Emanuele Feronato

var game;

var cars = [];
var carColors = [0xff0000, 0x0000ff];
var carTurnSpeed = 250;

var carGroup;
var obstacleGroup;

var obstacleSpeed = 120;
var obstacleDelay = 1500;

window.onload = function() {	
	game = new Phaser.Game(320, 480, Phaser.AUTO, "");
     game.state.add("PlayGame",playGame);
     game.state.start("PlayGame");
}

var playGame = function(game){};

playGame.prototype = {
	preload: function(){
          game.load.image("road", "road.png");
          game.load.image("car", "car.png");
          game.load.image("obstacle", "obstacle.png");
	},
  	create: function(){
          game.add.image(0, 0, "road");
          game.physics.startSystem(Phaser.Physics.ARCADE);
          carGroup = game.add.group();
          obstacleGroup = game.add.group();
          for(var i = 0; i < 2; i++){
               cars[i] = game.add.sprite(0, game.height - 40, "car");
               cars[i].positions = [game.width * (i * 4 + 1) / 8, game.width * (i * 4 + 3) / 8];
               cars[i].anchor.set(0.5);
               cars[i].tint = carColors[i];  
               cars[i].canMove = true;
               cars[i].side = i;
               cars[i].x = cars[i].positions[cars[i].side];
               game.physics.enable(cars[i], Phaser.Physics.ARCADE); 
               cars[i].body.allowRotation = false;
               cars[i].body.moves = false;  
               carGroup.add(cars[i]);
          }
          game.input.onDown.add(moveCar);
          game.time.events.loop(obstacleDelay, function(){
               var obstacle = new Obstacle(game);
               game.add.existing(obstacle);
               obstacleGroup.add(obstacle);
          });          
	},
     update: function(){
          game.physics.arcade.collide(carGroup, obstacleGroup, function(){
               game.state.start("PlayGame");     
          });
     }
}

function moveCar(e){
     var carToMove = Math.floor(e.position.x / (game.width / 2));
     if(cars[carToMove].canMove){
          cars[carToMove].canMove = false;
          cars[carToMove].side = 1 - cars[carToMove].side;
          var moveTween = game.add.tween(cars[carToMove]).to({ 
               x: cars[carToMove].positions[cars[carToMove].side],
          }, carTurnSpeed, Phaser.Easing.Linear.None, true);
          moveTween.onComplete.add(function(){
               cars[carToMove].canMove = true;
          })
     }
}

Obstacle = function (game) {
     var position = game.rnd.between(0, 3);
	Phaser.Sprite.call(this, game, game.width * (position * 2 + 1) / 8, -20, "obstacle");
	game.physics.enable(this, Phaser.Physics.ARCADE);
     this.anchor.set(0.5);
     this.tint = carColors[Math.floor(position / 2)];
};

Obstacle.prototype = Object.create(Phaser.Sprite.prototype);
Obstacle.prototype.constructor = Obstacle;

Obstacle.prototype.update = function() {
	this.body.velocity.y = obstacleSpeed;
	if(this.y > game.height){
		this.destroy();
	}
};