var Obstacle = Container.expand(function () {
	var self = Container.call(this);
	var obstacleGraphics = self.createAsset('obstacle', 'Obstacle', .5, .5);
	self.speed = 5;
	self.move = function () {
		self.y += self.speed;
		if (self.y > 2732) {
			self.y = 0;
		}
	};
});
var Wall = Container.expand(function () {
	var self = Container.call(this);
	var wallGraphics = self.createAsset('wall', 'Wall', .5, .5);
});
var Bird = Container.expand(function () {
	var self = Container.call(this);
	var birdGraphics = self.createAsset('bird', 'Bird character', .5, .5);
	birdGraphics.scale.x = -1;
	self.xSpeed = 5;
	self.ySpeed = 0;
	self.gravity = 0.5;
	self.lift = -15;
	self.flap = function () {
		self.ySpeed = self.lift;
	};
	self.update = function () {
		self.ySpeed += self.gravity;
		self.y += self.ySpeed;
		self.x += self.xSpeed;
		if (self.y <= 0 || self.y >= 2732) {
			self.speed = -self.speed;
		}
	};
	self.flip = function () {
		self.scale.x *= -1;
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	LK.stageContainer.setBackgroundColor(0xadd8e6);
	var bird = self.addChild(new Bird());
	var leftWall = self.addChild(new Wall());
	leftWall.x = 0;
	leftWall.y = 1366;
	var rightWall = self.addChild(new Wall());
	rightWall.x = 2048;
	rightWall.y = 1366;
	var leftObstacle, rightObstacle;
	var leftObstacleSpawnTime = Math.floor(Math.random() * 60) + 60;
	var rightObstacleSpawnTime = Math.floor(Math.random() * 60) + 60;
	bird.x = 1024;
	bird.y = 1366;
	stage.on('down', function (obj) {
		bird.flap();
	});
	LK.on('tick', function () {
		bird.update();
		if (LK.ticks == leftObstacleSpawnTime) {
			leftObstacle = self.addChild(new Obstacle());
			leftObstacle.x = 0;
			leftObstacle.y = 0;
			leftObstacleSpawnTime += Math.floor(Math.random() * 60) + 60;
		}
		if (LK.ticks == rightObstacleSpawnTime) {
			rightObstacle = self.addChild(new Obstacle());
			rightObstacle.x = 2048;
			rightObstacle.y = 0;
			rightObstacleSpawnTime += Math.floor(Math.random() * 60) + 60;
		}
		if (leftObstacle) leftObstacle.move();
		if (rightObstacle) rightObstacle.move();
		if (bird.intersects(leftWall) || bird.intersects(rightWall) || bird.intersects(leftObstacle) || bird.intersects(rightObstacle)) {
			bird.xSpeed = -bird.xSpeed;
			bird.flip();
		}
		if (bird.y < 0 || bird.y > 2732) {
			LK.showGameOver();
		}
	});
});

===================================================================
--- original.js
+++ change.js
@@ -45,23 +45,32 @@
 	leftWall.y = 1366;
 	var rightWall = self.addChild(new Wall());
 	rightWall.x = 2048;
 	rightWall.y = 1366;
-	var leftObstacle = self.addChild(new Obstacle());
-	leftObstacle.x = 0;
-	leftObstacle.y = 0;
-	var rightObstacle = self.addChild(new Obstacle());
-	rightObstacle.x = 2048;
-	rightObstacle.y = 0;
+	var leftObstacle, rightObstacle;
+	var leftObstacleSpawnTime = Math.floor(Math.random() * 60) + 60;
+	var rightObstacleSpawnTime = Math.floor(Math.random() * 60) + 60;
 	bird.x = 1024;
 	bird.y = 1366;
 	stage.on('down', function (obj) {
 		bird.flap();
 	});
 	LK.on('tick', function () {
 		bird.update();
-		leftObstacle.move();
-		rightObstacle.move();
+		if (LK.ticks == leftObstacleSpawnTime) {
+			leftObstacle = self.addChild(new Obstacle());
+			leftObstacle.x = 0;
+			leftObstacle.y = 0;
+			leftObstacleSpawnTime += Math.floor(Math.random() * 60) + 60;
+		}
+		if (LK.ticks == rightObstacleSpawnTime) {
+			rightObstacle = self.addChild(new Obstacle());
+			rightObstacle.x = 2048;
+			rightObstacle.y = 0;
+			rightObstacleSpawnTime += Math.floor(Math.random() * 60) + 60;
+		}
+		if (leftObstacle) leftObstacle.move();
+		if (rightObstacle) rightObstacle.move();
 		if (bird.intersects(leftWall) || bird.intersects(rightWall) || bird.intersects(leftObstacle) || bird.intersects(rightObstacle)) {
 			bird.xSpeed = -bird.xSpeed;
 			bird.flip();
 		}