/**** 
* Classes
****/ 
//<Assets used in the game will automatically appear here>
//<Write imports for supported plugins here>
// Bird class to handle the bird's behavior
var Bird = Container.expand(function () {
	var self = Container.call(this);
	var birdGraphics = self.attachAsset('bird', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.velocity = 0;
	self.gravity = 0.5;
	self.lift = -10;
	self.update = function () {
		self.velocity += self.gravity;
		self.y += self.velocity;
		// Prevent bird from going off the top of the screen
		if (self.y < 0) {
			self.y = 0;
			self.velocity = 0;
		}
	};
	self.flap = function () {
		self.velocity = self.lift;
	};
});
// Pipe class to handle the pipes
var Pipe = Container.expand(function () {
	var self = Container.call(this);
	var pipeGraphics = self.attachAsset('pipe', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = -5;
	self.update = function () {
		self.x += self.speed;
	};
	self.isOffScreen = function () {
		return self.x < -pipeGraphics.width;
	};
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x87CEEB // Sky blue background
});

/**** 
* Game Code
****/ 
// Initialize game variables
var bird;
var pipes = [];
var pipeSpacing = 600;
var pipeGap = 400;
var score = 0;
var scoreTxt = new Text2('0', {
	size: 150,
	fill: 0xFFFFFF
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
// Create a start screen
var startScreen = new Container();
var startText = new Text2('Tap to start', {
	size: 150,
	fill: 0xFFFFFF
});
startText.anchor.set(0.5, 0.5);
startText.x = 2048 / 2;
startText.y = 2732 / 2;
startScreen.addChild(startText);
game.addChild(startScreen);
// Handle screen tap to start the game
startScreen.down = function (x, y, obj) {
	if (!bird) {
		bird = game.addChild(new Bird());
		bird.x = 2048 / 4;
		bird.y = 2732 / 2;
		game.removeChild(startScreen);
	}
};
// Function to create a new set of pipes
function createPipes() {
	var pipeHeight = Math.random() * (2732 - pipeGap - 200) + 100;
	var topPipe = new Pipe();
	topPipe.y = pipeHeight - 2732;
	topPipe.x = 2048;
	pipes.push(topPipe);
	game.addChild(topPipe);
	var bottomPipe = new Pipe();
	bottomPipe.y = pipeHeight + pipeGap;
	bottomPipe.x = 2048;
	pipes.push(bottomPipe);
	game.addChild(bottomPipe);
}
// Handle screen tap to make the bird flap
game.down = function (x, y, obj) {
	if (bird) {
		bird.flap();
	}
};
// Update game logic
game.update = function () {
	if (document.hidden) {
		return;
	}
	if (bird) {
		bird.update();
	}
	// Create new pipes at intervals
	if (LK.ticks % 90 === 0) {
		createPipes();
	}
	// Update pipes and check for collisions
	for (var i = pipes.length - 1; i >= 0; i--) {
		pipes[i].update();
		// Check for collision with bird
		if (bird && pipes[i] && bird.intersects(pipes[i])) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
			return;
		}
		// Remove pipes that are off screen and update score
		if (pipes[i].isOffScreen()) {
			pipes[i].destroy();
			pipes.splice(i, 1);
			score++;
			scoreTxt.setText(score);
		}
	}
	// Check if bird hits the ground
	if (bird && bird.y > 2732) {
		LK.effects.flashScreen(0xff0000, 1000);
		LK.showGameOver();
	}
};

===================================================================
--- original.js
+++ change.js
@@ -105,8 +105,11 @@
 	}
 };
 // Update game logic
 game.update = function () {
+	if (document.hidden) {
+		return;
+	}
 	if (bird) {
 		bird.update();
 	}
 	// Create new pipes at intervals