/**** 
* Classes
****/ 
var Background = Container.expand(function () {
	var self = Container.call(this);
	var bg1 = self.attachAsset('background', {});
	var bg2 = self.attachAsset('background', {});
	var dimOverlay = new Container();
	var dimGraphics = dimOverlay.attachAsset('dimOverlay', {});
	dimGraphics.width = 2048;
	dimGraphics.height = 2732;
	dimGraphics.alpha = 0.3;
	bg1.width = bg2.width = 2048;
	bg1.height = bg2.height = 2732;
	bg2.x = 2048;
	self.addChild(bg1);
	self.addChild(bg2);
	self.addChild(dimOverlay);
	self._move_migrated = function () {
		bg1.x -= 1;
		bg2.x -= 1;
		if (bg1.x <= -2048) {
			bg1.x = bg2.x + 2048;
		}
		if (bg2.x <= -2048) {
			bg2.x = bg1.x + 2048;
		}
	};
});
var Cloud = Container.expand(function () {
	var self = Container.call(this);
	var cloudGraphics = self.attachAsset('cloud', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	cloudGraphics.alpha = 0.7;
	self.speed = -0.2;
	self._move_migrated = function () {
		self.x += self.speed;
		if (self.x <= -self.width) {
			self.x = 2048 + self.width;
		}
	};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	self.isHit = false;
	var enemyAssetIds = ['enemy1', 'enemy2', 'enemy3'];
	var selectedAssetId = enemyAssetIds[Math.floor(Math.random() * enemyAssetIds.length)];
	var enemyGraphics = self.createAsset(selectedAssetId, {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speedX = -1.8 * (1 + Math.random() * 0.5) * 1.5;
	self.speedY = 0;
	self.verticalMovementRange = 50;
	self.verticalSpeed = self.verticalMovementRange / (5 * 60);
	self.verticalDirection = 1;
	self.initialY = 0;
	self._move_migrated = function () {
		self.x += self.isHit ? self.speedX * 4 : self.speedX;
		if (self.initialY === 0) {
			self.initialY = self.y + 20;
		}
		self.y += self.verticalSpeed * self.verticalDirection;
		if (Math.abs(self.y - self.initialY) >= self.verticalMovementRange) {
			self.verticalDirection *= -1;
		}
	};
});
var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.attachAsset('hero', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	var wingGraphics = self.attachAsset('wing', {
		anchorX: 0.7,
		anchorY: 0.8
	});
	wingGraphics.direction = 1;
	self.speed = 0;
	self.bullets = [];
	self.gravity = 0.2;
	self.jump = function () {
		self.speed = -10;
	};
	self._update_migrated = function () {
		self.speed += self.gravity;
		self.y += self.speed;
		self.rotation = self.speed * 0.05;
		wingGraphics.y += wingGraphics.direction * 2 || -2;
		if (wingGraphics.y > 10 || wingGraphics.y < -10) {
			wingGraphics.direction = -wingGraphics.direction;
		}
		for (var i = self.bullets.length - 1; i >= 0; i--) {
			self.bullets[i]._move_migrated();
			if (self.bullets[i].y > 2732) {
				self.bullets[i].destroy();
				self.bullets.splice(i, 1);
			}
		}
	};
});
var HeroBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self._move_migrated = function () {
		self.y += self.speed;
	};
});
var Obstacle = Container.expand(function () {
	var self = Container.call(this);
	var obstacleGraphics = self.attachAsset('obstacle', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.baseSpeed = -5;
	self.speedIncrease = 0;
	self._move_migrated = function () {
		self.x += self.baseSpeed - self.speedIncrease;
		self.y += Math.sin(LK.ticks / 60) * 1;
	};
});
var SecondBackground = Container.expand(function () {
	var self = Container.call(this);
	var bg1 = self.attachAsset('second_background', {});
	var bg2 = self.attachAsset('second_background', {});
	bg1.width = bg2.width = 2048;
	bg1.height = bg2.height = 2732;
	bg2.x = 2048;
	self.addChild(bg1);
	self.addChild(bg2);
	self._move_migrated = function () {
		bg1.x += 0.5;
		bg2.x += 0.5;
		if (bg1.x >= 2048) {
			bg1.x = bg2.x - 2048;
		}
		if (bg2.x >= 2048) {
			bg2.x = bg1.x - 2048;
		}
	};
});

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

/**** 
* Game Code
****/ 
// Check if background music is playing, if not, then play it
LK.on('tick', function () {
	if (!LK.getSound('Background').playing) {
		LK.getSound('Background').play();
	}
});
var secondBackground = game.addChild(new SecondBackground());
var clouds = [];
for (var i = 0; i < 5; i++) {
	var cloud = new Cloud();
	cloud.x = Math.random() * 2048;
	cloud.y = Math.random() * 2732 * 0.3;
	var randomScale = 0.5 + Math.random() * 0.5;
	cloud.scale.x = randomScale;
	cloud.scale.y = randomScale;
	clouds.push(cloud);
	game.addChild(cloud);
}
var background = game.addChild(new Background());
game.setChildIndex(secondBackground, 0);
var hero = game.addChild(new Hero());
hero.x = 2048 / 2 - 200;
hero.y = 2732 / 2;
var obstacles = [];
var score = 0;
var scoreTxt = new Text2('0', {
	size: 150,
	fill: "#ffffff",
	font: "Gamer",
	dropShadow: true,
	dropShadowColor: "#000000",
	dropShadowBlur: 4,
	dropShadowAngle: Math.PI / 6,
	dropShadowDistance: 6
});
LK.gui.top.addChild(scoreTxt);
scoreTxt.anchor.set(.5, 0);
var isGameOver = false;
var tickOffset = 0;
var speedIncreaseFactor = 0;
var obstacleSpawnInterval = 36 * 4;
LK.on('tick', function () {
	secondBackground._move_migrated();
	clouds.forEach(function (cloud) {
		cloud._move_migrated();
	});
	background._move_migrated();
	hero._update_migrated();
	if (hero.y > 2732 || hero.y < 0) {
		isGameOver = true;
		LK.getSound('Gameover').play();
	}
	for (var i = obstacles.length - 1; i >= 0; i--) {
		obstacles[i]._move_migrated();
		if (obstacles[i].x < -50) {
			obstacles[i].destroy();
			obstacles.splice(i, 1);
			scoreTxt.setText(score);
		}
		var intersectionThreshold = 200;
		if (hero.intersects(obstacles[i]) && Math.sqrt(Math.pow(hero.x - obstacles[i].x, 2) + Math.pow(hero.y - obstacles[i].y, 2)) < intersectionThreshold) {
			isGameOver = true;
		} else {
			for (var j = hero.bullets.length - 1; j >= 0; j--) {
				if (hero.bullets[j].intersects(obstacles[i])) {
					if (obstacles[i] instanceof Enemy) {
						obstacles[i].isHit = true;
						obstacles[i].addChild(hero.bullets[j]);
						hero.bullets[j].x = 0;
						hero.bullets[j].y = -250;
						hero.bullets[j].width = 100;
						hero.bullets[j].height = 100;
						if (!obstacles[i].scoreAwarded) {
							score++;
							obstacles[i].scoreAwarded = true;
						}
						scoreTxt.setText(score);
						// Play 'Scream' sound when bullet hits enemy
						LK.getSound('Scream').play();
					} else {
						hero.bullets[j].destroy();
						hero.bullets.splice(j, 1);
						// Play 'Hit' sound when bullet hits obstacle
						LK.getSound('Hit').play();
					}
				}
			}
		}
	}
	if (tickOffset++ % obstacleSpawnInterval == 0) {
		var newObstacle = new Obstacle();
		newObstacle.x = 2048;
		newObstacle.y = Math.random() * (2732 - 500 - newObstacle.height) + newObstacle.height;
		newObstacle.speedIncrease = speedIncreaseFactor;
		obstacles.push(newObstacle);
		game.addChild(newObstacle);
	}
	if (tickOffset % 600 == 0) {
		speedIncreaseFactor += 0.5;
		obstacleSpawnInterval = Math.max(30, obstacleSpawnInterval - 15);
	}
	var enemySpawnVariance = Math.random() > 0.5 ? 1.5 : 0.5;
	if (tickOffset % Math.floor(360 * enemySpawnVariance) == 0) {
		var enemy = new Enemy();
		enemy.x = 2048;
		enemy.y = 2732 - enemy.height / 2;
		game.addChild(enemy);
		obstacles.push(enemy);
	}
	if (isGameOver) {
		LK.effects.flashScreen(0xff0000, 1000);
		LK.showGameOver();
	}
});
game.on('down', function (x, y, obj) {
	hero.jump();
	var bullet = new HeroBullet();
	bullet.x = hero.x;
	bullet.y = hero.y;
	game.addChild(bullet);
	hero.bullets.push(bullet);
	LK.getSound('Plop').play();
});
// Play background sound on game start
LK.getSound('Background').play();

===================================================================
--- original.js
+++ change.js
@@ -156,10 +156,14 @@
 
 /**** 
 * Game Code
 ****/ 
-// Play background sound on jgamei start
-LK.getSound('Background').play();
+// Check if background music is playing, if not, then play it
+LK.on('tick', function () {
+	if (!LK.getSound('Background').playing) {
+		LK.getSound('Background').play();
+	}
+});
 var secondBackground = game.addChild(new SecondBackground());
 var clouds = [];
 for (var i = 0; i < 5; i++) {
 	var cloud = new Cloud();
@@ -274,5 +278,7 @@
 	bullet.y = hero.y;
 	game.addChild(bullet);
 	hero.bullets.push(bullet);
 	LK.getSound('Plop').play();
-});
\ No newline at end of file
+});
+// Play background sound on game start
+LK.getSound('Background').play();
\ No newline at end of file