/**** 
* Classes
****/ 
var Bullet = Container.expand(function (gameInstance) {
	var self = Container.call(this);
	self.game = gameInstance;
	self._isDestroyed = false;
	var bulletGraphics = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self._move_migrated = function () {
		if (self._isDestroyed) return;
		self.x += 240;
		if (self.x > 2148) {
			if (!self._isDestroyed && self.parent) {
				self._isDestroyed = true;
				if (typeof self.destroy === "function") self.destroy();
			}
		}
	};
});
var Enemy = Container.expand(function (gameInstance) {
	var self = Container.call(this);
	self.game = gameInstance;
	self._isDestroyed = false;
	var enemyGraphics = self.attachAsset('enemy', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self._move_migrated = function () {
		if (self._isDestroyed) return;
		self.y += 25.6 * 0.7 * 0.6;
		if (self.y > 2732) {
			if (!self._isDestroyed && self.parent) {
				self._isDestroyed = true;
				if (typeof self.destroy === "function") self.destroy();
			}
		}
	};
});
var FrameRateCounter = Container.expand(function () {
	var self = Container.call(this);
	self.lastTime = Date.now();
	self.frameCount = 0;
	self.framerate = 0;
	self.display = new Text2('FPS: 0', {
		size: 150,
		fill: '#000000'
	});
	self.display.anchor.set(1, 0);
	self.updateDisplay = function () {
		self.display.setText('FPS: ' + Math.round(self.framerate).toString());
	};
	self._update_migrated = function () {
		var currentTime = Date.now();
		self.frameCount++;
		if (currentTime - self.lastTime >= 1000) {
			self.framerate = self.frameCount;
			self.updateDisplay();
			self.frameCount = 0;
			self.lastTime = currentTime;
		}
	};
});
var Plain = Container.expand(function () {
	var self = Container.call(this);
	var plainGraphics = self.attachAsset('correct_plain_asset_id', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	plainGraphics.scale.x = 2;
	plainGraphics.scale.y = 2;
	plainGraphics.alpha = 0;
	self.shoot = function (enemies, bulletsContainer) {
		if (self.cooldownTimer <= 0 && enemies.length > 0) {
			var bullet = new Bullet(self);
			bullet.x = self.x;
			bullet.y = self.y;
			bulletsContainer.addChild(bullet);
			self.cooldownTimer = self.cooldown;
		}
		self.cooldownTimer--;
	};
});
var Tower = Container.expand(function (gameInstance) {
	var self = Container.call(this);
	self.game = gameInstance;
	var towerGraphics = self.attachAsset('tower', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.cooldown = 0.625 / 0.7 * (1 / 0.6) * 1.3;
	self.cooldownTimer = 0;
	self.shoot = function (enemies, bullets) {
		if (self.cooldownTimer <= 0 && enemies.length > 0) {
			self.fireBullet(bullets);
		}
		self.cooldownTimer--;
	};
	self.fireBullet = function (bullets) {
		var bullet = new Bullet(self.game);
		bullet.x = self.x;
		bullet.y = self.y;
		gameInstance.bulletsContainer.addChild(bullet);
		gameInstance.bullets.push(bullet);
		self.cooldownTimer = self.cooldown;
	};
});

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

/**** 
* Game Code
****/ 
game.spawnEnemies = function () {
	enemiesSpawnedLastRound = enemiesSpawnedLastRound * 4;
	for (var i = 0; i < enemiesSpawnedLastRound; i++) {
		var newEnemy = new Enemy();
		newEnemy.x = Math.random() * 2048;
		newEnemy.y = -50 * (i + 1);
		game.enemies.push(newEnemy);
		game.enemiesContainer.addChild(newEnemy);
	}
	if (game.lastEnemyCount !== game.enemies.length) {
		game.enemyCounterTxt.setText('Enemies: ' + game.enemies.length.toString());
		game.lastEnemyCount = game.enemies.length;
	}
};
game.updateEnemyCounter = function () {};
game.score = 0;
game.gold = 100;
game.incrementScore = function () {
	this.score++;
};
game.frameRateCounter = new FrameRateCounter();
LK.gui.topRight.addChild(game.frameRateCounter.display);
var enemiesSpawnedLastRound = 1;
game.scoreTxt = new Text2(game.score.toString(), {
	size: 150,
	fill: 0xFFFFFF
});
game.scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(game.scoreTxt);
game.goldTxt = new Text2(game.gold.toString(), {
	size: 150,
	fill: 0xFFFF00
});
game.goldTxt.anchor.set(0, 0);
LK.gui.topLeft.addChild(game.goldTxt);
game.enemies = [];
game.enemiesContainer = game.addChild(new Container());
game.enemyCounterTxt = new Text2('Enemies: ' + game.enemies.length.toString(), {
	size: 150,
	fill: 0xFF0000
});
game.lastGold = game.gold;
game.lastScore = game.score;
game.lastEnemyCount = game.enemies.length;
game.enemyCounterTxt.anchor.set(0, 1);
LK.gui.bottomLeft.addChild(game.enemyCounterTxt);
game.setBackgroundColor(0xFFFFFF);
var towers = [];
game.bullets = [];
game.bulletsContainer = game.addChild(new Container());
var initialTower = new Tower(game);
initialTower.x = 0 + initialTower.width / 2 - 260;
initialTower.y = 500 + initialTower.height / 2 + 300 + 800 + 500;
towers.push(initialTower);
game.addChild(initialTower);
var plain = new Plain();
plain.x = 2048 / 2;
plain.y = 2732 / 2;
game.addChild(plain);
var enemy = new Enemy();
enemy.x = 2048 / 2;
enemy.y = -enemy.height / 2;
game.enemies.push(enemy);
game.enemiesContainer.addChild(enemy);
game.on('down', function (x, y, obj) {
	var event = obj;
	var pos = game.toLocal(event.global);
	if (game.gold >= 50) {
		var newTower = new Tower(game);
		newTower.x = pos.x;
		newTower.y = pos.y;
		game.addChild(newTower);
		towers.push(newTower);
		game.gold -= 50;
		if (game.lastGold !== game.gold) {
			game.goldTxt.setText(game.gold.toString());
			game.lastGold = game.gold;
		}
	}
});
LK.on('tick', function () {
	game.frameRateCounter._update_migrated();
	if (game.enemies.length === 0) {
		game.spawnEnemies();
	}
	towers.forEach(function (tower) {
		tower.shoot(game.enemies, game.bullets);
	});
	// Optimized update loop for both enemies and bullets to minimize per-frame iteration and array mutation
	var ei = 0;
	while (ei < game.enemies.length) {
		var enemy = game.enemies[ei];
		enemy._move_migrated();
		ei++;
	}
	// --- Begin spatial partitioning for collision checks ---
	if (!game._gridCellSize) {
		game._gridCellSize = 300;
		game._gridCols = Math.ceil(2048 / game._gridCellSize);
		game._gridRows = Math.ceil(2732 / game._gridCellSize);
	}
	var gridCellSize = game._gridCellSize;
	var gridCols = game._gridCols;
	var gridRows = game._gridRows;
	if (!game._enemyGrid) {
		game._enemyGrid = [];
		for (var gx = 0; gx < gridCols * gridRows; gx++) game._enemyGrid[gx] = [];
	}
	var enemyGrid = game._enemyGrid;
	for (var gx = 0; gx < gridCols * gridRows; gx++) enemyGrid[gx].length = 0;
	for (var ei = 0; ei < game.enemies.length; ei++) {
		var e = game.enemies[ei];
		var ex = Math.floor(e.x / gridCellSize);
		var ey = Math.floor(e.y / gridCellSize);
		var idx = ey * gridCols + ex;
		if (idx >= 0 && idx < enemyGrid.length) enemyGrid[idx].push(e);
	}
	var bi = 0;
	while (bi < game.bullets.length) {
		var bullet = game.bullets[bi];
		bullet._move_migrated();
		var destroyed = false;
		var bx = Math.floor(bullet.x / gridCellSize);
		var by = Math.floor(bullet.y / gridCellSize);
		for (var dx = -1; dx <= 1; dx++) {
			for (var dy = -1; dy <= 1; dy++) {
				var cx = bx + dx;
				var cy = by + dy;
				if (cx < 0 || cy < 0 || cx >= gridCols || cy >= gridRows) continue;
				var idx = cy * gridCols + cx;
				var cellEnemies = enemyGrid[idx];
				for (var j = cellEnemies.length - 1; j >= 0; j--) {
					var enemy = cellEnemies[j];
					if (!bullet._isDestroyed && !enemy._isDestroyed && bullet.intersects(enemy)) {
						enemy._isDestroyed = true;
						enemy.destroy();
						game.incrementScore();
						if (game.lastScore !== game.score) {
							game.scoreTxt.setText(game.score.toString());
							game.lastScore = game.score;
						}
						game.gold += 50;
						if (game.lastGold !== game.gold) {
							game.goldTxt.setText(game.gold.toString());
							game.lastGold = game.gold;
						}
						bullet._isDestroyed = true;
						bullet.destroy();
						destroyed = true;
						break;
					}
				}
				if (destroyed) break;
			}
			if (destroyed) break;
		}
		if (destroyed || bullet.x > 2048) {
			bullet._isDestroyed = true;
			bullet.destroy();
		}
		bi++;
	}
	// --- End spatial partitioning for collision checks ---
	// Batch remove destroyed enemies and bullets
	if (!game._reuseEnemies) game._reuseEnemies = [];
	if (!game._reuseBullets) game._reuseBullets = [];
	var newEnemies = game._reuseEnemies;
	newEnemies.length = 0;
	for (var i = 0; i < game.enemies.length; i++) {
		if (!game.enemies[i]._isDestroyed) {
			newEnemies.push(game.enemies[i]);
		} else {
			if (game.enemies[i].parent) {
				game.enemies[i].parent.removeChild(game.enemies[i]);
				if (typeof game.enemies[i].destroy === "function") game.enemies[i].destroy();
			}
		}
	}
	game.enemies = newEnemies;
	if (game.lastEnemyCount !== game.enemies.length) {
		game.enemyCounterTxt.setText('Enemies: ' + game.enemies.length.toString());
		game.lastEnemyCount = game.enemies.length;
	}
	var newBullets = game._reuseBullets;
	newBullets.length = 0;
	for (var i = 0; i < game.bullets.length; i++) {
		if (!game.bullets[i]._isDestroyed) {
			newBullets.push(game.bullets[i]);
		} else {
			if (game.bullets[i].parent) {
				game.bullets[i].parent.removeChild(game.bullets[i]);
				if (typeof game.bullets[i].destroy === "function") game.bullets[i].destroy();
			}
		}
	}
	game.bullets = newBullets;
});

===================================================================
--- original.js
+++ change.js
@@ -14,9 +14,9 @@
 		self.x += 240;
 		if (self.x > 2148) {
 			if (!self._isDestroyed && self.parent) {
 				self._isDestroyed = true;
-				self.destroy();
+				if (typeof self.destroy === "function") self.destroy();
 			}
 		}
 	};
 });
@@ -33,9 +33,9 @@
 		self.y += 25.6 * 0.7 * 0.6;
 		if (self.y > 2732) {
 			if (!self._isDestroyed && self.parent) {
 				self._isDestroyed = true;
-				self.destroy();
+				if (typeof self.destroy === "function") self.destroy();
 			}
 		}
 	};
 });