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

/**** 
* Classes
****/ 
// Enemy Car Class (basic)
var EnemyCar = Container.expand(function () {
	var self = Container.call(this);
	var car = self.attachAsset('enemyCar', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.width = car.width;
	self.height = car.height;
	self.speed = 12; // Will increase with level
	self.type = 1;
	self.hp = 1;
	self.crashed = false;
	// Crash effect
	self.showCrash = function () {
		var effect = LK.getAsset('crashEffect', {
			anchorX: 0.5,
			anchorY: 0.5,
			x: 0,
			y: 0,
			alpha: 0.8,
			scaleX: 0.5,
			scaleY: 0.5
		});
		self.addChild(effect);
		tween(effect, {
			scaleX: 1.5,
			scaleY: 1.5,
			alpha: 0
		}, {
			duration: 400,
			easing: tween.easeOut,
			onFinish: function onFinish() {
				effect.destroy();
			}
		});
	};
	return self;
});
// Enemy Car 2 (tougher, for higher levels)
var EnemyCar2 = Container.expand(function () {
	var self = Container.call(this);
	var car = self.attachAsset('enemyCar2', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.width = car.width;
	self.height = car.height;
	self.speed = 16;
	self.type = 2;
	self.hp = 2;
	self.crashed = false;
	self.showCrash = function () {
		var effect = LK.getAsset('crashEffect', {
			anchorX: 0.5,
			anchorY: 0.5,
			x: 0,
			y: 0,
			alpha: 0.8,
			scaleX: 0.5,
			scaleY: 0.5
		});
		self.addChild(effect);
		tween(effect, {
			scaleX: 1.5,
			scaleY: 1.5,
			alpha: 0
		}, {
			duration: 400,
			easing: tween.easeOut,
			onFinish: function onFinish() {
				effect.destroy();
			}
		});
	};
	return self;
});
// Player Car Class
var PlayerCar = Container.expand(function () {
	var self = Container.call(this);
	var car = self.attachAsset('playerCar', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.width = car.width;
	self.height = car.height;
	self.hp = 1; // Upgradable
	self.invincible = false;
	self.invincibleTimer = 0;
	self.upgradeLevel = 0;
	// Flash effect for invincibility
	self.flashInvincible = function () {
		self.invincible = true;
		self.invincibleTimer = 60; // 1 second at 60fps
		tween(self, {
			alpha: 0.5
		}, {
			duration: 100,
			easing: tween.easeInOut,
			onFinish: function onFinish() {
				tween(self, {
					alpha: 1
				}, {
					duration: 100,
					easing: tween.easeInOut
				});
			}
		});
	};
	// Upgrade effect
	self.showUpgrade = function () {
		var effect = LK.getAsset('upgradeEffect', {
			anchorX: 0.5,
			anchorY: 0.5,
			x: 0,
			y: 0,
			alpha: 0.7,
			scaleX: 0.5,
			scaleY: 0.5
		});
		self.addChild(effect);
		tween(effect, {
			scaleX: 1.5,
			scaleY: 1.5,
			alpha: 0
		}, {
			duration: 500,
			easing: tween.easeOut,
			onFinish: function onFinish() {
				effect.destroy();
			}
		});
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x222222
});

/**** 
* Game Code
****/ 
// Music: background
// Sound: upgrade
// Sound: crash
// Upgrade effect: purple ellipse
// Crash effect: yellow ellipse
// Enemy car 2: green box (for future levels)
// Enemy car: red box
// Player car: blue box
// Arena scroll speed (background illusion)
var scrollSpeed = 10;
// Player
var player = new PlayerCar();
player.x = 2048 / 2;
player.y = 2732 - 500;
game.addChild(player);
// Score
var score = 0;
var scoreTxt = new Text2('0', {
	size: 120,
	fill: "#fff"
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
// Level
var level = 1;
var levelTxt = new Text2('Lv.1', {
	size: 70,
	fill: "#fff"
});
levelTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(levelTxt);
levelTxt.y = 120;
// Upgrades
var upgradeTxt = new Text2('', {
	size: 70,
	fill: 0xFFD600
});
upgradeTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(upgradeTxt);
upgradeTxt.y = 200;
// Enemies
var enemies = [];
var enemySpawnTimer = 0;
var enemySpawnInterval = 60; // frames
// Dragging
var dragNode = null;
// Invincibility after crash
var invincibleFrames = 0;
// Arena bounds (leave 100px at top for menu)
var arenaLeft = 100;
var arenaRight = 2048 - 100;
var arenaTop = 100;
var arenaBottom = 2732 - 100;
// Music
LK.playMusic('arenaMusic');
// Helper: spawn enemy
function spawnEnemy() {
	var enemy;
	if (level < 3 || Math.random() < 0.7) {
		enemy = new EnemyCar();
	} else {
		enemy = new EnemyCar2();
	}
	// Random x within arena
	var minX = arenaLeft + enemy.width / 2;
	var maxX = arenaRight - enemy.width / 2;
	enemy.x = minX + Math.random() * (maxX - minX);
	enemy.y = -enemy.height / 2;
	// Speed up with level
	if (enemy.type === 1) {
		enemy.speed = 12 + level * 1.5;
	} else {
		enemy.speed = 16 + level * 1.2;
	}
	enemies.push(enemy);
	game.addChild(enemy);
}
// Helper: upgrade player
function upgradePlayer() {
	player.upgradeLevel += 1;
	player.hp += 1;
	player.showUpgrade();
	upgradeTxt.setText('Upgrade! HP: ' + player.hp);
	LK.getSound('upgrade').play();
	LK.setTimeout(function () {
		upgradeTxt.setText('');
	}, 1200);
}
// Handle move (dragging player)
function handleMove(x, y, obj) {
	if (dragNode === player) {
		// Clamp to arena
		var px = x;
		var py = y;
		var halfW = player.width / 2;
		var halfH = player.height / 2;
		if (px < arenaLeft + halfW) px = arenaLeft + halfW;
		if (px > arenaRight - halfW) px = arenaRight - halfW;
		if (py < arenaTop + halfH) py = arenaTop + halfH;
		if (py > arenaBottom - halfH) py = arenaBottom - halfH;
		player.x = px;
		player.y = py;
	}
}
// Touch/drag events
game.down = function (x, y, obj) {
	// Only start drag if touch is on player
	var dx = x - player.x;
	var dy = y - player.y;
	if (dx * dx + dy * dy < player.width / 2 * (player.width / 2)) {
		dragNode = player;
		handleMove(x, y, obj);
	}
};
game.move = function (x, y, obj) {
	handleMove(x, y, obj);
};
game.up = function (x, y, obj) {
	dragNode = null;
};
// Main update loop
game.update = function () {
	// Arena scroll illusion: move all enemies down
	for (var i = enemies.length - 1; i >= 0; i--) {
		var enemy = enemies[i];
		enemy.y += enemy.speed + scrollSpeed;
		// Remove if off screen
		if (enemy.y - enemy.height / 2 > 2732 + 100) {
			enemy.destroy();
			enemies.splice(i, 1);
			continue;
		}
		// End game if enemy passes player
		if (enemy.lastY === undefined) {
			enemy.lastY = enemy.y;
		}
		if (enemy.lastY <= player.y + player.height / 2 && enemy.y > player.y + player.height / 2) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
			return;
		}
		enemy.lastY = enemy.y;
	}
	// Spawn enemies
	enemySpawnTimer++;
	var spawnInt = Math.max(30, enemySpawnInterval - level * 2);
	if (enemySpawnTimer >= spawnInt) {
		spawnEnemy();
		enemySpawnTimer = 0;
	}
	// Collision: player vs enemies
	for (var i = enemies.length - 1; i >= 0; i--) {
		var enemy = enemies[i];
		if (enemy.crashed) continue;
		if (player.invincible) continue;
		if (player.intersects(enemy)) {
			// Crash!
			enemy.crashed = true;
			enemy.showCrash();
			LK.getSound('crash').play();
			score += 1;
			LK.setScore(score);
			scoreTxt.setText(score);
			// Remove enemy after effect
			LK.setTimeout(function (e, idx) {
				return function () {
					if (enemies[idx] === e) {
						e.destroy();
						enemies.splice(idx, 1);
					}
				};
			}(enemy, i), 400);
			// Player does not take damage, only enemy is destroyed
		}
	}
	// Invincibility timer
	if (player.invincible) {
		player.invincibleTimer--;
		if (player.invincibleTimer <= 0) {
			player.invincible = false;
			player.alpha = 1;
		}
	}
	// Level up every 10 points
	var newLevel = Math.floor(score / 10) + 1;
	if (newLevel > level) {
		level = newLevel;
		levelTxt.setText('Lv.' + level);
		// Every 2 levels, upgrade player
		if (level % 2 === 0) {
			upgradePlayer();
		}
	}
};

===================================================================
--- original.js
+++ change.js
@@ -283,8 +283,18 @@
 			enemy.destroy();
 			enemies.splice(i, 1);
 			continue;
 		}
+		// End game if enemy passes player
+		if (enemy.lastY === undefined) {
+			enemy.lastY = enemy.y;
+		}
+		if (enemy.lastY <= player.y + player.height / 2 && enemy.y > player.y + player.height / 2) {
+			LK.effects.flashScreen(0xff0000, 1000);
+			LK.showGameOver();
+			return;
+		}
+		enemy.lastY = enemy.y;
 	}
 	// Spawn enemies
 	enemySpawnTimer++;
 	var spawnInt = Math.max(30, enemySpawnInterval - level * 2);