diff --git a/.gitignore b/.gitignore
index fdf767042..2f3825877 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,10 +14,4 @@ npm-*
 
 # Build
 /dist
-/playground/assets
-/playground/media
-/playground/scratch-vm.js
-/playground/scratch-vm.js.map
-/playground/vendor.js
-/playground/vendor.js.map
-/playground/zenburn.css
+/playground
diff --git a/README.md b/README.md
index 2888fc6c0..512bc1645 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,7 @@ npm start
 ```
 
 ## Playground
-To run the Playground, make sure the dev server's running and go to [http://localhost:8073/](http://localhost:8073/) - you will be directed to the playground, which demonstrates various tools and internal state.
+To run the Playground, make sure the dev server's running and go to [http://localhost:8073/playground/](http://localhost:8073/playground/) - you will be directed to the playground, which demonstrates various tools and internal state.
 
 ![VM Playground Screenshot](https://i.imgur.com/nOCNqEc.gif)
 
@@ -50,7 +50,7 @@ npm run build
 ```
 
 ## How to include in a Node.js App
-For an extended setup example, check out the /playground directory, which includes a fully running VM instance.
+For an extended setup example, check out the /src/playground directory, which includes a fully running VM instance.
 ```js
 var VirtualMachine = require('scratch-vm');
 var vm = new VirtualMachine();
diff --git a/package.json b/package.json
index 6ab89c9f3..4418452f5 100644
--- a/package.json
+++ b/package.json
@@ -25,15 +25,16 @@
   },
   "devDependencies": {
     "adm-zip": "0.4.7",
-    "babel-eslint": "7.1.1",
+    "babel-eslint": "^7.1.1",
     "copy-webpack-plugin": "4.0.1",
-    "eslint": "3.15.0",
+    "eslint": "^3.16.0",
     "eslint-config-scratch": "^3.1.0",
-    "expose-loader": "0.7.1",
-    "gh-pages": "0.12.0",
-    "highlightjs": "9.8.0",
+    "expose-loader": "0.7.3",
+    "gh-pages": "^0.12.0",
+    "highlightjs": "^9.8.0",
     "htmlparser2": "3.9.2",
-    "json": "9.0.4",
+    "jsdom": "^9.11.0",
+    "json": "^9.0.4",
     "lodash.defaultsdeep": "4.6.0",
     "minilog": "3.1.0",
     "promise": "7.1.1",
@@ -41,10 +42,10 @@
     "scratch-blocks": "latest",
     "scratch-render": "latest",
     "script-loader": "0.7.0",
-    "stats.js": "0.17.0",
-    "tap": "10.0.2",
-    "travis-after-all": "1.4.4",
+    "stats.js": "^0.17.0",
+    "tap": "^10.2.0",
+    "travis-after-all": "^1.4.4",
     "webpack": "2.2.1",
-    "webpack-dev-server": "1.16.3"
+    "webpack-dev-server": "^2.4.1"
   }
 }
diff --git a/src/blocks/scratch3_control.js b/src/blocks/scratch3_control.js
index 28737b361..285b241ab 100644
--- a/src/blocks/scratch3_control.js
+++ b/src/blocks/scratch3_control.js
@@ -110,7 +110,7 @@ Scratch3ControlBlocks.prototype.stop = function (args, util) {
         option === 'other scripts in stage') {
         util.stopOtherTargetThreads();
     } else if (option === 'this script') {
-        util.stopThread();
+        util.stopThisScript();
     }
 };
 
diff --git a/src/blocks/scratch3_pen.js b/src/blocks/scratch3_pen.js
index c8f98341e..9b9f64919 100644
--- a/src/blocks/scratch3_pen.js
+++ b/src/blocks/scratch3_pen.js
@@ -147,6 +147,7 @@ Scratch3PenBlocks.prototype._updatePenColor = function (penState) {
     penState.penAttributes.color4f[0] = rgb.r / 255.0;
     penState.penAttributes.color4f[1] = rgb.g / 255.0;
     penState.penAttributes.color4f[2] = rgb.b / 255.0;
+    penState.penAttributes.color4f[3] = 1;
 };
 
 /**
@@ -260,6 +261,8 @@ Scratch3PenBlocks.prototype.setPenColorToColor = function (args, util) {
     penState.penAttributes.color4f[2] = rgb.b / 255.0;
     if (rgb.hasOwnProperty('a')) {  // Will there always be an 'a'?
         penState.penAttributes.color4f[3] = rgb.a / 255.0;
+    } else {
+        penState.penAttributes.color4f[3] = 1;
     }
 };
 
diff --git a/src/blocks/scratch3_sound.js b/src/blocks/scratch3_sound.js
index 20d137580..76c03f6fd 100644
--- a/src/blocks/scratch3_sound.js
+++ b/src/blocks/scratch3_sound.js
@@ -135,8 +135,9 @@ Scratch3SoundBlocks.prototype.playNoteForBeats = function (args, util) {
     var beats = Cast.toNumber(args.BEATS);
     var soundState = this._getSoundState(util.target);
     var inst = soundState.currentInstrument;
+    var vol = soundState.volume;
     if (typeof this.runtime.audioEngine === 'undefined') return;
-    return this.runtime.audioEngine.playNoteForBeatsWithInst(note, beats, inst);
+    return this.runtime.audioEngine.playNoteForBeatsWithInstAndVol(note, beats, inst, vol);
 };
 
 Scratch3SoundBlocks.prototype.playDrumForBeats = function (args, util) {
@@ -192,6 +193,7 @@ Scratch3SoundBlocks.prototype.changeEffect = function (args, util) {
 Scratch3SoundBlocks.prototype.clearEffects = function (args, util) {
     var soundState = this._getSoundState(util.target);
     for (var effect in soundState.effects) {
+        if (!soundState.effects.hasOwnProperty(effect)) continue;
         soundState.effects[effect] = 0;
     }
     if (util.target.audioPlayer === null) return;
diff --git a/src/engine/adapter.js b/src/engine/adapter.js
index 56275e1cb..88c8a18c5 100644
--- a/src/engine/adapter.js
+++ b/src/engine/adapter.js
@@ -24,6 +24,7 @@ var domToBlocks = function (blocksDOM) {
     // Flatten blocks object into a list.
     var blocksList = [];
     for (var b in blocks) {
+        if (!blocks.hasOwnProperty(b)) continue;
         blocksList.push(blocks[b]);
     }
     return blocksList;
diff --git a/src/engine/blocks.js b/src/engine/blocks.js
index ed03be324..d9172228c 100644
--- a/src/engine/blocks.js
+++ b/src/engine/blocks.js
@@ -149,6 +149,7 @@ Blocks.prototype.getTopLevelScript = function (id) {
  */
 Blocks.prototype.getProcedureDefinition = function (name) {
     for (var id in this._blocks) {
+        if (!this._blocks.hasOwnProperty(id)) continue;
         var block = this._blocks[id];
         if ((block.opcode === 'procedures_defnoreturn' ||
             block.opcode === 'procedures_defreturn') &&
@@ -166,6 +167,7 @@ Blocks.prototype.getProcedureDefinition = function (name) {
  */
 Blocks.prototype.getProcedureParamNames = function (name) {
     for (var id in this._blocks) {
+        if (!this._blocks.hasOwnProperty(id)) continue;
         var block = this._blocks[id];
         if ((block.opcode === 'procedures_defnoreturn' ||
             block.opcode === 'procedures_defreturn') &&
@@ -415,6 +417,7 @@ Blocks.prototype.blockToXML = function (blockId) {
     }
     // Add any inputs on this block.
     for (var input in block.inputs) {
+        if (!block.inputs.hasOwnProperty(input)) continue;
         var blockInput = block.inputs[input];
         // Only encode a value tag if the value input is occupied.
         if (blockInput.block || blockInput.shadow) {
@@ -431,6 +434,7 @@ Blocks.prototype.blockToXML = function (blockId) {
     }
     // Add any fields on this block.
     for (var field in block.fields) {
+        if (!block.fields.hasOwnProperty(field)) continue;
         var blockField = block.fields[field];
         var value = blockField.value;
         if (typeof value === 'string') {
diff --git a/src/engine/execute.js b/src/engine/execute.js
index 44951aba3..9d6342f3f 100644
--- a/src/engine/execute.js
+++ b/src/engine/execute.js
@@ -110,6 +110,7 @@ var execute = function (sequencer, thread) {
                 Object.keys(inputs).length === 0) {
                 // One field and no inputs - treat as arg.
                 for (var fieldKey in fields) { // One iteration.
+                    if (!fields.hasOwnProperty(fieldKey)) continue;
                     handleReport(fields[fieldKey].value);
                 }
             } else {
@@ -126,11 +127,13 @@ var execute = function (sequencer, thread) {
 
     // Add all fields on this block to the argValues.
     for (var fieldName in fields) {
+        if (!fields.hasOwnProperty(fieldName)) continue;
         argValues[fieldName] = fields[fieldName].value;
     }
 
     // Recursively evaluate input blocks.
     for (var inputName in inputs) {
+        if (!inputs.hasOwnProperty(inputName)) continue;
         var input = inputs[inputName];
         var inputBlockId = input.block;
         // Is there no value for this input waiting in the stack frame?
@@ -183,8 +186,8 @@ var execute = function (sequencer, thread) {
         stopOtherTargetThreads: function () {
             runtime.stopForTarget(target, thread);
         },
-        stopThread: function () {
-            sequencer.retireThread(thread);
+        stopThisScript: function () {
+            thread.stopThisScript();
         },
         startProcedure: function (procedureCode) {
             sequencer.stepToProcedure(thread, procedureCode);
@@ -233,8 +236,23 @@ var execute = function (sequencer, thread) {
         primitiveReportedValue.then(function (resolvedValue) {
             handleReport(resolvedValue);
             if (typeof resolvedValue === 'undefined') {
-                var popped = thread.popStack();
-                var nextBlockId = thread.target.blocks.getNextBlock(popped);
+                do {
+                    // In the case that the promise is the last block in the current thread stack
+                    // We need to pop out repeatedly until we find the next block.
+                    var popped = thread.popStack();
+                    if (popped === null) {
+                        return;
+                    }
+                    var nextBlockId = thread.target.blocks.getNextBlock(popped);
+                    if (nextBlockId !== null) {
+                        // A next block exists so break out this loop
+                        break;
+                    }
+                    // Investigate the next block and if not in a loop,
+                    // then repeat and pop the next item off the stack frame
+                    var stackFrame = thread.peekStackFrame();
+                } while (stackFrame !== null && !stackFrame.isLoop);
+
                 thread.pushStack(nextBlockId);
             } else {
                 thread.popStack();
diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index f196a6a69..130c4ae95 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -414,7 +414,7 @@ Runtime.prototype.allScriptsDo = function (f, optTarget) {
     if (optTarget) {
         targets = [optTarget];
     }
-    for (var t = 0; t < targets.length; t++) {
+    for (var t = targets.length - 1; t >= 0; t--) {
         var target = targets[t];
         var scripts = target.blocks.getScripts();
         for (var j = 0; j < scripts.length; j++) {
@@ -439,6 +439,12 @@ Runtime.prototype.startHats = function (requestedHatOpcode,
     }
     var instance = this;
     var newThreads = [];
+
+    for (var opts in optMatchFields) {
+        if (!optMatchFields.hasOwnProperty(opts)) continue;
+        optMatchFields[opts] = optMatchFields[opts].toUpperCase();
+    }
+
     // Consider all scripts, looking for hats with opcode `requestedHatOpcode`.
     this.allScriptsDo(function (topBlockId, target) {
         var potentialHatOpcode = target.blocks.getBlock(topBlockId).opcode;
@@ -458,6 +464,7 @@ Runtime.prototype.startHats = function (requestedHatOpcode,
         if (Object.keys(hatFields).length === 0) {
             var hatInputs = target.blocks.getInputs(topBlockId);
             for (var input in hatInputs) {
+                if (!hatInputs.hasOwnProperty(input)) continue;
                 var id = hatInputs[input].block;
                 var fields = target.blocks.getFields(id);
                 hatFields = Object.assign(fields, hatFields);
@@ -466,7 +473,7 @@ Runtime.prototype.startHats = function (requestedHatOpcode,
 
         if (optMatchFields) {
             for (var matchField in optMatchFields) {
-                if (hatFields[matchField].value !==
+                if (hatFields[matchField].value.toUpperCase() !==
                     optMatchFields[matchField]) {
                     // Field mismatch.
                     return;
@@ -587,6 +594,7 @@ Runtime.prototype.stopAll = function () {
 Runtime.prototype._step = function () {
     // Find all edge-activated hats, and add them to threads to be evaluated.
     for (var hatType in this._hats) {
+        if (!this._hats.hasOwnProperty(hatType)) continue;
         var hat = this._hats[hatType];
         if (hat.edgeActivated) {
             this.startHats(hatType);
@@ -785,6 +793,18 @@ Runtime.prototype.getSpriteTargetByName = function (spriteName) {
     }
 };
 
+/**
+ * Get a target by its drawable id.
+ * @param {number} drawableID drawable id of target to find
+ * @return {?Target} The target, if found
+ */
+Runtime.prototype.getTargetByDrawableId = function (drawableID) {
+    for (var i = 0; i < this.targets.length; i++) {
+        var target = this.targets[i];
+        if (target.drawableID === drawableID) return target;
+    }
+};
+
 /**
  * Update the clone counter to track how many clones are created.
  * @param {number} changeAmount How many clones have been created/destroyed.
diff --git a/src/engine/thread.js b/src/engine/thread.js
index 9693b26f1..f093f886e 100644
--- a/src/engine/thread.js
+++ b/src/engine/thread.js
@@ -140,6 +140,27 @@ Thread.prototype.popStack = function () {
     return this.stack.pop();
 };
 
+/**
+ * Pop back down the stack frame until we hit a procedure call or the stack frame is emptied
+ */
+Thread.prototype.stopThisScript = function () {
+    var blockID = this.peekStack();
+    while (blockID !== null) {
+        var block = this.target.blocks.getBlock(blockID);
+        if (typeof block !== 'undefined' && block.opcode === 'procedures_callnoreturn') {
+            break;
+        }
+        this.popStack();
+        blockID = this.peekStack();
+    }
+
+    if (this.stack.length === 0) {
+        // Clean up!
+        this.requestScriptGlowInFrame = false;
+        this.status = Thread.STATUS_DONE;
+    }
+};
+
 /**
  * Get top stack item.
  * @return {?string} Block ID on top of stack.
diff --git a/src/io/keyboard.js b/src/io/keyboard.js
index da0e41625..c7a210803 100644
--- a/src/io/keyboard.js
+++ b/src/io/keyboard.js
@@ -56,7 +56,7 @@ Keyboard.prototype._keyCodeToScratchKey = function (keyCode) {
     case 39: return 'right arrow';
     case 40: return 'down arrow';
     }
-    return null;
+    return '';
 };
 
 /**
diff --git a/src/io/mouse.js b/src/io/mouse.js
index bcd19087e..4a7361fa4 100644
--- a/src/io/mouse.js
+++ b/src/io/mouse.js
@@ -46,7 +46,7 @@ Mouse.prototype.postData = function (data) {
     }
     if (typeof data.isDown !== 'undefined') {
         this._isDown = data.isDown;
-        if (this._isDown) {
+        if (!this._isDown) {
             this._activateClickHats(data.x, data.y);
         }
     }
diff --git a/playground/index.html b/src/playground/index.html
similarity index 100%
rename from playground/index.html
rename to src/playground/index.html
diff --git a/playground/playground.css b/src/playground/playground.css
similarity index 100%
rename from playground/playground.css
rename to src/playground/playground.css
diff --git a/playground/playground.js b/src/playground/playground.js
similarity index 90%
rename from playground/playground.js
rename to src/playground/playground.js
index cb5a81a3e..f32e17ef9 100644
--- a/playground/playground.js
+++ b/src/playground/playground.js
@@ -1,4 +1,3 @@
-
 var loadProject = function () {
     var id = location.hash.substring(1);
     if (id.length < 1 || !isFinite(id)) {
@@ -7,7 +6,7 @@ var loadProject = function () {
     var url = 'https://projects.scratch.mit.edu/internalapi/project/' +
         id + '/get/';
     var r = new XMLHttpRequest();
-    r.onreadystatechange = function() {
+    r.onreadystatechange = function () {
         if (this.readyState === 4) {
             if (r.status === 200) {
                 window.vm.loadProject(this.responseText);
@@ -18,7 +17,7 @@ var loadProject = function () {
     r.send();
 };
 
-window.onload = function() {
+window.onload = function () {
     // Lots of global variables to make debugging easier
     // Instantiate the VM.
     var vm = new window.VirtualMachine();
@@ -60,6 +59,11 @@ window.onload = function() {
     });
     window.workspace = workspace;
 
+    // Filter available blocks
+    var toolbox = vm.filterToolbox(workspace.options.languageTree);
+    // var toolbox = workspace.options.languageTree;
+    workspace.updateToolbox(toolbox);
+
     // Attach scratch-blocks events to VM.
     workspace.addChangeListener(vm.blockListener);
     var flyoutWorkspace = workspace.getFlyout().getWorkspace();
@@ -74,7 +78,7 @@ window.onload = function() {
     // Playground data tabs.
     // Block representation tab.
     var blockexplorer = document.getElementById('blockexplorer');
-    var updateBlockExplorer = function(blocks) {
+    var updateBlockExplorer = function (blocks) {
         blockexplorer.innerHTML = JSON.stringify(blocks, null, 2);
         window.hljs.highlightBlock(blockexplorer);
     };
@@ -83,7 +87,7 @@ window.onload = function() {
     var threadexplorer = document.getElementById('threadexplorer');
     var cachedThreadJSON = '';
     var updateThreadExplorer = function (newJSON) {
-        if (newJSON != cachedThreadJSON) {
+        if (newJSON !== cachedThreadJSON) {
             cachedThreadJSON = newJSON;
             threadexplorer.innerHTML = cachedThreadJSON;
             window.hljs.highlightBlock(threadexplorer);
@@ -101,7 +105,7 @@ window.onload = function() {
 
     // VM handlers.
     // Receipt of new playground data (thread, block representations).
-    vm.on('playgroundData', function(data) {
+    vm.on('playgroundData', function (data) {
         updateThreadExplorer(data.threads);
         updateBlockExplorer(data.blocks);
     });
@@ -125,7 +129,7 @@ window.onload = function() {
             var targetOption = document.createElement('option');
             targetOption.setAttribute('value', data.targetList[i].id);
             // If target id matches editingTarget id, select it.
-            if (data.targetList[i].id == data.editingTarget) {
+            if (data.targetList[i].id === data.editingTarget) {
                 targetOption.setAttribute('selected', 'selected');
             }
             targetOption.appendChild(
@@ -139,23 +143,23 @@ window.onload = function() {
     };
 
     // Feedback for stacks and blocks running.
-    vm.on('SCRIPT_GLOW_ON', function(data) {
+    vm.on('SCRIPT_GLOW_ON', function (data) {
         workspace.glowStack(data.id, true);
     });
-    vm.on('SCRIPT_GLOW_OFF', function(data) {
+    vm.on('SCRIPT_GLOW_OFF', function (data) {
         workspace.glowStack(data.id, false);
     });
-    vm.on('BLOCK_GLOW_ON', function(data) {
+    vm.on('BLOCK_GLOW_ON', function (data) {
         workspace.glowBlock(data.id, true);
     });
-    vm.on('BLOCK_GLOW_OFF', function(data) {
+    vm.on('BLOCK_GLOW_OFF', function (data) {
         workspace.glowBlock(data.id, false);
     });
-    vm.on('VISUAL_REPORT', function(data) {
+    vm.on('VISUAL_REPORT', function (data) {
         workspace.reportValue(data.id, data.value);
     });
 
-    vm.on('SPRITE_INFO_REPORT', function(data) {
+    vm.on('SPRITE_INFO_REPORT', function (data) {
         if (data.id !== selectedTarget.value) return; // Not the editingTarget
         document.getElementById('sinfo-x').value = data.x;
         document.getElementById('sinfo-y').value = data.y;
@@ -213,7 +217,7 @@ window.onload = function() {
     // Feed keyboard events as VM I/O events.
     document.addEventListener('keydown', function (e) {
         // Don't capture keys intended for Blockly inputs.
-        if (e.target != document && e.target != document.body) {
+        if (e.target !== document && e.target !== document.body) {
             return;
         }
         window.vm.postIOData('keyboard', {
@@ -222,7 +226,7 @@ window.onload = function() {
         });
         e.preventDefault();
     });
-    document.addEventListener('keyup', function(e) {
+    document.addEventListener('keyup', function (e) {
         // Always capture up events,
         // even those that have switched to other targets.
         window.vm.postIOData('keyboard', {
@@ -230,7 +234,7 @@ window.onload = function() {
             isDown: false
         });
         // E.g., prevent scroll.
-        if (e.target != document && e.target != document.body) {
+        if (e.target !== document && e.target !== document.body) {
             e.preventDefault();
         }
     });
@@ -239,25 +243,25 @@ window.onload = function() {
     vm.start();
 
     // Inform VM of animation frames.
-    var animate = function() {
+    var animate = function () {
         stats.update();
         requestAnimationFrame(animate);
     };
     requestAnimationFrame(animate);
 
     // Handlers for green flag and stop all.
-    document.getElementById('greenflag').addEventListener('click', function() {
+    document.getElementById('greenflag').addEventListener('click', function () {
         vm.greenFlag();
     });
-    document.getElementById('stopall').addEventListener('click', function() {
+    document.getElementById('stopall').addEventListener('click', function () {
         vm.stopAll();
     });
-    document.getElementById('turbomode').addEventListener('change', function() {
+    document.getElementById('turbomode').addEventListener('change', function () {
         var turboOn = document.getElementById('turbomode').checked;
         vm.setTurboMode(turboOn);
     });
     document.getElementById('compatmode').addEventListener('change',
-    function() {
+    function () {
         var compatibilityMode = document.getElementById('compatmode').checked;
         vm.setCompatibilityMode(compatibilityMode);
     });
diff --git a/src/serialization/sb2.js b/src/serialization/sb2.js
index a07bb7232..3ef4f24f7 100644
--- a/src/serialization/sb2.js
+++ b/src/serialization/sb2.js
@@ -104,6 +104,9 @@ var parseScratchObject = function (object, runtime, topLevel) {
     if (object.hasOwnProperty('direction')) {
         target.direction = object.direction;
     }
+    if (object.hasOwnProperty('isDraggable')) {
+        target.draggable = object.isDraggable;
+    }
     if (object.hasOwnProperty('scale')) {
         // SB2 stores as 1.0 = 100%; we use % in the VM.
         target.size = object.scale * 100;
diff --git a/src/sprites/rendered-target.js b/src/sprites/rendered-target.js
index 18440e679..f96ca9240 100644
--- a/src/sprites/rendered-target.js
+++ b/src/sprites/rendered-target.js
@@ -33,6 +33,13 @@ var RenderedTarget = function (sprite, runtime) {
      */
     this.drawableID = null;
 
+    /**
+     * Drag state of this rendered target. If true, x/y position can't be
+     * changed by blocks.
+     * @type {boolean}
+     */
+    this.dragging = false;
+
     /**
      * Map of current graphic effect values.
      * @type {!Object.<string, number>}
@@ -106,6 +113,12 @@ RenderedTarget.prototype.y = 0;
  */
 RenderedTarget.prototype.direction = 90;
 
+/**
+ * Whether the rendered target is draggable on the stage
+ * @type {boolean}
+ */
+RenderedTarget.prototype.draggable = false;
+
 /**
  * Whether the rendered target is currently visible.
  * @type {boolean}
@@ -160,22 +173,27 @@ RenderedTarget.prototype.rotationStyle = (
  * Set the X and Y coordinates.
  * @param {!number} x New X coordinate, in Scratch coordinates.
  * @param {!number} y New Y coordinate, in Scratch coordinates.
+ * @param {?boolean} force Force setting X/Y, in case of dragging
  */
-RenderedTarget.prototype.setXY = function (x, y) {
-    if (this.isStage) {
-        return;
-    }
+RenderedTarget.prototype.setXY = function (x, y, force) {
+    if (this.isStage) return;
+    if (this.dragging && !force) return;
     var oldX = this.x;
     var oldY = this.y;
-    this.x = x;
-    this.y = y;
     if (this.renderer) {
+        var position = this.renderer.getFencedPositionOfDrawable(this.drawableID, [x, y]);
+        this.x = position[0];
+        this.y = position[1];
+
         this.renderer.updateDrawableProperties(this.drawableID, {
-            position: [this.x, this.y]
+            position: position
         });
         if (this.visible) {
             this.runtime.requestRedraw();
         }
+    } else {
+        this.x = x;
+        this.y = y;
     }
     this.emit(RenderedTarget.EVENT_TARGET_MOVED, this, oldX, oldY);
     this.runtime.spriteInfoReport(this);
@@ -224,6 +242,16 @@ RenderedTarget.prototype.setDirection = function (direction) {
     this.runtime.spriteInfoReport(this);
 };
 
+/**
+ * Set draggability; i.e., whether it's able to be dragged in the player
+ * @param {!boolean} draggable True if should be draggable.
+ */
+RenderedTarget.prototype.setDraggable = function (draggable) {
+    if (this.isStage) return;
+    this.draggable = !!draggable;
+    this.runtime.spriteInfoReport(this);
+};
+
 /**
  * Set a say bubble.
  * @param {?string} type Type of say bubble: "say", "think", or null.
@@ -315,6 +343,7 @@ RenderedTarget.prototype.setEffect = function (effectName, value) {
  */
 RenderedTarget.prototype.clearEffects = function () {
     for (var effectName in this.effects) {
+        if (!this.effects.hasOwnProperty(effectName)) continue;
         this.effects[effectName] = 0;
     }
     if (this.renderer) {
@@ -422,20 +451,23 @@ RenderedTarget.prototype.updateAllDrawableProperties = function () {
     if (this.renderer) {
         var renderedDirectionScale = this._getRenderedDirectionAndScale();
         var costume = this.sprite.costumes[this.currentCostume];
+        var bitmapResolution = costume.bitmapResolution || 1;
         var props = {
             position: [this.x, this.y],
             direction: renderedDirectionScale.direction,
+            draggable: this.draggable,
             scale: renderedDirectionScale.scale,
             visible: this.visible,
             skin: costume.skin,
-            costumeResolution: costume.bitmapResolution,
+            costumeResolution: bitmapResolution,
             rotationCenter: [
-                costume.rotationCenterX / costume.bitmapResolution,
-                costume.rotationCenterY / costume.bitmapResolution
+                costume.rotationCenterX / bitmapResolution,
+                costume.rotationCenterY / bitmapResolution
             ]
         };
-        for (var effectID in this.effects) {
-            props[effectID] = this.effects[effectID];
+        for (var effectName in this.effects) {
+            if (!this.effects.hasOwnProperty(effectName)) continue;
+            props[effectName] = this.effects[effectName];
         }
         this.renderer.updateDrawableProperties(this.drawableID, props);
         if (this.visible) {
@@ -582,7 +614,7 @@ RenderedTarget.prototype.goBackLayers = function (nLayers) {
 
 /**
  * Move behind some other rendered target.
- * @param {!Clone} other Other rendered target to move behind.
+ * @param {!RenderedTarget} other Other rendered target to move behind.
  */
 RenderedTarget.prototype.goBehindOther = function (other) {
     if (this.renderer) {
@@ -637,11 +669,11 @@ RenderedTarget.prototype.keepInFence = function (newX, newY, optFence) {
 /**
  * Make a clone, copying any run-time properties.
  * If we've hit the global clone limit, returns null.
- * @return {!RenderedTarget} New clone.
+ * @return {RenderedTarget} New clone.
  */
 RenderedTarget.prototype.makeClone = function () {
     if (!this.runtime.clonesAvailable() || this.isStage) {
-        return; // Hit max clone limit, or this is the stage.
+        return null; // Hit max clone limit, or this is the stage.
     }
     this.runtime.changeCloneCounter(1);
     var newClone = this.sprite.createClone();
@@ -649,6 +681,7 @@ RenderedTarget.prototype.makeClone = function () {
     newClone.x = this.x;
     newClone.y = this.y;
     newClone.direction = this.direction;
+    newClone.draggable = this.draggable;
     newClone.visible = this.visible;
     newClone.size = this.size;
     newClone.currentCostume = this.currentCostume;
@@ -687,15 +720,19 @@ RenderedTarget.prototype.onStopAll = function () {
  * @param {object} data An object with sprite info data to set.
  */
 RenderedTarget.prototype.postSpriteInfo = function (data) {
+    var force = data.hasOwnProperty('force') ? data.force : null;
     if (data.hasOwnProperty('x')) {
-        this.setXY(data.x, this.y);
+        this.setXY(data.x, this.y, force);
     }
     if (data.hasOwnProperty('y')) {
-        this.setXY(this.x, data.y);
+        this.setXY(this.x, data.y, force);
     }
     if (data.hasOwnProperty('direction')) {
         this.setDirection(data.direction);
     }
+    if (data.hasOwnProperty('draggable')) {
+        this.setDraggable(data.draggable);
+    }
     if (data.hasOwnProperty('rotationStyle')) {
         this.setRotationStyle(data.rotationStyle);
     }
@@ -704,6 +741,20 @@ RenderedTarget.prototype.postSpriteInfo = function (data) {
     }
 };
 
+/**
+ * Put the sprite into the drag state. While in effect, setXY must be forced
+ */
+RenderedTarget.prototype.startDrag = function () {
+    this.dragging = true;
+};
+
+/**
+ * Remove the sprite from the drag state.
+ */
+RenderedTarget.prototype.stopDrag = function () {
+    this.dragging = false;
+};
+
 /**
  * Serialize sprite info, used when emitting events about the sprite
  * @returns {object} Sprite data as a simple object
@@ -717,6 +768,7 @@ RenderedTarget.prototype.toJSON = function () {
         y: this.y,
         size: this.size,
         direction: this.direction,
+        draggable: this.draggable,
         costume: this.getCurrentCostume(),
         costumeCount: this.getCostumes().length,
         currentCostume: this.currentCostume,
diff --git a/src/sprites/sprite.js b/src/sprites/sprite.js
index bccc5d909..81626f3a7 100644
--- a/src/sprites/sprite.js
+++ b/src/sprites/sprite.js
@@ -46,7 +46,7 @@ var Sprite = function (blocks, runtime) {
 
 /**
  * Create a clone of this sprite.
- * @returns {!Clone} Newly created clone.
+ * @returns {!RenderedTarget} Newly created clone.
  */
 Sprite.prototype.createClone = function () {
     var newClone = new RenderedTarget(this, this.runtime);
diff --git a/src/util/cast.js b/src/util/cast.js
index a8a1535b8..79e76b134 100644
--- a/src/util/cast.js
+++ b/src/util/cast.js
@@ -90,6 +90,15 @@ Cast.toRgbColorObject = function (value) {
     return color;
 };
 
+/**
+ * Determine if a Scratch argument is a white space string (or null / empty).
+ * @param {*} val value to check.
+ * @return {boolean} True if the argument is all white spaces or null / empty.
+ */
+Cast.isWhiteSpace = function (val) {
+    return val === null || typeof val === 'string' && val.trim().length === 0;
+};
+
 /**
  * Compare two values, using Scratch cast, case-insensitive string compare, etc.
  * In Scratch 2.0, this is captured by `interp.compare.`
@@ -100,6 +109,11 @@ Cast.toRgbColorObject = function (value) {
 Cast.compare = function (v1, v2) {
     var n1 = Number(v1);
     var n2 = Number(v2);
+    if (n1 === 0 && Cast.isWhiteSpace(v1)) {
+        n1 = NaN;
+    } else if (n2 === 0 && Cast.isWhiteSpace(v2)) {
+        n2 = NaN;
+    }
     if (isNaN(n1) || isNaN(n2)) {
         // At least one argument can't be converted to a number.
         // Scratch compares strings as case insensitive.
diff --git a/src/util/filter-toolbox.js b/src/util/filter-toolbox.js
new file mode 100644
index 000000000..54d59ced8
--- /dev/null
+++ b/src/util/filter-toolbox.js
@@ -0,0 +1,53 @@
+/**
+ * Filter Blockly toolbox XML node containing blocks to only those with
+ * valid opcodes. Return a copy of the node with valid blocks.
+ * @param {HTMLElement} node Blockly toolbox XML node
+ * @param {Array.<string>} opcodes Valid opcodes. Blocks producing other opcodes
+ * will be filtered.
+ * @returns {HTMLElement} filtered toolbox XML node
+ */
+var filterToolboxNode = function (node, opcodes) {
+    var filteredCategory = node.cloneNode();
+    for (var block = node.firstElementChild; block; block = block.nextElementSibling) {
+        if (block.nodeName.toLowerCase() !== 'block') continue;
+        var opcode = block.getAttribute('type').toLowerCase();
+        if (opcodes.indexOf(opcode) !== -1) {
+            filteredCategory.appendChild(block.cloneNode(true));
+        }
+    }
+    return filteredCategory;
+};
+
+/**
+ * Filter Blockly toolbox XML and return a copy which only contains blocks with
+ * existent opcodes. Categories with no valid children will be removed.
+ * @param {HTMLElement} toolbox Blockly toolbox XML node
+ * @param {Array.<string>} opcodes Valid opcodes. Blocks producing other opcodes
+ * will be filtered.
+ * @returns {HTMLElement} filtered toolbox XML node
+ */
+var filterToolbox = function (toolbox, opcodes) {
+    if (!toolbox.hasChildNodes()) return toolbox;
+    var filteredToolbox;
+    if (toolbox.firstElementChild.nodeName.toLowerCase() === 'category') {
+        filteredToolbox = toolbox.cloneNode();
+        for (
+            var category = toolbox.firstElementChild;
+            category;
+            category = category.nextElementSibling
+        ) {
+            if (category.nodeName.toLowerCase() !== 'category') continue;
+            var filteredCategory = filterToolboxNode(category, opcodes);
+            if (filteredCategory.hasChildNodes() ||
+                filteredCategory.hasAttribute('custom')
+            ) {
+                filteredToolbox.appendChild(filteredCategory);
+            }
+        }
+    } else {
+        filteredToolbox = filterToolboxNode(toolbox, opcodes);
+    }
+    return filteredToolbox;
+};
+
+module.exports = filterToolbox;
diff --git a/src/util/timer.js b/src/util/timer.js
index 17c66a567..9a60e5688 100644
--- a/src/util/timer.js
+++ b/src/util/timer.js
@@ -23,16 +23,35 @@ var Timer = function () {};
  */
 Timer.prototype.startTime = 0;
 
+/**
+ * Disable use of self.performance for now as it results in lower performance
+ * However, instancing it like below (caching the self.performance to a local variable) negates most of the issues.
+ * @type {boolean}
+ */
+var USE_PERFORMANCE = false;
+
+/**
+ * Legacy object to allow for us to call now to get the old style date time (for backwards compatibility)
+ * @deprecated This is only called via the nowObj.now() if no other means is possible...
+ */
+var legacyDateCode = {
+    now: function () {
+        return new Date().getTime();
+    }
+};
+
+/**
+ * Use this object to route all time functions through single access points.
+ */
+var nowObj = (USE_PERFORMANCE && typeof self !== 'undefined' && self.performance && 'now' in self.performance) ?
+    self.performance : Date.now ? Date : legacyDateCode;
+
 /**
  * Return the currently known absolute time, in ms precision.
  * @returns {number} ms elapsed since 1 January 1970 00:00:00 UTC.
  */
 Timer.prototype.time = function () {
-    if (Date.now) {
-        return Date.now();
-    } else {
-        return new Date().getTime();
-    }
+    return nowObj.now();
 };
 
 /**
@@ -43,12 +62,7 @@ Timer.prototype.time = function () {
  * @returns {number} ms-scale accurate time relative to other relative times.
  */
 Timer.prototype.relativeTime = function () {
-    if (typeof self !== 'undefined' &&
-        self.performance && 'now' in self.performance) {
-        return self.performance.now();
-    } else {
-        return this.time();
-    }
+    return nowObj.now();
 };
 
 /**
@@ -56,15 +70,11 @@ Timer.prototype.relativeTime = function () {
  * at the most accurate precision possible.
  */
 Timer.prototype.start = function () {
-    this.startTime = this.relativeTime();
+    this.startTime = nowObj.now();
 };
 
-/**
- * Check time elapsed since `timer.start` was called.
- * @returns {number} Time elapsed, in ms (possibly sub-ms precision).
- */
 Timer.prototype.timeElapsed = function () {
-    return this.relativeTime() - this.startTime;
+    return nowObj.now() - this.startTime;
 };
 
 module.exports = Timer;
diff --git a/src/virtual-machine.js b/src/virtual-machine.js
index 7aa5d6654..d70725cd3 100644
--- a/src/virtual-machine.js
+++ b/src/virtual-machine.js
@@ -1,6 +1,7 @@
 var EventEmitter = require('events');
 var util = require('util');
 
+var filterToolbox = require('./util/filter-toolbox');
 var Runtime = require('./engine/runtime');
 
 var sb2 = require('./serialization/sb2');
@@ -379,6 +380,41 @@ VirtualMachine.prototype.emitWorkspaceUpdate = function () {
     });
 };
 
+/**
+ * Get a target id for a drawable id. Useful for interacting with the renderer
+ * @param {int} drawableId The drawable id to request the target id for
+ * @returns {?string} The target id, if found. Will also be null if the target found is the stage.
+ */
+VirtualMachine.prototype.getTargetIdForDrawableId = function (drawableId) {
+    var target = this.runtime.getTargetByDrawableId(drawableId);
+    if (target.hasOwnProperty('id') && target.hasOwnProperty('isStage') && !target.isStage) {
+        return target.id;
+    }
+    return null;
+};
+
+/**
+ * Put a target into a "drag" state, during which its X/Y positions will be unaffected
+ * by blocks.
+ * @param {string} targetId The id for the target to put into a drag state
+ */
+VirtualMachine.prototype.startDrag = function (targetId) {
+    var target = this.runtime.getTargetById(targetId);
+    if (target) {
+        target.startDrag();
+        this.setEditingTarget(target.id);
+    }
+};
+
+/**
+ * Remove a target from a drag state, so blocks may begin affecting X/Y position again
+ * @param {string} targetId The id for the target to remove from the drag state
+ */
+VirtualMachine.prototype.stopDrag = function (targetId) {
+    var target = this.runtime.getTargetById(targetId);
+    if (target) target.stopDrag();
+};
+
 /**
  * Post/edit sprite info for the current editing target.
  * @param {object} data An object with sprite info data to set.
@@ -387,4 +423,17 @@ VirtualMachine.prototype.postSpriteInfo = function (data) {
     this.editingTarget.postSpriteInfo(data);
 };
 
+
+/**
+ * Filter Blockly toolbox XML and return a copy which only contains blocks with
+ * existent opcodes. Categories with no valid children will be removed.
+ * @param {HTMLElement} toolbox Blockly toolbox XML node
+ * @returns {HTMLElement} filtered toolbox XML node
+ */
+VirtualMachine.prototype.filterToolbox = function (toolbox) {
+    var opcodes = Object.keys(this.runtime._primitives)
+        .concat(Object.keys(this.runtime._hats));
+    return filterToolbox(toolbox, opcodes);
+};
+
 module.exports = VirtualMachine;
diff --git a/test/fixtures/.eslintrc.js b/test/fixtures/.eslintrc.js
new file mode 100644
index 000000000..8df47e667
--- /dev/null
+++ b/test/fixtures/.eslintrc.js
@@ -0,0 +1,5 @@
+module.exports = {
+    rules: {
+        'max-len': [0]
+    }
+};
diff --git a/test/fixtures/hat-execution-order.sb2 b/test/fixtures/hat-execution-order.sb2
new file mode 100644
index 000000000..f9a7efdcc
Binary files /dev/null and b/test/fixtures/hat-execution-order.sb2 differ
diff --git a/test/fixtures/toolboxes.js b/test/fixtures/toolboxes.js
new file mode 100644
index 000000000..5f74c89df
--- /dev/null
+++ b/test/fixtures/toolboxes.js
@@ -0,0 +1,840 @@
+var jsdom = require('jsdom').jsdom;
+var categories = '<xml id="toolbox-categories" style="display: none">' +
+  '<category name="Motion" colour="#4C97FF" secondaryColour="#3373CC">' +
+    '<block type="motion_movesteps">' +
+      '<value name="STEPS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_turnright">' +
+      '<value name="DEGREES">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">15</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_turnleft">' +
+      '<value name="DEGREES">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">15</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_pointindirection">' +
+      '<value name="DIRECTION">' +
+        '<shadow type="math_angle">' +
+          '<field name="NUM">90</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_pointtowards">' +
+      '<value name="TOWARDS">' +
+        '<shadow type="motion_pointtowards_menu">' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_gotoxy">' +
+      '<value name="X">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="Y">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_goto">' +
+      '<value name="TO">' +
+        '<shadow type="motion_goto_menu">' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_glidesecstoxy">' +
+      '<value name="SECS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="X">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="Y">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_changexby">' +
+      '<value name="DX">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_setx">' +
+      '<value name="X">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_changeyby">' +
+      '<value name="DY">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_sety">' +
+      '<value name="Y">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_ifonedgebounce"></block>' +
+    '<block type="motion_setrotationstyle">' +
+      '<value name="STYLE">' +
+        '<shadow type="motion_setrotationstyle_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_xposition"></block>' +
+    '<block type="motion_yposition"></block>' +
+    '<block type="motion_direction"></block>' +
+  '</category>' +
+  '<category name="Looks" colour="#9966FF" secondaryColour="#774DCB">' +
+    '<block type="looks_sayforsecs">' +
+      '<value name="MESSAGE">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">Hello!</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="SECS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">2</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_say">' +
+      '<value name="MESSAGE">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">Hello!</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_thinkforsecs">' +
+      '<value name="MESSAGE">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">Hmm...</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="SECS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">2</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_think">' +
+      '<value name="MESSAGE">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">Hmm...</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_show"></block>' +
+    '<block type="looks_hide"></block>' +
+    '<block type="looks_switchcostumeto">' +
+      '<value name="COSTUME">' +
+        '<shadow type="looks_costume"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_nextcostume"></block>' +
+    '<block type="looks_nextbackdrop"></block>' +
+    '<block type="looks_switchbackdropto">' +
+      '<value name="BACKDROP">' +
+        '<shadow type="looks_backdrops"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_switchbackdroptoandwait">' +
+      '<value name="BACKDROP">' +
+        '<shadow type="looks_backdrops"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_changeeffectby">' +
+      '<value name="EFFECT">' +
+        '<shadow type="looks_effectmenu"></shadow>' +
+      '</value>' +
+      '<value name="CHANGE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_seteffectto">' +
+      '<value name="EFFECT">' +
+        '<shadow type="looks_effectmenu"></shadow>' +
+      '</value>' +
+      '<value name="VALUE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_cleargraphiceffects"></block>' +
+    '<block type="looks_changesizeby">' +
+      '<value name="CHANGE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_setsizeto">' +
+      '<value name="SIZE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">100</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_gotofront"></block>' +
+    '<block type="looks_gobacklayers">' +
+      '<value name="NUM">' +
+        '<shadow type="math_integer">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="looks_costumeorder"></block>' +
+    '<block type="looks_backdroporder"></block>' +
+    '<block type="looks_backdropname"></block>' +
+    '<block type="looks_size"></block>' +
+  '</category>' +
+  '<category name="Sound" colour="#D65CD6" secondaryColour="#BD42BD">' +
+    '<block type="sound_play">' +
+      '<value name="SOUND_MENU">' +
+        '<shadow type="sound_sounds_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_playuntildone">' +
+      '<value name="SOUND_MENU">' +
+        '<shadow type="sound_sounds_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_stopallsounds"></block>' +
+    '<block type="sound_playdrumforbeats">' +
+      '<value name="DRUM">' +
+        '<shadow type="sound_drums_menu"></shadow>' +
+      '</value>' +
+      '<value name="BEATS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0.25</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_restforbeats">' +
+      '<value name="BEATS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0.25</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_playnoteforbeats">' +
+      '<value name="NOTE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">60</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="BEATS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0.5</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_setinstrumentto">' +
+      '<value name="INSTRUMENT">' +
+        '<shadow type="sound_instruments_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_seteffectto">' +
+      '<value name="EFFECT">' +
+        '<shadow type="sound_effects_menu"></shadow>' +
+      '</value>' +
+      '<value name="VALUE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">100</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_changeeffectby">' +
+      '<value name="EFFECT">' +
+        '<shadow type="sound_effects_menu"></shadow>' +
+      '</value>' +
+      '<value name="VALUE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_cleareffects"></block>' +
+    '<block type="sound_changevolumeby">' +
+      '<value name="VOLUME">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">-10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_setvolumeto">' +
+      '<value name="VOLUME">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">100</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_volume"></block>' +
+    '<block type="sound_changetempoby">' +
+      '<value name="TEMPO">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">20</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_settempotobpm">' +
+      '<value name="TEMPO">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">60</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sound_tempo"></block>' +
+  '</category>' +
+  '<category name="Pen" colour="#00B295" secondaryColour="#0B8E69">' +
+    '<block type="pen_clear"></block>' +
+    '<block type="pen_stamp"></block>' +
+    '<block type="pen_pendown"></block>' +
+    '<block type="pen_penup"></block>' +
+    '<block type="pen_setpencolortocolor">' +
+      '<value name="COLOR">' +
+        '<shadow type="colour_picker">' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="pen_changepencolorby">' +
+      '<value name="COLOR">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="pen_setpencolortonum">' +
+      '<value name="COLOR">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="pen_changepenshadeby">' +
+      '<value name="SHADE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="pen_setpenshadeto">' +
+      '<value name="SHADE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">50</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="pen_changepensizeby">' +
+      '<value name="SIZE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="pen_setpensizeto">' +
+      '<value name="SIZE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+  '</category>' +
+  '<category name="Data" colour="#FF8C1A" secondaryColour="#DB6E00" custom="VARIABLE">' +
+  '</category>' +
+  '<category name="Lists" colour="#FF8C1A" secondaryColour="#DB6E00">' +
+    '<block type="data_listcontents"></block>' +
+    '<block type="data_addtolist">' +
+      '<value name="ITEM">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">thing</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="data_deleteoflist">' +
+      '<value name="INDEX">' +
+        '<shadow type="data_listindexall">' +
+          '<field name="INDEX">1</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="data_insertatlist">' +
+      '<value name="INDEX">' +
+        '<shadow type="data_listindexrandom">' +
+          '<field name="INDEX">1</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="ITEM">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">thing</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="data_replaceitemoflist">' +
+      '<value name="INDEX">' +
+        '<shadow type="data_listindexrandom">' +
+          '<field name="INDEX">1</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="ITEM">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">thing</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="data_itemoflist">' +
+      '<value name="INDEX">' +
+        '<shadow type="data_listindexrandom">' +
+          '<field name="INDEX">1</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="data_lengthoflist"></block>' +
+    '<block type="data_listcontainsitem">' +
+      '<value name="ITEM">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">thing</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="data_showlist"></block>' +
+    '<block type="data_hidelist"></block>' +
+  '</category>' +
+  '<category name="Events" colour="#FFD500" secondaryColour="#CC9900">' +
+    '<block type="event_whenflagclicked"></block>' +
+    '<block type="event_whenkeypressed">' +
+    '</block>' +
+    '<block type="event_whenthisspriteclicked"></block>' +
+    '<block type="event_whenbackdropswitchesto">' +
+    '</block>' +
+    '<block type="event_whengreaterthan">' +
+      '<value name="VALUE">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="event_whenbroadcastreceived">' +
+    '</block>' +
+    '<block type="event_broadcast">' +
+      '<value name="BROADCAST_OPTION">' +
+        '<shadow type="event_broadcast_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="event_broadcastandwait">' +
+      '<value name="BROADCAST_OPTION">' +
+        '<shadow type="event_broadcast_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+  '</category>' +
+  '<category name="Control" colour="#FFAB19" secondaryColour="#CF8B17">' +
+    '<block type="control_wait">' +
+      '<value name="DURATION">' +
+        '<shadow type="math_positive_number">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="control_repeat">' +
+      '<value name="TIMES">' +
+        '<shadow type="math_whole_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="control_forever"></block>' +
+    '<block type="control_if"></block>' +
+    '<block type="control_if_else"></block>' +
+    '<block type="control_wait_until"></block>' +
+    '<block type="control_repeat_until"></block>' +
+    '<block type="control_stop"></block>' +
+    '<block type="control_start_as_clone"></block>' +
+    '<block type="control_create_clone_of">' +
+      '<value name="CLONE_OPTION">' +
+        '<shadow type="control_create_clone_of_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="control_delete_this_clone"></block>' +
+  '</category>' +
+  '<category name="Sensing" colour="#4CBFE6" secondaryColour="#2E8EB8">' +
+    '<block type="sensing_touchingobject">' +
+      '<value name="TOUCHINGOBJECTMENU">' +
+        '<shadow type="sensing_touchingobjectmenu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sensing_touchingcolor">' +
+      '<value name="COLOR">' +
+        '<shadow type="colour_picker"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sensing_coloristouchingcolor">' +
+      '<value name="COLOR">' +
+        '<shadow type="colour_picker"></shadow>' +
+      '</value>' +
+      '<value name="COLOR2">' +
+        '<shadow type="colour_picker"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sensing_distanceto">' +
+      '<value name="DISTANCETOMENU">' +
+        '<shadow type="sensing_distancetomenu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="sensing_askandwait">' +
+      '<value name="QUESTION">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">What\'s your name?</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+  '<block type="sensing_answer"></block>' +
+  '<block type="sensing_keypressed">' +
+      '<value name="KEY_OPTION">' +
+        '<shadow type="sensing_keyoptions"></shadow>' +
+      '</value>' +
+  '</block>' +
+  '<block type="sensing_mousedown"></block>' +
+  '<block type="sensing_mousex"></block>' +
+  '<block type="sensing_mousey"></block>' +
+  '<block type="sensing_loudness"></block>' +
+  '<block type="sensing_videoon">' +
+      '<value name="VIDEOONMENU1">' +
+        '<shadow type="sensing_videoonmenuone"></shadow>' +
+      '</value>' +
+      '<value name="VIDEOONMENU2">' +
+        '<shadow type="sensing_videoonmenutwo"></shadow>' +
+      '</value>' +
+  '</block>' +
+  '<block type="sensing_videotoggle">' +
+      '<value name="VIDEOTOGGLEMENU">' +
+        '<shadow type="sensing_videotogglemenu"></shadow>' +
+      '</value>' +
+  '</block>' +
+  '<block type="sensing_setvideotransparency">' +
+    '<value name="TRANSPARENCY">' +
+      '<shadow type="math_number">' +
+        '<field name="NUM">50</field>' +
+      '</shadow>' +
+    '</value>' +
+  '</block>' +
+  '<block type="sensing_timer"></block>' +
+  '<block type="sensing_resettimer"></block>' +
+  '<block type="sensing_of">' +
+    '<value name="PROPERTY">' +
+      '<shadow type="sensing_of_property_menu"></shadow>' +
+    '</value>' +
+    '<value name="OBJECT">' +
+      '<shadow type="sensing_of_object_menu"></shadow>' +
+    '</value>' +
+  '</block>' +
+  '<block type="sensing_current">' +
+    '<value name="CURRENTMENU">' +
+      '<shadow type="sensing_currentmenu"></shadow>' +
+    '</value>' +
+  '</block>' +
+  '<block type="sensing_dayssince2000"></block>' +
+  '<block type="sensing_username"></block>' +
+  '</category>' +
+  '<category name="Operators" colour="#40BF4A" secondaryColour="#389438">' +
+    '<block type="operator_add">' +
+      '<value name="NUM1">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="NUM2">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_subtract">' +
+      '<value name="NUM1">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="NUM2">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_multiply">' +
+      '<value name="NUM1">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="NUM2">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_divide">' +
+      '<value name="NUM1">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="NUM2">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_random">' +
+      '<value name="FROM">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="TO">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_lt">' +
+      '<value name="OPERAND1">' +
+        '<shadow type="text">' +
+          '<field name="TEXT"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="OPERAND2">' +
+        '<shadow type="text">' +
+          '<field name="TEXT"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_equals">' +
+      '<value name="OPERAND1">' +
+        '<shadow type="text">' +
+          '<field name="TEXT"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="OPERAND2">' +
+        '<shadow type="text">' +
+          '<field name="TEXT"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_gt">' +
+      '<value name="OPERAND1">' +
+        '<shadow type="text">' +
+          '<field name="TEXT"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="OPERAND2">' +
+        '<shadow type="text">' +
+          '<field name="TEXT"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_and"></block>' +
+    '<block type="operator_or"></block>' +
+    '<block type="operator_not"></block>' +
+    '<block type="operator_join">' +
+      '<value name="STRING1">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">hello</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="STRING2">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">world</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_letter_of">' +
+      '<value name="LETTER">' +
+        '<shadow type="math_whole_number">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="STRING">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">world</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_length">' +
+      '<value name="STRING">' +
+        '<shadow type="text">' +
+          '<field name="TEXT">world</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_mod">' +
+      '<value name="NUM1">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="NUM2">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_round">' +
+      '<value name="NUM">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="operator_mathop">' +
+      '<value name="OPERATOR">' +
+        '<shadow type="operator_mathop_menu"></shadow>' +
+      '</value>' +
+      '<value name="NUM">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM"></field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+  '</category>' +
+  '<category name="More Blocks" colour="#FF6680" secondaryColour="#FF3355" custom="PROCEDURE"></category>' +
+  '</xml>';
+var simple = '<xml id="toolbox-simple" style="display: none">' +
+    '<block type="motion_movesteps">' +
+      '<value name="STEPS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_turnright">' +
+      '<value name="DEGREES">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">15</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_turnleft">' +
+      '<value name="DEGREES">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">15</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_pointindirection">' +
+      '<value name="DIRECTION">' +
+        '<shadow type="math_angle">' +
+          '<field name="NUM">90</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_pointtowards">' +
+      '<value name="TOWARDS">' +
+        '<shadow type="motion_pointtowards_menu">' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_gotoxy">' +
+      '<value name="X">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="Y">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_goto">' +
+      '<value name="TO">' +
+        '<shadow type="motion_goto_menu">' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_glidesecstoxy">' +
+      '<value name="SECS">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">1</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="X">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+      '<value name="Y">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_changexby">' +
+      '<value name="DX">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_setx">' +
+      '<value name="X">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_changeyby">' +
+      '<value name="DY">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">10</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_sety">' +
+      '<value name="Y">' +
+        '<shadow type="math_number">' +
+          '<field name="NUM">0</field>' +
+        '</shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_ifonedgebounce"></block>' +
+    '<block type="motion_setrotationstyle">' +
+      '<value name="STYLE">' +
+        '<shadow type="motion_setrotationstyle_menu"></shadow>' +
+      '</value>' +
+    '</block>' +
+    '<block type="motion_xposition"></block>' +
+    '<block type="motion_yposition"></block>' +
+    '<block type="motion_direction"></block>' +
+'</xml>';
+var empty = '<xml id="toolbox-simple" style="display: none"></xml>';
+module.exports = {
+    categories: jsdom(categories).body.firstElementChild,
+    simple: jsdom(simple).body.firstElementChild,
+    empty: jsdom(empty).body.firstElementChild
+};
diff --git a/test/integration/complex.js b/test/integration/complex.js
index 1ff1d384f..dea8d40bc 100644
--- a/test/integration/complex.js
+++ b/test/integration/complex.js
@@ -34,6 +34,7 @@ test('complex', function (t) {
                 x: 0,
                 y: 10,
                 direction: 90,
+                draggable: true,
                 rotationStyle: 'all around',
                 visible: true
             });
diff --git a/test/integration/hat-execution-order.js b/test/integration/hat-execution-order.js
new file mode 100644
index 000000000..0a302624b
--- /dev/null
+++ b/test/integration/hat-execution-order.js
@@ -0,0 +1,39 @@
+var path = require('path');
+var test = require('tap').test;
+var extract = require('../fixtures/extract');
+var VirtualMachine = require('../../src/index');
+
+var projectUri = path.resolve(__dirname, '../fixtures/hat-execution-order.sb2');
+var project = extract(projectUri);
+
+test('complex', function (t) {
+    var vm = new VirtualMachine();
+
+    // Evaluate playground data and exit
+    vm.on('playgroundData', function (e) {
+        var threads = JSON.parse(e.threads);
+        t.ok(threads.length === 0);
+
+        var results = vm.runtime.targets[0].lists.results.contents;
+        t.deepEqual(results, ['3', '2', '1', 'stage']);
+
+        t.end();
+        process.nextTick(process.exit);
+    });
+
+    // Start VM, load project, and run
+    t.doesNotThrow(function () {
+        vm.start();
+        vm.clear();
+        vm.setCompatibilityMode(false);
+        vm.setTurboMode(false);
+        vm.loadProject(project);
+        vm.greenFlag();
+    });
+
+    // After two seconds, get playground data and stop
+    setTimeout(function () {
+        vm.getPlaygroundData();
+        vm.stopAll();
+    }, 2000);
+});
diff --git a/test/unit/blocks_control.js b/test/unit/blocks_control.js
index 2dc6049df..7867524ce 100644
--- a/test/unit/blocks_control.js
+++ b/test/unit/blocks_control.js
@@ -104,7 +104,7 @@ test('stop', function (t) {
     var state = {
         stopAll: 0,
         stopOtherTargetThreads: 0,
-        stopThread: 0
+        stopThisScript: 0
     };
     var util = {
         stopAll: function () {
@@ -113,8 +113,8 @@ test('stop', function (t) {
         stopOtherTargetThreads: function () {
             state.stopOtherTargetThreads++;
         },
-        stopThread: function () {
-            state.stopThread++;
+        stopThisScript: function () {
+            state.stopThisScript++;
         }
     };
 
@@ -125,6 +125,6 @@ test('stop', function (t) {
     c.stop({STOP_OPTION: 'this script'}, util);
     t.strictEqual(state.stopAll, 1);
     t.strictEqual(state.stopOtherTargetThreads, 2);
-    t.strictEqual(state.stopThread, 1);
+    t.strictEqual(state.stopThisScript, 1);
     t.end();
 });
diff --git a/test/unit/engine_sequencer.js b/test/unit/engine_sequencer.js
index 23ec4c13d..1e000ad36 100644
--- a/test/unit/engine_sequencer.js
+++ b/test/unit/engine_sequencer.js
@@ -1,8 +1,178 @@
 var test = require('tap').test;
 var Sequencer = require('../../src/engine/sequencer');
+var Runtime = require('../../src/engine/runtime');
+var Thread = require('../../src/engine/thread');
+var RenderedTarget = require('../../src/sprites/rendered-target');
+var Sprite = require('../../src/sprites/sprite');
 
 test('spec', function (t) {
     t.type(Sequencer, 'function');
-    // @todo
+    
+    var r = new Runtime();
+    var s = new Sequencer(r);
+
+    t.type(s, 'object');
+    t.ok(s instanceof Sequencer);
+    
+    t.type(s.stepThreads, 'function');
+    t.type(s.stepThread, 'function');
+    t.type(s.stepToBranch, 'function');
+    t.type(s.stepToProcedure, 'function');
+    t.type(s.retireThread, 'function');
+
+    t.end();
+});
+
+var randomString = function () {
+    var top = Math.random().toString(36);
+    return top.substring(7);
+};
+
+var generateBlock = function (id) {
+    var block = {fields: Object,
+        id: id,
+        inputs: {},
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'fakeName',
+        next: null,
+        opcode: 'procedures_defnoreturn',
+        mutation: {proccode: 'fakeCode'},
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    return block;
+};
+
+var generateBlockInput = function (id, next, inp) {
+    var block = {fields: Object,
+        id: id,
+        inputs: {SUBSTACK: {block: inp, name: 'SUBSTACK'}},
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'fakeName',
+        next: next,
+        opcode: 'procedures_defnoreturn',
+        mutation: {proccode: 'fakeCode'},
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    return block;
+};
+
+var generateThread = function (runtime) {
+    var s = new Sprite();
+    var rt = new RenderedTarget(s, runtime);
+    var th = new Thread(randomString());
+    
+    var next = randomString();
+    var inp = randomString();
+    var name = th.topBlock;
+    
+    rt.blocks.createBlock(generateBlockInput(name, next, inp));
+    th.pushStack(name);
+    rt.blocks.createBlock(generateBlock(inp));
+    
+    for (var i = 0; i < 10; i++) {
+        name = next;
+        next = randomString();
+        inp = randomString();
+        
+        rt.blocks.createBlock(generateBlockInput(name, next, inp));
+        th.pushStack(name);
+        rt.blocks.createBlock(generateBlock(inp));
+    }
+    rt.blocks.createBlock(generateBlock(next));
+    th.pushStack(next);
+    th.target = rt;
+    
+    runtime.threads.push(th);
+
+    return th;
+};
+
+test('stepThread', function (t) {
+    var r = new Runtime();
+    var s = new Sequencer(r);
+    var th = generateThread(r);
+    t.notEquals(th.status, Thread.STATUS_DONE);
+    s.stepThread(th);
+    t.strictEquals(th.status, Thread.STATUS_DONE);
+    th = generateThread(r);
+    th.status = Thread.STATUS_YIELD;
+    s.stepThread(th);
+    t.notEquals(th.status, Thread.STATUS_DONE);
+    th.status = Thread.STATUS_PROMISE_WAIT;
+    s.stepThread(th);
+    t.notEquals(th.status, Thread.STATUS_DONE);
+    
+    t.end();
+});
+
+test('stepToBranch', function (t) {
+    var r = new Runtime();
+    var s = new Sequencer(r);
+    var th = generateThread(r);
+    s.stepToBranch(th, 2, false);
+    t.strictEquals(th.peekStack(), null);
+    th.popStack();
+    s.stepToBranch(th, 1, false);
+    t.strictEquals(th.peekStack(), null);
+    th.popStack();
+    th.popStack();
+    s.stepToBranch(th, 1, false);
+    t.notEquals(th.peekStack(), null);
+    
+    t.end();
+});
+
+test('retireThread', function (t) {
+    var r = new Runtime();
+    var s = new Sequencer(r);
+    var th = generateThread(r);
+    t.strictEquals(th.stack.length, 12);
+    s.retireThread(th);
+    t.strictEquals(th.stack.length, 0);
+    t.strictEquals(th.status, Thread.STATUS_DONE);
+    
+    t.end();
+});
+
+test('stepToProcedure', function (t) {
+    var r = new Runtime();
+    var s = new Sequencer(r);
+    var th = generateThread(r);
+    var expectedBlock = th.peekStack();
+    s.stepToProcedure(th, '');
+    t.strictEquals(th.peekStack(), expectedBlock);
+    s.stepToProcedure(th, 'faceCode');
+    t.strictEquals(th.peekStack(), expectedBlock);
+    s.stepToProcedure(th, 'faceCode');
+    th.target.blocks.getBlock(th.stack[th.stack.length - 4]).mutation.proccode = 'othercode';
+    expectedBlock = th.stack[th.stack.length - 4];
+    s.stepToProcedure(th, 'othercode');
+    t.strictEquals(th.peekStack(), expectedBlock);
+    
+    
+    t.end();
+});
+
+test('stepThreads', function (t) {
+    var r = new Runtime();
+    r.currentStepTime = Infinity;
+    var s = new Sequencer(r);
+    t.strictEquals(s.stepThreads().length, 0);
+    generateThread(r);
+    t.strictEquals(r.threads.length, 1);
+    t.strictEquals(s.stepThreads().length, 0);
+    r.threads[0].status = Thread.STATUS_RUNNING;
+    t.strictEquals(s.stepThreads().length, 1);
+    
     t.end();
 });
diff --git a/test/unit/engine_thread.js b/test/unit/engine_thread.js
index 3bda4fc69..815de5ca3 100644
--- a/test/unit/engine_thread.js
+++ b/test/unit/engine_thread.js
@@ -1,8 +1,277 @@
 var test = require('tap').test;
 var Thread = require('../../src/engine/thread');
+var RenderedTarget = require('../../src/sprites/rendered-target');
+var Sprite = require('../../src/sprites/sprite');
 
 test('spec', function (t) {
     t.type(Thread, 'function');
-    // @todo
+    
+    var th = new Thread('arbitraryString');
+    t.type(th, 'object');
+    t.ok(th instanceof Thread);
+    t.type(th.pushStack, 'function');
+    t.type(th.reuseStackForNextBlock, 'function');
+    t.type(th.popStack, 'function');
+    t.type(th.stopThisScript, 'function');
+    t.type(th.peekStack, 'function');
+    t.type(th.peekStackFrame, 'function');
+    t.type(th.peekParentStackFrame, 'function');
+    t.type(th.pushReportedValue, 'function');
+    t.type(th.pushParam, 'function');
+    t.type(th.peekStack, 'function');
+    t.type(th.getParam, 'function');
+    t.type(th.atStackTop, 'function');
+    t.type(th.goToNextBlock, 'function');
+    t.type(th.isRecursiveCall, 'function');
+    
+    t.end();
+});
+
+test('pushStack', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    
+    t.end();
+});
+
+test('popStack', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    t.strictEquals(th.popStack(), 'arbitraryString');
+    t.strictEquals(th.popStack(), undefined);
+    
+    t.end();
+});
+
+test('atStackTop', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    th.pushStack('secondString');
+    t.strictEquals(th.atStackTop(), false);
+    th.popStack();
+    t.strictEquals(th.atStackTop(), true);
+    
+    t.end();
+});
+
+test('reuseStackForNextBlock', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    th.reuseStackForNextBlock('secondString');
+    t.strictEquals(th.popStack(), 'secondString');
+    
+    t.end();
+});
+
+test('peekStackFrame', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    t.strictEquals(th.peekStackFrame().warpMode, false);
+    th.popStack();
+    t.strictEquals(th.peekStackFrame(), null);
+    
+    t.end();
+});
+
+test('peekParentStackFrame', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    th.peekStackFrame().warpMode = true;
+    t.strictEquals(th.peekParentStackFrame(), null);
+    th.pushStack('secondString');
+    t.strictEquals(th.peekParentStackFrame().warpMode, true);
+    
+    t.end();
+});
+
+test('pushReportedValue', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    th.pushStack('secondString');
+    th.pushReportedValue('value');
+    t.strictEquals(th.peekParentStackFrame().reported.null, 'value');
+    
+    t.end();
+});
+
+test('peekStack', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    t.strictEquals(th.peekStack(), 'arbitraryString');
+    th.popStack();
+    t.strictEquals(th.peekStack(), null);
+    
+    t.end();
+});
+
+test('PushGetParam', function (t) {
+    var th = new Thread('arbitraryString');
+    th.pushStack('arbitraryString');
+    th.pushParam('testParam', 'testValue');
+    t.strictEquals(th.peekStackFrame().params.testParam, 'testValue');
+    t.strictEquals(th.getParam('testParam'), 'testValue');
+    
+    t.end();
+});
+
+test('goToNextBlock', function (t) {
+    var th = new Thread('arbitraryString');
+    var s = new Sprite();
+    var rt = new RenderedTarget(s, null);
+    var block1 = {fields: Object,
+        id: 'arbitraryString',
+        inputs: Object,
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'STEPS',
+        next: 'secondString',
+        opcode: 'motion_movesteps',
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    var block2 = {fields: Object,
+        id: 'secondString',
+        inputs: Object,
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'STEPS',
+        next: null,
+        opcode: 'procedures_callnoreturn',
+        mutation: {proccode: 'fakeCode'},
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    
+    rt.blocks.createBlock(block1);
+    rt.blocks.createBlock(block2);
+    rt.blocks.createBlock(block2);
+    th.target = rt;
+    
+    t.strictEquals(th.peekStack(), null);
+    th.pushStack('secondString');
+    t.strictEquals(th.peekStack(), 'secondString');
+    th.goToNextBlock();
+    t.strictEquals(th.peekStack(), null);
+    th.pushStack('secondString');
+    th.pushStack('arbitraryString');
+    t.strictEquals(th.peekStack(), 'arbitraryString');
+    th.goToNextBlock();
+    t.strictEquals(th.peekStack(), 'secondString');
+    th.goToNextBlock();
+    t.strictEquals(th.peekStack(), null);
+    
+    t.end();
+});
+
+test('stopThisScript', function (t) {
+    var th = new Thread('arbitraryString');
+    var s = new Sprite();
+    var rt = new RenderedTarget(s, null);
+    var block1 = {fields: Object,
+        id: 'arbitraryString',
+        inputs: Object,
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'STEPS',
+        next: null,
+        opcode: 'motion_movesteps',
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    var block2 = {fields: Object,
+        id: 'secondString',
+        inputs: Object,
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'STEPS',
+        next: null,
+        opcode: 'procedures_callnoreturn',
+        mutation: {proccode: 'fakeCode'},
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    
+    rt.blocks.createBlock(block1);
+    rt.blocks.createBlock(block2);
+    th.target = rt;
+    
+    th.stopThisScript();
+    t.strictEquals(th.peekStack(), null);
+    th.pushStack('arbitraryString');
+    t.strictEquals(th.peekStack(), 'arbitraryString');
+    th.stopThisScript();
+    t.strictEquals(th.peekStack(), null);
+    th.pushStack('arbitraryString');
+    th.pushStack('secondString');
+    th.stopThisScript();
+    t.strictEquals(th.peekStack(), 'secondString');
+    
+    t.end();
+});
+
+test('isRecursiveCall', function (t) {
+    var th = new Thread('arbitraryString');
+    var s = new Sprite();
+    var rt = new RenderedTarget(s, null);
+    var block1 = {fields: Object,
+        id: 'arbitraryString',
+        inputs: Object,
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'STEPS',
+        next: null,
+        opcode: 'motion_movesteps',
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    var block2 = {fields: Object,
+        id: 'secondString',
+        inputs: Object,
+        STEPS: Object,
+        block: 'fakeBlock',
+        name: 'STEPS',
+        next: null,
+        opcode: 'procedures_callnoreturn',
+        mutation: {proccode: 'fakeCode'},
+        parent: null,
+        shadow: false,
+        topLevel: true,
+        x: 0,
+        y: 0
+    };
+    
+    rt.blocks.createBlock(block1);
+    rt.blocks.createBlock(block2);
+    th.target = rt;
+    
+    t.strictEquals(th.isRecursiveCall('fakeCode'), false);
+    th.pushStack('secondString');
+    t.strictEquals(th.isRecursiveCall('fakeCode'), false);
+    th.pushStack('arbitraryString');
+    t.strictEquals(th.isRecursiveCall('fakeCode'), true);
+    th.pushStack('arbitraryString');
+    t.strictEquals(th.isRecursiveCall('fakeCode'), true);
+    th.popStack();
+    t.strictEquals(th.isRecursiveCall('fakeCode'), true);
+    th.popStack();
+    t.strictEquals(th.isRecursiveCall('fakeCode'), false);
+    th.popStack();
+    t.strictEquals(th.isRecursiveCall('fakeCode'), false);
+    
     t.end();
 });
diff --git a/test/unit/util_filter-toolbox.js b/test/unit/util_filter-toolbox.js
new file mode 100644
index 000000000..9c3ea073c
--- /dev/null
+++ b/test/unit/util_filter-toolbox.js
@@ -0,0 +1,22 @@
+var toolboxes = require('../fixtures/toolboxes');
+var test = require('tap').test;
+var filterToolbox = require('../../src/util/filter-toolbox');
+
+test('categories', function (t) {
+    var filteredToolbox = filterToolbox(toolboxes.categories, ['motion_movesteps']);
+    t.strictEqual(filteredToolbox.children.length, 3);
+    t.strictEqual(filteredToolbox.firstElementChild.children.length, 1);
+    t.end();
+});
+
+test('simple', function (t) {
+    var filteredToolbox = filterToolbox(toolboxes.simple, ['motion_movesteps']);
+    t.strictEqual(filteredToolbox.children.length, 1);
+    t.end();
+});
+
+test('empty', function (t) {
+    var filteredToolbox = filterToolbox(toolboxes.empty, ['motion_movesteps']);
+    t.strictEqual(filteredToolbox.children.length, 0);
+    t.end();
+});
diff --git a/webpack.config.js b/webpack.config.js
index f58b7a1bf..29edbfcd1 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -5,7 +5,7 @@ var webpack = require('webpack');
 
 var base = {
     devServer: {
-        contentBase: path.resolve(__dirname, 'playground'),
+        contentBase: false,
         host: '0.0.0.0',
         port: process.env.PORT || 8073
     },
@@ -108,6 +108,8 @@ module.exports = [
                 to: 'media'
             }, {
                 from: 'node_modules/highlightjs/styles/zenburn.css'
+            }, {
+                from: 'src/playground'
             }])
         ])
     })