===================================================================
--- original.js
+++ change.js
@@ -1,6 +1,185 @@
-/****
+/**** 
+* Plugins
+****/ 
+var tween = LK.import("@upit/tween.v1");
+
+/**** 
+* Classes
+****/ 
+// Ninja class
+var Ninja = Container.expand(function () {
+	var self = Container.call(this);
+	var ninjaAsset = self.attachAsset('ninja', {
+		anchorX: 0.5,
+		anchorY: 1
+	});
+	// Physics
+	self.vy = 0;
+	self.isJumping = false;
+	// Update method for gravity and jump
+	self.update = function () {
+		if (!self.isJumping) return;
+		self.y += self.vy;
+		self.vy += gravity;
+		// Land on ground
+		if (self.y >= groundY) {
+			self.y = groundY;
+			self.vy = 0;
+			self.isJumping = false;
+		}
+	};
+	// Jump method
+	self.jump = function () {
+		if (!self.isJumping) {
+			self.vy = jumpVelocity;
+			self.isJumping = true;
+		}
+	};
+	return self;
+});
+// Obstacle class
+var Obstacle = Container.expand(function () {
+	var self = Container.call(this);
+	var obsAsset = self.attachAsset('obstacle', {
+		anchorX: 0.5,
+		anchorY: 1
+	});
+	self.passed = false; // For scoring
+	// Update method for moving left
+	self.update = function () {
+		self.x -= obstacleSpeed;
+	};
+	return self;
+});
+
+/**** 
 * Initialize Game
-****/
+****/ 
 var game = new LK.Game({
-	backgroundColor: 0x000000
-});
\ No newline at end of file
+	backgroundColor: 0xf0f0f0
+});
+
+/**** 
+* Game Code
+****/ 
+// Ground: a box, green
+// Obstacle: a box, gray
+// Ninja character: a box, dark blue
+// Constants
+var groundY = 2400; // Y position of ground top
+var gravity = 5.2; // Gravity per frame
+var jumpVelocity = -90; // Initial jump velocity
+var obstacleSpeed = 28; // Obstacle speed per frame
+var obstacleMinGap = 600; // Minimum distance between obstacles
+var obstacleMaxGap = 950; // Maximum distance between obstacles
+// Game state
+var ninja;
+var ground;
+var obstacles = [];
+var score = 0;
+var scoreTxt;
+var gameStarted = false;
+var lastObstacleX = 0;
+// Add ground
+ground = LK.getAsset('ground', {
+	anchorX: 0,
+	anchorY: 0
+});
+ground.x = 0;
+ground.y = groundY;
+game.addChild(ground);
+// Add ninja
+ninja = new Ninja();
+ninja.x = 420;
+ninja.y = groundY;
+game.addChild(ninja);
+// Score text
+scoreTxt = new Text2('0', {
+	size: 120,
+	fill: "#222"
+});
+scoreTxt.anchor.set(0.5, 0);
+LK.gui.top.addChild(scoreTxt);
+// Helper: spawn obstacle
+function spawnObstacle() {
+	var obs = new Obstacle();
+	obs.x = 2048 + 100;
+	obs.y = groundY;
+	obstacles.push(obs);
+	game.addChild(obs);
+	lastObstacleX = obs.x;
+}
+// Helper: reset game state
+function resetGame() {
+	// Remove obstacles
+	for (var i = 0; i < obstacles.length; i++) {
+		obstacles[i].destroy();
+	}
+	obstacles = [];
+	// Reset ninja
+	ninja.x = 420;
+	ninja.y = groundY;
+	ninja.vy = 0;
+	ninja.isJumping = false;
+	// Reset score
+	score = 0;
+	scoreTxt.setText(score);
+	// Reset obstacle spawn
+	lastObstacleX = 0;
+	// Spawn first obstacle
+	spawnObstacle();
+	gameStarted = true;
+}
+// Start game on first tap
+game.down = function (x, y, obj) {
+	if (!gameStarted) {
+		resetGame();
+		ninja.jump();
+		return;
+	}
+	// Only jump if not already jumping
+	ninja.jump();
+};
+// Main update loop
+game.update = function () {
+	if (!gameStarted) return;
+	// Update ninja
+	ninja.update();
+	// Update obstacles
+	for (var i = obstacles.length - 1; i >= 0; i--) {
+		var obs = obstacles[i];
+		obs.update();
+		// Check for collision
+		if (ninja.intersects(obs)) {
+			// Flash screen and game over
+			LK.effects.flashScreen(0xff0000, 800);
+			LK.showGameOver();
+			gameStarted = false;
+			return;
+		}
+		// Scoring: passed obstacle
+		if (!obs.passed && obs.x + 60 < ninja.x) {
+			obs.passed = true;
+			score += 1;
+			scoreTxt.setText(score);
+		}
+		// Remove off-screen obstacles
+		if (obs.x < -200) {
+			obs.destroy();
+			obstacles.splice(i, 1);
+		}
+	}
+	// Spawn new obstacles
+	if (obstacles.length === 0 || 2048 - lastObstacleX > obstacleMinGap + Math.floor(Math.random() * (obstacleMaxGap - obstacleMinGap))) {
+		spawnObstacle();
+	}
+};
+// On game over, allow restart on tap
+game.up = function (x, y, obj) {
+	if (!gameStarted) {
+		// Wait for LK.showGameOver to reset game
+	}
+};
+// Initial state: show "Tap to Start"
+gameStarted = false;
+scoreTxt.setText('0');
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