diff --git a/.gitignore b/.gitignore
index 753e3f651..aad54ff5e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,7 @@ npm-*
 /dist.js
 /vm.js
 /vm.min.js
+/playground/assets
 /playground/media
 /playground/vendor.js
 /playground/vm.js
diff --git a/src/blocks/scratch3_control.js b/src/blocks/scratch3_control.js
index efa0c2fb6..a2bab50e1 100644
--- a/src/blocks/scratch3_control.js
+++ b/src/blocks/scratch3_control.js
@@ -167,6 +167,7 @@ Scratch3ControlBlocks.prototype.createClone = function (args, util) {
 };
 
 Scratch3ControlBlocks.prototype.deleteClone = function (args, util) {
+    if (util.target.isOriginal) return;
     this.runtime.disposeTarget(util.target);
     this.runtime.stopForTarget(util.target);
 };
diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index 4a101147d..ea47a3ba9 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -369,17 +369,25 @@ Runtime.prototype.startHats = function (requestedHatOpcode,
 };
 
 /**
- * Dispose of a target.
- * @param {!Target} target Target to dispose of.
+ * Dispose all targets. Return to clean state.
  */
-Runtime.prototype.disposeTarget = function (target) {
-    // Allow target to do dispose actions.
-    target.dispose();
-    // Remove from list of targets.
-    var index = this.targets.indexOf(target);
-    if (index > -1) {
-        this.targets.splice(index, 1);
-    }
+Runtime.prototype.dispose = function () {
+    this.stopAll();
+    this.targets.map(this.disposeTarget, this);
+};
+
+/**
+ * Dispose of a target.
+ * @param {!Target} disposingTarget Target to dispose of.
+ */
+Runtime.prototype.disposeTarget = function (disposingTarget) {
+    this.targets = this.targets.filter(function (target) {
+        if (disposingTarget !== target) return true;
+        // Allow target to do dispose actions.
+        target.dispose();
+        // Remove from list of targets.
+        return false;
+    });
 };
 
 /**
diff --git a/src/index.js b/src/index.js
index 469e3fec0..818ea4f1a 100644
--- a/src/index.js
+++ b/src/index.js
@@ -73,6 +73,15 @@ VirtualMachine.prototype.stopAll = function () {
     this.runtime.stopAll();
 };
 
+/**
+ * Clear out current running project data.
+ */
+VirtualMachine.prototype.clear = function () {
+    this.runtime.dispose();
+    this.editingTarget = null;
+    this.emitTargetsUpdate();
+};
+
 /**
  * Get data for playground. Data comes back in an emitted event.
  */
@@ -116,6 +125,7 @@ VirtualMachine.prototype.postIOData = function (device, data) {
  * @param {?string} json JSON string representing the project.
  */
 VirtualMachine.prototype.loadProject = function (json) {
+    this.clear();
     // @todo: Handle other formats, e.g., Scratch 1.4, Scratch 3.0.
     sb2import(json, this.runtime);
     // Select the first target for editing, e.g., the stage.
@@ -237,7 +247,7 @@ VirtualMachine.prototype.emitTargetsUpdate = function () {
             return [target.id, target.getName()];
         }),
         // Currently editing target id.
-        editingTarget: this.editingTarget.id
+        editingTarget: this.editingTarget ? this.editingTarget.id : null
     });
 };
 
diff --git a/src/sprites/clone.js b/src/sprites/clone.js
index 4d7c3672c..f63bbfe09 100644
--- a/src/sprites/clone.js
+++ b/src/sprites/clone.js
@@ -418,9 +418,6 @@ Clone.prototype.onGreenFlag = function () {
  * Dispose of this clone, destroying any run-time properties.
  */
 Clone.prototype.dispose = function () {
-    if (this.isOriginal) { // Don't allow a non-clone to delete itself.
-        return;
-    }
     this.runtime.changeCloneCounter(-1);
     if (this.renderer && this.drawableID !== null) {
         this.renderer.destroyDrawable(this.drawableID);