===================================================================
--- original.js
+++ change.js
@@ -1,6 +1,481 @@
-/****
+/**** 
+* Plugins
+****/ 
+var tween = LK.import("@upit/tween.v1");
+
+/**** 
+* Classes
+****/ 
+// Alien Invader
+var Alien = Container.expand(function () {
+	var self = Container.call(this);
+	var alien = self.attachAsset('alien', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.width = alien.width;
+	self.height = alien.height;
+	self.row = 0;
+	self.col = 0;
+	self.type = 0; // for future: different types
+	self.alive = true;
+	self.shootCooldown = 0;
+	return self;
+});
+// Alien Bullet
+var AlienBullet = Container.expand(function () {
+	var self = Container.call(this);
+	var bullet = self.attachAsset('alienBullet', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.width = bullet.width;
+	self.height = bullet.height;
+	self.speed = 22; // Downwards
+	self.update = function () {
+		self.y += self.speed;
+	};
+	return self;
+});
+// Player Bullet
+var PlayerBullet = Container.expand(function () {
+	var self = Container.call(this);
+	var bullet = self.attachAsset('playerBullet', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.width = bullet.width;
+	self.height = bullet.height;
+	self.speed = -32; // Upwards
+	self.update = function () {
+		self.y += self.speed;
+	};
+	return self;
+});
+// Player Cannon
+var PlayerCannon = Container.expand(function () {
+	var self = Container.call(this);
+	var cannon = self.attachAsset('playerCannon', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.width = cannon.width;
+	self.height = cannon.height;
+	self.shootCooldown = 0; // frames until next shot allowed
+	self.lives = 3;
+	self.invincible = false;
+	self.invincibleTimer = 0;
+	// Flash when hit
+	self.flash = function () {
+		tween(self, {
+			alpha: 0.3
+		}, {
+			duration: 80,
+			onFinish: function onFinish() {
+				tween(self, {
+					alpha: 1
+				}, {
+					duration: 80
+				});
+			}
+		});
+	};
+	return self;
+});
+// Powerup
+var Powerup = Container.expand(function () {
+	var self = Container.call(this);
+	var p = self.attachAsset('powerup', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.width = p.width;
+	self.height = p.height;
+	self.type = 'life'; // only one type for MVP
+	self.speed = 12;
+	self.update = function () {
+		self.y += self.speed;
+	};
+	return self;
+});
+
+/**** 
 * Initialize Game
-****/
+****/ 
 var game = new LK.Game({
 	backgroundColor: 0x000000
-});
\ No newline at end of file
+});
+
+/**** 
+* Game Code
+****/ 
+// Music
+// Sound effects
+// Power-up
+// Alien bullet
+// Alien invader
+// Player bullet
+// Player cannon
+// Game constants
+var GAME_WIDTH = 2048;
+var GAME_HEIGHT = 2732;
+var PLAYER_Y = GAME_HEIGHT - 180;
+var PLAYER_SPEED = 36;
+var PLAYER_SHOOT_COOLDOWN = 18; // frames
+var ALIEN_ROWS = 4;
+var ALIEN_COLS = 8;
+var ALIEN_X_MARGIN = 120;
+var ALIEN_Y_MARGIN = 120;
+var ALIEN_X_SPACING = 180;
+var ALIEN_Y_SPACING = 140;
+var ALIEN_MOVE_INTERVAL = 32; // frames between moves
+var ALIEN_MOVE_STEP = 48;
+var ALIEN_DESCEND_STEP = 80;
+var ALIEN_SHOOT_CHANCE = 0.012; // per alien per move
+var ALIEN_SPEEDUP_EVERY = 6; // speed up every N moves
+var ALIEN_MIN_MOVE_INTERVAL = 10;
+var POWERUP_CHANCE = 0.08; // chance per alien death
+var POWERUP_DURATION = 600; // frames to stay on screen
+// Game state
+var player;
+var playerBullets = [];
+var alienBullets = [];
+var aliens = [];
+var powerups = [];
+var score = 0;
+var lives = 3;
+var level = 1;
+var alienMoveDir = 1; // 1: right, -1: left
+var alienMoveTimer = 0;
+var alienMoveCount = 0;
+var alienMoveInterval = ALIEN_MOVE_INTERVAL;
+var alienLeftBound = 0;
+var alienRightBound = 0;
+var gameOver = false;
+var youWin = false;
+var dragNode = null;
+var lastTouchX = 0;
+var scoreTxt, livesTxt, levelTxt;
+// Music
+LK.playMusic('arcadeLoop');
+// GUI
+scoreTxt = new Text2('Score: 0', {
+	size: 90,
+	fill: "#fff"
+});
+scoreTxt.anchor.set(0.5, 0);
+LK.gui.top.addChild(scoreTxt);
+livesTxt = new Text2('Lives: 3', {
+	size: 70,
+	fill: "#fff"
+});
+livesTxt.anchor.set(0, 0);
+LK.gui.top.addChild(livesTxt);
+livesTxt.x = 120; // avoid top left menu
+levelTxt = new Text2('Level: 1', {
+	size: 70,
+	fill: "#fff"
+});
+levelTxt.anchor.set(1, 0);
+LK.gui.top.addChild(levelTxt);
+levelTxt.x = LK.gui.top.width - 120;
+// Initialize player
+player = new PlayerCannon();
+game.addChild(player);
+player.x = GAME_WIDTH / 2;
+player.y = PLAYER_Y;
+// Initialize aliens
+function spawnAliens() {
+	aliens = [];
+	var startX = (GAME_WIDTH - (ALIEN_COLS - 1) * ALIEN_X_SPACING) / 2;
+	var startY = 260;
+	for (var row = 0; row < ALIEN_ROWS; row++) {
+		for (var col = 0; col < ALIEN_COLS; col++) {
+			var alien = new Alien();
+			alien.x = startX + col * ALIEN_X_SPACING;
+			alien.y = startY + row * ALIEN_Y_SPACING;
+			alien.row = row;
+			alien.col = col;
+			game.addChild(alien);
+			aliens.push(alien);
+		}
+	}
+	updateAlienBounds();
+	alienMoveDir = 1;
+	alienMoveTimer = 0;
+	alienMoveCount = 0;
+	alienMoveInterval = Math.max(ALIEN_MOVE_INTERVAL - (level - 1) * 2, ALIEN_MIN_MOVE_INTERVAL);
+}
+function updateAlienBounds() {
+	if (aliens.length === 0) {
+		alienLeftBound = 0;
+		alienRightBound = 0;
+		return;
+	}
+	var minX = GAME_WIDTH,
+		maxX = 0;
+	for (var i = 0; i < aliens.length; i++) {
+		if (!aliens[i].alive) continue;
+		if (aliens[i].x < minX) minX = aliens[i].x;
+		if (aliens[i].x > maxX) maxX = aliens[i].x;
+	}
+	alienLeftBound = minX;
+	alienRightBound = maxX;
+}
+// Reset game state for new game or level
+function resetGameState() {
+	// Remove all bullets, aliens, powerups
+	for (var i = 0; i < playerBullets.length; i++) playerBullets[i].destroy();
+	for (var i = 0; i < alienBullets.length; i++) alienBullets[i].destroy();
+	for (var i = 0; i < powerups.length; i++) powerups[i].destroy();
+	for (var i = 0; i < aliens.length; i++) aliens[i].destroy();
+	playerBullets = [];
+	alienBullets = [];
+	powerups = [];
+	aliens = [];
+	// Reset player
+	player.x = GAME_WIDTH / 2;
+	player.y = PLAYER_Y;
+	player.lives = lives;
+	player.invincible = false;
+	player.alpha = 1;
+	// Spawn aliens
+	spawnAliens();
+}
+// Start first level
+resetGameState();
+// Handle player movement and shooting
+game.down = function (x, y, obj) {
+	// Only allow drag on player area
+	if (y > GAME_HEIGHT - 500) {
+		dragNode = player;
+		lastTouchX = x;
+	}
+};
+game.move = function (x, y, obj) {
+	if (dragNode === player) {
+		// Move player horizontally, clamp to screen
+		var dx = x - lastTouchX;
+		player.x += dx;
+		if (player.x < player.width / 2) player.x = player.width / 2;
+		if (player.x > GAME_WIDTH - player.width / 2) player.x = GAME_WIDTH - player.width / 2;
+		lastTouchX = x;
+	}
+};
+game.up = function (x, y, obj) {
+	dragNode = null;
+};
+// Tap anywhere in lower half to shoot
+game.downAnywhere = function (x, y, obj) {
+	if (y > GAME_HEIGHT / 2) {
+		tryShoot();
+	}
+};
+// Register downAnywhere
+LK.on('down', function (obj) {
+	if (obj && obj.x !== undefined && obj.y !== undefined) {
+		game.downAnywhere(obj.x, obj.y, obj);
+	}
+});
+// Player shooting
+function tryShoot() {
+	if (player.shootCooldown <= 0 && !gameOver && !youWin) {
+		var bullet = new PlayerBullet();
+		bullet.x = player.x;
+		bullet.y = player.y - player.height / 2 - bullet.height / 2;
+		playerBullets.push(bullet);
+		game.addChild(bullet);
+		player.shootCooldown = PLAYER_SHOOT_COOLDOWN;
+		LK.getSound('shoot').play();
+	}
+}
+// Main game update loop
+game.update = function () {
+	if (gameOver || youWin) return;
+	// Player shoot cooldown
+	if (player.shootCooldown > 0) player.shootCooldown--;
+	// Player invincibility
+	if (player.invincible) {
+		player.invincibleTimer--;
+		if (player.invincibleTimer <= 0) {
+			player.invincible = false;
+			player.alpha = 1;
+		}
+	}
+	// Move player bullets
+	for (var i = playerBullets.length - 1; i >= 0; i--) {
+		var b = playerBullets[i];
+		b.update();
+		if (b.y < -b.height) {
+			b.destroy();
+			playerBullets.splice(i, 1);
+			continue;
+		}
+		// Check collision with aliens
+		for (var j = 0; j < aliens.length; j++) {
+			var a = aliens[j];
+			if (a.alive && b.intersects(a)) {
+				a.alive = false;
+				a.visible = false;
+				b.destroy();
+				playerBullets.splice(i, 1);
+				LK.getSound('alienDown').play();
+				// Score
+				score += 10;
+				LK.setScore(score);
+				scoreTxt.setText('Score: ' + score);
+				// Powerup chance
+				if (Math.random() < POWERUP_CHANCE) {
+					var p = new Powerup();
+					p.x = a.x;
+					p.y = a.y;
+					p.type = 'life';
+					p.timer = POWERUP_DURATION;
+					powerups.push(p);
+					game.addChild(p);
+				}
+				break;
+			}
+		}
+	}
+	// Move alien bullets
+	for (var i = alienBullets.length - 1; i >= 0; i--) {
+		var b = alienBullets[i];
+		b.update();
+		if (b.y > GAME_HEIGHT + b.height) {
+			b.destroy();
+			alienBullets.splice(i, 1);
+			continue;
+		}
+		// Check collision with player
+		if (!player.invincible && b.intersects(player)) {
+			b.destroy();
+			alienBullets.splice(i, 1);
+			loseLife();
+			break;
+		}
+	}
+	// Move powerups
+	for (var i = powerups.length - 1; i >= 0; i--) {
+		var p = powerups[i];
+		p.update();
+		p.timer--;
+		if (p.y > GAME_HEIGHT + p.height || p.timer <= 0) {
+			p.destroy();
+			powerups.splice(i, 1);
+			continue;
+		}
+		// Collect powerup
+		if (p.intersects(player)) {
+			LK.getSound('powerup').play();
+			p.destroy();
+			powerups.splice(i, 1);
+			gainLife();
+		}
+	}
+	// Move aliens
+	alienMoveTimer++;
+	if (alienMoveTimer >= alienMoveInterval) {
+		alienMoveTimer = 0;
+		var shouldDescend = false;
+		// Check if any alien at edge
+		updateAlienBounds();
+		if (alienMoveDir === 1 && alienRightBound + ALIEN_MOVE_STEP > GAME_WIDTH - ALIEN_X_MARGIN) {
+			shouldDescend = true;
+			alienMoveDir = -1;
+		} else if (alienMoveDir === -1 && alienLeftBound - ALIEN_MOVE_STEP < ALIEN_X_MARGIN) {
+			shouldDescend = true;
+			alienMoveDir = 1;
+		}
+		for (var i = 0; i < aliens.length; i++) {
+			var a = aliens[i];
+			if (!a.alive) continue;
+			if (shouldDescend) {
+				a.y += ALIEN_DESCEND_STEP;
+			} else {
+				a.x += ALIEN_MOVE_STEP * alienMoveDir;
+			}
+		}
+		if (shouldDescend) {
+			// Check for game over (aliens reach player line)
+			for (var i = 0; i < aliens.length; i++) {
+				var a = aliens[i];
+				if (!a.alive) continue;
+				if (a.y + a.height / 2 >= PLAYER_Y - player.height / 2) {
+					triggerGameOver();
+					return;
+				}
+			}
+		}
+		// Aliens shoot
+		for (var i = 0; i < aliens.length; i++) {
+			var a = aliens[i];
+			if (!a.alive) continue;
+			if (Math.random() < ALIEN_SHOOT_CHANCE) {
+				var b = new AlienBullet();
+				b.x = a.x;
+				b.y = a.y + a.height / 2 + b.height / 2;
+				alienBullets.push(b);
+				game.addChild(b);
+				LK.getSound('alienShoot').play();
+			}
+		}
+		alienMoveCount++;
+		// Speed up
+		if (alienMoveCount % ALIEN_SPEEDUP_EVERY === 0 && alienMoveInterval > ALIEN_MIN_MOVE_INTERVAL) {
+			alienMoveInterval--;
+		}
+	}
+	// Remove dead aliens
+	var aliveAliens = 0;
+	for (var i = 0; i < aliens.length; i++) {
+		if (aliens[i].alive) aliveAliens++;
+	}
+	if (aliveAliens === 0) {
+		// Next level
+		level++;
+		levelTxt.setText('Level: ' + level);
+		resetGameState();
+	}
+	// Update lives
+	livesTxt.setText('Lives: ' + player.lives);
+};
+// Lose a life
+function loseLife() {
+	if (player.invincible) return;
+	player.lives--;
+	lives = player.lives;
+	player.flash();
+	LK.getSound('loseLife').play();
+	if (player.lives <= 0) {
+		triggerGameOver();
+	} else {
+		// Invincible for a short time
+		player.invincible = true;
+		player.invincibleTimer = 90;
+		player.alpha = 0.5;
+	}
+}
+// Gain a life (powerup)
+function gainLife() {
+	player.lives++;
+	lives = player.lives;
+	livesTxt.setText('Lives: ' + player.lives);
+}
+// Game over
+function triggerGameOver() {
+	if (gameOver) return;
+	gameOver = true;
+	LK.effects.flashScreen(0xff0000, 900);
+	LK.showGameOver();
+}
+// Win (not used in MVP, but for future)
+function triggerYouWin() {
+	if (youWin) return;
+	youWin = true;
+	LK.effects.flashScreen(0x00ff00, 900);
+	LK.showYouWin();
+}
+// Set initial score
+LK.setScore(score);
+scoreTxt.setText('Score: ' + score);
\ No newline at end of file