soulwire/Coffee-Physics

// Create a physics instance which uses the Verlet integration method
var physics = new Physics();
physics.integrator = new Verlet();

// Design some behaviours for particles
var avoidMouse = new Attraction();
var pullToCenter = new Attraction();

// Allow particle collisions to make things interesting
var collision = new Collision();

// Use Sketch.js to make life much easier
var example = Sketch.create({ container: document.body });

example.setup = function() {

    for ( var i = 0; i < 200; i++ ) {

        // Create a particle
        var particle = new Particle( Math.random() );
        var position = new Vector( random( this.width ), random( this.height ) );
        particle.setRadius( particle.mass * 10 );
        particle.moveTo( position );

        // Make it collidable
        collision.pool.push( particle );

        // Apply behaviours
        particle.behaviours.push( avoidMouse, pullToCenter, collision );

        // Add to the simulation
        physics.particles.push( particle );
    }
    
    pullToCenter.target.x = this.width / 2;
    pullToCenter.target.y = this.height / 2;
    pullToCenter.strength = 120;
    
    avoidMouse.setRadius( 60 );
    avoidMouse.strength = -1000;
    
    example.fillStyle = '#ff00ff';
}

example.draw = function() {

    // Step the simulation
    physics.step();

    // Render particles
    for ( var i = 0, n = physics.particles.length; i < n; i++ ) {

        var particle = physics.particles[i];
        example.beginPath();
        example.arc( particle.pos.x, particle.pos.y, particle.radius, 0, Math.PI * 2 );
        example.fill();
    }
}

example.mousemove = function() {
    avoidMouse.target.x = example.mouse.x;
    avoidMouse.target.y = example.mouse.y;
}