diff --git a/src/playground/index.html b/src/playground/index.html
index 2d2f1698c..d248b9847 100644
--- a/src/playground/index.html
+++ b/src/playground/index.html
@@ -73,7 +73,7 @@
     <script>
         function toJson() {
             var output = document.getElementById('importExport');
-            var json = window.vm.toPrettyJSON(Scratch.workspace);
+            var json = window.Scratch.vm.toJSON();
             output.value = json;
             output.focus();
             output.select();
@@ -81,7 +81,7 @@
 
           function fromJson() {
             var input = document.getElementById('importExport');
-            window.vm.fromJSON(input.value);
+            window.Scratch.vm.fromJSON(input.value);
           }
     </script>
 </body>
diff --git a/src/serialization/sb2.js b/src/serialization/sb2.js
index 53a7cfc4d..4278656f2 100644
--- a/src/serialization/sb2.js
+++ b/src/serialization/sb2.js
@@ -15,8 +15,8 @@ const specMap = require('./sb2_specmap');
 const Variable = require('../engine/variable');
 const List = require('../engine/list');
 
-const loadCostume = require('./load-costume.js');
-const loadSound = require('./load-sound.js');
+const loadCostume = require('../import/load-costume.js');
+const loadSound = require('../import/load-sound.js');
 
 /**
  * Convert a Scratch 2.0 procedure string (e.g., "my_procedure %s %b %n")
diff --git a/src/serialization/sb3.js b/src/serialization/sb3.js
index 7543b4cd1..4eb06dd5e 100644
--- a/src/serialization/sb3.js
+++ b/src/serialization/sb3.js
@@ -4,27 +4,26 @@
  * JSON and then generates all needed scratch-vm runtime structures.
  */
 
-var package = require('../../package.json');
-var Blocks = require('../engine/blocks');
-var RenderedTarget = require('../sprites/rendered-target');
-var Sprite = require('../sprites/sprite');
-var Variable = require('../engine/variable');
-var List = require('../engine/list');
+const vmPackage = require('../../package.json');
+const Blocks = require('../engine/blocks');
+const Sprite = require('../sprites/sprite');
+const Variable = require('../engine/variable');
+const List = require('../engine/list');
 
 /**
  * Serializes the specified VM runtime.
  * @param  {!Runtime} runtime VM runtime instance to be serialized.
  * @return {string}    Serialized runtime instance.
  */
-var serialize = function (runtime) {
+const serialize = function (runtime) {
     // Fetch targets
-    var obj = Object.create(null);
+    const obj = Object.create(null);
     obj.targets = runtime.targets;
 
     // Assemble metadata
-    var meta = Object.create(null);
+    const meta = Object.create(null);
     meta.semver = '3.0.0';
-    meta.vm = package.version;
+    meta.vm = vmPackage.version;
 
     // Attach full user agent string to metadata if available
     meta.agent = null;
@@ -37,36 +36,36 @@ var serialize = function (runtime) {
 
 /**
  * Parse a single "Scratch object" and create all its in-memory VM objects.
- * @param {!Object} object From-JSON "Scratch object:" sprite, stage, watcher.
+ * @param {!object} object From-JSON "Scratch object:" sprite, stage, watcher.
  * @param {!Runtime} runtime Runtime object to load all structures into.
  * @return {?Target} Target created (stage or sprite).
  */
-var parseScratchObject = function (object, runtime) {
+const parseScratchObject = function (object, runtime) {
     if (!object.hasOwnProperty('name')) {
         // Watcher/monitor - skip this object until those are implemented in VM.
         // @todo
         return;
     }
     // Blocks container for this object.
-    var blocks = new Blocks();
+    const blocks = new Blocks();
 
     // @todo: For now, load all Scratch objects (stage/sprites) as a Sprite.
-    var sprite = new Sprite(blocks, runtime);
+    const sprite = new Sprite(blocks, runtime);
 
     // Sprite/stage name from JSON.
     if (object.hasOwnProperty('name')) {
         sprite.name = object.name;
     }
     if (object.hasOwnProperty('blocks')) {
-        for (blockId in object.blocks) {
+        for (let blockId in object.blocks) {
             blocks.createBlock(object.blocks[blockId]);
         }
-        console.log(blocks);
+        // console.log(blocks);
     }
     // Costumes from JSON.
     if (object.hasOwnProperty('costumes') || object.hasOwnProperty('costume')) {
-        for (var i = 0; i < object.costumeCount; i++) {
-            var costume = object.costumes[i];
+        for (let i = 0; i < object.costumeCount; i++) {
+            const costume = object.costumes[i];
             // @todo: Make sure all the relevant metadata is being pulled out.
             sprite.costumes.push({
                 skin: costume.skin,
@@ -79,8 +78,8 @@ var parseScratchObject = function (object, runtime) {
     }
     // Sounds from JSON
     if (object.hasOwnProperty('sounds')) {
-        for (var s = 0; s < object.sounds.length; s++) {
-            var sound = object.sounds[s];
+        for (let s = 0; s < object.sounds.length; s++) {
+            const sound = object.sounds[s];
             sprite.sounds.push({
                 format: sound.format,
                 fileUrl: sound.fileUrl,
@@ -93,13 +92,13 @@ var parseScratchObject = function (object, runtime) {
         }
     }
     // Create the first clone, and load its run-state from JSON.
-    var target = sprite.createClone();
+    const target = sprite.createClone();
     // Add it to the runtime's list of targets.
     runtime.targets.push(target);
     // Load target properties from JSON.
     if (object.hasOwnProperty('variables')) {
-        for (var j = 0; j < object.variables.length; j++) {
-            var variable = object.variables[j];
+        for (let j = 0; j < object.variables.length; j++) {
+            const variable = object.variables[j];
             target.variables[variable.name] = new Variable(
                 variable.name,
                 variable.value,
@@ -108,8 +107,8 @@ var parseScratchObject = function (object, runtime) {
         }
     }
     if (object.hasOwnProperty('lists')) {
-        for (var k = 0; k < object.lists.length; k++) {
-            var list = object.lists[k];
+        for (let k = 0; k < object.lists.length; k++) {
+            const list = object.lists[k];
             // @todo: monitor properties.
             target.lists[list.listName] = new List(
                 list.listName,
@@ -143,8 +142,8 @@ var parseScratchObject = function (object, runtime) {
     }
     target.updateAllDrawableProperties();
 
-    console.log("returning target:");
-    console.log(target);
+    // console.log('returning target:');
+    // console.log(target);
     return target;
 };
 
@@ -154,8 +153,8 @@ var parseScratchObject = function (object, runtime) {
  * @param  {string}  json    Stringified JSON representation of a VM runtime.
  * @param  {Runtime} runtime Runtime instance
  */
-var deserialize = function (json, runtime) {
-    for (var i = 0; i < json.targets.length; i++) {
+const deserialize = function (json, runtime) {
+    for (let i = 0; i < json.targets.length; i++) {
         parseScratchObject(json.targets[i], runtime);
     }
 };
diff --git a/src/virtual-machine.js b/src/virtual-machine.js
index a69539a06..745d9089a 100644
--- a/src/virtual-machine.js
+++ b/src/virtual-machine.js
@@ -145,22 +145,7 @@ class VirtualMachine extends EventEmitter {
      */
     loadProject (json) {
         // @todo: Handle other formats, e.g., Scratch 1.4, Scratch 3.0.
-        return this.fromJSON(json, this.runtime).then(targets => {
-            this.clear();
-            for (let n = 0; n < targets.length; n++) {
-                if (targets[n] !== null) {
-                    this.runtime.targets.push(targets[n]);
-                    targets[n].updateAllDrawableProperties();
-                }
-            }
-        // Select the first target for editing, e.g., the first sprite.
-            this.editingTarget = this.runtime.targets[1];
-
-        // Update the VM user's knowledge of targets and blocks on the workspace.
-            this.emitTargetsUpdate();
-            this.emitWorkspaceUpdate();
-            this.runtime.setEditingTarget(this.editingTarget);
-        });
+        return this.fromJSON(json);
     }
 
     /**
@@ -181,7 +166,7 @@ class VirtualMachine extends EventEmitter {
     }
 
     /**
-     * return a project in a Scratch 3.0 JSON representation.
+     * @returns {string} Project in a Scratch 3.0 JSON representation.
      */
     saveProjectSb3 () {
         // @todo: Handle other formats, e.g., Scratch 1.4, Scratch 2.0.
@@ -199,6 +184,7 @@ class VirtualMachine extends EventEmitter {
     /**
      * Load a project from a Scratch JSON representation.
      * @param {string} json JSON string representing a project.
+     * @returns {Promise} Promise that resolves after the project has loaded
      */
     fromJSON (json) {
         // Clear the current runtime
@@ -214,38 +200,46 @@ class VirtualMachine extends EventEmitter {
         // @todo This is an extremely naïve / dangerous way of determining version.
         //       See `scratch-parser` for a more sophisticated validation
         //       methodology that should be adapted for use here
-        if ((typeof json.meta !== 'undefined') && (typeof json.meta.semver !== 'undefined') ) {
-            sb3.deserialize(json, this.runtime);
+        let deserializer;
+        if ((typeof json.meta !== 'undefined') && (typeof json.meta.semver !== 'undefined')) {
+            deserializer = sb3;
         } else {
-            sb2.deserialize(json, this.runtime);
+            deserializer = sb2;
         }
 
-        // Select the first target for editing, e.g., the first sprite.
-        this.editingTarget = this.runtime.targets[1];
+        return deserializer.deserialize(json, this.runtime).then(targets => {
+            this.clear();
+            for (let n = 0; n < targets.length; n++) {
+                if (targets[n] !== null) {
+                    this.runtime.targets.push(targets[n]);
+                    targets[n].updateAllDrawableProperties();
+                }
+            }
+            // Select the first target for editing, e.g., the first sprite.
+            this.editingTarget = this.runtime.targets[1];
 
-        // Update the VM user's knowledge of targets and blocks on the workspace.
-        this.emitTargetsUpdate();
-        this.emitWorkspaceUpdate();
-        this.runtime.setEditingTarget(this.editingTarget);
+            // Update the VM user's knowledge of targets and blocks on the workspace.
+            this.emitTargetsUpdate();
+            this.emitWorkspaceUpdate();
+            this.runtime.setEditingTarget(this.editingTarget);
+        });
     }
 
     /**
      * Add a single sprite from the "Sprite2" (i.e., SB2 sprite) format.
      * @param {string} json JSON string representing the sprite.
+     * @returns {Promise} Promise that resolves after the sprite is added
      */
     addSprite2 (json) {
     // Select new sprite.
-        this.editingTarget = sb2.deserialize(json, this.runtime, true);
-        /* @todo Promisify this
-            .then(targets => {
-                this.runtime.targets.push(targets[0]);
-                this.editingTarget = targets[0];
-            })
-        */
-        // Update the VM user's knowledge of targets and blocks on the workspace.
-        this.emitTargetsUpdate();
-        this.emitWorkspaceUpdate();
-        this.runtime.setEditingTarget(this.editingTarget);
+        return sb2.deserialize(json, this.runtime, true).then(targets => {
+            this.runtime.targets.push(targets[0]);
+            this.editingTarget = targets[0];
+            // Update the VM user's knowledge of targets and blocks on the workspace.
+            this.emitTargetsUpdate();
+            this.emitWorkspaceUpdate();
+            this.runtime.setEditingTarget(this.editingTarget);
+        });
     }
 
     /**
diff --git a/test/integration/import_sb2.js b/test/integration/import_sb2.js
index 547b645ea..2602783fd 100644
--- a/test/integration/import_sb2.js
+++ b/test/integration/import_sb2.js
@@ -5,7 +5,7 @@ const extract = require('../fixtures/extract');
 
 const renderedTarget = require('../../src/sprites/rendered-target');
 const runtime = require('../../src/engine/runtime');
-const sb2 = require('../../src/import/sb2import');
+const sb2 = require('../../src/serialization/sb2');
 
 test('spec', t => {
     t.type(sb2, 'function');
diff --git a/test/unit/serialization_sb2.js b/test/unit/serialization_sb2.js
index 530311d33..7a0bec03f 100644
--- a/test/unit/serialization_sb2.js
+++ b/test/unit/serialization_sb2.js
@@ -1,51 +1,53 @@
-var path = require('path');
-var test = require('tap').test;
-var extract = require('../fixtures/extract');
+const path = require('path');
+const test = require('tap').test;
+const extract = require('../fixtures/extract');
 
-var renderedTarget = require('../../src/sprites/rendered-target');
-var runtime = require('../../src/engine/runtime');
-var sb2 = require('../../src/serialization/sb2');
+const RenderedTarget = require('../../src/sprites/rendered-target');
+const Runtime = require('../../src/engine/runtime');
+const sb2 = require('../../src/serialization/sb2');
 
-test('spec', function (t) {
+test('spec', t => {
     t.type(sb2, 'object');
     t.type(sb2.deserialize, 'function');
     t.end();
 });
 
-test('default', function (t) {
+test('default', t => {
     // Get SB2 JSON (string)
-    var uri = path.resolve(__dirname, '../fixtures/default.sb2');
-    var file = extract(uri);
+    const uri = path.resolve(__dirname, '../fixtures/default.sb2');
+    const file = extract(uri);
 
     // Create runtime instance & load SB2 into it
-    var rt = new runtime();
-    sb2.deserialize(file, rt);
+    const rt = new Runtime();
+    sb2.deserialize(file, rt).then(targets => {
+        console.dir(targets);
 
-    // Test
-    t.type(file, 'string');
-    t.type(rt, 'object');
-    t.type(rt.targets, 'object');
+        // Test
+        t.type(file, 'string');
+        t.type(rt, 'object');
+        t.type(targets, 'object');
 
-    t.ok(rt.targets[0] instanceof renderedTarget);
-    t.type(rt.targets[0].id, 'string');
-    t.type(rt.targets[0].blocks, 'object');
-    t.type(rt.targets[0].variables, 'object');
-    t.type(rt.targets[0].lists, 'object');
+        t.ok(targets[0] instanceof RenderedTarget);
+        t.type(targets[0].id, 'string');
+        t.type(targets[0].blocks, 'object');
+        t.type(targets[0].variables, 'object');
+        t.type(targets[0].lists, 'object');
 
-    t.equal(rt.targets[0].isOriginal, true);
-    t.equal(rt.targets[0].currentCostume, 0);
-    t.equal(rt.targets[0].isOriginal, true);
-    t.equal(rt.targets[0].isStage, true);
+        t.equal(targets[0].isOriginal, true);
+        t.equal(targets[0].currentCostume, 0);
+        t.equal(targets[0].isOriginal, true);
+        t.equal(targets[0].isStage, true);
 
-    t.ok(rt.targets[1] instanceof renderedTarget);
-    t.type(rt.targets[1].id, 'string');
-    t.type(rt.targets[1].blocks, 'object');
-    t.type(rt.targets[1].variables, 'object');
-    t.type(rt.targets[1].lists, 'object');
+        t.ok(targets[1] instanceof RenderedTarget);
+        t.type(targets[1].id, 'string');
+        t.type(targets[1].blocks, 'object');
+        t.type(targets[1].variables, 'object');
+        t.type(targets[1].lists, 'object');
 
-    t.equal(rt.targets[1].isOriginal, true);
-    t.equal(rt.targets[1].currentCostume, 0);
-    t.equal(rt.targets[1].isOriginal, true);
-    t.equal(rt.targets[1].isStage, false);
-    t.end();
+        t.equal(targets[1].isOriginal, true);
+        t.equal(targets[1].currentCostume, 0);
+        t.equal(targets[1].isOriginal, true);
+        t.equal(targets[1].isStage, false);
+        t.end();
+    });
 });
diff --git a/test/unit/serialization_sb3.js b/test/unit/serialization_sb3.js
index 0ec56284d..761b0b54c 100644
--- a/test/unit/serialization_sb3.js
+++ b/test/unit/serialization_sb3.js
@@ -1,19 +1,19 @@
-var test = require('tap').test;
-var VirtualMachine = require('../../src/index');
-var sb3 = require('../../src/serialization/sb3');
+const test = require('tap').test;
+const VirtualMachine = require('../../src/index');
+const sb3 = require('../../src/serialization/sb3');
 
-test('serialize', function (t) {
-    var vm = new VirtualMachine();
+test('serialize', t => {
+    const vm = new VirtualMachine();
     vm.fromJSON(JSON.stringify(require('../fixtures/demo.json')));
-    var result = sb3.serialize(vm.runtime);
+    const result = sb3.serialize(vm.runtime);
     console.dir(JSON.stringify(result));
-    // @todo Analyize
+    // @todo Analyze
     t.end();
 });
 
-test('deserialize', function (t) {
-    var vm = new VirtualMachine();
-    var result = sb3.deserialize('', vm.runtime);
+test('deserialize', t => {
+    const vm = new VirtualMachine();
+    const result = sb3.deserialize('', vm.runtime);
     // @todo Analyize
     t.end();
 });