/**** 
* Plugins
****/ 
var tween = LK.import("@upit/tween.v1");

/**** 
* Classes
****/ 
// Class for Bird
var Bird = Container.expand(function () {
	var self = Container.call(this);
	var birdGraphics = self.attachAsset('bird', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.update = function () {
		self.x += self.speed;
		self.y += Math.sin(self.x / 100) * 2; // Add vertical movement based on sine wave
		if (self.x > 2048 + birdGraphics.width / 2) {
			self.x = -birdGraphics.width / 2;
		}
	};
});
// Class for Crane
var Crane = Container.expand(function () {
	var self = Container.call(this);
	var craneGraphics = self.attachAsset('crane', {
		anchorX: 0.5,
		anchorY: 0.0
	});
});
// Class for Dove
var Dove = Container.expand(function () {
	var self = Container.call(this);
	var doveGraphics = self.attachAsset('bird', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 3;
	self.update = function () {
		self.x += self.speed;
		self.y += Math.sin(self.x / 100) * 2; // Add vertical movement based on sine wave
		if (self.x > 2048 + doveGraphics.width / 2) {
			self.x = -doveGraphics.width / 2;
		}
	};
});
var DoveBird = Container.expand(function () {
	var self = Container.call(this);
	var doveBirdGraphics = self.attachAsset('dovebird', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 4;
	self.update = function () {
		self.x -= self.speed;
		self.y += Math.sin(self.x / 100) * 2; // Add vertical movement based on sine wave
		if (self.x < -doveBirdGraphics.width / 2) {
			self.x = 2048 + doveBirdGraphics.width / 2;
		}
	};
});
// Class for TowerBlock
var TowerBlock = Container.expand(function () {
	var self = Container.call(this);
	var blockGraphics = self.attachAsset('towerBlock', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.swayDirection = 1;
	self.swaySpeed = 1;
	self.update = function () {
		self.x += self.swaySpeed * self.swayDirection * 1.5;
		if (self.x > 2048 - blockGraphics.width / 2 || self.x < blockGraphics.width / 2) {
			self.swayDirection *= -1; // Reverse direction when reaching the edge
		}
	};
});

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

/**** 
* Game Code
****/ 
var sky = game.addChild(LK.getAsset('sky', {
	anchorX: 0,
	anchorY: 0,
	x: 0,
	y: 0
}));
var crane = new Crane();
crane.x = currentBlock ? currentBlock.x : 2048 / 2;
crane.y = 0;
game.addChild(crane);
var grass = game.addChild(LK.getAsset('grass', {
	anchorX: 0,
	anchorY: 1,
	x: 0,
	y: 2732
}));
// Initialize variables
var towerBlocks = [];
var baseY = 2500; // Base row position
var currentBlock = null;
var blockCount = 0; // Track number of blocks created
var dropCooldownActive = false; // Track if drop cooldown is active
// Function to drop the current block
function dropBlock() {
	if (currentBlock) {
		currentBlock.swaySpeed = 0; // Stop swaying
		towerBlocks.push(currentBlock);
		currentBlock = null;
	}
}
// Create a new block at the top of the screen
function createNewBlock() {
	if (blockCount < 20) {
		currentBlock = new TowerBlock();
		currentBlock.x = crane.x;
		currentBlock.y = crane.y + 100;
		game.addChild(currentBlock);
		blockCount++;
	}
}
// Handle screen tap to drop the block
game.down = function (x, y, obj) {
	// Prevent dropping if cooldown is active
	if (dropCooldownActive) {
		return;
	}
	if (!currentBlock) {
		if (blockCount < 20) {
			currentBlock = new TowerBlock();
			currentBlock.x = crane.x;
			currentBlock.y = crane.y + 100;
			game.addChild(currentBlock);
			blockCount++;
		}
	}
	var lastSwayDirection = currentBlock ? currentBlock.swayDirection : 1; // Save the sway direction of the current block, default to 1 if null
	dropBlock();
	if (blockCount < 20) {
		createNewBlock();
	}
	if (currentBlock) {
		currentBlock.x = towerBlocks[towerBlocks.length - 1].x; // Set the x position of the new block to the x position of the last block in the towerBlocks array
		currentBlock.swayDirection = lastSwayDirection; // Set the sway direction of the new block to the saved sway direction
		// Reduce opacity during cooldown
		tween(currentBlock, {
			alpha: 0.5
		}, {
			duration: 1000,
			onFinish: function onFinish() {
				// Restore full opacity when cooldown ends
				if (currentBlock) {
					currentBlock.alpha = 1.0;
				}
				dropCooldownActive = false;
			}
		});
	}
	// Activate cooldown
	dropCooldownActive = true;
};
// Initialize the first block
createNewBlock();
// Add birds to the game
for (var i = 0; i < 2; i++) {
	var bird = new Bird();
	bird.x = Math.random() * 2048;
	bird.y = Math.random() * (2732 / 2);
	game.addChild(bird);
}
// Add doves to the game
for (var i = 0; i < 3; i++) {
	var dove = new Dove();
	dove.x = Math.random() * 2048;
	dove.y = Math.random() * (2732 / 2);
	game.addChild(dove);
}
// Add dovebirds to the game
for (var i = 0; i < 2; i++) {
	var doveBird = new DoveBird();
	doveBird.x = Math.random() * 2048;
	doveBird.y = Math.random() * (2732 / 2);
	game.addChild(doveBird);
}
// Update function for the game
game.update = function () {
	if (currentBlock) {
		currentBlock.update();
		crane.x = currentBlock ? currentBlock.x : towerBlocks.length > 0 ? towerBlocks[towerBlocks.length - 1].x : crane.x;
	}
	// Update positions of all blocks
	for (var i = towerBlocks.length - 1; i >= 0; i--) {
		towerBlocks[i].y += 10; // Increase the falling speed of blocks
		// Check if the block has collided with the grass
		if (towerBlocks[i].intersects(grass)) {
			towerBlocks[i].y = grass.y - towerBlocks[i].height / 2; // Position the block on top of the grass
			towerBlocks[i].swaySpeed = 0; // Stop the block from moving
		}
		// Check if the block has collided with another block
		for (var j = 0; j < towerBlocks.length; j++) {
			if (i != j && towerBlocks[i] && towerBlocks[j] && towerBlocks[i].intersects(towerBlocks[j])) {
				towerBlocks[i].y = towerBlocks[j].y - towerBlocks[i].height; // Position the block on top of the other block
				towerBlocks[i].swaySpeed = 0; // Stop the block from moving
				towerBlocks[i].swayDirection = 0; // Ensure no further movement occurs
				// Initialize lastX for tracking changes on X
				if (towerBlocks[i].lastX === undefined) {
					towerBlocks[i].lastX = towerBlocks[i].x;
				}
				// Check if at least 90% of the tower block fits on the underlying one
				if (towerBlocks[j] && Math.abs(towerBlocks[i].x - towerBlocks[j].x) > towerBlocks[i].width * 0.1) {
					// If not, slide it off animatedly
					if (towerBlocks[i].isSliding === undefined) {
						towerBlocks[i].isSliding = true;
					}
					towerBlocks[i].x += towerBlocks[i].x < towerBlocks[j].x ? -5 : 5;
					// Check if the block has fallen off completely
					if (towerBlocks[i].x < 0 || towerBlocks[i].x > 2048) {
						towerBlocks[i].destroy(); // Remove the block from the game
						towerBlocks.splice(i, 1); // Remove the block from the array
					}
				} else if (towerBlocks[i].y > 2732) {
					towerBlocks[i].destroy(); // Remove the block from the game
					towerBlocks.splice(i, 1); // Remove the block from the array
				}
				// Update last known states
				if (towerBlocks[i]) {
					towerBlocks[i].lastX = towerBlocks[i].x;
				}
				break; // Prevent block from bouncing by breaking the loop once a collision is detected
			}
		}
	}
	// Play dove sound in loop
	if (LK.ticks % 420 == 0) {
		LK.getSound('Dove').play();
		LK.playMusic('Birds');
	}
};

===================================================================
--- original.js
+++ change.js
@@ -197,25 +197,24 @@
 		currentBlock.update();
 		crane.x = currentBlock ? currentBlock.x : towerBlocks.length > 0 ? towerBlocks[towerBlocks.length - 1].x : crane.x;
 	}
 	// Update positions of all blocks
-	for (var i = 0; i < towerBlocks.length; i++) {
+	for (var i = towerBlocks.length - 1; i >= 0; i--) {
 		towerBlocks[i].y += 10; // Increase the falling speed of blocks
 		// Check if the block has collided with the grass
 		if (towerBlocks[i].intersects(grass)) {
 			towerBlocks[i].y = grass.y - towerBlocks[i].height / 2; // Position the block on top of the grass
 			towerBlocks[i].swaySpeed = 0; // Stop the block from moving
 		}
 		// Check if the block has collided with another block
 		for (var j = 0; j < towerBlocks.length; j++) {
-			if (i != j && towerBlocks[i].intersects(towerBlocks[j])) {
+			if (i != j && towerBlocks[i] && towerBlocks[j] && towerBlocks[i].intersects(towerBlocks[j])) {
 				towerBlocks[i].y = towerBlocks[j].y - towerBlocks[i].height; // Position the block on top of the other block
 				towerBlocks[i].swaySpeed = 0; // Stop the block from moving
 				towerBlocks[i].swayDirection = 0; // Ensure no further movement occurs
 				// Initialize lastX for tracking changes on X
 				if (towerBlocks[i].lastX === undefined) {
 					towerBlocks[i].lastX = towerBlocks[i].x;
-					towerBlocks[i].lastX = towerBlocks[i].x;
 				}
 				// Check if at least 90% of the tower block fits on the underlying one
 				if (towerBlocks[j] && Math.abs(towerBlocks[i].x - towerBlocks[j].x) > towerBlocks[i].width * 0.1) {
 					// If not, slide it off animatedly
@@ -226,17 +225,17 @@
 					// Check if the block has fallen off completely
 					if (towerBlocks[i].x < 0 || towerBlocks[i].x > 2048) {
 						towerBlocks[i].destroy(); // Remove the block from the game
 						towerBlocks.splice(i, 1); // Remove the block from the array
-						i--; // Adjust the index after removal
 					}
 				} else if (towerBlocks[i].y > 2732) {
 					towerBlocks[i].destroy(); // Remove the block from the game
 					towerBlocks.splice(i, 1); // Remove the block from the array
-					i--; // Adjust the index after removal
 				}
 				// Update last known states
-				towerBlocks[i].lastX = towerBlocks[i].x;
+				if (towerBlocks[i]) {
+					towerBlocks[i].lastX = towerBlocks[i].x;
+				}
 				break; // Prevent block from bouncing by breaking the loop once a collision is detected
 			}
 		}
 	}