(index, name);
       this.renderLayerList_();
     }
   };
diff --git a/src/js/controller/PiskelController.js b/src/js/controller/piskel/PiskelController.js
similarity index 82%
rename from src/js/controller/PiskelController.js
rename to src/js/controller/piskel/PiskelController.js
index 776f220a..630ceb6d 100644
--- a/src/js/controller/PiskelController.js
+++ b/src/js/controller/piskel/PiskelController.js
@@ -1,5 +1,5 @@
 (function () {
-  var ns = $.namespace('pskl.controller');
+  var ns = $.namespace('pskl.controller.piskel');
 
   ns.PiskelController = function (piskel) {
     if (piskel) {
@@ -15,16 +15,9 @@
     this.currentFrameIndex = 0;
 
     this.layerIdCounter = 1;
-
-    $.publish(Events.FRAME_SIZE_CHANGED);
-    $.publish(Events.PISKEL_RESET);
   };
 
   ns.PiskelController.prototype.init = function () {
-    pskl.app.shortcutService.addShortcut('up', this.selectPreviousFrame.bind(this));
-    pskl.app.shortcutService.addShortcut('down', this.selectNextFrame.bind(this));
-    pskl.app.shortcutService.addShortcut('n', this.addFrameAtCurrentIndex.bind(this));
-    pskl.app.shortcutService.addShortcut('shift+n', this.duplicateCurrentFrame.bind(this));
   };
 
   ns.PiskelController.prototype.getHeight = function () {
@@ -51,7 +44,11 @@
   };
 
   ns.PiskelController.prototype.getCurrentLayer = function () {
-    return this.piskel.getLayerAt(this.currentLayerIndex);
+    return this.getLayerAt(this.currentLayerIndex);
+  };
+
+  ns.PiskelController.prototype.getLayerAt = function (index) {
+    return this.piskel.getLayerAt(index);
   };
 
   ns.PiskelController.prototype.getCurrentFrame = function () {
@@ -59,6 +56,19 @@
     return layer.getFrameAt(this.currentFrameIndex);
   };
 
+
+  ns.PiskelController.prototype.getCurrentLayerIndex = function () {
+    return this.currentLayerIndex;
+  };
+
+  ns.PiskelController.prototype.getCurrentFrameIndex = function () {
+    return this.currentFrameIndex;
+  };
+
+  ns.PiskelController.prototype.getPiskel = function () {
+    return this.piskel;
+  };
+
   ns.PiskelController.prototype.getFrameAt = function (index) {
     var frames = this.getLayers().map(function (l) {
       return l.getFrameAt(index);
@@ -79,12 +89,9 @@
   };
 
   ns.PiskelController.prototype.addFrameAt = function (index) {
-    var layers = this.getLayers();
-    layers.forEach(function (l) {
+    this.getLayers().forEach(function (l) {
       l.addFrameAt(this.createEmptyFrame_(), index);
     }.bind(this));
-
-    $.publish(Events.PISKEL_RESET);
   };
 
   ns.PiskelController.prototype.createEmptyFrame_ = function () {
@@ -93,16 +100,13 @@
   };
 
   ns.PiskelController.prototype.removeFrameAt = function (index) {
-    var layers = this.getLayers();
-    layers.forEach(function (l) {
+    this.getLayers().forEach(function (l) {
       l.removeFrameAt(index);
     });
     // Current frame index is impacted if the removed frame was before the current frame
     if (this.currentFrameIndex >= index && this.currentFrameIndex > 0) {
       this.setCurrentFrameIndex(this.currentFrameIndex - 1);
     }
-
-    $.publish(Events.PISKEL_RESET);
   };
 
   ns.PiskelController.prototype.duplicateCurrentFrame = function () {
@@ -110,17 +114,13 @@
   };
 
   ns.PiskelController.prototype.duplicateFrameAt = function (index) {
-    var layers = this.getLayers();
-    layers.forEach(function (l) {
+    this.getLayers().forEach(function (l) {
       l.duplicateFrameAt(index);
     });
-
-    $.publish(Events.PISKEL_RESET);
   };
 
   ns.PiskelController.prototype.moveFrame = function (fromIndex, toIndex) {
-    var layers = this.getLayers();
-    layers.forEach(function (l) {
+    this.getLayers().forEach(function (l) {
       l.moveFrame(fromIndex, toIndex);
     });
   };
@@ -132,7 +132,6 @@
 
   ns.PiskelController.prototype.setCurrentFrameIndex = function (index) {
     this.currentFrameIndex = index;
-    $.publish(Events.PISKEL_RESET);
   };
 
   ns.PiskelController.prototype.selectNextFrame = function () {
@@ -151,7 +150,6 @@
 
   ns.PiskelController.prototype.setCurrentLayerIndex = function (index) {
     this.currentLayerIndex = index;
-    $.publish(Events.PISKEL_RESET);
   };
 
   ns.PiskelController.prototype.selectLayer = function (layer) {
@@ -161,6 +159,13 @@
     }
   };
 
+  ns.PiskelController.prototype.renameLayerAt = function (index, name) {
+    var layer = this.getLayerByIndex(index);
+    if (layer) {
+      layer.setName(name);
+    }
+  };
+
   ns.PiskelController.prototype.getLayerByIndex = function (index) {
     var layers = this.getLayers();
     if (layers[index]) {
@@ -190,6 +195,7 @@
       }
       this.piskel.addLayer(layer);
       this.setCurrentLayerIndex(this.piskel.getLayers().length - 1);
+
     } else {
       throw 'Layer name should be unique';
     }
@@ -219,11 +225,7 @@
     }
   };
 
-  ns.PiskelController.prototype.serialize = function () {
-    return pskl.utils.Serializer.serializePiskel(this.piskel);
-  };
-
-  ns.PiskelController.prototype.load = function (data) {
-    this.deserialize(JSON.stringify(data));
+  ns.PiskelController.prototype.serialize = function (expanded) {
+    return pskl.utils.Serializer.serializePiskel(this.piskel, expanded);
   };
 })();
\ No newline at end of file
diff --git a/src/js/controller/piskel/PublicPiskelController.js b/src/js/controller/piskel/PublicPiskelController.js
new file mode 100644
index 00000000..d9e5002b
--- /dev/null
+++ b/src/js/controller/piskel/PublicPiskelController.js
@@ -0,0 +1,143 @@
+(function () {
+  var ns = $.namespace('pskl.controller.piskel');
+
+  ns.PublicPiskelController = function (piskelController) {
+    this.piskelController = piskelController;
+    pskl.utils.wrap(this, this.piskelController);
+  };
+
+  ns.PublicPiskelController.prototype.init = function () {
+    pskl.app.shortcutService.addShortcut('up', this.selectPreviousFrame.bind(this));
+    pskl.app.shortcutService.addShortcut('down', this.selectNextFrame.bind(this));
+    pskl.app.shortcutService.addShortcut('n', this.addFrameAtCurrentIndex.bind(this));
+    pskl.app.shortcutService.addShortcut('shift+n', this.duplicateCurrentFrame.bind(this));
+  };
+
+  ns.PublicPiskelController.prototype.setPiskel = function (piskel) {
+    this.piskelController.setPiskel(piskel);
+
+    $.publish(Events.FRAME_SIZE_CHANGED);
+    $.publish(Events.PISKEL_RESET);
+    $.publish(Events.PISKEL_SAVE_STATE, {
+      type : pskl.service.HistoryService.SNAPSHOT
+    });
+  };
+
+  ns.PublicPiskelController.prototype.addFrame = function () {
+    this.addFrameAt(this.getFrameCount());
+  };
+
+  ns.PublicPiskelController.prototype.addFrameAtCurrentIndex = function () {
+    this.addFrameAt(this.getCurrentFrameIndex());
+  };
+
+  ns.PublicPiskelController.prototype.addFrameAt = function (index) {
+    this.raiseSaveStateEvent_(this.piskelController.addFrameAt, [index]);
+    this.piskelController.addFrameAt(index);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.removeFrameAt = function (index) {
+    this.raiseSaveStateEvent_(this.piskelController.removeFrameAt, [index]);
+    this.piskelController.removeFrameAt(index);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.duplicateCurrentFrame = function () {
+    this.piskelController.duplicateFrameAt(this.getCurrentFrameIndex());
+  };
+
+  ns.PublicPiskelController.prototype.raiseSaveStateEvent_ = function (fn, args) {
+    $.publish(Events.PISKEL_SAVE_STATE, {
+      type : pskl.service.HistoryService.REPLAY,
+      scope : this,
+      replay : {
+        fn : fn,
+        args : args
+      }
+    });
+  };
+
+  ns.PublicPiskelController.prototype.replay = function (frame, replayData) {
+    replayData.fn.apply(this.piskelController, replayData.args);
+  };
+
+  ns.PublicPiskelController.prototype.duplicateFrameAt = function (index) {
+    this.raiseSaveStateEvent_(this.piskelController.duplicateFrameAt, [index]);
+    this.piskelController.duplicateFrameAt(index);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.moveFrame = function (fromIndex, toIndex) {
+    this.raiseSaveStateEvent_(this.piskelController.moveFrame, [fromIndex, toIndex]);
+    this.piskelController.moveFrame(fromIndex, toIndex);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.setCurrentFrameIndex = function (index) {
+    this.piskelController.setCurrentFrameIndex(index);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.selectNextFrame = function () {
+    this.piskelController.selectNextFrame();
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.selectPreviousFrame = function () {
+    this.piskelController.selectPreviousFrame();
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.setCurrentLayerIndex = function (index) {
+    this.piskelController.setCurrentLayerIndex(index);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.selectLayer = function (layer) {
+    this.piskelController.selectLayer(layer);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.renameLayerAt = function (index, name) {
+    this.raiseSaveStateEvent_(this.piskelController.renameLayerAt, [index, name]);
+    this.piskelController.renameLayerAt(index, name);
+  };
+
+  ns.PublicPiskelController.prototype.createLayer = function (name) {
+    this.raiseSaveStateEvent_(this.piskelController.createLayer, [name]);
+    this.piskelController.createLayer(name);
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.moveLayerUp = function () {
+    this.raiseSaveStateEvent_(this.piskelController.moveLayerUp, []);
+    this.piskelController.moveLayerUp();
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.moveLayerDown = function () {
+    this.raiseSaveStateEvent_(this.piskelController.moveLayerDown, []);
+    this.piskelController.moveLayerDown();
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.removeCurrentLayer = function () {
+    this.raiseSaveStateEvent_(this.piskelController.removeCurrentLayer, []);
+    this.piskelController.removeCurrentLayer();
+    $.publish(Events.PISKEL_RESET);
+  };
+
+  ns.PublicPiskelController.prototype.getCurrentLayerIndex = function () {
+    return this.piskelController.currentLayerIndex;
+  };
+
+  ns.PublicPiskelController.prototype.getCurrentFrameIndex = function () {
+    return this.piskelController.currentFrameIndex;
+  };
+
+  ns.PublicPiskelController.prototype.getPiskel = function () {
+    return this.piskelController.piskel;
+  };
+
+})();
\ No newline at end of file
diff --git a/src/js/controller/settings/PngExportController.js b/src/js/controller/settings/PngExportController.js
index 33e9e546..5afba0b9 100644
--- a/src/js/controller/settings/PngExportController.js
+++ b/src/js/controller/settings/PngExportController.js
@@ -56,7 +56,7 @@
   };
 
   ns.PngExportController.prototype.getPiskelName_ = function () {
-    return this.piskelController.piskel.getDescriptor().name;
+    return this.piskelController.getPiskel().getDescriptor().name;
   };
 
   ns.PngExportController.prototype.getFramesheetAsBase64Png = function () {
diff --git a/src/js/controller/settings/ResizeController.js b/src/js/controller/settings/ResizeController.js
index 7ed4cec9..550946d7 100644
--- a/src/js/controller/settings/ResizeController.js
+++ b/src/js/controller/settings/ResizeController.js
@@ -39,7 +39,7 @@
       layers.push(layer);
     }
 
-    var piskel = pskl.model.Piskel.fromLayers(layers, this.piskelController.piskel.getDescriptor());
+    var piskel = pskl.model.Piskel.fromLayers(layers, this.piskelController.getPiskel().getDescriptor());
     pskl.app.piskelController.setPiskel(piskel);
     $.publish(Events.CLOSE_SETTINGS_DRAWER);
   };
diff --git a/src/js/controller/settings/SaveController.js b/src/js/controller/settings/SaveController.js
index 01c7a6f9..fc083339 100644
--- a/src/js/controller/settings/SaveController.js
+++ b/src/js/controller/settings/SaveController.js
@@ -21,7 +21,7 @@
 
     this.status = $('#save-status');
 
-    var descriptor = this.piskelController.piskel.getDescriptor();
+    var descriptor = this.piskelController.getPiskel().getDescriptor();
     this.nameInput.val(descriptor.name);
     this.descriptionInput.val(descriptor.description);
 
@@ -46,7 +46,7 @@
     var isPublic = !!this.isPublicCheckbox.prop('checked');
 
     var descriptor = new pskl.model.piskel.Descriptor(name, description, isPublic);
-    this.piskelController.piskel.setDescriptor(descriptor);
+    this.piskelController.getPiskel().setDescriptor(descriptor);
 
     this.beforeSaving_();
     pskl.app.store({
diff --git a/src/js/drawingtools/BaseTool.js b/src/js/drawingtools/BaseTool.js
index c9cca264..a408e453 100644
--- a/src/js/drawingtools/BaseTool.js
+++ b/src/js/drawingtools/BaseTool.js
@@ -6,16 +6,17 @@
 (function() {
   var ns = $.namespace("pskl.drawingtools");
 
-  ns.BaseTool = function() {};
+  ns.BaseTool = function() {
+    this.toolId = "tool-base";
+  };
 
   ns.BaseTool.prototype.applyToolAt = function(col, row, color, frame, overlay, event) {};
 
-  ns.BaseTool.prototype.moveToolAt = function(col, row, color, frame, overlay, event) {
-    $.publish(Events.CURSOR_MOVED, [col, row]);
-  };
+  ns.BaseTool.prototype.moveToolAt = function(col, row, color, frame, overlay, event) {};
+
+  ns.BaseTool.prototype.replay = Constants.ABSTRACT_FUNCTION;
 
   ns.BaseTool.prototype.moveUnactiveToolAt = function(col, row, color, frame, overlay, event) {
-    $.publish(Events.CURSOR_MOVED, [col, row]);
 
     if (overlay.containsPixel(col, row)) {
       if (!isNaN(this.highlightedPixelCol) &&
@@ -49,6 +50,14 @@
     }
   };
 
+  ns.BaseTool.prototype.raiseSaveStateEvent = function (replayData) {
+    $.publish(Events.PISKEL_SAVE_STATE, {
+      type : pskl.service.HistoryService.REPLAY,
+      scope : this,
+      replay : replayData
+    });
+  };
+
 
   ns.BaseTool.prototype.releaseToolAt = function(col, row, color, frame, overlay, event) {};
 
diff --git a/src/js/drawingtools/Eraser.js b/src/js/drawingtools/Eraser.js
index 57570fe9..27e169c7 100644
--- a/src/js/drawingtools/Eraser.js
+++ b/src/js/drawingtools/Eraser.js
@@ -8,6 +8,7 @@
   var ns = $.namespace("pskl.drawingtools");
 
   ns.Eraser = function() {
+    this.superclass.constructor.call(this);
     this.toolId = "tool-eraser";
     this.helpText = "Eraser tool";
   };
diff --git a/src/js/drawingtools/Move.js b/src/js/drawingtools/Move.js
index 30baac06..630a5729 100644
--- a/src/js/drawingtools/Move.js
+++ b/src/js/drawingtools/Move.js
@@ -29,7 +29,6 @@
   };
 
   ns.Move.prototype.moveToolAt = function(col, row, color, frame, overlay, event) {
-    $.publish(Events.CURSOR_MOVED, [col, row]);
     var colDiff = col - this.startCol, rowDiff = row - this.startRow;
     this.shiftFrame(colDiff, rowDiff, frame, this.frameClone);
   };
@@ -53,5 +52,14 @@
    */
   ns.Move.prototype.releaseToolAt = function(col, row, color, frame, overlay, event) {
     this.moveToolAt(col, row, color, frame, overlay);
+
+    this.raiseSaveStateEvent({
+      colDiff : col - this.startCol,
+      rowDiff : row - this.startRow
+    });
+  };
+
+  ns.Move.prototype.replay = function(frame, replayData) {
+    this.shiftFrame(replayData.colDiff, replayData.rowDiff, frame, frame.clone());
   };
 })();
diff --git a/src/js/drawingtools/PaintBucket.js b/src/js/drawingtools/PaintBucket.js
index 34fc4714..c2ece067 100644
--- a/src/js/drawingtools/PaintBucket.js
+++ b/src/js/drawingtools/PaintBucket.js
@@ -17,8 +17,17 @@
    * @override
    */
   ns.PaintBucket.prototype.applyToolAt = function(col, row, color, frame, overlay, event) {
-
     pskl.PixelUtils.paintSimilarConnectedPixelsFromFrame(frame, col, row, color);
+
+    this.raiseSaveStateEvent({
+      col : col,
+      row : row,
+      color : color
+    });
+  };
+
+  ns.PaintBucket.prototype.replay = function (frame, replayData) {
+    pskl.PixelUtils.paintSimilarConnectedPixelsFromFrame(frame, replayData.col, replayData.row, replayData.color);
   };
 })();
 
diff --git a/src/js/drawingtools/ShapeTool.js b/src/js/drawingtools/ShapeTool.js
index d0de3a0e..a99965d2 100644
--- a/src/js/drawingtools/ShapeTool.js
+++ b/src/js/drawingtools/ShapeTool.js
@@ -49,7 +49,24 @@
     }
     var coords = this.getCoordinates_(col, row, event);
     this.draw_(coords.col, coords.row, color, frame);
+
     $.publish(Events.DRAG_END, [col, row]);
+    this.raiseSaveStateEvent({
+      col : col,
+      row : row,
+      startCol : this.startCol,
+      startRow : this.startRow,
+      color : color
+    });
+  };
+
+  /**
+   * @override
+   */
+  ns.ShapeTool.prototype.replay = function(frame, replayData) {
+    this.startCol = replayData.startCol;
+    this.startRow = replayData.startRow;
+    this.draw_(replayData.col, replayData.row, replayData.color, frame);
   };
 
   /**
diff --git a/src/js/drawingtools/SimplePen.js b/src/js/drawingtools/SimplePen.js
index 64349e7a..ffbfa845 100644
--- a/src/js/drawingtools/SimplePen.js
+++ b/src/js/drawingtools/SimplePen.js
@@ -13,6 +13,7 @@
     this.previousCol = null;
     this.previousRow = null;
 
+    this.pixels = [];
   };
 
   pskl.utils.inherit(ns.SimplePen, ns.BaseTool);
@@ -21,18 +22,19 @@
    * @override
    */
   ns.SimplePen.prototype.applyToolAt = function(col, row, color, frame, overlay, event) {
-    if (frame.containsPixel(col, row)) {
-      frame.setPixel(col, row, color);
-    }
+    frame.setPixel(col, row, color);
     this.previousCol = col;
     this.previousRow = row;
+    this.pixels.push({
+      col : col,
+      row : row
+    });
   };
 
   /**
    * @override
    */
   ns.SimplePen.prototype.moveToolAt = function(col, row, color, frame, overlay, event) {
-    $.publish(Events.CURSOR_MOVED, [col, row]);
     if((Math.abs(col - this.previousCol) > 1) || (Math.abs(row - this.previousRow) > 1)) {
       // The pen movement is too fast for the mousemove frequency, there is a gap between the
       // current point and the previously drawn one.
@@ -40,7 +42,7 @@
       var interpolatedPixels = this.getLinePixels_(col, this.previousCol, row, this.previousRow);
       for(var i=0, l=interpolatedPixels.length; i<l; i++) {
         var coords = interpolatedPixels[i];
-        this.applyToolAt(coords.col, coords.row, color, frame, overlay);
+        this.applyToolAt(coords.col, coords.row, color, frame, overlay, event);
       }
     }
     else {
@@ -50,4 +52,20 @@
     this.previousCol = col;
     this.previousRow = row;
   };
+
+
+  ns.SimplePen.prototype.releaseToolAt = function(col, row, color, frame, overlay, event) {
+    this.raiseSaveStateEvent({
+      pixels : this.pixels.slice(0),
+      color : color
+    });
+    this.pixels = [];
+  };
+
+  ns.SimplePen.prototype.replay = function (frame, replayData) {
+    var pixels = replayData.pixels;
+    pixels.forEach(function (pixel) {
+      frame.setPixel(pixel.col, pixel.row, replayData.color);
+    });
+  };
 })();
diff --git a/src/js/drawingtools/Stroke.js b/src/js/drawingtools/Stroke.js
index 0152806d..27c115ae 100644
--- a/src/js/drawingtools/Stroke.js
+++ b/src/js/drawingtools/Stroke.js
@@ -37,8 +37,6 @@
   };
 
   ns.Stroke.prototype.moveToolAt = function(col, row, color, frame, overlay, event) {
-    $.publish(Events.CURSOR_MOVED, [col, row]);
-
     overlay.clear();
 
     // When the user moussemove (before releasing), we dynamically compute the
@@ -65,18 +63,25 @@
    * @override
    */
   ns.Stroke.prototype.releaseToolAt = function(col, row, color, frame, overlay, event) {
-    // If the stroke tool is released outside of the canvas, we cancel the stroke:
-    // TODO: Mutualize this check in common method
-    if(frame.containsPixel(col, row)) {
-      // The user released the tool to draw a line. We will compute the pixel coordinate, impact
-      // the model and draw them in the drawing canvas (not the fake overlay anymore)
-      var strokePoints = this.getLinePixels_(this.startCol, col, this.startRow, row);
-      for(var i = 0; i< strokePoints.length; i++) {
-        // Change model:
-        frame.setPixel(strokePoints[i].col, strokePoints[i].row, color);
-      }
+    // The user released the tool to draw a line. We will compute the pixel coordinate, impact
+    // the model and draw them in the drawing canvas (not the fake overlay anymore)
+    var strokePoints = this.getLinePixels_(this.startCol, col, this.startRow, row);
+    for(var i = 0; i< strokePoints.length; i++) {
+      // Change model:
+      frame.setPixel(strokePoints[i].col, strokePoints[i].row, color);
     }
     // For now, we are done with the stroke tool and don't need an overlay anymore:
     overlay.clear();
+
+    this.raiseSaveStateEvent({
+      pixels : strokePoints,
+      color : color
+    });
+  };
+
+  ns.Stroke.prototype.replay = function(frame, replayData) {
+    replayData.pixels.forEach(function (pixel) {
+      frame.setPixel(pixel.col, pixel.row, replayData.color);
+    });
   };
 })();
diff --git a/src/js/drawingtools/VerticalMirrorPen.js b/src/js/drawingtools/VerticalMirrorPen.js
index 435805e8..44841ea8 100644
--- a/src/js/drawingtools/VerticalMirrorPen.js
+++ b/src/js/drawingtools/VerticalMirrorPen.js
@@ -2,12 +2,12 @@
   var ns = $.namespace("pskl.drawingtools");
 
   ns.VerticalMirrorPen = function() {
+    this.superclass.constructor.call(this);
+
     this.toolId = "tool-vertical-mirror-pen";
     this.helpText = "vertical mirror pen tool";
 
     this.swap = null;
-    this.mirroredPreviousCol = null;
-    this.mirroredPreviousRow = null;
   };
 
   pskl.utils.inherit(ns.VerticalMirrorPen, ns.SimplePen);
diff --git a/src/js/drawingtools/selectiontools/BaseSelect.js b/src/js/drawingtools/selectiontools/BaseSelect.js
index 5892a9bb..896fac11 100644
--- a/src/js/drawingtools/selectiontools/BaseSelect.js
+++ b/src/js/drawingtools/selectiontools/BaseSelect.js
@@ -13,6 +13,8 @@
     // Select's first point coordinates (set in applyToolAt)
     this.startCol = null;
     this.startRow = null;
+
+    this.selection = null;
   };
 
   pskl.utils.inherit(ns.BaseSelect, ns.BaseTool);
@@ -48,11 +50,9 @@
    * @override
    */
   ns.BaseSelect.prototype.moveToolAt = function(col, row, color, frame, overlay, event) {
-    $.publish(Events.CURSOR_MOVED, [col, row]);
     if(this.mode == "select") {
       this.onSelect_(col, row, color, frame, overlay);
-    }
-    else if(this.mode == "moveSelection") {
+    } else if(this.mode == "moveSelection") {
       this.onSelectionDrag_(col, row, color, frame, overlay);
     }
   };
@@ -75,7 +75,6 @@
    * @override
    */
   ns.BaseSelect.prototype.moveUnactiveToolAt = function(col, row, color, frame, overlay, event) {
-    $.publish(Events.CURSOR_MOVED, [col, row]);
     if (overlay.containsPixel(col, row)) {
       if(overlay.getPixel(col, row) != Constants.SELECTION_TRANSPARENT_COLOR) {
         // We're hovering the selection, show the move tool:
@@ -97,31 +96,13 @@
    * For each pixel in the selection draw it in white transparent on the tool overlay
    * @protected
    */
-  ns.BaseSelect.prototype.drawSelectionOnOverlay_ = function (selection, overlay) {
-    var pixels = selection.pixels;
+  ns.BaseSelect.prototype.drawSelectionOnOverlay_ = function (overlay) {
+    var pixels = this.selection.pixels;
     for(var i=0, l=pixels.length; i<l; i++) {
       overlay.setPixel(pixels[i].col, pixels[i].row, Constants.SELECTION_TRANSPARENT_COLOR);
     }
   };
 
-  /**
-   * Move the overlay frame filled with semi-transparent pixels that represent the selection.
-   * @private
-   */
-  ns.BaseSelect.prototype.shiftOverlayFrame_ = function (colDiff, rowDiff, overlayFrame, reference) {
-    var color;
-    for (var col = 0 ; col < overlayFrame.getWidth() ; col++) {
-      for (var row = 0 ; row < overlayFrame.getHeight() ; row++) {
-        if (reference.containsPixel(col - colDiff, row - rowDiff)) {
-          color = reference.getPixel(col - colDiff, row - rowDiff);
-        } else {
-          color = Constants.TRANSPARENT_COLOR;
-        }
-        overlayFrame.setPixel(col, row, color);
-      }
-    }
-  };
-
 
   // The list of callbacks to implement by specialized tools to implement the selection creation behavior.
   /** @protected */
@@ -135,9 +116,6 @@
   // The list of callbacks that define the drag'n drop behavior of the selection.
   /** @private */
   ns.BaseSelect.prototype.onSelectionDragStart_ = function (col, row, color, frame, overlay) {
-    // Since we will move the overlayFrame in which  the current selection is rendered,
-    // we clone it to have a reference for the later shifting process.
-    this.overlayFrameReference = overlay.clone();
   };
 
   /** @private */
@@ -147,11 +125,10 @@
 
     var colDiff = col - this.startCol, rowDiff = row - this.startRow;
 
-    // Shifting selection on overlay frame:
-    this.shiftOverlayFrame_(colDiff, rowDiff, overlay, this.overlayFrameReference);
+    this.selection.move(deltaCol, deltaRow);
 
-    // Update selection model:
-    $.publish(Events.SELECTION_MOVE_REQUEST, [deltaCol, deltaRow]);
+    overlay.clear();
+    this.drawSelectionOnOverlay_(overlay);
 
     this.lastCol = col;
     this.lastRow = row;
diff --git a/src/js/drawingtools/selectiontools/RectangleSelect.js b/src/js/drawingtools/selectiontools/RectangleSelect.js
index 5e6282c5..4eaa6bd1 100644
--- a/src/js/drawingtools/selectiontools/RectangleSelect.js
+++ b/src/js/drawingtools/selectiontools/RectangleSelect.js
@@ -11,6 +11,7 @@
     this.helpText = "Rectangle selection tool";
 
     ns.BaseSelect.call(this);
+    this.hasSelection = false;
   };
 
   pskl.utils.inherit(ns.RectangleSelect, ns.BaseSelect);
@@ -20,9 +21,16 @@
    * @override
    */
   ns.RectangleSelect.prototype.onSelectStart_ = function (col, row, color, frame, overlay) {
-    $.publish(Events.DRAG_START, [col, row]);
-    // Drawing the first point of the rectangle in the fake overlay canvas:
-    overlay.setPixel(col, row, color);
+    if (this.hasSelection) {
+      this.hasSelection = false;
+      overlay.clear();
+      $.publish(Events.SELECTION_DISMISSED);
+    } else {
+      this.hasSelection = true;
+      $.publish(Events.DRAG_START, [col, row]);
+      // Drawing the first point of the rectangle in the fake overlay canvas:
+      overlay.setPixel(col, row, color);
+    }
   };
 
   /**
@@ -32,23 +40,20 @@
    * @override
    */
   ns.RectangleSelect.prototype.onSelect_ = function (col, row, color, frame, overlay) {
-    overlay.clear();
-    if(this.startCol == col &&this.startRow == row) {
-      $.publish(Events.SELECTION_DISMISSED);
-    } else {
-      var selection = new pskl.selection.RectangularSelection(
+    if (this.hasSelection) {
+      overlay.clear();
+      this.selection = new pskl.selection.RectangularSelection(
         this.startCol, this.startRow, col, row);
-      $.publish(Events.SELECTION_CREATED, [selection]);
-      this.drawSelectionOnOverlay_(selection, overlay);
+      $.publish(Events.SELECTION_CREATED, [this.selection]);
+      this.drawSelectionOnOverlay_(overlay);
     }
   };
 
-  /**
-   * @override
-   */
   ns.RectangleSelect.prototype.onSelectEnd_ = function (col, row, color, frame, overlay) {
-    this.onSelect_(col, row, color, frame, overlay);
-    $.publish(Events.DRAG_END, [col, row]);
+    if (this.hasSelection) {
+      this.onSelect_(col, row, color, frame, overlay);
+      $.publish(Events.DRAG_END, [col, row]);
+    }
   };
 
 })();
diff --git a/src/js/drawingtools/selectiontools/ShapeSelect.js b/src/js/drawingtools/selectiontools/ShapeSelect.js
index ffe3a628..1c7690a1 100644
--- a/src/js/drawingtools/selectiontools/ShapeSelect.js
+++ b/src/js/drawingtools/selectiontools/ShapeSelect.js
@@ -9,12 +9,12 @@
   ns.ShapeSelect = function() {
     this.toolId = "tool-shape-select";
     this.helpText = "Shape selection tool";
-    
+
     ns.BaseSelect.call(this);
   };
 
   pskl.utils.inherit(ns.ShapeSelect, ns.BaseSelect);
-  
+
   /**
    * For the shape select tool, you just need to click one time to create a selection.
    * So we jsut need to implement onSelectStart_ (no need for onSelect_ & onSelectEnd_)
@@ -24,13 +24,13 @@
     // Clean previous selection:
     $.publish(Events.SELECTION_DISMISSED);
     overlay.clear();
-    
+
     // From the pixel cliked, get shape using an algorithm similar to the paintbucket one:
     var pixels = pskl.PixelUtils.getSimilarConnectedPixelsFromFrame(frame, col, row);
-    var selection = new pskl.selection.ShapeSelection(pixels);
+    this.selection = new pskl.selection.ShapeSelection(pixels);
 
-    $.publish(Events.SELECTION_CREATED, [selection]);
-    this.drawSelectionOnOverlay_(selection, overlay);
+    $.publish(Events.SELECTION_CREATED, [this.selection]);
+    this.drawSelectionOnOverlay_(overlay);
   };
 
 })();
diff --git a/src/js/model/Frame.js b/src/js/model/Frame.js
index 98b4d75d..8fb85ccf 100644
--- a/src/js/model/Frame.js
+++ b/src/js/model/Frame.js
@@ -1,11 +1,12 @@
 (function () {
   var ns = $.namespace("pskl.model");
-
+  var __idCounter = 0;
   ns.Frame = function (width, height) {
     if (width && height) {
       this.width = width;
       this.height = height;
-
+      this.id = __idCounter++;
+      this.version = 0;
       this.pixels = ns.Frame.createEmptyPixelGrid_(width, height);
       this.previousStates = [this.getPixels()];
       this.stateIndex = 0;
@@ -59,6 +60,7 @@
    */
   ns.Frame.prototype.setPixels = function (pixels) {
     this.pixels = this.clonePixels_(pixels);
+    this.version++;
   };
 
   ns.Frame.prototype.clear = function () {
@@ -78,13 +80,17 @@
     return clonedPixels;
   };
 
-  ns.Frame.prototype.serialize = function () {
-    return JSON.stringify(this.pixels);
+  ns.Frame.prototype.getHash = function () {
+    return [this.id, this.version].join('-');
   };
 
   ns.Frame.prototype.setPixel = function (col, row, color) {
     if (this.containsPixel(col, row)) {
-      this.pixels[col][row] = color;
+      var p = this.pixels[col][row];
+      if (p !== color) {
+        this.pixels[col][row] = color;
+        this.version++;
+      }
     }
   };
 
diff --git a/src/js/rendering/frame/CachedFrameRenderer.js b/src/js/rendering/frame/CachedFrameRenderer.js
index 6bdd69ea..0c77ac07 100644
--- a/src/js/rendering/frame/CachedFrameRenderer.js
+++ b/src/js/rendering/frame/CachedFrameRenderer.js
@@ -36,9 +36,10 @@
       this.getGridWidth(),
       offset.x, offset.y,
       size.width, size.height,
-      frame.serialize()
+      frame.getHash()
     ].join('-');
     if (this.serializedFrame != serializedFrame) {
+      // console.log('rendering')
       this.serializedFrame = serializedFrame;
       this.superclass.render.call(this, frame);
     }
diff --git a/src/js/rendering/layer/LayersRenderer.js b/src/js/rendering/layer/LayersRenderer.js
index fd09a45c..2c5763a1 100644
--- a/src/js/rendering/layer/LayersRenderer.js
+++ b/src/js/rendering/layer/LayersRenderer.js
@@ -22,8 +22,8 @@
     var offset = this.getOffset();
     var size = this.getDisplaySize();
     var layers = this.piskelController.getLayers();
-    var currentFrameIndex = this.piskelController.currentFrameIndex;
-    var currentLayerIndex = this.piskelController.currentLayerIndex;
+    var currentFrameIndex = this.piskelController.getCurrentFrameIndex();
+    var currentLayerIndex = this.piskelController.getCurrentLayerIndex();
 
     var serializedRendering = [
       this.getZoom(),
diff --git a/src/js/selection/BaseSelection.js b/src/js/selection/BaseSelection.js
index 74513b58..baf28ca1 100644
--- a/src/js/selection/BaseSelection.js
+++ b/src/js/selection/BaseSelection.js
@@ -23,12 +23,9 @@
   };
 
   ns.BaseSelection.prototype.fillSelectionFromFrame = function (targetFrame) {
-    var pixelWithCopiedColor;
-    for(var i=0, l=this.pixels.length; i<l; i++) {
-      pixelWithCopiedColor = this.pixels[i];
-      pixelWithCopiedColor.copiedColor =
-        targetFrame.getPixel(pixelWithCopiedColor.col, pixelWithCopiedColor.row);
-    }
+    this.pixels.forEach(function (pixel) {
+      pixel.color = targetFrame.getPixel(pixel.col, pixel.row);
+    });
     this.hasPastedContent = true;
   };
 })();
\ No newline at end of file
diff --git a/src/js/selection/SelectionManager.js b/src/js/selection/SelectionManager.js
index 7b2e81e0..6a63c6ce 100644
--- a/src/js/selection/SelectionManager.js
+++ b/src/js/selection/SelectionManager.js
@@ -1,6 +1,11 @@
 (function () {
   var ns = $.namespace("pskl.selection");
 
+  var SELECTION_REPLAY = {
+    PASTE : 'REPLAY_PASTE',
+    ERASE : 'REPLAY_ERASE'
+  };
+
   ns.SelectionManager = function (piskelController) {
 
     this.piskelController = piskelController;
@@ -17,6 +22,7 @@
     pskl.app.shortcutService.addShortcut('ctrl+X', this.cut.bind(this));
     pskl.app.shortcutService.addShortcut('ctrl+C', this.copy.bind(this));
     pskl.app.shortcutService.addShortcut('del', this.erase.bind(this));
+    pskl.app.shortcutService.addShortcut('back', this.onBackPressed_.bind(this));
 
     $.subscribe(Events.TOOL_SELECTED, $.proxy(this.onToolSelected_, this));
   };
@@ -27,6 +33,7 @@
   ns.SelectionManager.prototype.cleanSelection_ = function() {
     if(this.currentSelection) {
       this.currentSelection.reset();
+      this.currentSelection = null;
     }
   };
 
@@ -47,16 +54,29 @@
     this.cleanSelection_();
   };
 
+  ns.SelectionManager.prototype.onBackPressed_ = function(evt) {
+    if (this.currentSelection) {
+      this.erase();
+    } else {
+      return true; // bubble
+    }
+  };
+
   ns.SelectionManager.prototype.erase = function () {
     var pixels = this.currentSelection.pixels;
     var currentFrame = this.piskelController.getCurrentFrame();
     for(var i=0, l=pixels.length; i<l; i++) {
-      try {
-        currentFrame.setPixel(pixels[i].col, pixels[i].row, Constants.TRANSPARENT_COLOR);
-      } catch(e) {
-        // Catching out of frame's bound pixels without testing
-      }
+      currentFrame.setPixel(pixels[i].col, pixels[i].row, Constants.TRANSPARENT_COLOR);
     }
+
+    $.publish(Events.PISKEL_SAVE_STATE, {
+      type : pskl.service.HistoryService.REPLAY,
+      scope : this,
+      replay : {
+        type : SELECTION_REPLAY.ERASE,
+        pixels : JSON.parse(JSON.stringify(pixels.slice(0)))
+      }
+    });
   };
 
   ns.SelectionManager.prototype.cut = function() {
@@ -74,18 +94,30 @@
     if(this.currentSelection && this.currentSelection.hasPastedContent) {
       var pixels = this.currentSelection.pixels;
       var currentFrame = this.piskelController.getCurrentFrame();
-      for(var i=0, l=pixels.length; i<l; i++) {
-        try {
-          currentFrame.setPixel(
-            pixels[i].col, pixels[i].row,
-            pixels[i].copiedColor);
-        } catch(e) {
-          // Catching out of frame's bound pixels without testing
+
+      $.publish(Events.PISKEL_SAVE_STATE, {
+        type : pskl.service.HistoryService.REPLAY,
+        scope : this,
+        replay : {
+          type : SELECTION_REPLAY.PASTE,
+          pixels : JSON.parse(JSON.stringify(pixels.slice(0)))
         }
-      }
+      });
+
+      pixels.forEach(function (pixel) {
+        currentFrame.setPixel(pixel.col,pixel.row,pixel.color);
+      });
     }
   };
 
+  ns.SelectionManager.prototype.replay = function (frame, replayData) {
+    var pixels = replayData.pixels;
+    pixels.forEach(function (pixel) {
+      var color = replayData.type === SELECTION_REPLAY.PASTE ? pixel.color : Constants.TRANSPARENT_COLOR;
+      frame.setPixel(pixel.col, pixel.row, color);
+    });
+  };
+
   ns.SelectionManager.prototype.copy = function() {
     if(this.currentSelection && this.piskelController.getCurrentFrame()) {
       this.currentSelection.fillSelectionFromFrame(this.piskelController.getCurrentFrame());
diff --git a/src/js/service/AppEngineStorageService.js b/src/js/service/AppEngineStorageService.js
index 47184b37..8c93f23a 100644
--- a/src/js/service/AppEngineStorageService.js
+++ b/src/js/service/AppEngineStorageService.js
@@ -29,7 +29,7 @@
   };
 
   ns.AppEngineStorageService.prototype.prepareFormData_ = function () {
-    var piskel = this.piskelController.piskel;
+    var piskel = this.piskelController.getPiskel();
     var descriptor = piskel.getDescriptor();
 
     var formData = new FormData();
diff --git a/src/js/service/HistoryService.js b/src/js/service/HistoryService.js
index a9067ac5..a84988de 100644
--- a/src/js/service/HistoryService.js
+++ b/src/js/service/HistoryService.js
@@ -1,35 +1,136 @@
 (function () {
-  var ns = $.namespace("pskl.service");
+  var ns = $.namespace('pskl.service');
+
+  var SNAPSHOT_PERIOD = 50;
+  var LOAD_STATE_INTERVAL = 50;
+
   ns.HistoryService = function (piskelController) {
     this.piskelController = piskelController;
-    this.saveState__b = this.saveState.bind(this);
+    this.stateQueue = [];
+    this.currentIndex = -1;
+    this.saveState__b = this.onSaveStateEvent.bind(this);
+
+    this.lastLoadState = -1;
   };
 
-  ns.HistoryService.prototype.init = function () {
+  ns.HistoryService.SNAPSHOT = 'SNAPSHOT';
+  ns.HistoryService.REPLAY = 'REPLAY';
 
-    $.subscribe(Events.PISKEL_RESET, this.saveState__b);
-    $.subscribe(Events.TOOL_RELEASED, this.saveState__b);
+  ns.HistoryService.prototype.init = function () {
+    $.subscribe(Events.PISKEL_SAVE_STATE, this.saveState__b);
 
     pskl.app.shortcutService.addShortcut('ctrl+Z', this.undo.bind(this));
     pskl.app.shortcutService.addShortcut('ctrl+Y', this.redo.bind(this));
+
+    this.saveState({
+      type : ns.HistoryService.SNAPSHOT
+    });
   };
 
-  ns.HistoryService.prototype.saveState = function () {
-    this.piskelController.getCurrentFrame().saveState();
+  ns.HistoryService.prototype.onSaveStateEvent = function (evt, stateInfo) {
+    this.saveState(stateInfo);
+  };
+
+  ns.HistoryService.prototype.saveState = function (stateInfo) {
+    this.stateQueue = this.stateQueue.slice(0, this.currentIndex + 1);
+    this.currentIndex = this.currentIndex + 1;
+
+    var state = {
+      action : stateInfo,
+      frameIndex : this.piskelController.currentFrameIndex,
+      layerIndex : this.piskelController.currentLayerIndex
+    };
+
+    if (stateInfo.type === ns.HistoryService.SNAPSHOT || this.currentIndex % SNAPSHOT_PERIOD === 0) {
+      state.piskel = this.piskelController.serialize(true);
+    }
+
+    this.stateQueue.push(state);
   };
 
   ns.HistoryService.prototype.undo = function () {
-    this.piskelController.getCurrentFrame().loadPreviousState();
-    $.unsubscribe(Events.PISKEL_RESET, this.saveState__b);
-    $.publish(Events.PISKEL_RESET);
-    $.subscribe(Events.PISKEL_RESET, this.saveState__b);
+    this.loadState(this.currentIndex - 1);
   };
 
   ns.HistoryService.prototype.redo = function () {
-    this.piskelController.getCurrentFrame().loadNextState();
-    $.unsubscribe(Events.PISKEL_RESET, this.saveState__b);
+    this.loadState(this.currentIndex + 1);
+  };
+
+  ns.HistoryService.prototype.isLoadStateAllowed_ = function (index) {
+    var timeOk = (Date.now() - this.lastLoadState) > LOAD_STATE_INTERVAL;
+    var indexInRange = index >= 0 && index < this.stateQueue.length;
+    return timeOk && indexInRange;
+  };
+
+  ns.HistoryService.prototype.getPreviousSnapshotIndex_ = function (index) {
+    while (this.stateQueue[index] && !this.stateQueue[index].piskel) {
+      index = index - 1;
+    }
+    return index;
+  };
+
+  ns.HistoryService.prototype.loadState = function (index) {
+    if (this.isLoadStateAllowed_(index)) {
+      this.lastLoadState = Date.now();
+
+      var snapshotIndex = this.getPreviousSnapshotIndex_(index);
+      if (snapshotIndex < 0) {
+        throw 'Could not find previous SNAPSHOT saved in history stateQueue';
+      }
+
+      var piskelSnapshot = this.getSnapshotFromState_(snapshotIndex);
+      this.loadPiskel(piskelSnapshot, this.onPiskelLoadedCallback.bind(this, index, snapshotIndex));
+    }
+  };
+
+  ns.HistoryService.prototype.getSnapshotFromState_ = function (stateIndex) {
+    var state = this.stateQueue[stateIndex];
+    var piskelSnapshot = state.piskel;
+
+    // If the snapshot is stringified, parse it and backup the result for faster access next time
+    // FIXME : Memory consumption might go crazy if we keep unpacking big piskels indefinitely
+    // ==> should ensure I remove some of them :)
+    if (typeof piskelSnapshot === "string") {
+      piskelSnapshot = JSON.parse(piskelSnapshot);
+      state.piskel = piskelSnapshot;
+    }
+
+    return piskelSnapshot;
+  };
+
+  ns.HistoryService.prototype.loadPiskel = function (piskel, callback) {
+    var descriptor = this.piskelController.piskel.getDescriptor();
+    pskl.utils.serialization.Deserializer.deserialize(piskel, function (deserializedPiskel) {
+      deserializedPiskel.setDescriptor(descriptor);
+      this.piskelController.setPiskel(deserializedPiskel);
+      callback(deserializedPiskel);
+    }.bind(this));
+  };
+
+  ns.HistoryService.prototype.onPiskelLoadedCallback = function (index, snapshotIndex, piskel) {
+    for (var i = snapshotIndex + 1 ; i <= index ; i++) {
+      var state = this.stateQueue[i];
+      this.setupState(state);
+      this.replayState(state);
+    }
+
+    var lastState = this.stateQueue[index];
+    this.setupState(lastState);
+    this.currentIndex = index;
     $.publish(Events.PISKEL_RESET);
-    $.subscribe(Events.PISKEL_RESET, this.saveState__b);
+  };
+
+  ns.HistoryService.prototype.setupState = function (state) {
+    this.piskelController.setCurrentFrameIndex(state.frameIndex);
+    this.piskelController.setCurrentLayerIndex(state.layerIndex);
+  };
+
+  ns.HistoryService.prototype.replayState = function (state) {
+    var action = state.action;
+    var type = action.type;
+    var layer = this.piskelController.getLayerAt(state.layerIndex);
+    var frame = layer.getFrameAt(state.frameIndex);
+    action.scope.replay(frame, action.replay);
   };
 
 })();
\ No newline at end of file
diff --git a/src/js/service/SavedStatusService.js b/src/js/service/SavedStatusService.js
index ac3d6a23..04ab950b 100644
--- a/src/js/service/SavedStatusService.js
+++ b/src/js/service/SavedStatusService.js
@@ -2,7 +2,7 @@
   var ns = $.namespace('pskl.service');
 
   ns.SavedStatusService = function (piskelController) {
-    this.piskelController_ = piskelController;
+    this.piskelController = piskelController;
   };
 
   ns.SavedStatusService.prototype.init = function () {
@@ -15,7 +15,7 @@
   };
 
   ns.SavedStatusService.prototype.onPiskelReset = function () {
-    var piskel = this.piskelController_.piskel;
+    var piskel = this.piskelController.getPiskel();
     // A first PISKEL_RESET is triggered during the load of a new Piskel, it should be ignored
     // putting a firstResetDone flag as a nasty workaround for this
     if (piskel.firstResetDone_) {
@@ -34,7 +34,7 @@
   };
 
   ns.SavedStatusService.prototype.updateDirtyStatus = function (status) {
-    var piskel = this.piskelController_.piskel;
+    var piskel = this.piskelController.getPiskel();
     if (piskel.isDirty_ !== status) {
       // Redraw piskel name only if dirty status actually changed
       piskel.isDirty_ = status;
@@ -43,7 +43,7 @@
   };
 
   ns.SavedStatusService.prototype.updatePiskelName = function () {
-    var piskel = this.piskelController_.piskel;
+    var piskel = this.piskelController.getPiskel();
     var name = piskel.getDescriptor().name;
     if (piskel.isDirty_) {
       $('.piskel-name').html(name + ' *');
@@ -53,7 +53,7 @@
   };
 
   ns.SavedStatusService.prototype.onBeforeUnload = function (evt) {
-    var piskel = this.piskelController_.piskel;
+    var piskel = this.piskelController.getPiskel();
     if (piskel.isDirty_) {
       var confirmationMessage = "Your Piskel seems to have unsaved changes";
 
diff --git a/src/js/service/keyboard/KeycodeTranslator.js b/src/js/service/keyboard/KeycodeTranslator.js
index d478dd66..00005dc7 100644
--- a/src/js/service/keyboard/KeycodeTranslator.js
+++ b/src/js/service/keyboard/KeycodeTranslator.js
@@ -1,6 +1,7 @@
 (function () {
   var specialKeys = {
     191 : "?",
+    8 : "back",
     27 : "esc",
     38 : "up",
     40 : "down",
diff --git a/src/js/service/keyboard/ShortcutService.js b/src/js/service/keyboard/ShortcutService.js
index bd2aea39..ca921e81 100644
--- a/src/js/service/keyboard/ShortcutService.js
+++ b/src/js/service/keyboard/ShortcutService.js
@@ -12,6 +12,13 @@
     $(document.body).keydown($.proxy(this.onKeyUp_, this));
   };
 
+  /**
+   * Add a keyboard shortcut
+   * @param {String}   rawKey   (case insensitive) key can be a meta (optional) + [a-z0-9] or
+   *                            a special key (check list of supported keys in KeycodeTranslator)
+   *                            eg. 'ctrl+A', 'del'
+   * @param {Function} callback should return true to let the original event perform its default action
+   */
   ns.ShortcutService.prototype.addShortcut = function (rawKey, callback) {
     var parsedKey = this.parseKey_(rawKey.toLowerCase());
 
@@ -78,8 +85,10 @@
         }
 
         if(cb) {
-          cb(charkey);
-          evt.preventDefault();
+          var bubble = cb(charkey);
+          if (bubble !== true) {
+            evt.preventDefault();
+          }
         }
       }
     }
diff --git a/src/js/utils/core.js b/src/js/utils/core.js
index c37a7033..13633d7a 100644
--- a/src/js/utils/core.js
+++ b/src/js/utils/core.js
@@ -47,5 +47,13 @@ if (typeof Function.prototype.bind !== "function") {
     extendedObject.prototype.superclass = inheritFrom.prototype;
   };
 
+  ns.wrap = function (wrapper, wrappedObject) {
+    for (var prop in wrappedObject) {
+      if (typeof wrappedObject[prop] === 'function' && typeof wrapper[prop] === 'undefined') {
+        wrapper[prop] = wrappedObject[prop].bind(wrappedObject);
+      }
+    }
+  };
+
 })();
 
diff --git a/src/js/utils/serialization/Deserializer.js b/src/js/utils/serialization/Deserializer.js
index 5c35322a..8c0b43e4 100644
--- a/src/js/utils/serialization/Deserializer.js
+++ b/src/js/utils/serialization/Deserializer.js
@@ -29,11 +29,11 @@
     this.piskel_ = new pskl.model.Piskel(piskelData.width, piskelData.height, descriptor);
 
     this.layersToLoad_ = piskelData.layers.length;
-
-    piskelData.layers.forEach(function (serializedLayer) {
-      var layer = this.deserializeLayer(serializedLayer);
-      this.piskel_.addLayer(layer);
-    }.bind(this));
+    if (piskelData.expanded) {
+      piskelData.layers.forEach(this.loadExpandedLayer.bind(this));
+    } else {
+      piskelData.layers.forEach(this.deserializeLayer.bind(this));
+    }
   };
 
   ns.Deserializer.prototype.deserializeLayer = function (layerString) {
@@ -48,11 +48,8 @@
     image.onload = function () {
       // 5 - extract the frames from the loaded image
       var frames = pskl.utils.LayerUtils.createFromImage(image, layerData.frameCount);
-
       // 6 - add each image to the layer
-      frames.forEach(layer.addFrame.bind(layer));
-
-      this.onLayerLoaded_();
+      this.addFramesToLayer(frames, layer);
     }.bind(this);
 
     // 3 - set the source of the image
@@ -62,6 +59,24 @@
     return layer;
   };
 
+  ns.Deserializer.prototype.loadExpandedLayer = function (layerData) {
+    var layer = new pskl.model.Layer(layerData.name);
+    var frames = layerData.grids.map(function (grid) {
+      return pskl.model.Frame.fromPixelGrid(grid);
+    });
+    this.addFramesToLayer(frames, layer);
+
+    // 4 - return a pointer to the new layer instance
+    return layer;
+  };
+
+  ns.Deserializer.prototype.addFramesToLayer = function (frames, layer) {
+    frames.forEach(layer.addFrame.bind(layer));
+
+    this.piskel_.addLayer(layer);
+    this.onLayerLoaded_();
+  };
+
   ns.Deserializer.prototype.onLayerLoaded_ = function () {
     this.layersToLoad_ = this.layersToLoad_ - 1;
     if (this.layersToLoad_ === 0) {
diff --git a/src/js/utils/serialization/Serializer.js b/src/js/utils/serialization/Serializer.js
index 934de4b4..271d41ae 100644
--- a/src/js/utils/serialization/Serializer.js
+++ b/src/js/utils/serialization/Serializer.js
@@ -2,30 +2,35 @@
   var ns = $.namespace('pskl.utils');
 
   ns.Serializer = {
-    serializePiskel : function (piskel) {
+    serializePiskel : function (piskel, expanded) {
       var serializedLayers = piskel.getLayers().map(function (l) {
-        return pskl.utils.Serializer.serializeLayer(l);
+        return pskl.utils.Serializer.serializeLayer(l, expanded);
       });
       return JSON.stringify({
         modelVersion : Constants.MODEL_VERSION,
         piskel : {
           height : piskel.getHeight(),
           width : piskel.getWidth(),
-          layers : serializedLayers
+          layers : serializedLayers,
+          expanded : expanded
         }
       });
     },
 
-    serializeLayer : function (layer) {
+    serializeLayer : function (layer, expanded) {
       var frames = layer.getFrames();
       var renderer = new pskl.rendering.FramesheetRenderer(frames);
-      var base64PNG = renderer.renderAsCanvas().toDataURL();
-
-      return JSON.stringify({
+      var layerToSerialize = {
         name : layer.getName(),
-        base64PNG : base64PNG,
         frameCount : frames.length
-      });
+      };
+      if (expanded) {
+        layerToSerialize.grids = frames.map(function (f) {return f.pixels;});
+        return layerToSerialize;
+      } else {
+        layerToSerialize.base64PNG = renderer.renderAsCanvas().toDataURL();
+        return JSON.stringify(layerToSerialize);
+      }
     }
   };
 })();
diff --git a/src/piskel-script-list.js b/src/piskel-script-list.js
index 3a7b8809..26eb3d22 100644
--- a/src/piskel-script-list.js
+++ b/src/piskel-script-list.js
@@ -65,7 +65,8 @@
   "js/rendering/PiskelRenderer.js",
 
   // Controllers
-  "js/controller/PiskelController.js",
+  "js/controller/piskel/PiskelController.js",
+  "js/controller/piskel/PublicPiskelController.js",
   "js/controller/CursorCoordinatesController.js",
   "js/controller/DrawingController.js",
   "js/controller/PreviewFilmController.js",