var game = new Phaser.Game(800, 600, Phaser.CANVAS, 'phaser-example', { preload: preload, create: create, update: update, render: render });

function preload() {

    game.load.image('atari', 'assets/sprites/atari130xe.png');
    game.load.image('mushroom', 'assets/sprites/mushroom2.png');

}

var sprite1;
var sprite2;

function create() {

    game.stage.backgroundColor = '#2d2d2d';

    //  This will check Sprite vs. Sprite collision using a custom process callback
    sprite1 = game.add.sprite(0, 200, 'atari');
    sprite2 = game.add.sprite(750, 220, 'mushroom');

    //  We'll use random velocities so we can test it in our processCallback
    sprite1.body.velocity.x = 50 + Math.random() * 100;
    sprite2.body.velocity.x = -(50 + Math.random() * 100);

}

function update() {

    game.physics.collide(sprite1, sprite2, collisionCallback, processCallback, this);

}

function processCallback (obj1, obj2) {

    //  This function can perform your own additional checks on the 2 objects that collided.
    //  For example you could test for velocity, health, etc.
    //  This function needs to return either true or false. If it returns true then collision carries on (separating the two objects).
    //  If it returns false the collision is assumed to have failed and aborts, no further checks or separation happen.

    if (obj1.body.speed > obj2.body.speed)
    {
        return true;
    }
    else
    {
        return false;
    }

}

function collisionCallback (obj1, obj2) {

    game.stage.backgroundColor = '#992d2d';

}

function render() {

    game.debug.renderText('The processCallback will only collide if sprite1 is going fastest.', 32, 32);
    game.debug.renderText('Sprite 1 speed: ' + sprite1.body.speed, 32, 64);
    game.debug.renderText('Sprite 2 speed: ' + sprite2.body.speed, 32, 96);

}