/**** 
* Classes
****/ 
// Bus class
var Bus = Container.expand(function () {
	var self = Container.call(this);
	var busGraphics = self.attachAsset('bus', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 3;
	self.update = function () {
		self.y += self.speed;
		if (self.y > 2732) {
			self.destroy();
		}
	};
});
// Assets will be automatically created and loaded during gameplay
// Car class
var Car = Container.expand(function () {
	var self = Container.call(this);
	var carGraphics = self.attachAsset('car', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.update = function () {
		self.y += self.speed;
		if (self.y > 2732) {
			self.destroy();
		}
	};
});
// Player class
var Player = Container.expand(function () {
	var self = Container.call(this);
	var playerGraphics = self.attachAsset('player', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.lane = 2;
	self.lives = 3;
	self.moveLeft = function () {
		if (self.lane > 1) {
			self.lane--;
			self.x = self.lane * 512 - 256;
		}
	};
	self.moveRight = function () {
		if (self.lane < 4) {
			self.lane++;
			self.x = self.lane * 512 - 256;
		}
	};
	self.loseLife = function () {
		self.lives--;
		livesTxt.setText('Lives: ' + self.lives);
		if (self.lives <= 0) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		}
	};
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x000000 // Init game with black background
});

/**** 
* Game Code
****/ 
var player = game.addChild(new Player());
player.x = 512; // Set player's initial x position to the second lane
player.y = 2400;
var cars = [];
var buses = [];
var score = 0;
var scoreTxt = new Text2('0', {
	size: 150,
	fill: "#ffffff"
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
var livesTxt = new Text2('Lives: 3', {
	size: 100,
	fill: "#ffffff"
});
livesTxt.anchor.set(0, 0);
LK.gui.topLeft.addChild(livesTxt);
function spawnVehicle() {
	var lane = Math.floor(Math.random() * 4) + 1;
	var vehicle;
	if (Math.random() < 0.5) {
		vehicle = new Car();
		cars.push(vehicle);
	} else {
		vehicle = new Bus();
		buses.push(vehicle);
	}
	vehicle.x = lane * 512 - 256;
	vehicle.y = -100;
	game.addChild(vehicle);
}
LK.on('keydown', function (event) {
	switch (event.keyCode) {
		case 37:
			// Left arrow key
			player.moveLeft();
			break;
		case 39:
			// Right arrow key
			player.moveRight();
			break;
	}
});
game.update = function () {
	for (var i = cars.length - 1; i >= 0; i--) {
		if (cars[i].intersects(player)) {
			player.loseLife();
			cars[i].destroy();
			cars.splice(i, 1);
			continue;
		}
		for (var j = buses.length - 1; j >= 0; j--) {
			if (cars[i].intersects(buses[j])) {
				cars[i].speed = buses[j].speed;
			}
		}
		cars[i].update();
	}
	for (var j = buses.length - 1; j >= 0; j--) {
		if (buses[j].intersects(player)) {
			player.loseLife();
			buses[j].destroy();
			buses.splice(j, 1);
			continue;
		}
		buses[j].update();
	}
	if (LK.ticks % Math.max(10, 60 - Math.floor(score / 10)) == 0) {
		spawnVehicle();
		score++;
		scoreTxt.setText(score);
	}
};

===================================================================
--- original.js
+++ change.js
@@ -104,9 +104,9 @@
 	vehicle.x = lane * 512 - 256;
 	vehicle.y = -100;
 	game.addChild(vehicle);
 }
-window.addEventListener('keydown', function (event) {
+LK.on('keydown', function (event) {
 	switch (event.keyCode) {
 		case 37:
 			// Left arrow key
 			player.moveLeft();