/**** 
* Classes
****/
var Boot = Container.expand(function () {
	var self = Container.call(this);
	var bootGraphics = self.attachAsset('boot', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.realWidth = bootGraphics.width * 0.7;
	self.velocityX = 0;
	self.velocityY = 0;
	self.previousX = 0;
	self.previousY = 0;
	self.calculateVelocity = function () {
		self.velocityX = self.x - self.previousX;
		self.velocityY = self.y - self.previousY;
		self.previousX = self.x;
		self.previousY = self.y;
		var targetRotation = -Math.atan2(self.velocityY, 0) / 2 + Math.PI / 9;
		self.rotation += (targetRotation - self.rotation) * 0.1;
	};
});
var Ball = Container.expand(function () {
	var self = Container.call(this);
	var ballGraphics = self.attachAsset('ball', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.velocityX = 0;
	self.velocityY = 0;
	self.gravity = 1.5;
	self.bounceFactor = 0.7;
	self.move = function () {
		self.x += self.velocityX;
		self.y += self.velocityY;
		self.velocityY += self.gravity;
		self.rotation += self.velocityX * 0.005;
		if (self.x - self.width / 2 < 0) {
			self.velocityX *= -0.7;
			self.x = self.width / 2;
		}
		if (self.x + self.width / 2 > 2048) {
			self.velocityX *= -0.7;
			self.x = 2048 - self.width / 2;
		}
	};
	self.bounce = function (boot) {
		var dx = self.x - boot.x;
		var dy = self.y - boot.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		if (distance < boot.realWidth / 2 + self.width / 2) {
			var angle = Math.atan2(dy, dx);
			var sin = Math.sin(angle);
			var cos = Math.cos(angle);
			var bootSpeed = Math.sqrt(boot.velocityX * boot.velocityX + boot.velocityY * boot.velocityY);
			var ballSpeed = Math.sqrt(self.velocityX * self.velocityX + self.velocityY * self.velocityY);
			var totalSpeed = (bootSpeed + ballSpeed) * self.bounceFactor;
			var directionX = cos * totalSpeed;
			var directionY = sin * totalSpeed;
			var scoreIncrement = Math.max(0, Math.round(totalSpeed) - 20);
			self.parent.score += scoreIncrement;
			LK.setScore(self.parent.score);
			self.velocityX = directionX;
			self.velocityY = directionY;
			var overlap = boot.realWidth / 2 + self.width / 2 - distance;
			self.x += 2 * overlap * cos;
			self.y += 2 * overlap * sin;
		}
	};
});

/**** 
* Initialize Game
****/
var game = new LK.Game({
	backgroundColor: 0x36759c
});

/**** 
* Game Code
****/
var stadiumBackground = game.attachAsset('stadium', {
	anchorX: 0.5,
	anchorY: 0.5
});
stadiumBackground.x = 2048 / 2;
stadiumBackground.y = 2732 / 2;
stadiumBackground.alpha = .8;
game.on('move', function (obj) {
	var pos = obj.event.getLocalPosition(game);
	boot.x = pos.x;
	boot.y = pos.y;
});
var ball = game.addChild(new Ball());
ball.x = 2048 / 2;
ball.y = 2732 / 4;
var boot = game.addChild(new Boot());
boot.x = 2048 / 2;
boot.y = 2732 / 2;
boot.visible = true;
var scoreTxt = new Text2('0', {
	size: 150,
	fill: "#ffffff"
});
scoreTxt.anchor.set(.5, 0);
LK.gui.topCenter.addChild(scoreTxt);
var tutorialTxt = new Text2('Kick harder for more points', {
	size: 100,
	fill: "#ffffff",
	dropShadow: true,
	dropShadowColor: '#000000',
	dropShadowBlur: 4,
	dropShadowAngle: Math.PI / 6,
	dropShadowDistance: 6
});
tutorialTxt.anchor.set(.5, 1);
LK.gui.bottom.addChild(tutorialTxt);
var isGameOver = false;
var isGameStarted = false;
game.score = 0;
game.on('down', function (obj) {
	var pos = obj.event.getLocalPosition(game);
	boot.x = pos.x;
	boot.y = pos.y;
	boot.visible = true;
});
LK.on('tick', function () {
	boot.calculateVelocity();
	if (!isGameStarted) {
		var dx = boot.x - ball.x;
		var dy = boot.y - ball.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		if (distance < boot.realWidth / 2 + ball.width / 2) {
			ball.bounce(boot);
			isGameStarted = true;
		}
	} else {
		ball.move();
		var dx = boot.x - ball.x;
		var dy = boot.y - ball.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		if (distance < boot.realWidth / 2 + ball.width / 2) {
			ball.bounce(boot);
		}
	}
	if (ball.y > 2732 - ball.height / 2) {
		isGameOver = true;
	}
	if (isGameOver) {
		LK.effects.flashScreen(0xff0000, 1000);
		LK.showGameOver();
	}
	LK.setScore(game.score);
	scoreTxt.setText(LK.getScore());
});

===================================================================
--- original.js
+++ change.js
@@ -73,9 +73,9 @@
 /**** 
 * Initialize Game
 ****/
 var game = new LK.Game({
-	backgroundColor: 0x000000
+	backgroundColor: 0x36759c
 });
 
 /**** 
 * Game Code