diff --git a/demo.html b/demo.html
index 380d637..f44b0b6 100644
--- a/demo.html
+++ b/demo.html
@@ -29,7 +29,7 @@ graph.newEdge(dennis, bianca, {color: '#CC333F'});
 graph.newEdge(bianca, monty, {color: '#EB6841'});
 
 jQuery(function(){
-  var springy = jQuery('#springydemo').springy({
+  var springy = window.springy = jQuery('#springydemo').springy({
     graph: graph,
     nodeSelected: function(node){
       console.log('Node selected: ' + JSON.stringify(node.data));
diff --git a/springy.js b/springy.js
index ca75a8e..9bb9871 100644
--- a/springy.js
+++ b/springy.js
@@ -168,6 +168,10 @@ of nodes and edges:
     }
 
 **/
+	// parse if a string is passed (EC5+ browsers)
+	if (typeof json == 'string' || json instanceof String) {
+		json = JSON.parse( json );
+	}
 
 	if ('nodes' in json || 'edges' in json) {
 		this.addNodes.apply(this, json['nodes']);
@@ -464,6 +468,7 @@ Layout.ForceDirected.prototype.start = function(render, done) {
 
 	if (this._started) return;
 	this._started = true;
+	this._stop = false;
 
 	Layout.requestAnimationFrame(function step() {
 		t.applyCoulombsLaw();
@@ -477,7 +482,7 @@ Layout.ForceDirected.prototype.start = function(render, done) {
                 }
 
 		// stop simulation when energy of the system goes below a threshold
-		if (t.totalEnergy() < 0.01) {
+		if (t._stop || t.totalEnergy() < 0.01) {
 			t._started = false;
 			if (done !== undefined) { done(); }
 		} else {
@@ -486,6 +491,10 @@ Layout.ForceDirected.prototype.start = function(render, done) {
 	});
 };
 
+Layout.ForceDirected.prototype.stop = function() {
+  this._stop = true;
+}
+
 // Find the nearest point to a particular position
 Layout.ForceDirected.prototype.nearest = function(pos) {
 	var min = {node: null, point: null, distance: null};
@@ -624,6 +633,10 @@ Renderer.prototype.start = function() {
 	});
 };
 
+Renderer.prototype.stop = function() {
+  this.layout.stop();
+};
+
 // Array.forEach implementation for IE support..
 //https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/forEach
 if ( !Array.prototype.forEach ) {
diff --git a/springyui.js b/springyui.js
index 771dec9..8f80a3a 100755
--- a/springyui.js
+++ b/springyui.js
@@ -131,7 +131,7 @@ jQuery.fn.springy = function(params) {
 		return 20;
 	};
 
-	var renderer = new Renderer(layout,
+	var renderer = this.renderer = new Renderer(layout,
 		function clear() {
 			ctx.clearRect(0,0,canvas.width,canvas.height);
 		},