/**** 
* Classes
****/
var Star = Container.expand(function () {
	var self = Container.call(this);
	var starGraphics = self.attachAsset('star', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = Math.random() * 2 + 1;
	self.alpha = self.speed / 3;
	self.move = function () {
		self.y += self.speed;
		if (self.y > 2732 + self.height / 2) {
			self.y = -self.height / 2;
		}
	};
});
var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.attachAsset('hero', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 10;
	self.move = function (x, y) {
		var dx = x - self.x;
		var dy = y - self.y;
		var angle = Math.atan2(dy, dx);
		self.x += Math.cos(angle) * self.speed;
		self.y += Math.sin(angle) * self.speed;
	};
	self.shoot = function () {
		var bullet = new HeroBullet();
		bullet.x = self.x;
		bullet.y = self.y - self.height / 2;
		game.addChild(bullet);
		return bullet;
	};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.attachAsset('enemy', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 2;
	self.direction = Math.random() > 0.5 ? 1 : -1;
	self.move = function () {
		self.y += self.speed;
		if (LK.ticks % 60 == 0) {
			self.direction = Math.random() > 0.5 ? 1 : -1;
			self.speed = Math.random() * 3 + 2;
		}
		self.x += self.speed * self.direction;
		if (self.x < 0) {
			self.x = 0;
		}
		if (self.x > 2048) {
			self.x = 2048;
		}
		if (self.y > 2732 + self.height / 2) {
			self.destroy();
		}
	};
	self.shoot = function () {
		var bullet = new EnemyBullet();
		bullet.x = self.x;
		bullet.y = self.y + self.height / 2;
		game.addChild(bullet);
		return bullet;
	};
});
var HeroBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('heroBullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = -10;
	self.move = function () {
		self.y += self.speed;
		if (self.y < -self.height / 2) {
			self.destroy();
		}
	};
});
var EnemyBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('enemyBullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 10;
	self.move = function () {
		self.y += self.speed;
		if (self.y > 2732 + self.height / 2) {
			self.destroy();
		}
	};
});

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

/**** 
* Game Code
****/
var stars = [];
for (var i = 0; i < 40; i++) {
	var star = new Star();
	star.x = Math.random() * 2048;
	star.y = Math.random() * 2732;
	stars.push(star);
	game.addChild(star);
}
var hero = game.addChild(new Hero());
hero.x = 2048 / 2;
hero.y = 2732 - 100;
var enemies = [];
var heroBullets = [];
var enemyBullets = [];
var score = 0;
var scoreTxt = new Text2(score.toString(), {
	size: 150,
	fill: "#ffffff"
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
var targetPos = {
	x: hero.x,
	y: hero.y
};
game.on('down', function (obj) {
	targetPos = obj.event.getLocalPosition(game);
});
game.on('move', function (obj) {
	targetPos = obj.event.getLocalPosition(game);
});
LK.on('tick', function () {
	for (var i = 0; i < stars.length; i++) {
		stars[i].move();
	}
	hero.move(targetPos.x, targetPos.y);
	// Move hero bullets
	for (var i = heroBullets.length - 1; i >= 0; i--) {
		heroBullets[i].move();
		if (heroBullets[i].y < 0) {
			heroBullets[i].destroy();
			heroBullets.splice(i, 1);
		}
	}
	// Move enemies bullets
	for (var i = enemyBullets.length - 1; i >= 0; i--) {
		enemyBullets[i].move();
		if (enemyBullets[i].y < 0) {
			enemyBullets[i].destroy();
			enemyBullets.splice(i, 1);
		}
	}
	// Move enemies and make them shoot
	for (var j = enemies.length - 1; j >= 0; j--) {
		enemies[j].move();
		if (LK.ticks % 60 == 0) {
			enemyBullets.push(enemies[j].shoot());
		}
		if (enemies[j].y > 2732) {
			enemies[j].destroy();
			enemies.splice(j, 1);
		}
	}
	// Check for collisions
	for (var k = heroBullets.length - 1; k >= 0; k--) {
		for (var l = enemies.length - 1; l >= 0; l--) {
			if (heroBullets[k].intersects(enemies[l])) {
				heroBullets[k].destroy();
				heroBullets.splice(k, 1);
				enemies[l].destroy();
				enemies.splice(l, 1);
				score += 10;
				scoreTxt.setText(score.toString());
				break;
			}
		}
	}
	// Check if hero is hit by enemy bullet or enemy
	for (var m = enemyBullets.length - 1; m >= 0; m--) {
		if (hero.intersects(enemyBullets[m])) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		}
	}
	for (var n = enemies.length - 1; n >= 0; n--) {
		if (hero.intersects(enemies[n])) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		}
	}
	// Spawn enemies
	if (LK.ticks % 120 == 0) {
		var enemy = new Enemy();
		enemy.x = Math.random() * (2048 - enemy.width) + enemy.width / 2;
		enemy.y = -enemy.height / 2;
		enemies.push(enemy);
		game.addChild(enemy);
	}
	// Hero shoot
	if (LK.ticks % 80 == 0) {
		heroBullets.push(hero.shoot());
	}
});

===================================================================
--- original.js
+++ change.js
@@ -49,8 +49,9 @@
 	self.move = function () {
 		self.y += self.speed;
 		if (LK.ticks % 60 == 0) {
 			self.direction = Math.random() > 0.5 ? 1 : -1;
+			self.speed = Math.random() * 3 + 2;
 		}
 		self.x += self.speed * self.direction;
 		if (self.x < 0) {
 			self.x = 0;
@@ -109,9 +110,9 @@
 /**** 
 * Game Code
 ****/
 var stars = [];
-for (var i = 0; i < 50; i++) {
+for (var i = 0; i < 40; i++) {
 	var star = new Star();
 	star.x = Math.random() * 2048;
 	star.y = Math.random() * 2732;
 	stars.push(star);