diff --git a/demo-json.html b/demo-json.html
index 2cd8760..8979a1e 100644
--- a/demo-json.html
+++ b/demo-json.html
@@ -22,7 +22,7 @@ var graphJSON = {
 };
 
 jQuery(function(){
-  var graph = new Graph();
+  var graph = new Springy.Graph();
   graph.loadJSON(graphJSON);
 
   var springy = jQuery('#springydemo').springy({
diff --git a/demo-raphael.html b/demo-raphael.html
index 03d0f68..60edd80 100644
--- a/demo-raphael.html
+++ b/demo-raphael.html
@@ -112,7 +112,7 @@ Raphael.fn.connection = function (obj1, obj2, style) {
 </script>
 
 <script>
-var graph = new Graph();
+var graph = new Springy.Graph();
 
 var dennis = graph.newNode({label: 'Dennis'});
 var michael = graph.newNode({label: 'Michael'});
@@ -166,16 +166,16 @@ function moveSet(set, x, y) {
 }
 
 function doit() {
-    var layout = new Layout.ForceDirected(graph, 640, 480.0, 0.5);
+    var layout = new Springy.Layout.ForceDirected(graph, 640, 480.0, 0.5);
 
     var r = Raphael("holder", 640, 480);
 
 	// calculate bounding box of graph layout.. with ease-in
 	var currentBB = layout.getBoundingBox();
-	var targetBB = {bottomleft: new Vector(-2, -2), topright: new Vector(2, 2)};
+	var targetBB = {bottomleft: new Springy.Vector(-2, -2), topright: new Springy.Vector(2, 2)};
 
 	// auto adjusting bounding box
-	Layout.requestAnimationFrame(function adjust() {
+	Springy.requestAnimationFrame(function adjust() {
 		targetBB = layout.getBoundingBox();
 		// current gets 20% closer to target every iteration
 		currentBB = {
@@ -185,7 +185,7 @@ function doit() {
 				.divide(10))
 		};
 
-		Layout.requestAnimationFrame(adjust);
+		Springy.requestAnimationFrame(adjust);
 	});
 
 	// convert to/from screen coordinates
@@ -193,11 +193,11 @@ function doit() {
 		var size = currentBB.topright.subtract(currentBB.bottomleft);
 		var sx = p.subtract(currentBB.bottomleft).divide(size.x).x * r.width;
 		var sy = p.subtract(currentBB.bottomleft).divide(size.y).y * r.height;
-		return new Vector(sx, sy);
+		return new Springy.Vector(sx, sy);
 	};
 
 
-    var renderer = new Renderer(layout,
+    var renderer = new Springy.Renderer(layout,
         function clear() {
             // code to clear screen
         },
diff --git a/demo-simple.html b/demo-simple.html
index 84195be..6a0eb57 100644
--- a/demo-simple.html
+++ b/demo-simple.html
@@ -4,7 +4,7 @@
 <script src="springy.js"></script>
 <script src="springyui.js"></script>
 <script>
-var graph = new Graph();
+var graph = new Springy.Graph();
 graph.addNodes('Dennis', 'Michael', 'Jessica', 'Timothy', 'Barbara')
 graph.addNodes('Amphitryon', 'Alcmene', 'Iphicles', 'Heracles');
 
diff --git a/demo.html b/demo.html
index b402107..8035277 100644
--- a/demo.html
+++ b/demo.html
@@ -4,7 +4,7 @@
 <script src="springy.js"></script>
 <script src="springyui.js"></script>
 <script>
-var graph = new Graph();
+var graph = new Springy.Graph();
 
 var dennis = graph.newNode({
   label: 'Dennis',
diff --git a/springy.js b/springy.js
index bb15d15..569ebe0 100644
--- a/springy.js
+++ b/springy.js
@@ -25,643 +25,655 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
-// Enable strict mode for EC5 compatible browsers
-"use strict";
+(function() {
+	// Enable strict mode for EC5 compatible browsers
+	"use strict";
 
-var Graph = function() {
-	this.nodeSet = {};
-	this.nodes = [];
-	this.edges = [];
-	this.adjacency = {};
+	// Establish the root object, `window` in the browser, or `global` on the server.
+	var root = this;
 
-	this.nextNodeId = 0;
-	this.nextEdgeId = 0;
-	this.eventListeners = [];
-};
-
-var Node = function(id, data) {
-	this.id = id;
-	this.data = (data !== undefined) ? data : {};
-
-// Data fields used by layout algorithm in this file:
-// this.data.mass
-// Data used by default renderer in springyui.js
-// this.data.label
-};
-
-var Edge = function(id, source, target, data) {
-	this.id = id;
-				/** @type {Node} */
-	this.source = source;
-	this.target = target;
-	this.data = (data !== undefined) ? data : {};
-
-// Edge data field used by layout alorithm
-// this.data.length
-// this.data.type
-};
-
-Graph.prototype.addNode = function(node) {
-	if (!(node.id in this.nodeSet)) {
-		this.nodes.push(node);
+	// The top-level namespace. All public Springy classes and modules will
+	// be attached to this. Exported for both CommonJS and the browser.
+	var Springy;
+	if (typeof exports !== 'undefined') {
+		Springy = exports;
+	} else {
+		Springy = root.Springy = {};
 	}
 
-	this.nodeSet[node.id] = node;
+	var Graph = Springy.Graph = function() {
+		this.nodeSet = {};
+		this.nodes = [];
+		this.edges = [];
+		this.adjacency = {};
 
-	this.notify();
-	return node;
-};
+		this.nextNodeId = 0;
+		this.nextEdgeId = 0;
+		this.eventListeners = [];
+	};
 
-Graph.prototype.addNodes = function() {
-	// accepts variable number of arguments, where each argument
-	// is a string that becomes both node identifier and label
-	for (var i = 0; i < arguments.length; i++) {
-		var name = arguments[i];
-		var node = new Node(name, {label:name});
-		this.addNode(node);
-	}
-};
+	var Node = Springy.Node = function(id, data) {
+		this.id = id;
+		this.data = (data !== undefined) ? data : {};
 
-Graph.prototype.addEdge = function(edge) {
-	var exists = false;
-	this.edges.forEach(function(e) {
-		if (edge.id === e.id) { exists = true; }
-	});
+	// Data fields used by layout algorithm in this file:
+	// this.data.mass
+	// Data used by default renderer in springyui.js
+	// this.data.label
+	};
 
-	if (!exists) {
-		this.edges.push(edge);
-	}
+	var Edge = Springy.Edge = function(id, source, target, data) {
+		this.id = id;
+		this.source = source;
+		this.target = target;
+		this.data = (data !== undefined) ? data : {};
 
-	if (!(edge.source.id in this.adjacency)) {
-		this.adjacency[edge.source.id] = {};
-	}
-	if (!(edge.target.id in this.adjacency[edge.source.id])) {
-		this.adjacency[edge.source.id][edge.target.id] = [];
-	}
+	// Edge data field used by layout alorithm
+	// this.data.length
+	// this.data.type
+	};
 
-	exists = false;
-	this.adjacency[edge.source.id][edge.target.id].forEach(function(e) {
+	Graph.prototype.addNode = function(node) {
+		if (!(node.id in this.nodeSet)) {
+			this.nodes.push(node);
+		}
+
+		this.nodeSet[node.id] = node;
+
+		this.notify();
+		return node;
+	};
+
+	Graph.prototype.addNodes = function() {
+		// accepts variable number of arguments, where each argument
+		// is a string that becomes both node identifier and label
+		for (var i = 0; i < arguments.length; i++) {
+			var name = arguments[i];
+			var node = new Node(name, {label:name});
+			this.addNode(node);
+		}
+	};
+
+	Graph.prototype.addEdge = function(edge) {
+		var exists = false;
+		this.edges.forEach(function(e) {
 			if (edge.id === e.id) { exists = true; }
-	});
+		});
 
-	if (!exists) {
-		this.adjacency[edge.source.id][edge.target.id].push(edge);
-	}
-
-	this.notify();
-	return edge;
-};
-
-Graph.prototype.addEdges = function() {
-	// accepts variable number of arguments, where each argument
-	// is a triple [nodeid1, nodeid2, attributes]
-	for (var i = 0; i < arguments.length; i++) {
-		var e = arguments[i];
-		var node1 = this.nodeSet[e[0]];
-		if (node1 == undefined) {
-			throw new TypeError("invalid node name: " + e[0]);
+		if (!exists) {
+			this.edges.push(edge);
 		}
-		var node2 = this.nodeSet[e[1]];
-		if (node2 == undefined) {
-			throw new TypeError("invalid node name: " + e[1]);
+
+		if (!(edge.source.id in this.adjacency)) {
+			this.adjacency[edge.source.id] = {};
+		}
+		if (!(edge.target.id in this.adjacency[edge.source.id])) {
+			this.adjacency[edge.source.id][edge.target.id] = [];
 		}
-		var attr = e[2];
 
-		this.newEdge(node1, node2, attr);
-	}
-};
+		exists = false;
+		this.adjacency[edge.source.id][edge.target.id].forEach(function(e) {
+				if (edge.id === e.id) { exists = true; }
+		});
 
-Graph.prototype.newNode = function(data) {
-	var node = new Node(this.nextNodeId++, data);
-	this.addNode(node);
-	return node;
-};
+		if (!exists) {
+			this.adjacency[edge.source.id][edge.target.id].push(edge);
+		}
 
-Graph.prototype.newEdge = function(source, target, data) {
-	var edge = new Edge(this.nextEdgeId++, source, target, data);
-	this.addEdge(edge);
-	return edge;
-};
+		this.notify();
+		return edge;
+	};
+
+	Graph.prototype.addEdges = function() {
+		// accepts variable number of arguments, where each argument
+		// is a triple [nodeid1, nodeid2, attributes]
+		for (var i = 0; i < arguments.length; i++) {
+			var e = arguments[i];
+			var node1 = this.nodeSet[e[0]];
+			if (node1 == undefined) {
+				throw new TypeError("invalid node name: " + e[0]);
+			}
+			var node2 = this.nodeSet[e[1]];
+			if (node2 == undefined) {
+				throw new TypeError("invalid node name: " + e[1]);
+			}
+			var attr = e[2];
+
+			this.newEdge(node1, node2, attr);
+		}
+	};
+
+	Graph.prototype.newNode = function(data) {
+		var node = new Node(this.nextNodeId++, data);
+		this.addNode(node);
+		return node;
+	};
+
+	Graph.prototype.newEdge = function(source, target, data) {
+		var edge = new Edge(this.nextEdgeId++, source, target, data);
+		this.addEdge(edge);
+		return edge;
+	};
 
 
-// add nodes and edges from JSON object
-Graph.prototype.loadJSON = function(json) {
-/**
-Springy's simple JSON format for graphs.
+	// add nodes and edges from JSON object
+	Graph.prototype.loadJSON = function(json) {
+	/**
+	Springy's simple JSON format for graphs.
 
-historically, Springy uses separate lists
-of nodes and edges:
+	historically, Springy uses separate lists
+	of nodes and edges:
 
-	{
-		"nodes": [
-			"center",
-			"left",
-			"right",
-			"up",
-			"satellite"
-		],
-		"edges": [
-			["center", "left"],
-			["center", "right"],
-			["center", "up"]
-		]
-	}
+		{
+			"nodes": [
+				"center",
+				"left",
+				"right",
+				"up",
+				"satellite"
+			],
+			"edges": [
+				["center", "left"],
+				["center", "right"],
+				["center", "up"]
+			]
+		}
 
-**/
-	// parse if a string is passed (EC5+ browsers)
-	if (typeof json == 'string' || json instanceof String) {
-		json = JSON.parse( json );
-	}
+	**/
+		// 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']);
-		this.addEdges.apply(this, json['edges']);
-	}
-}
-
-
-// find the edges from node1 to node2
-Graph.prototype.getEdges = function(node1, node2) {
-	if (node1.id in this.adjacency
-		&& node2.id in this.adjacency[node1.id]) {
-		return this.adjacency[node1.id][node2.id];
-	}
-
-	return [];
-};
-
-// remove a node and it's associated edges from the graph
-Graph.prototype.removeNode = function(node) {
-	if (node.id in this.nodeSet) {
-		delete this.nodeSet[node.id];
-	}
-
-	for (var i = this.nodes.length - 1; i >= 0; i--) {
-		if (this.nodes[i].id === node.id) {
-			this.nodes.splice(i, 1);
+		if ('nodes' in json || 'edges' in json) {
+			this.addNodes.apply(this, json['nodes']);
+			this.addEdges.apply(this, json['edges']);
 		}
 	}
 
-	this.detachNode(node);
 
-};
-
-// removes edges associated with a given node
-Graph.prototype.detachNode = function(node) {
-	var tmpEdges = this.edges.slice();
-	tmpEdges.forEach(function(e) {
-		if (e.source.id === node.id || e.target.id === node.id) {
-			this.removeEdge(e);
+	// find the edges from node1 to node2
+	Graph.prototype.getEdges = function(node1, node2) {
+		if (node1.id in this.adjacency
+			&& node2.id in this.adjacency[node1.id]) {
+			return this.adjacency[node1.id][node2.id];
 		}
-	}, this);
 
-	this.notify();
-};
+		return [];
+	};
 
-// remove a node and it's associated edges from the graph
-Graph.prototype.removeEdge = function(edge) {
-	for (var i = this.edges.length - 1; i >= 0; i--) {
-		if (this.edges[i].id === edge.id) {
-			this.edges.splice(i, 1);
+	// remove a node and it's associated edges from the graph
+	Graph.prototype.removeNode = function(node) {
+		if (node.id in this.nodeSet) {
+			delete this.nodeSet[node.id];
 		}
-	}
 
-	for (var x in this.adjacency) {
-		for (var y in this.adjacency[x]) {
-			var edges = this.adjacency[x][y];
+		for (var i = this.nodes.length - 1; i >= 0; i--) {
+			if (this.nodes[i].id === node.id) {
+				this.nodes.splice(i, 1);
+			}
+		}
 
-			for (var j=edges.length - 1; j>=0; j--) {
-				if (this.adjacency[x][y][j].id === edge.id) {
-					this.adjacency[x][y].splice(j, 1);
+		this.detachNode(node);
+
+	};
+
+	// removes edges associated with a given node
+	Graph.prototype.detachNode = function(node) {
+		var tmpEdges = this.edges.slice();
+		tmpEdges.forEach(function(e) {
+			if (e.source.id === node.id || e.target.id === node.id) {
+				this.removeEdge(e);
+			}
+		}, this);
+
+		this.notify();
+	};
+
+	// remove a node and it's associated edges from the graph
+	Graph.prototype.removeEdge = function(edge) {
+		for (var i = this.edges.length - 1; i >= 0; i--) {
+			if (this.edges[i].id === edge.id) {
+				this.edges.splice(i, 1);
+			}
+		}
+
+		for (var x in this.adjacency) {
+			for (var y in this.adjacency[x]) {
+				var edges = this.adjacency[x][y];
+
+				for (var j=edges.length - 1; j>=0; j--) {
+					if (this.adjacency[x][y][j].id === edge.id) {
+						this.adjacency[x][y].splice(j, 1);
+					}
 				}
 			}
 		}
-	}
 
-	this.notify();
-};
-
-/* Merge a list of nodes and edges into the current graph. eg.
-var o = {
-	nodes: [
-		{id: 123, data: {type: 'user', userid: 123, displayname: 'aaa'}},
-		{id: 234, data: {type: 'user', userid: 234, displayname: 'bbb'}}
-	],
-	edges: [
-		{from: 0, to: 1, type: 'submitted_design', directed: true, data: {weight: }}
-	]
-}
-*/
-Graph.prototype.merge = function(data) {
-	var nodes = [];
-	data.nodes.forEach(function(n) {
-		nodes.push(this.addNode(new Node(n.id, n.data)));
-	}, this);
-
-	data.edges.forEach(function(e) {
-		var from = nodes[e.from];
-		var to = nodes[e.to];
-
-		var id = (e.directed)
-			? (id = e.type + "-" + from.id + "-" + to.id)
-			: (from.id < to.id) // normalise id for non-directed edges
-				? e.type + "-" + from.id + "-" + to.id
-				: e.type + "-" + to.id + "-" + from.id;
-
-		var edge = this.addEdge(new Edge(id, from, to, e.data));
-		edge.data.type = e.type;
-	}, this);
-};
-
-Graph.prototype.filterNodes = function(fn) {
-	var tmpNodes = this.nodes.slice();
-	tmpNodes.forEach(function(n) {
-		if (!fn(n)) {
-			this.removeNode(n);
-		}
-	}, this);
-};
-
-Graph.prototype.filterEdges = function(fn) {
-	var tmpEdges = this.edges.slice();
-	tmpEdges.forEach(function(e) {
-		if (!fn(e)) {
-			this.removeEdge(e);
-		}
-	}, this);
-};
-
-
-Graph.prototype.addGraphListener = function(obj) {
-	this.eventListeners.push(obj);
-};
-
-Graph.prototype.notify = function() {
-	this.eventListeners.forEach(function(obj){
-		obj.graphChanged();
-	});
-};
-
-// -----------
-var Layout = {};
-Layout.ForceDirected = function(graph, stiffness, repulsion, damping) {
-	this.graph = graph;
-	this.stiffness = stiffness; // spring stiffness constant
-	this.repulsion = repulsion; // repulsion constant
-	this.damping = damping; // velocity damping factor
-
-	this.nodePoints = {}; // keep track of points associated with nodes
-	this.edgeSprings = {}; // keep track of springs associated with edges
-};
-
-Layout.ForceDirected.prototype.point = function(node) {
-	if (!(node.id in this.nodePoints)) {
-		var mass = (node.data.mass !== undefined) ? node.data.mass : 1.0;
-		this.nodePoints[node.id] = new Layout.ForceDirected.Point(Vector.random(), mass);
-	}
-
-	return this.nodePoints[node.id];
-};
-
-Layout.ForceDirected.prototype.spring = function(edge) {
-	if (!(edge.id in this.edgeSprings)) {
-		var length = (edge.data.length !== undefined) ? edge.data.length : 1.0;
-
-		var existingSpring = false;
-
-		var from = this.graph.getEdges(edge.source, edge.target);
-		from.forEach(function(e) {
-			if (existingSpring === false && e.id in this.edgeSprings) {
-				existingSpring = this.edgeSprings[e.id];
-			}
-		}, this);
-
-		if (existingSpring !== false) {
-			return new Layout.ForceDirected.Spring(existingSpring.point1, existingSpring.point2, 0.0, 0.0);
-		}
-
-		var to = this.graph.getEdges(edge.target, edge.source);
-		from.forEach(function(e){
-			if (existingSpring === false && e.id in this.edgeSprings) {
-				existingSpring = this.edgeSprings[e.id];
-			}
-		}, this);
-
-		if (existingSpring !== false) {
-			return new Layout.ForceDirected.Spring(existingSpring.point2, existingSpring.point1, 0.0, 0.0);
-		}
-
-		this.edgeSprings[edge.id] = new Layout.ForceDirected.Spring(
-			this.point(edge.source), this.point(edge.target), length, this.stiffness
-		);
-	}
-
-	return this.edgeSprings[edge.id];
-};
-
-// callback should accept two arguments: Node, Point
-Layout.ForceDirected.prototype.eachNode = function(callback) {
-	var t = this;
-	this.graph.nodes.forEach(function(n){
-		callback.call(t, n, t.point(n));
-	});
-};
-
-// callback should accept two arguments: Edge, Spring
-Layout.ForceDirected.prototype.eachEdge = function(callback) {
-	var t = this;
-	this.graph.edges.forEach(function(e){
-		callback.call(t, e, t.spring(e));
-	});
-};
-
-// callback should accept one argument: Spring
-Layout.ForceDirected.prototype.eachSpring = function(callback) {
-	var t = this;
-	this.graph.edges.forEach(function(e){
-		callback.call(t, t.spring(e));
-	});
-};
-
-
-// Physics stuff
-Layout.ForceDirected.prototype.applyCoulombsLaw = function() {
-	this.eachNode(function(n1, point1) {
-		this.eachNode(function(n2, point2) {
-			if (point1 !== point2)
-			{
-				var d = point1.p.subtract(point2.p);
-				var distance = d.magnitude() + 0.1; // avoid massive forces at small distances (and divide by zero)
-				var direction = d.normalise();
-
-				// apply force to each end point
-				point1.applyForce(direction.multiply(this.repulsion).divide(distance * distance * 0.5));
-				point2.applyForce(direction.multiply(this.repulsion).divide(distance * distance * -0.5));
-			}
-		});
-	});
-};
-
-Layout.ForceDirected.prototype.applyHookesLaw = function() {
-	this.eachSpring(function(spring){
-		var d = spring.point2.p.subtract(spring.point1.p); // the direction of the spring
-		var displacement = spring.length - d.magnitude();
-		var direction = d.normalise();
-
-		// apply force to each end point
-		spring.point1.applyForce(direction.multiply(spring.k * displacement * -0.5));
-		spring.point2.applyForce(direction.multiply(spring.k * displacement * 0.5));
-	});
-};
-
-Layout.ForceDirected.prototype.attractToCentre = function() {
-	this.eachNode(function(node, point) {
-		var direction = point.p.multiply(-1.0);
-		point.applyForce(direction.multiply(this.repulsion / 50.0));
-	});
-};
-
-
-Layout.ForceDirected.prototype.updateVelocity = function(timestep) {
-	this.eachNode(function(node, point) {
-		// Is this, along with updatePosition below, the only places that your
-		// integration code exist?
-		point.v = point.v.add(point.a.multiply(timestep)).multiply(this.damping);
-		point.a = new Vector(0,0);
-	});
-};
-
-Layout.ForceDirected.prototype.updatePosition = function(timestep) {
-	this.eachNode(function(node, point) {
-		// Same question as above; along with updateVelocity, is this all of
-		// your integration code?
-		point.p = point.p.add(point.v.multiply(timestep));
-	});
-};
-
-// Calculate the total kinetic energy of the system
-Layout.ForceDirected.prototype.totalEnergy = function(timestep) {
-	var energy = 0.0;
-	this.eachNode(function(node, point) {
-		var speed = point.v.magnitude();
-		energy += 0.5 * point.m * speed * speed;
-	});
-
-	return energy;
-};
-
-var __bind = function(fn, me){ return function(){ return fn.apply(me, arguments); }; }; // stolen from coffeescript, thanks jashkenas! ;-)
-
-Layout.requestAnimationFrame = __bind(window.requestAnimationFrame ||
-	window.webkitRequestAnimationFrame ||
-	window.mozRequestAnimationFrame ||
-	window.oRequestAnimationFrame ||
-	window.msRequestAnimationFrame ||
-	function(callback, element) {
-		window.setTimeout(callback, 10);
-	}, window);
-
-
-// start simulation
-Layout.ForceDirected.prototype.start = function(render, done) {
-	var t = this;
-
-	if (this._started) return;
-	this._started = true;
-	this._stop = false;
-
-	Layout.requestAnimationFrame(function step() {
-		t.applyCoulombsLaw();
-		t.applyHookesLaw();
-		t.attractToCentre();
-		t.updateVelocity(0.03);
-		t.updatePosition(0.03);
-
-		if (render !== undefined) {
-			render();
-		}
-
-		// stop simulation when energy of the system goes below a threshold
-		if (t._stop || t.totalEnergy() < 0.01) {
-			t._started = false;
-			if (done !== undefined) { done(); }
-		} else {
-			Layout.requestAnimationFrame(step);
-		}
-	});
-};
-
-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};
-	var t = this;
-	this.graph.nodes.forEach(function(n){
-		var point = t.point(n);
-		var distance = point.p.subtract(pos).magnitude();
-
-		if (min.distance === null || distance < min.distance) {
-			min = {node: n, point: point, distance: distance};
-		}
-	});
-
-	return min;
-};
-
-// returns [bottomleft, topright]
-Layout.ForceDirected.prototype.getBoundingBox = function() {
-	var bottomleft = new Vector(-2,-2);
-	var topright = new Vector(2,2);
-
-	this.eachNode(function(n, point) {
-		if (point.p.x < bottomleft.x) {
-			bottomleft.x = point.p.x;
-		}
-		if (point.p.y < bottomleft.y) {
-			bottomleft.y = point.p.y;
-		}
-		if (point.p.x > topright.x) {
-			topright.x = point.p.x;
-		}
-		if (point.p.y > topright.y) {
-			topright.y = point.p.y;
-		}
-	});
-
-	var padding = topright.subtract(bottomleft).multiply(0.07); // ~5% padding
-
-	return {bottomleft: bottomleft.subtract(padding), topright: topright.add(padding)};
-};
-
-
-// Vector
-var Vector = function(x, y) {
-	this.x = x;
-	this.y = y;
-};
-
-Vector.random = function() {
-	return new Vector(10.0 * (Math.random() - 0.5), 10.0 * (Math.random() - 0.5));
-};
-
-Vector.prototype.add = function(v2) {
-	return new Vector(this.x + v2.x, this.y + v2.y);
-};
-
-Vector.prototype.subtract = function(v2) {
-	return new Vector(this.x - v2.x, this.y - v2.y);
-};
-
-Vector.prototype.multiply = function(n) {
-	return new Vector(this.x * n, this.y * n);
-};
-
-Vector.prototype.divide = function(n) {
-	return new Vector((this.x / n) || 0, (this.y / n) || 0); // Avoid divide by zero errors..
-};
-
-Vector.prototype.magnitude = function() {
-	return Math.sqrt(this.x*this.x + this.y*this.y);
-};
-
-Vector.prototype.normal = function() {
-	return new Vector(-this.y, this.x);
-};
-
-Vector.prototype.normalise = function() {
-	return this.divide(this.magnitude());
-};
-
-// Point
-Layout.ForceDirected.Point = function(position, mass) {
-	this.p = position; // position
-	this.m = mass; // mass
-	this.v = new Vector(0, 0); // velocity
-	this.a = new Vector(0, 0); // acceleration
-};
-
-Layout.ForceDirected.Point.prototype.applyForce = function(force) {
-	this.a = this.a.add(force.divide(this.m));
-};
-
-// Spring
-Layout.ForceDirected.Spring = function(point1, point2, length, k) {
-	this.point1 = point1;
-	this.point2 = point2;
-	this.length = length; // spring length at rest
-	this.k = k; // spring constant (See Hooke's law) .. how stiff the spring is
-};
-
-// Layout.ForceDirected.Spring.prototype.distanceToPoint = function(point)
-// {
-// 	// hardcore vector arithmetic.. ohh yeah!
-// 	// .. see http://stackoverflow.com/questions/849211/shortest-distance-between-a-point-and-a-line-segment/865080#865080
-// 	var n = this.point2.p.subtract(this.point1.p).normalise().normal();
-// 	var ac = point.p.subtract(this.point1.p);
-// 	return Math.abs(ac.x * n.x + ac.y * n.y);
-// };
-
-// Renderer handles the layout rendering loop
-function Renderer(layout, clear, drawEdge, drawNode) {
-	this.layout = layout;
-	this.clear = clear;
-	this.drawEdge = drawEdge;
-	this.drawNode = drawNode;
-
-	this.layout.graph.addGraphListener(this);
-}
-
-Renderer.prototype.graphChanged = function(e) {
-	this.start();
-};
-
-Renderer.prototype.start = function() {
-	var t = this;
-	this.layout.start(function render() {
-		t.clear();
-
-		t.layout.eachEdge(function(edge, spring) {
-			t.drawEdge(edge, spring.point1.p, spring.point2.p);
-		});
-
-		t.layout.eachNode(function(node, point) {
-			t.drawNode(node, point.p);
-		});
-	});
-};
-
-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 ) {
-	Array.prototype.forEach = function( callback, thisArg ) {
-		var T, k;
-		if ( this == null ) {
-			throw new TypeError( " this is null or not defined" );
-		}
-		var O = Object(this);
-		var len = O.length >>> 0; // Hack to convert O.length to a UInt32
-		if ( {}.toString.call(callback) != "[object Function]" ) {
-			throw new TypeError( callback + " is not a function" );
-		}
-		if ( thisArg ) {
-			T = thisArg;
-		}
-		k = 0;
-		while( k < len ) {
-			var kValue;
-			if ( k in O ) {
-				kValue = O[ k ];
-				callback.call( T, kValue, k, O );
-			}
-			k++;
-		}
+		this.notify();
 	};
-}
 
+	/* Merge a list of nodes and edges into the current graph. eg.
+	var o = {
+		nodes: [
+			{id: 123, data: {type: 'user', userid: 123, displayname: 'aaa'}},
+			{id: 234, data: {type: 'user', userid: 234, displayname: 'bbb'}}
+		],
+		edges: [
+			{from: 0, to: 1, type: 'submitted_design', directed: true, data: {weight: }}
+		]
+	}
+	*/
+	Graph.prototype.merge = function(data) {
+		var nodes = [];
+		data.nodes.forEach(function(n) {
+			nodes.push(this.addNode(new Node(n.id, n.data)));
+		}, this);
+
+		data.edges.forEach(function(e) {
+			var from = nodes[e.from];
+			var to = nodes[e.to];
+
+			var id = (e.directed)
+				? (id = e.type + "-" + from.id + "-" + to.id)
+				: (from.id < to.id) // normalise id for non-directed edges
+					? e.type + "-" + from.id + "-" + to.id
+					: e.type + "-" + to.id + "-" + from.id;
+
+			var edge = this.addEdge(new Edge(id, from, to, e.data));
+			edge.data.type = e.type;
+		}, this);
+	};
+
+	Graph.prototype.filterNodes = function(fn) {
+		var tmpNodes = this.nodes.slice();
+		tmpNodes.forEach(function(n) {
+			if (!fn(n)) {
+				this.removeNode(n);
+			}
+		}, this);
+	};
+
+	Graph.prototype.filterEdges = function(fn) {
+		var tmpEdges = this.edges.slice();
+		tmpEdges.forEach(function(e) {
+			if (!fn(e)) {
+				this.removeEdge(e);
+			}
+		}, this);
+	};
+
+
+	Graph.prototype.addGraphListener = function(obj) {
+		this.eventListeners.push(obj);
+	};
+
+	Graph.prototype.notify = function() {
+		this.eventListeners.forEach(function(obj){
+			obj.graphChanged();
+		});
+	};
+
+	// -----------
+	var Layout = Springy.Layout = {};
+	Layout.ForceDirected = function(graph, stiffness, repulsion, damping) {
+		this.graph = graph;
+		this.stiffness = stiffness; // spring stiffness constant
+		this.repulsion = repulsion; // repulsion constant
+		this.damping = damping; // velocity damping factor
+
+		this.nodePoints = {}; // keep track of points associated with nodes
+		this.edgeSprings = {}; // keep track of springs associated with edges
+	};
+
+	Layout.ForceDirected.prototype.point = function(node) {
+		if (!(node.id in this.nodePoints)) {
+			var mass = (node.data.mass !== undefined) ? node.data.mass : 1.0;
+			this.nodePoints[node.id] = new Layout.ForceDirected.Point(Vector.random(), mass);
+		}
+
+		return this.nodePoints[node.id];
+	};
+
+	Layout.ForceDirected.prototype.spring = function(edge) {
+		if (!(edge.id in this.edgeSprings)) {
+			var length = (edge.data.length !== undefined) ? edge.data.length : 1.0;
+
+			var existingSpring = false;
+
+			var from = this.graph.getEdges(edge.source, edge.target);
+			from.forEach(function(e) {
+				if (existingSpring === false && e.id in this.edgeSprings) {
+					existingSpring = this.edgeSprings[e.id];
+				}
+			}, this);
+
+			if (existingSpring !== false) {
+				return new Layout.ForceDirected.Spring(existingSpring.point1, existingSpring.point2, 0.0, 0.0);
+			}
+
+			var to = this.graph.getEdges(edge.target, edge.source);
+			from.forEach(function(e){
+				if (existingSpring === false && e.id in this.edgeSprings) {
+					existingSpring = this.edgeSprings[e.id];
+				}
+			}, this);
+
+			if (existingSpring !== false) {
+				return new Layout.ForceDirected.Spring(existingSpring.point2, existingSpring.point1, 0.0, 0.0);
+			}
+
+			this.edgeSprings[edge.id] = new Layout.ForceDirected.Spring(
+				this.point(edge.source), this.point(edge.target), length, this.stiffness
+			);
+		}
+
+		return this.edgeSprings[edge.id];
+	};
+
+	// callback should accept two arguments: Node, Point
+	Layout.ForceDirected.prototype.eachNode = function(callback) {
+		var t = this;
+		this.graph.nodes.forEach(function(n){
+			callback.call(t, n, t.point(n));
+		});
+	};
+
+	// callback should accept two arguments: Edge, Spring
+	Layout.ForceDirected.prototype.eachEdge = function(callback) {
+		var t = this;
+		this.graph.edges.forEach(function(e){
+			callback.call(t, e, t.spring(e));
+		});
+	};
+
+	// callback should accept one argument: Spring
+	Layout.ForceDirected.prototype.eachSpring = function(callback) {
+		var t = this;
+		this.graph.edges.forEach(function(e){
+			callback.call(t, t.spring(e));
+		});
+	};
+
+
+	// Physics stuff
+	Layout.ForceDirected.prototype.applyCoulombsLaw = function() {
+		this.eachNode(function(n1, point1) {
+			this.eachNode(function(n2, point2) {
+				if (point1 !== point2)
+				{
+					var d = point1.p.subtract(point2.p);
+					var distance = d.magnitude() + 0.1; // avoid massive forces at small distances (and divide by zero)
+					var direction = d.normalise();
+
+					// apply force to each end point
+					point1.applyForce(direction.multiply(this.repulsion).divide(distance * distance * 0.5));
+					point2.applyForce(direction.multiply(this.repulsion).divide(distance * distance * -0.5));
+				}
+			});
+		});
+	};
+
+	Layout.ForceDirected.prototype.applyHookesLaw = function() {
+		this.eachSpring(function(spring){
+			var d = spring.point2.p.subtract(spring.point1.p); // the direction of the spring
+			var displacement = spring.length - d.magnitude();
+			var direction = d.normalise();
+
+			// apply force to each end point
+			spring.point1.applyForce(direction.multiply(spring.k * displacement * -0.5));
+			spring.point2.applyForce(direction.multiply(spring.k * displacement * 0.5));
+		});
+	};
+
+	Layout.ForceDirected.prototype.attractToCentre = function() {
+		this.eachNode(function(node, point) {
+			var direction = point.p.multiply(-1.0);
+			point.applyForce(direction.multiply(this.repulsion / 50.0));
+		});
+	};
+
+
+	Layout.ForceDirected.prototype.updateVelocity = function(timestep) {
+		this.eachNode(function(node, point) {
+			// Is this, along with updatePosition below, the only places that your
+			// integration code exist?
+			point.v = point.v.add(point.a.multiply(timestep)).multiply(this.damping);
+			point.a = new Vector(0,0);
+		});
+	};
+
+	Layout.ForceDirected.prototype.updatePosition = function(timestep) {
+		this.eachNode(function(node, point) {
+			// Same question as above; along with updateVelocity, is this all of
+			// your integration code?
+			point.p = point.p.add(point.v.multiply(timestep));
+		});
+	};
+
+	// Calculate the total kinetic energy of the system
+	Layout.ForceDirected.prototype.totalEnergy = function(timestep) {
+		var energy = 0.0;
+		this.eachNode(function(node, point) {
+			var speed = point.v.magnitude();
+			energy += 0.5 * point.m * speed * speed;
+		});
+
+		return energy;
+	};
+
+	var __bind = function(fn, me){ return function(){ return fn.apply(me, arguments); }; }; // stolen from coffeescript, thanks jashkenas! ;-)
+
+	Springy.requestAnimationFrame = __bind(window.requestAnimationFrame ||
+		window.webkitRequestAnimationFrame ||
+		window.mozRequestAnimationFrame ||
+		window.oRequestAnimationFrame ||
+		window.msRequestAnimationFrame ||
+		function(callback, element) {
+			window.setTimeout(callback, 10);
+		}, window);
+
+
+	// start simulation
+	Layout.ForceDirected.prototype.start = function(render, done) {
+		var t = this;
+
+		if (this._started) return;
+		this._started = true;
+		this._stop = false;
+
+		Springy.requestAnimationFrame(function step() {
+			t.applyCoulombsLaw();
+			t.applyHookesLaw();
+			t.attractToCentre();
+			t.updateVelocity(0.03);
+			t.updatePosition(0.03);
+
+			if (render !== undefined) {
+				render();
+			}
+
+			// stop simulation when energy of the system goes below a threshold
+			if (t._stop || t.totalEnergy() < 0.01) {
+				t._started = false;
+				if (done !== undefined) { done(); }
+			} else {
+				Springy.requestAnimationFrame(step);
+			}
+		});
+	};
+
+	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};
+		var t = this;
+		this.graph.nodes.forEach(function(n){
+			var point = t.point(n);
+			var distance = point.p.subtract(pos).magnitude();
+
+			if (min.distance === null || distance < min.distance) {
+				min = {node: n, point: point, distance: distance};
+			}
+		});
+
+		return min;
+	};
+
+	// returns [bottomleft, topright]
+	Layout.ForceDirected.prototype.getBoundingBox = function() {
+		var bottomleft = new Vector(-2,-2);
+		var topright = new Vector(2,2);
+
+		this.eachNode(function(n, point) {
+			if (point.p.x < bottomleft.x) {
+				bottomleft.x = point.p.x;
+			}
+			if (point.p.y < bottomleft.y) {
+				bottomleft.y = point.p.y;
+			}
+			if (point.p.x > topright.x) {
+				topright.x = point.p.x;
+			}
+			if (point.p.y > topright.y) {
+				topright.y = point.p.y;
+			}
+		});
+
+		var padding = topright.subtract(bottomleft).multiply(0.07); // ~5% padding
+
+		return {bottomleft: bottomleft.subtract(padding), topright: topright.add(padding)};
+	};
+
+
+	// Vector
+	var Vector = Springy.Vector = function(x, y) {
+		this.x = x;
+		this.y = y;
+	};
+
+	Vector.random = function() {
+		return new Vector(10.0 * (Math.random() - 0.5), 10.0 * (Math.random() - 0.5));
+	};
+
+	Vector.prototype.add = function(v2) {
+		return new Vector(this.x + v2.x, this.y + v2.y);
+	};
+
+	Vector.prototype.subtract = function(v2) {
+		return new Vector(this.x - v2.x, this.y - v2.y);
+	};
+
+	Vector.prototype.multiply = function(n) {
+		return new Vector(this.x * n, this.y * n);
+	};
+
+	Vector.prototype.divide = function(n) {
+		return new Vector((this.x / n) || 0, (this.y / n) || 0); // Avoid divide by zero errors..
+	};
+
+	Vector.prototype.magnitude = function() {
+		return Math.sqrt(this.x*this.x + this.y*this.y);
+	};
+
+	Vector.prototype.normal = function() {
+		return new Vector(-this.y, this.x);
+	};
+
+	Vector.prototype.normalise = function() {
+		return this.divide(this.magnitude());
+	};
+
+	// Point
+	Layout.ForceDirected.Point = function(position, mass) {
+		this.p = position; // position
+		this.m = mass; // mass
+		this.v = new Vector(0, 0); // velocity
+		this.a = new Vector(0, 0); // acceleration
+	};
+
+	Layout.ForceDirected.Point.prototype.applyForce = function(force) {
+		this.a = this.a.add(force.divide(this.m));
+	};
+
+	// Spring
+	Layout.ForceDirected.Spring = function(point1, point2, length, k) {
+		this.point1 = point1;
+		this.point2 = point2;
+		this.length = length; // spring length at rest
+		this.k = k; // spring constant (See Hooke's law) .. how stiff the spring is
+	};
+
+	// Layout.ForceDirected.Spring.prototype.distanceToPoint = function(point)
+	// {
+	// 	// hardcore vector arithmetic.. ohh yeah!
+	// 	// .. see http://stackoverflow.com/questions/849211/shortest-distance-between-a-point-and-a-line-segment/865080#865080
+	// 	var n = this.point2.p.subtract(this.point1.p).normalise().normal();
+	// 	var ac = point.p.subtract(this.point1.p);
+	// 	return Math.abs(ac.x * n.x + ac.y * n.y);
+	// };
+
+	// Renderer handles the layout rendering loop
+	var Renderer = Springy.Renderer = function(layout, clear, drawEdge, drawNode) {
+		this.layout = layout;
+		this.clear = clear;
+		this.drawEdge = drawEdge;
+		this.drawNode = drawNode;
+
+		this.layout.graph.addGraphListener(this);
+	}
+
+	Renderer.prototype.graphChanged = function(e) {
+		this.start();
+	};
+
+	Renderer.prototype.start = function() {
+		var t = this;
+		this.layout.start(function render() {
+			t.clear();
+
+			t.layout.eachEdge(function(edge, spring) {
+				t.drawEdge(edge, spring.point1.p, spring.point2.p);
+			});
+
+			t.layout.eachNode(function(node, point) {
+				t.drawNode(node, point.p);
+			});
+		});
+	};
+
+	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 ) {
+		Array.prototype.forEach = function( callback, thisArg ) {
+			var T, k;
+			if ( this == null ) {
+				throw new TypeError( " this is null or not defined" );
+			}
+			var O = Object(this);
+			var len = O.length >>> 0; // Hack to convert O.length to a UInt32
+			if ( {}.toString.call(callback) != "[object Function]" ) {
+				throw new TypeError( callback + " is not a function" );
+			}
+			if ( thisArg ) {
+				T = thisArg;
+			}
+			k = 0;
+			while( k < len ) {
+				var kValue;
+				if ( k in O ) {
+					kValue = O[ k ];
+					callback.call( T, kValue, k, O );
+				}
+				k++;
+			}
+		};
+	}
+}).call(this);
diff --git a/springyui.js b/springyui.js
index 9f09f52..9811c95 100755
--- a/springyui.js
+++ b/springyui.js
@@ -26,7 +26,7 @@ Copyright (c) 2010 Dennis Hotson
 (function() {
 
 jQuery.fn.springy = function(params) {
-	var graph = this.graph = params.graph || new Graph();
+	var graph = this.graph = params.graph || new Springy.Graph();
 
 	var stiffness = params.stiffness || 400.0;
 	var repulsion = params.repulsion || 400.0;
@@ -36,14 +36,14 @@ jQuery.fn.springy = function(params) {
 	var canvas = this[0];
 	var ctx = canvas.getContext("2d");
 
-	var layout = this.layout = new Layout.ForceDirected(graph, stiffness, repulsion, damping);
+	var layout = this.layout = new Springy.Layout.ForceDirected(graph, stiffness, repulsion, damping);
 
 	// calculate bounding box of graph layout.. with ease-in
 	var currentBB = layout.getBoundingBox();
-	var targetBB = {bottomleft: new Vector(-2, -2), topright: new Vector(2, 2)};
+	var targetBB = {bottomleft: new Springy.Vector(-2, -2), topright: new Springy.Vector(2, 2)};
 
 	// auto adjusting bounding box
-	Layout.requestAnimationFrame(function adjust() {
+	Springy.requestAnimationFrame(function adjust() {
 		targetBB = layout.getBoundingBox();
 		// current gets 20% closer to target every iteration
 		currentBB = {
@@ -53,7 +53,7 @@ jQuery.fn.springy = function(params) {
 				.divide(10))
 		};
 
-		Layout.requestAnimationFrame(adjust);
+		Springy.requestAnimationFrame(adjust);
 	});
 
 	// convert to/from screen coordinates
@@ -61,14 +61,14 @@ jQuery.fn.springy = function(params) {
 		var size = currentBB.topright.subtract(currentBB.bottomleft);
 		var sx = p.subtract(currentBB.bottomleft).divide(size.x).x * canvas.width;
 		var sy = p.subtract(currentBB.bottomleft).divide(size.y).y * canvas.height;
-		return new Vector(sx, sy);
+		return new Springy.Vector(sx, sy);
 	};
 
 	fromScreen = function(s) {
 		var size = currentBB.topright.subtract(currentBB.bottomleft);
 		var px = (s.x / canvas.width) * size.x + currentBB.bottomleft.x;
 		var py = (s.y / canvas.height) * size.y + currentBB.bottomleft.y;
-		return new Vector(px, py);
+		return new Springy.Vector(px, py);
 	};
 
 	// half-assed drag and drop
@@ -120,7 +120,7 @@ jQuery.fn.springy = function(params) {
 		dragged = null;
 	});
 
-	Node.prototype.getWidth = function() {
+	Springy.Node.prototype.getWidth = function() {
 		var text = (this.data.label !== undefined) ? this.data.label : this.id;
 		if (this._width && this._width[text])
 			return this._width[text];
@@ -136,11 +136,11 @@ jQuery.fn.springy = function(params) {
 		return width;
 	};
 
-	Node.prototype.getHeight = function() {
+	Springy.Node.prototype.getHeight = function() {
 		return 20;
 	};
 
-	var renderer = this.renderer = new Renderer(layout,
+	var renderer = this.renderer = new Springy.Renderer(layout,
 		function clear() {
 			ctx.clearRect(0,0,canvas.width,canvas.height);
 		},
@@ -150,7 +150,7 @@ jQuery.fn.springy = function(params) {
 			var x2 = toScreen(p2).x;
 			var y2 = toScreen(p2).y;
 
-			var direction = new Vector(x2-x1, y2-y1);
+			var direction = new Springy.Vector(x2-x1, y2-y1);
 			var normal = direction.normal().normalise();
 
 			var from = graph.getEdges(edge.source, edge.target);
@@ -290,7 +290,7 @@ jQuery.fn.springy = function(params) {
 			return false;
 		}
 
-		return new Vector(p1.x + ua * (p2.x - p1.x), p1.y + ua * (p2.y - p1.y));
+		return new Springy.Vector(p1.x + ua * (p2.x - p1.x), p1.y + ua * (p2.y - p1.y));
 	}
 
 	function intersect_line_box(p1, p2, p3, w, h) {