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

/**** 
* Classes
****/ 
var Block = Container.expand(function () {
	var self = Container.call(this);
	var blockGraphics = self.attachAsset('block', {
		anchorX: 0.5,
		anchorY: 1.0
	});
	self.speed = -8;
	self.update = function () {
		self.x += self.speed;
	};
	return self;
});
var Character = Container.expand(function () {
	var self = Container.call(this);
	var characterGraphics = self.attachAsset('character', {
		anchorX: 0.5,
		anchorY: 1.0
	});
	self.velocityY = 0;
	self.gravity = 0.8;
	self.jumpPower = -16;
	self.isGrounded = false;
	self.groundY = 2652; // Ground level
	self.jump = function () {
		if (self.isGrounded) {
			self.velocityY = self.jumpPower;
			self.isGrounded = false;
			LK.getSound('jump').play();
		}
	};
	self.update = function () {
		// Apply gravity
		self.velocityY += self.gravity;
		self.y += self.velocityY;
		// Ground collision
		if (self.y >= self.groundY) {
			self.y = self.groundY;
			self.velocityY = 0;
			self.isGrounded = true;
		}
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x87CEEB
});

/**** 
* Game Code
****/ 
// Game variables
var character;
var blocks = [];
var gameSpeed = 8;
var blockSpawnTimer = 0;
var blockSpawnInterval = 90; // frames between spawns
var distance = 0;
var lastGroundCheck = true;
var lastDistanceMilestone = 0;
// Create ground
var ground = game.addChild(LK.getAsset('ground', {
	anchorX: 0,
	anchorY: 1.0,
	x: 0,
	y: 2732
}));
// Create character
character = game.addChild(new Character());
character.x = 300;
character.y = character.groundY;
// Create score display
var scoreText = new Text2('Distance: 0', {
	size: 60,
	fill: 0xFFFFFF
});
scoreText.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreText);
// Touch controls
game.down = function (x, y, obj) {
	character.jump();
};
// Game update loop
game.update = function () {
	// Update distance
	distance += gameSpeed;
	LK.setScore(Math.floor(distance / 10));
	scoreText.setText('Distance: ' + Math.floor(distance / 10));
	// Spawn blocks
	blockSpawnTimer++;
	// Random spawn interval for varied timing
	var randomSpawnInterval = blockSpawnInterval + Math.floor(Math.random() * 40) - 20; // ±20 frames variation
	if (blockSpawnTimer >= randomSpawnInterval) {
		blockSpawnTimer = 0;
		// Create new block on top of ground
		var newBlock = new Block();
		newBlock.x = 2200; // Spawn off-screen right
		// Spawn blocks on top of the ground surface
		newBlock.y = 2652; // Ground surface level (2732 - 80)
		// Set speed based on current distance milestone
		var currentMilestone = Math.floor(distance / 1000);
		var speedMultiplier = 1 + currentMilestone * 0.5;
		newBlock.speed = -8 * speedMultiplier;
		blocks.push(newBlock);
		game.addChild(newBlock);
	}
	// Update blocks
	for (var i = blocks.length - 1; i >= 0; i--) {
		var block = blocks[i];
		// Track previous position for collision detection
		if (block.lastIntersecting === undefined) {
			block.lastIntersecting = false;
		}
		// Remove blocks that have moved off-screen
		if (block.x < -200) {
			block.destroy();
			blocks.splice(i, 1);
			continue;
		}
		// Check collision with character
		var currentIntersecting = character.intersects(block);
		if (!block.lastIntersecting && currentIntersecting) {
			// Collision detected
			LK.getSound('collision').play();
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
			return;
		}
		block.lastIntersecting = currentIntersecting;
	}
	// Check if character fell off screen
	var currentGroundCheck = character.y <= character.groundY + 10;
	if (lastGroundCheck && !currentGroundCheck && character.y > 2800) {
		// Character fell off screen
		LK.showGameOver();
		return;
	}
	lastGroundCheck = currentGroundCheck;
	// Speed up blocks every 1000 distance
	var currentDistanceMilestone = Math.floor(distance / 1000);
	if (currentDistanceMilestone > (lastDistanceMilestone || 0)) {
		// Calculate new speed multiplier (0.5x faster each 1000 distance)
		var speedMultiplier = 1 + currentDistanceMilestone * 0.5;
		var newBlockSpeed = -8 * speedMultiplier;
		// Update speed for all existing blocks
		for (var k = 0; k < blocks.length; k++) {
			blocks[k].speed = newBlockSpeed;
		}
		// Change background color for day/night cycle
		if (currentDistanceMilestone % 2 === 0) {
			// Even milestones: Day (light blue sky)
			game.setBackgroundColor(0x87CEEB);
		} else {
			// Odd milestones: Night (dark blue/purple sky)
			game.setBackgroundColor(0x191970);
		}
		// Update the milestone tracker
		lastDistanceMilestone = currentDistanceMilestone;
	}
	// Increase difficulty over time
	if (LK.ticks % 600 === 0) {
		// Every 10 seconds
		if (blockSpawnInterval > 45) {
			blockSpawnInterval -= 5;
		}
		if (gameSpeed < 12) {
			gameSpeed += 0.5;
		}
	}
};

===================================================================
--- original.js
+++ change.js
@@ -156,8 +156,16 @@
 		// Update speed for all existing blocks
 		for (var k = 0; k < blocks.length; k++) {
 			blocks[k].speed = newBlockSpeed;
 		}
+		// Change background color for day/night cycle
+		if (currentDistanceMilestone % 2 === 0) {
+			// Even milestones: Day (light blue sky)
+			game.setBackgroundColor(0x87CEEB);
+		} else {
+			// Odd milestones: Night (dark blue/purple sky)
+			game.setBackgroundColor(0x191970);
+		}
 		// Update the milestone tracker
 		lastDistanceMilestone = currentDistanceMilestone;
 	}
 	// Increase difficulty over time