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

/**** 
* Classes
****/ 
// Bullet class
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGfx = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.dx = 0;
	self.dy = 0;
	self.damage = 1;
	self.lifetime = 60; // ticks
	self.update = function () {
		self.x += self.dx;
		self.y += self.dy;
		self.lifetime--;
		if (self.lifetime <= 0) {
			self.destroy();
		}
	};
	return self;
});
// Enemy class
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGfx = self.attachAsset('enemyUnit', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.hp = 2 + wave;
	self.speed = 2 + 0.2 * wave;
	self.targetX = commandCenterPos.x;
	self.targetY = commandCenterPos.y;
	self.reward = 10 + 2 * wave;
	self.update = function () {
		var dx = self.targetX - self.x;
		var dy = self.targetY - self.y;
		var dist = Math.sqrt(dx * dx + dy * dy);
		if (dist > 2) {
			self.x += dx / dist * self.speed;
			self.y += dy / dist * self.speed;
		}
	};
	return self;
});
// Turret class
var Turret = Container.expand(function () {
	var self = Container.call(this);
	// Attach base
	var base = self.attachAsset('turretBase', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	// Attach barrel
	var barrel = self.attachAsset('turretBarrel', {
		anchorX: 0.5,
		anchorY: 0.85,
		y: -30
	});
	self.level = 1;
	self.fireRate = 60; // ticks between shots
	self.lastShot = 0;
	self.range = 500;
	self.damage = 1;
	self.upgrade = function () {
		if (self.level < 3) {
			self.level += 1;
			self.fireRate = Math.max(30, self.fireRate - 10);
			self.range += 80;
			self.damage += 1;
			// Animate upgrade
			tween(self, {
				scaleX: 1.2,
				scaleY: 1.2
			}, {
				duration: 120,
				easing: tween.easeOut,
				onFinish: function onFinish() {
					tween(self, {
						scaleX: 1,
						scaleY: 1
					}, {
						duration: 120,
						easing: tween.easeIn
					});
				}
			});
		}
	};
	// Find nearest enemy in range
	self.findTarget = function () {
		var minDist = self.range;
		var target = null;
		for (var i = 0; i < enemies.length; i++) {
			var e = enemies[i];
			var dx = e.x - self.x;
			var dy = e.y - self.y;
			var dist = Math.sqrt(dx * dx + dy * dy);
			if (dist < minDist) {
				minDist = dist;
				target = e;
			}
		}
		return target;
	};
	// Called every tick
	self.update = function () {
		// Find target
		var target = self.findTarget();
		if (target) {
			// Rotate barrel towards target
			var dx = target.x - self.x;
			var dy = target.y - self.y;
			var angle = Math.atan2(dy, dx) - Math.PI / 2;
			barrel.rotation = angle;
			// Fire if ready
			if (LK.ticks - self.lastShot >= self.fireRate) {
				self.lastShot = LK.ticks;
				var b = new Bullet();
				b.x = self.x;
				b.y = self.y;
				b.rotation = angle + Math.PI / 2;
				b.dx = Math.cos(angle + Math.PI / 2) * 32;
				b.dy = Math.sin(angle + Math.PI / 2) * 32;
				b.damage = self.damage;
				bullets.push(b);
				game.addChild(b);
			}
		}
	};
	// Touch to upgrade
	self.down = function (x, y, obj) {
		if (resources >= turretUpgradeCost(self.level)) {
			resources -= turretUpgradeCost(self.level);
			self.upgrade();
			updateResourceText();
		}
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x222831
});

/**** 
* Game Code
****/ 
// Build button
// Upgrade button
// Bullet
// Enemy unit
// Command center
// Turret barrel
// Turret base
// Game constants
var baseWidth = 2048;
var baseHeight = 2732;
var commandCenterPos = {
	x: baseWidth / 2,
	y: baseHeight - 350
};
var turretSpots = [{
	x: baseWidth / 2 - 350,
	y: baseHeight - 700
}, {
	x: baseWidth / 2 + 350,
	y: baseHeight - 700
}, {
	x: baseWidth / 2 - 600,
	y: baseHeight - 1100
}, {
	x: baseWidth / 2 + 600,
	y: baseHeight - 1100
}, {
	x: baseWidth / 2,
	y: baseHeight - 1100
}];
var maxTurrets = 5;
var turretBuildCost = 50;
function turretUpgradeCost(level) {
	return 40 * level;
}
var wave = 1;
var enemies = [];
var bullets = [];
var turrets = [];
var resources = 100;
var commandCenterHP = 10;
var isPlacingTurret = false;
// Command Center
var commandCenter = LK.getAsset('commandCenter', {
	anchorX: 0.5,
	anchorY: 0.5,
	x: commandCenterPos.x,
	y: commandCenterPos.y
});
game.addChild(commandCenter);
// GUI: Resource display
var resourceTxt = new Text2('Resources: 100', {
	size: 80,
	fill: "#fff"
});
resourceTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(resourceTxt);
// GUI: Wave display
var waveTxt = new Text2('Wave: 1', {
	size: 80,
	fill: "#fff"
});
waveTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(waveTxt);
waveTxt.y = 90;
// GUI: Command Center HP
var hpTxt = new Text2('Base HP: 10', {
	size: 80,
	fill: "#fff"
});
hpTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(hpTxt);
hpTxt.y = 180;
// GUI: Build Turret Button
var buildBtn = LK.getAsset('buildBtn', {
	anchorX: 0.5,
	anchorY: 0.5,
	x: baseWidth / 2 - 250,
	y: baseHeight - 180
});
var buildBtnTxt = new Text2('Build Turret\n50', {
	size: 48,
	fill: "#fff"
});
buildBtnTxt.anchor.set(0.5, 0.5);
buildBtn.addChild(buildBtnTxt);
game.addChild(buildBtn);
// GUI: Upgrade All Button
var upgradeBtn = LK.getAsset('upgradeBtn', {
	anchorX: 0.5,
	anchorY: 0.5,
	x: baseWidth / 2 + 250,
	y: baseHeight - 180
});
var upgradeBtnTxt = new Text2('Upgrade All', {
	size: 48,
	fill: "#fff"
});
upgradeBtnTxt.anchor.set(0.5, 0.5);
upgradeBtn.addChild(upgradeBtnTxt);
game.addChild(upgradeBtn);
// Update resource text
function updateResourceText() {
	resourceTxt.setText('Resources: ' + resources);
}
function updateWaveText() {
	waveTxt.setText('Wave: ' + wave);
}
function updateHPText() {
	hpTxt.setText('Base HP: ' + commandCenterHP);
}
// Build turret on next available spot
function buildTurret() {
	if (resources < turretBuildCost) return;
	if (turrets.length >= maxTurrets) return;
	var spot = turretSpots[turrets.length];
	var t = new Turret();
	t.x = spot.x;
	t.y = spot.y;
	turrets.push(t);
	game.addChild(t);
	resources -= turretBuildCost;
	updateResourceText();
}
// Upgrade all turrets
function upgradeAllTurrets() {
	for (var i = 0; i < turrets.length; i++) {
		var t = turrets[i];
		if (t.level < 3 && resources >= turretUpgradeCost(t.level)) {
			resources -= turretUpgradeCost(t.level);
			t.upgrade();
		}
	}
	updateResourceText();
}
// Build button event
buildBtn.down = function (x, y, obj) {
	buildTurret();
};
// Upgrade button event
upgradeBtn.down = function (x, y, obj) {
	upgradeAllTurrets();
};
// Place initial turret
buildTurret();
// Enemy spawn logic
var spawnTimer = 0;
var enemiesToSpawn = 0;
function startWave() {
	enemiesToSpawn = 4 + wave * 2;
	spawnTimer = 0;
	updateWaveText();
}
startWave();
// Main game update
game.update = function () {
	// Turrets update
	for (var i = 0; i < turrets.length; i++) {
		turrets[i].update();
	}
	// Bullets update
	for (var i = bullets.length - 1; i >= 0; i--) {
		var b = bullets[i];
		b.update();
		// Remove if out of bounds
		if (b.x < -100 || b.x > baseWidth + 100 || b.y < -100 || b.y > baseHeight + 100 || b.lifetime <= 0) {
			b.destroy();
			bullets.splice(i, 1);
			continue;
		}
		// Check collision with enemies
		for (var j = enemies.length - 1; j >= 0; j--) {
			var e = enemies[j];
			if (b.intersects(e)) {
				e.hp -= b.damage;
				b.destroy();
				bullets.splice(i, 1);
				// Animate hit
				tween(e, {
					scaleX: 1.2,
					scaleY: 1.2
				}, {
					duration: 80,
					onFinish: function onFinish() {
						tween(e, {
							scaleX: 1,
							scaleY: 1
						}, {
							duration: 80
						});
					}
				});
				if (e.hp <= 0) {
					// Enemy destroyed
					resources += e.reward;
					updateResourceText();
					e.destroy();
					enemies.splice(j, 1);
				}
				break;
			}
		}
	}
	// Enemies update
	for (var i = enemies.length - 1; i >= 0; i--) {
		var e = enemies[i];
		e.update();
		// Check if reached command center
		if (e.intersects(commandCenter)) {
			commandCenterHP -= 1;
			updateHPText();
			// Animate base hit
			LK.effects.flashObject(commandCenter, 0xff0000, 300);
			e.destroy();
			enemies.splice(i, 1);
			if (commandCenterHP <= 0) {
				LK.effects.flashScreen(0xff0000, 1000);
				LK.showGameOver();
				return;
			}
		}
	}
	// Enemy spawn
	if (enemiesToSpawn > 0) {
		if (spawnTimer <= 0) {
			// Spawn enemy at random edge
			var edge = Math.floor(Math.random() * 3);
			var ex, ey;
			if (edge === 0) {
				// left
				ex = 100;
				ey = 600 + Math.random() * 800;
			} else if (edge === 1) {
				// right
				ex = baseWidth - 100;
				ey = 600 + Math.random() * 800;
			} else {
				// top
				ex = baseWidth / 2 - 400 + Math.random() * 800;
				ey = 100;
			}
			var enemy = new Enemy();
			enemy.x = ex;
			enemy.y = ey;
			enemies.push(enemy);
			game.addChild(enemy);
			enemiesToSpawn--;
			spawnTimer = Math.max(30, 90 - wave * 2);
		} else {
			spawnTimer--;
		}
	} else if (enemies.length === 0) {
		// Next wave
		wave++;
		commandCenterHP = Math.min(10, commandCenterHP + 2);
		updateHPText();
		startWave();
	}
};
// Touch to upgrade turrets directly
game.down = function (x, y, obj) {
	// Check if touch is on a turret
	for (var i = 0; i < turrets.length; i++) {
		var t = turrets[i];
		var dx = x - t.x;
		var dy = y - t.y;
		if (dx * dx + dy * dy < 100 * 100) {
			// Try upgrade
			if (resources >= turretUpgradeCost(t.level) && t.level < 3) {
				resources -= turretUpgradeCost(t.level);
				t.upgrade();
				updateResourceText();
			}
			return;
		}
	}
};
// Prevent placing elements in top left 100x100
// (All GUI is centered or at bottom, so nothing to do here)

===================================================================
--- original.js
+++ change.js