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

/**** 
* Classes
****/ 
// Barrier (obstacle)
var Barrier = Container.expand(function () {
	var self = Container.call(this);
	var barrierSprite = self.attachAsset('barrier', {
		anchorX: 0.5,
		anchorY: 1
	});
	self.width = barrierSprite.width;
	self.height = barrierSprite.height;
	self.speed = 0; // Will be set by game
	// Called every tick
	self.update = function () {
		self.x -= self.speed;
	};
	return self;
});
// Runner (player character)
var Runner = Container.expand(function () {
	var self = Container.call(this);
	var runnerSprite = self.attachAsset('runner', {
		anchorX: 0.5,
		anchorY: 1
	});
	self.width = runnerSprite.width;
	self.height = runnerSprite.height;
	self.groundY = 0; // Will be set after ground is created
	self.isJumping = false;
	self.jumpStartY = 0;
	self.jumpStartTime = 0;
	self.jumpDuration = 0;
	self.jumpHeight = 0;
	self.velocityY = 0;
	// Physics
	self.gravity = 1.2; // px per tick^2 (reduced for slower fall)
	self.jumpVelocity = -52; // px per tick (negative is up)
	// Called every tick
	self.update = function () {
		// If jumping, apply velocity
		if (self.isJumping) {
			self.y += self.velocityY;
			self.velocityY += self.gravity;
			// Landed
			if (self.y >= self.groundY) {
				self.y = self.groundY;
				self.isJumping = false;
				self.velocityY = 0;
			}
		}
	};
	// Start jump
	self.jump = function () {
		if (!self.isJumping) {
			self.isJumping = true;
			self.velocityY = self.jumpVelocity;
		}
	};
	// Cancel jump (for variable jump height)
	self.cancelJump = function () {
		if (self.isJumping && self.velocityY < -18) {
			self.velocityY = -18;
		}
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x222b3a
});

/**** 
* Game Code
****/ 
// Ground: long rectangle
// Barrier: tall rectangle
// Character: pixelated box
// Game constants
var GROUND_Y = 2200; // y position of ground top
var RUNNER_START_X = 400;
var BARRIER_MIN_GAP = 600;
var BARRIER_MAX_GAP = 950;
var BARRIER_MIN_HEIGHT = 180;
var BARRIER_MAX_HEIGHT = 320;
var BARRIER_WIDTH = 80;
var SCROLL_START_SPEED = 18;
var SCROLL_MAX_SPEED = 38;
var SCROLL_ACCEL = 0.012; // px per tick^2
// Game state
var runner = null;
var ground = null;
var barriers = [];
var score = 0;
var scrollSpeed = SCROLL_START_SPEED;
var lastBarrierX = 0;
var isGameOver = false;
var isTouching = false;
// Score display
var scoreTxt = new Text2('0', {
	size: 140,
	fill: 0xFFFFFF
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
// Create ground
ground = LK.getAsset('ground', {
	anchorX: 0,
	anchorY: 0,
	x: 0,
	y: GROUND_Y
});
game.addChild(ground);
// Create runner
runner = new Runner();
runner.x = RUNNER_START_X;
runner.groundY = GROUND_Y;
runner.y = GROUND_Y;
game.addChild(runner);
// Helper: spawn a barrier at x
function spawnBarrier(x) {
	var barrier = new Barrier();
	barrier.x = x;
	// Randomize height
	var h = BARRIER_MIN_HEIGHT + Math.floor(Math.random() * (BARRIER_MAX_HEIGHT - BARRIER_MIN_HEIGHT + 1));
	barrier.height = h;
	barrier.children[0].height = h;
	barrier.y = 320; // Place barrier at the top of the screen (barrier height)
	barrier.speed = scrollSpeed;
	barriers.push(barrier);
	game.addChild(barrier);
}
// Helper: reset game state
function resetGame() {
	// Remove barriers
	for (var i = 0; i < barriers.length; i++) {
		barriers[i].destroy();
	}
	barriers = [];
	score = 0;
	scrollSpeed = SCROLL_START_SPEED;
	lastBarrierX = 1400;
	isGameOver = false;
	runner.x = RUNNER_START_X;
	runner.y = GROUND_Y;
	runner.isJumping = false;
	runner.velocityY = 0;
	scoreTxt.setText('0');
	// Spawn initial barriers
	for (var i = 0; i < 3; i++) {
		var gap = BARRIER_MIN_GAP + Math.floor(Math.random() * (BARRIER_MAX_GAP - BARRIER_MIN_GAP + 1));
		lastBarrierX += gap;
		spawnBarrier(lastBarrierX);
	}
}
// Start game
resetGame();
// Touch/press to jump
game.down = function (x, y, obj) {
	if (isGameOver) return;
	isTouching = true;
	runner.jump();
};
// Release to cut jump short
game.up = function (x, y, obj) {
	if (isGameOver) return;
	isTouching = false;
	runner.cancelJump();
};
// Main update loop
game.update = function () {
	if (isGameOver) return;
	// Accelerate scroll speed
	if (scrollSpeed < SCROLL_MAX_SPEED) {
		scrollSpeed += SCROLL_ACCEL;
		if (scrollSpeed > SCROLL_MAX_SPEED) scrollSpeed = SCROLL_MAX_SPEED;
	}
	// Update runner
	runner.update();
	// Update barriers
	for (var i = barriers.length - 1; i >= 0; i--) {
		var barrier = barriers[i];
		barrier.speed = scrollSpeed;
		barrier.update();
		// Passed barrier
		if (!barrier.passed && barrier.x + BARRIER_WIDTH / 2 < runner.x - runner.width / 2) {
			barrier.passed = true;
			score += 1;
			scoreTxt.setText(score + '');
			LK.setScore(score);
		}
		// Remove off-screen barriers
		if (barrier.x < -BARRIER_WIDTH) {
			barrier.destroy();
			barriers.splice(i, 1);
		}
	}
	// Spawn new barriers
	if (barriers.length === 0 || barriers[barriers.length - 1].x < 2048 - BARRIER_MAX_GAP) {
		var gap = BARRIER_MIN_GAP + Math.floor(Math.random() * (BARRIER_MAX_GAP - BARRIER_MIN_GAP + 1));
		var newX = 2048 + gap;
		spawnBarrier(newX);
	}
	// Collision detection
	for (var i = 0; i < barriers.length; i++) {
		var barrier = barriers[i];
		if (runner.intersects(barrier)) {
			// Game over
			isGameOver = true;
			LK.effects.flashScreen(0xff0000, 800);
			LK.showGameOver();
			return;
		}
	}
};
// On game over, reset state for next run
LK.on('gameover', function () {
	resetGame();
});
// Prevent elements in top left 100x100
// (All elements are placed away from this area by design)

===================================================================
--- original.js
+++ change.js
@@ -132,9 +132,9 @@
 	// Randomize height
 	var h = BARRIER_MIN_HEIGHT + Math.floor(Math.random() * (BARRIER_MAX_HEIGHT - BARRIER_MIN_HEIGHT + 1));
 	barrier.height = h;
 	barrier.children[0].height = h;
-	barrier.y = GROUND_Y;
+	barrier.y = 320; // Place barrier at the top of the screen (barrier height)
 	barrier.speed = scrollSpeed;
 	barriers.push(barrier);
 	game.addChild(barrier);
 }