Simple Fluid Simulation with Famo.us

fluid.js

// Note: Edit to Force.js
// The Engine sends applyForce a list of bodies, even when a single body is attached
// eg..
// engine.attach(gravity,body)
// DOES NOT WORK

// applyForce to work with the current physics engine must be defined as follows:
// 
//    Force.prototype.applyForce = function applyForce(bodies) {
//        for (var i = 0; i < bodies.length; i++) {
//            b = bodies[i];
//            b.applyForce(this.force);
//        };
//    };



define(function(require, exports, module) {

	var Engine          = require('famous/core/Engine');
	var Surface         = require('famous/core/Surface');
	var Modifier        = require('famous/core/Modifier');

	var Draggable       = require('famous/modifiers/Draggable');

	var PhysicsEngine   = require('famous/physics/PhysicsEngine');
	var Circle          = require('famous/physics/bodies/Circle');
	var Force           = require('famous/physics/forces/Force');
	var Collision       = require('famous/physics/constraints/Collision');
	var Wall            = require('famous/physics/constraints/Wall');

	var Random          = require('famous/math/Random');


	var pe = new PhysicsEngine();

	var context = Engine.createContext();

	// Play with this Number
	var numBodies = 100;

	var moleculeBodies = [];

	for (var i = 0; i < numBodies; i++) {

		// Play with this range
		radius = Random.integer(5,25);

		var molecule = new Surface({
			size:[radius*2,radius*2],
			properties: {
				backgroundColor: 'black',
				borderRadius: radius + 'px',
			}
		});

		molecule.body = new Circle({
			radius:radius*0.5,
			mass: 1
		});
		pe.addBody(molecule.body);

		moleculeBodies.push(molecule.body);

		molecule.state = new Modifier({origin:[0.5,0.5]});
		molecule.state.transformFrom( function(){ return this.getTransform()}.bind(molecule.body) );

		context.add(molecule.state).add(molecule);

	};

	var collision = new Collision({restitution:0});

	for (var i = 0; i < moleculeBodies.length; i++) {
		b1 = moleculeBodies[i];
		if ((i+1) < moleculeBodies.length) {
			for (var j = i+1; j < moleculeBodies.length; j++) {
				b2 = moleculeBodies[j];
				pe.attach(collision,b1,b2);
			};
		}
	};

	var gravity = new Force([0,0.002,0]);
	pe.attach(gravity,moleculeBodies);

	var floor = new Wall({normal:[0,-1,0], distance:200, restitution : 0});
	pe.attach(floor, moleculeBodies);

	var left = new Wall({normal:[1,0,0],distance:150, restitution:0 });
	pe.attach(left,moleculeBodies);

	var right = new Wall({normal:[-1,0,0],distance:150, restitution:0 });
	pe.attach(right,moleculeBodies);

	var dragger = new Surface({
		size:[300,300],
		properties: {
			border: "2px solid black",
			borderRadius: '150px'
		}
	});

	dragger.body = new Circle({
		radius:150,
		mass: 100
	});

	pe.addBody(dragger.body);

	dragger.state = new Modifier({origin:[0.5,0.5]});

	dragger.draggable = new Draggable();
	dragger.pipe(dragger.draggable);


	Engine.on('prerender',function(){
		var pos = dragger.draggable.getPosition();
		dragger.body.setPosition([pos[0],pos[1]]);
	});

	pe.attach(collision,moleculeBodies,dragger.body);

	context.add(dragger.state).add(dragger.draggable).add(dragger);

});

i'm getting an error at line 66:
Uncaught TypeError: undefined is not a function (its actually at famous.min.js:48, but comes originally from the above line)

Has something changed in famo.us since you made this - i'm using the famo.us boilerplate and am pasting this in.