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

/**** 
* Classes
****/ 
// Coin
var Coin = Container.expand(function () {
	var self = Container.call(this);
	var coinGfx = self.attachAsset('coin', {
		anchorX: 0.5,
		anchorY: 1
	});
	self.lane = 1;
	self.collected = false;
	return self;
});
// Magnet Powerup
var Magnet = Container.expand(function () {
	var self = Container.call(this);
	var magGfx = self.attachAsset('magnet', {
		anchorX: 0.5,
		anchorY: 1
	});
	self.lane = 1;
	self.collected = false;
	return self;
});
// Obstacle (train/barrier)
var Obstacle = Container.expand(function () {
	var self = Container.call(this);
	var obsGfx = self.attachAsset('obstacle', {
		anchorX: 0.5,
		anchorY: 1
	});
	self.lane = 1; // 0,1,2
	self.passed = false;
	return self;
});
// Player Runner
var Runner = Container.expand(function () {
	var self = Container.call(this);
	var runnerGfx = self.attachAsset('runner', {
		anchorX: 0.5,
		anchorY: 1
	});
	self.lane = 1; // 0: left, 1: center, 2: right
	self.isShielded = false;
	self.magnetActive = false;
	self.shieldActive = false;
	self.magnetTimer = 0;
	self.shieldTimer = 0;
	// Animate shield effect
	self.showShield = function () {
		if (!self.shieldCircle) {
			self.shieldCircle = self.attachAsset('shield', {
				anchorX: 0.5,
				anchorY: 1,
				scaleX: 1.3,
				scaleY: 1.3,
				alpha: 0.5
			});
		}
		self.shieldCircle.visible = true;
	};
	self.hideShield = function () {
		if (self.shieldCircle) self.shieldCircle.visible = false;
	};
	// Animate magnet effect
	self.showMagnet = function () {
		if (!self.magnetCircle) {
			self.magnetCircle = self.attachAsset('magnet', {
				anchorX: 0.5,
				anchorY: 1,
				scaleX: 1.5,
				scaleY: 1.5,
				alpha: 0.3
			});
		}
		self.magnetCircle.visible = true;
	};
	self.hideMagnet = function () {
		if (self.magnetCircle) self.magnetCircle.visible = false;
	};
	return self;
});
// Shield Powerup
var Shield = Container.expand(function () {
	var self = Container.call(this);
	var shGfx = self.attachAsset('shield', {
		anchorX: 0.5,
		anchorY: 1
	});
	self.lane = 1;
	self.collected = false;
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	// No title, no description
	// Always backgroundColor is black
	backgroundColor: 0x000000
});

/**** 
* Game Code
****/ 
// Lane positions (3 lanes)
// Character (player)
// Obstacle (train/barrier)
// Coin
// Magnet Powerup
// Shield Powerup
// Add rails and grass background
var railWidth = 180;
var railSpacing = 260;
var grassWidth = (2048 - (railWidth * 3 + railSpacing * 2)) / 2;
// Grass left
var grassLeft = LK.getAsset('grass', {
	anchorX: 0,
	anchorY: 0,
	x: 0,
	y: 0,
	width: grassWidth,
	height: 2732
});
game.addChild(grassLeft);
// Grass right
var grassRight = LK.getAsset('grass', {
	anchorX: 0,
	anchorY: 0,
	x: 2048 - grassWidth,
	y: 0,
	width: grassWidth,
	height: 2732
});
game.addChild(grassRight);
// Rails
var railX = [grassWidth, grassWidth + railWidth + railSpacing, grassWidth + (railWidth + railSpacing) * 2];
for (var i = 0; i < 3; ++i) {
	var rail = LK.getAsset('rail', {
		anchorX: 0,
		anchorY: 0,
		x: railX[i],
		y: 0,
		width: railWidth,
		height: 2732
	});
	game.addChild(rail);
}
// Lane positions (center of each rail)
var laneX = [railX[0] + railWidth / 2, railX[1] + railWidth / 2, railX[2] + railWidth / 2];
// Track Y positions
var groundY = 2732 - 200;
// Game state
var runner;
var obstacles = [];
var coins = [];
var magnets = [];
var shields = [];
var speed = 18; // Initial speed (pixels per frame)
var maxSpeed = 38;
var speedInc = 0.0007; // Speed increase per tick
var score = 0;
var coinScore = 0;
var lastObstacleTick = 0;
var lastCoinTick = 0;
var lastPowerupTick = 0;
var dragStartX = null;
var dragStartY = null;
var dragStartTime = null;
var swipeThreshold = 80; // px
var swipeTime = 350; // ms
var isMovingLane = false;
var moveTween = null;
var magnetDuration = 600; // ticks (10s)
var shieldDuration = 600; // ticks (10s)
var gameOver = false;
// Score text
var scoreTxt = new Text2('0', {
	size: 120,
	fill: "#fff"
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
// Coin text
var coinTxt = new Text2('0', {
	size: 80,
	fill: 0xFFE066
});
coinTxt.anchor.set(0, 0);
LK.gui.topRight.addChild(coinTxt);
// Helper: spawn runner
function spawnRunner() {
	runner = new Runner();
	runner.x = laneX[1];
	runner.y = groundY;
	runner.lane = 1;
	game.addChild(runner);
}
// Helper: spawn obstacle
function spawnObstacle() {
	var obs = new Obstacle();
	obs.lane = Math.floor(Math.random() * 3);
	obs.x = laneX[obs.lane];
	obs.y = -20;
	obstacles.push(obs);
	game.addChild(obs);
}
// Helper: spawn coin
function spawnCoin() {
	var coin = new Coin();
	coin.lane = Math.floor(Math.random() * 3);
	coin.x = laneX[coin.lane];
	coin.y = -20;
	coins.push(coin);
	game.addChild(coin);
}
// Helper: spawn magnet
function spawnMagnet() {
	var mag = new Magnet();
	mag.lane = Math.floor(Math.random() * 3);
	mag.x = laneX[mag.lane];
	mag.y = -20;
	magnets.push(mag);
	game.addChild(mag);
}
// Helper: spawn shield
function spawnShield() {
	var sh = new Shield();
	sh.lane = Math.floor(Math.random() * 3);
	sh.x = laneX[sh.lane];
	sh.y = -20;
	shields.push(sh);
	game.addChild(sh);
}
// Helper: move runner to lane
function moveRunnerToLane(targetLane) {
	if (isMovingLane || targetLane < 0 || targetLane > 2 || targetLane === runner.lane) return;
	isMovingLane = true;
	if (moveTween) tween.stop(runner, {
		x: true
	});
	moveTween = tween(runner, {
		x: laneX[targetLane]
	}, {
		duration: 120,
		easing: tween.cubicOut,
		onFinish: function onFinish() {
			runner.lane = targetLane;
			isMovingLane = false;
		}
	});
}
// Helper: handle swipe
function handleSwipe(startX, startY, endX, endY, dt) {
	var dx = endX - startX;
	var dy = endY - startY;
	if (Math.abs(dx) > Math.abs(dy) && Math.abs(dx) > swipeThreshold && dt < swipeTime) {
		// Horizontal swipe
		if (dx > 0) {
			// Swipe right
			if (runner) moveRunnerToLane(runner.lane + 1);
		} else {
			// Swipe left
			if (runner) moveRunnerToLane(runner.lane - 1);
		}
	}
}
// Helper: reset game state
function resetGame() {
	// Remove all obstacles, coins, powerups
	for (var i = 0; i < obstacles.length; ++i) obstacles[i].destroy();
	for (var i = 0; i < coins.length; ++i) coins[i].destroy();
	for (var i = 0; i < magnets.length; ++i) magnets[i].destroy();
	for (var i = 0; i < shields.length; ++i) shields[i].destroy();
	obstacles = [];
	coins = [];
	magnets = [];
	shields = [];
	if (runner) runner.destroy();
	runner = null;
	speed = 18;
	score = 0;
	coinScore = 0;
	lastObstacleTick = 0;
	lastCoinTick = 0;
	lastPowerupTick = 0;
	isMovingLane = false;
	moveTween = null;
	gameOver = false;
	scoreTxt.setText('0');
	coinTxt.setText('0');
	spawnRunner();
}
// Game move handler (for swipe)
game.down = function (x, y, obj) {
	dragStartX = x;
	dragStartY = y;
	dragStartTime = Date.now();
};
game.up = function (x, y, obj) {
	if (dragStartX !== null && dragStartY !== null && dragStartTime !== null) {
		var dt = Date.now() - dragStartTime;
		handleSwipe(dragStartX, dragStartY, x, y, dt);
	}
	dragStartX = null;
	dragStartY = null;
	dragStartTime = null;
};
game.move = function (x, y, obj) {
	// No drag-to-move, only swipe
};
// Main game update loop
game.update = function () {
	if (gameOver) return;
	// Increase speed over time
	if (speed < maxSpeed) speed += speedInc;
	// Score increases with distance
	score += Math.floor(speed / 8);
	scoreTxt.setText(score + '');
	// Spawn obstacles
	if (LK.ticks - lastObstacleTick > 38 + Math.floor(60 / speed * 10)) {
		spawnObstacle();
		lastObstacleTick = LK.ticks;
	}
	// Spawn coins
	if (LK.ticks - lastCoinTick > 28 + Math.floor(60 / speed * 6)) {
		spawnCoin();
		lastCoinTick = LK.ticks;
	}
	// Spawn powerups (magnet/shield) occasionally
	if (LK.ticks - lastPowerupTick > 600 && Math.random() < 0.015) {
		if (Math.random() < 0.5) {
			spawnMagnet();
		} else {
			spawnShield();
		}
		lastPowerupTick = LK.ticks;
	}
	// Move obstacles
	for (var i = obstacles.length - 1; i >= 0; --i) {
		var obs = obstacles[i];
		obs.y += speed;
		if (obs.y > 2732 + 100) {
			obs.destroy();
			obstacles.splice(i, 1);
			continue;
		}
		// Collision with runner
		if (!gameOver && runner &&
		// Defensive: runner must be defined
		obs.lane === runner.lane && !obs.passed && obs.y + 180 > runner.y - 200 && obs.y < runner.y) {
			if (runner.shieldActive) {
				// Shield absorbs hit
				runner.shieldActive = false;
				runner.hideShield();
				obs.passed = true;
				LK.effects.flashObject(runner, 0x00ffff, 400);
			} else {
				// Game over
				gameOver = true;
				LK.effects.flashScreen(0xff0000, 900);
				LK.showGameOver();
				return;
			}
		}
	}
	// Move coins
	for (var i = coins.length - 1; i >= 0; --i) {
		var coin = coins[i];
		coin.y += speed;
		if (coin.y > 2732 + 100) {
			coin.destroy();
			coins.splice(i, 1);
			continue;
		}
		// Magnet effect: attract coins in any lane if active
		if (runner && runner.magnetActive && Math.abs(coin.y - runner.y) < 400) {
			var dx = laneX[runner.lane] - coin.x;
			coin.x += dx * 0.18;
		}
		// Collect coin
		if (runner && !coin.collected && Math.abs(coin.lane - runner.lane) <= (runner.magnetActive ? 1 : 0) && Math.abs(coin.y - runner.y) < 120) {
			coin.collected = true;
			coin.destroy();
			coins.splice(i, 1);
			coinScore += 1;
			coinTxt.setText(coinScore + '');
			LK.effects.flashObject(runner, 0xf7d21a, 200);
		}
	}
	// Move magnets
	for (var i = magnets.length - 1; i >= 0; --i) {
		var mag = magnets[i];
		mag.y += speed;
		if (mag.y > 2732 + 100) {
			mag.destroy();
			magnets.splice(i, 1);
			continue;
		}
		// Collect magnet
		if (runner && !mag.collected && mag.lane === runner.lane && Math.abs(mag.y - runner.y) < 120) {
			mag.collected = true;
			mag.destroy();
			magnets.splice(i, 1);
			runner.magnetActive = true;
			runner.magnetTimer = magnetDuration;
			runner.showMagnet();
			LK.effects.flashObject(runner, 0xff00ff, 300);
		}
	}
	// Move shields
	for (var i = shields.length - 1; i >= 0; --i) {
		var sh = shields[i];
		sh.y += speed;
		if (sh.y > 2732 + 100) {
			sh.destroy();
			shields.splice(i, 1);
			continue;
		}
		// Collect shield
		if (runner && !sh.collected && sh.lane === runner.lane && Math.abs(sh.y - runner.y) < 120) {
			sh.collected = true;
			sh.destroy();
			shields.splice(i, 1);
			runner.shieldActive = true;
			runner.shieldTimer = shieldDuration;
			runner.showShield();
			LK.effects.flashObject(runner, 0x00ffff, 300);
		}
	}
	// Powerup timers
	if (runner && runner.magnetActive) {
		runner.magnetTimer--;
		if (runner.magnetTimer <= 0) {
			runner.magnetActive = false;
			runner.hideMagnet();
		}
	}
	if (runner && runner.shieldActive) {
		runner.shieldTimer--;
		if (runner.shieldTimer <= 0) {
			runner.shieldActive = false;
			runner.hideShield();
		}
	}
};
// On game over, reset state for replay
LK.on('gameover', function () {
	resetGame();
});
// On you win (not used in endless runner, but for completeness)
LK.on('youwin', function () {
	resetGame();
});

===================================================================
--- original.js
+++ change.js
@@ -424,9 +424,9 @@
 			shields.splice(i, 1);
 			continue;
 		}
 		// Collect shield
-		if (!sh.collected && sh.lane === runner.lane && Math.abs(sh.y - runner.y) < 120) {
+		if (runner && !sh.collected && sh.lane === runner.lane && Math.abs(sh.y - runner.y) < 120) {
 			sh.collected = true;
 			sh.destroy();
 			shields.splice(i, 1);
 			runner.shieldActive = true;