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

/**** 
* Classes
****/ 
// Block class: a draggable block with a given shape and color
var Block = Container.expand(function () {
	var self = Container.call(this);
	// Properties
	self.shape = null; // {cells, size}
	self.color = null; // asset id
	self.cellSize = 180;
	self.cells = []; // graphical cell assets
	self.ghostCells = []; // for ghost preview
	self.isDragging = false;
	self.gridX = null; // grid position if placed
	self.gridY = null;
	// Set up block with shape and color
	self.setup = function (shape, color) {
		self.shape = shape;
		self.color = color;
		// Remove old cells
		for (var i = 0; i < self.cells.length; ++i) self.removeChild(self.cells[i]);
		self.cells = [];
		// Add new cells
		for (var i = 0; i < shape.cells.length; ++i) {
			var c = shape.cells[i];
			var cell = self.attachAsset(color, {
				anchorX: 0.5,
				anchorY: 0.5,
				x: c[0] * self.cellSize,
				y: c[1] * self.cellSize
			});
			self.cells.push(cell);
		}
		// Center anchor
		var w = shape.size[0] * self.cellSize,
			h = shape.size[1] * self.cellSize;
		self.pivot.x = w / 2 - self.cellSize / 2;
		self.pivot.y = h / 2 - self.cellSize / 2;
	};
	// Show ghost preview at given grid position
	self.showGhost = function (gridX, gridY, grid) {
		self.hideGhost();
		for (var i = 0; i < self.shape.cells.length; ++i) {
			var c = self.shape.cells[i];
			var gx = gridX + c[0],
				gy = gridY + c[1];
			if (gx < 0 || gx >= grid.cols || gy < 0 || gy >= grid.rows) continue;
			var ghost = LK.getAsset(self.color, {
				anchorX: 0.5,
				anchorY: 0.5,
				x: grid.gridOriginX + gx * self.cellSize + self.cellSize / 2,
				y: grid.gridOriginY + gy * self.cellSize + self.cellSize / 2,
				alpha: 0.4
			});
			self.ghostCells.push(ghost);
			grid.addChild(ghost);
		}
	};
	self.hideGhost = function () {
		for (var i = 0; i < self.ghostCells.length; ++i) {
			if (self.ghostCells[i].parent) self.ghostCells[i].parent.removeChild(self.ghostCells[i]);
		}
		self.ghostCells = [];
	};
	// Animate block on placement
	self.animatePlace = function () {
		for (var i = 0; i < self.cells.length; ++i) {
			var cell = self.cells[i];
			cell.scaleX = 1.2;
			cell.scaleY = 1.2;
			tween(cell, {
				scaleX: 1,
				scaleY: 1
			}, {
				duration: 120,
				easing: tween.easeOut
			});
		}
	};
	return self;
});
// Grid class: the main play area
var Grid = Container.expand(function () {
	var self = Container.call(this);
	self.rows = 9;
	self.cols = 9;
	self.cellSize = 180;
	self.grid = []; // 2D array: grid[y][x] = {block: Block, color: assetId}
	self.cellNodes = []; // graphical cell backgrounds
	self.gridOriginX = 0;
	self.gridOriginY = 0;
	// Set up grid
	self.setup = function () {
		// Center grid
		var totalW = self.cols * self.cellSize;
		var totalH = self.rows * self.cellSize;
		self.gridOriginX = Math.floor((2048 - totalW) / 2);
		self.gridOriginY = Math.floor((2732 - totalH) / 2);
		// Draw cells
		for (var y = 0; y < self.rows; ++y) {
			self.grid[y] = [];
			self.cellNodes[y] = [];
			for (var x = 0; x < self.cols; ++x) {
				self.grid[y][x] = null;
				var cell = self.attachAsset('cell', {
					anchorX: 0.5,
					anchorY: 0.5,
					x: self.gridOriginX + x * self.cellSize + self.cellSize / 2,
					y: self.gridOriginY + y * self.cellSize + self.cellSize / 2
				});
				self.cellNodes[y][x] = cell;
			}
		}
	};
	// Check if a block can be placed at gridX,gridY
	self.canPlace = function (block, gridX, gridY) {
		for (var i = 0; i < block.shape.cells.length; ++i) {
			var c = block.shape.cells[i];
			var x = gridX + c[0],
				y = gridY + c[1];
			if (x < 0 || x >= self.cols || y < 0 || y >= self.rows) return false;
			if (self.grid[y][x]) return false;
		}
		return true;
	};
	// Place a block at gridX,gridY
	self.placeBlock = function (block, gridX, gridY) {
		for (var i = 0; i < block.shape.cells.length; ++i) {
			var c = block.shape.cells[i];
			var x = gridX + c[0],
				y = gridY + c[1];
			self.grid[y][x] = {
				color: block.color
			};
			// Animate cell
			var cell = self.cellNodes[y][x];
			cell.scaleX = 1.2;
			cell.scaleY = 1.2;
			// Set tint to the color value of the asset
			if (block.color === 'block_blue') cell.tint = 0x3b82f6;else if (block.color === 'block_red') cell.tint = 0xef4444;else if (block.color === 'block_green') cell.tint = 0x22c55e;else if (block.color === 'block_yellow') cell.tint = 0xfacc15;else if (block.color === 'block_purple') cell.tint = 0xa21caf;else if (block.color === 'block_orange') cell.tint = 0xf97316;
			tween(cell, {
				scaleX: 1,
				scaleY: 1
			}, {
				duration: 120,
				easing: tween.easeOut
			});
		}
	};
	// Clear full rows/columns, return number of cleared lines
	self.clearLines = function () {
		var cleared = 0;
		var toClearRows = [];
		var toClearCols = [];
		// Check rows
		for (var y = 0; y < self.rows; ++y) {
			var full = true;
			for (var x = 0; x < self.cols; ++x) {
				if (!self.grid[y][x]) {
					full = false;
					break;
				}
			}
			if (full) toClearRows.push(y);
		}
		// Check columns
		for (var x = 0; x < self.cols; ++x) {
			var full = true;
			for (var y = 0; y < self.rows; ++y) {
				if (!self.grid[y][x]) {
					full = false;
					break;
				}
			}
			if (full) toClearCols.push(x);
		}
		// Clear rows
		for (var i = 0; i < toClearRows.length; ++i) {
			var y = toClearRows[i];
			for (var x = 0; x < self.cols; ++x) {
				self.grid[y][x] = null;
				var cell = self.cellNodes[y][x];
				cell.tint = 0xe0e0e0;
				// Animate
				cell.alpha = 0.2;
				tween(cell, {
					alpha: 1
				}, {
					duration: 200,
					easing: tween.easeOut
				});
			}
			cleared++;
		}
		// Clear columns
		for (var i = 0; i < toClearCols.length; ++i) {
			var x = toClearCols[i];
			for (var y = 0; y < self.rows; ++y) {
				self.grid[y][x] = null;
				var cell = self.cellNodes[y][x];
				cell.tint = 0xe0e0e0;
				cell.alpha = 0.2;
				tween(cell, {
					alpha: 1
				}, {
					duration: 200,
					easing: tween.easeOut
				});
			}
			cleared++;
		}
		return cleared;
	};
	// Check if any of the given blocks can be placed anywhere
	self.anyValidPlacement = function (blocks) {
		for (var b = 0; b < blocks.length; ++b) {
			var block = blocks[b];
			for (var y = 0; y <= self.rows - block.shape.size[1]; ++y) {
				for (var x = 0; x <= self.cols - block.shape.size[0]; ++x) {
					if (self.canPlace(block, x, y)) return true;
				}
			}
		}
		return false;
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	background: 'Background'
});

/**** 
* Game Code
****/ 
// --- Game variables ---
/*
We use only shapes for blocks and grid cells. Each block color is a unique asset.
Block shapes: 1x1, 1x2, 2x1, 2x2, 1x3, 3x1, L-shape (2x2 with one missing), etc.
Colors: blue, red, green, yellow, purple, orange.
Grid cell: light gray.
*/
// Block shapes definition
var BLOCK_SHAPES = [
// Each shape: {cells: [[x,y],...], size: [w,h]}
{
	cells: [[0, 0]],
	size: [1, 1]
},
// single
{
	cells: [[0, 0], [1, 0]],
	size: [2, 1]
},
// 1x2 horizontal
{
	cells: [[0, 0], [0, 1]],
	size: [1, 2]
},
// 2x1 vertical
{
	cells: [[0, 0], [1, 0], [0, 1], [1, 1]],
	size: [2, 2]
},
// 2x2
{
	cells: [[0, 0], [1, 0], [2, 0]],
	size: [3, 1]
},
// 1x3 horizontal
{
	cells: [[0, 0], [0, 1], [0, 2]],
	size: [1, 3]
},
// 3x1 vertical
{
	cells: [[0, 0], [1, 0], [0, 1]],
	size: [2, 2]
},
// L-shape (top-left)
{
	cells: [[1, 0], [0, 1], [1, 1]],
	size: [2, 2]
},
// L-shape (top-right)
{
	cells: [[0, 0], [1, 0], [1, 1]],
	size: [2, 2]
},
// L-shape (bottom-right)
{
	cells: [[0, 0], [0, 1], [1, 1]],
	size: [2, 2]
} // L-shape (bottom-left)
];
// Block colors
var BLOCK_COLORS = ['block_blue', 'block_red', 'block_green', 'block_yellow', 'block_purple', 'block_orange'];
// Utility: pick random element from array
function randArr(arr) {
	return arr[Math.floor(Math.random() * arr.length)];
}
var grid = new Grid();
grid.setup();
game.addChild(grid);
var score = 0;
var scoreTxt = new Text2('0', {
	size: 120,
	fill: 0x222222
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
// Block tray: 3 blocks to choose from
var trayBlocks = [];
var trayY = 2732 - 250;
var trayX0 = 2048 / 2 - 2 * 270;
var traySpacing = 540;
// Drag state
var dragBlock = null;
var dragOffsetX = 0;
var dragOffsetY = 0;
// Helper: create a new random block
function createRandomBlock() {
	var block = new Block();
	var shape = randArr(BLOCK_SHAPES);
	var color = randArr(BLOCK_COLORS);
	block.setup(shape, color);
	return block;
}
// Helper: refill tray with up to 3 blocks
function refillTray() {
	// Remove old blocks
	for (var i = 0; i < trayBlocks.length; ++i) {
		if (trayBlocks[i].parent) trayBlocks[i].parent.removeChild(trayBlocks[i]);
	}
	trayBlocks = [];
	for (var i = 0; i < 3; ++i) {
		var block = createRandomBlock();
		block.x = trayX0 + i * traySpacing;
		block.y = trayY;
		block.scaleX = block.scaleY = 1.1;
		trayBlocks.push(block);
		game.addChild(block);
	}
}
// Helper: update score display
function updateScore(val) {
	score = val;
	scoreTxt.setText(score);
}
// Helper: get grid cell under (x, y) in game coordinates
function getGridCellAt(x, y) {
	var gx = Math.floor((x - grid.gridOriginX) / grid.cellSize);
	var gy = Math.floor((y - grid.gridOriginY) / grid.cellSize);
	if (gx < 0 || gx >= grid.cols || gy < 0 || gy >= grid.rows) return null;
	return {
		x: gx,
		y: gy
	};
}
// Helper: snap block to tray
function snapBlockToTray(block) {
	var idx = trayBlocks.indexOf(block);
	if (idx >= 0) {
		block.x = trayX0 + idx * traySpacing;
		block.y = trayY;
		block.scaleX = block.scaleY = 1.1;
		block.zIndex = 0;
	}
}
// --- Input handlers ---
// Find block in tray under pointer
function blockUnderPointer(x, y) {
	for (var i = 0; i < trayBlocks.length; ++i) {
		var block = trayBlocks[i];
		// Check bounding box
		var bx = block.x - block.pivot.x * block.scaleX;
		var by = block.y - block.pivot.y * block.scaleY;
		var bw = block.shape.size[0] * block.cellSize * block.scaleX;
		var bh = block.shape.size[1] * block.cellSize * block.scaleY;
		if (x >= bx && x <= bx + bw && y >= by && y <= by + bh) {
			return block;
		}
	}
	return null;
}
// Drag start
game.down = function (x, y, obj) {
	if (dragBlock) return;
	var block = blockUnderPointer(x, y);
	if (block) {
		dragBlock = block;
		dragBlock.isDragging = true;
		dragBlock.zIndex = 100;
		dragOffsetX = x - dragBlock.x;
		dragOffsetY = y - dragBlock.y;
		// Animate up
		tween(dragBlock, {
			scaleX: 1.2,
			scaleY: 1.2
		}, {
			duration: 80,
			easing: tween.easeOut
		});
	}
};
// Drag move
game.move = function (x, y, obj) {
	if (!dragBlock) return;
	dragBlock.x = x - dragOffsetX;
	dragBlock.y = y - dragOffsetY;
	// Show ghost preview if over grid
	dragBlock.hideGhost();
	var cell = getGridCellAt(x, y);
	if (cell) {
		var can = grid.canPlace(dragBlock, cell.x, cell.y);
		if (can) {
			dragBlock.showGhost(cell.x, cell.y, grid);
		}
	}
};
// Drag end
game.up = function (x, y, obj) {
	if (!dragBlock) return;
	// Try to find the nearest valid cell to drop the block, even if not perfectly centered
	var cell = getGridCellAt(x, y);
	var placed = false;
	var foundCell = null;
	if (cell) {
		// Try the cell under pointer first
		if (grid.canPlace(dragBlock, cell.x, cell.y)) {
			foundCell = cell;
		} else {
			// Search nearby cells within a 1-cell radius for a valid placement
			var minDist = 99999;
			var bestCell = null;
			for (var dy = -1; dy <= 1; ++dy) {
				for (var dx = -1; dx <= 1; ++dx) {
					var cx = cell.x + dx;
					var cy = cell.y + dy;
					if (cx < 0 || cx >= grid.cols || cy < 0 || cy >= grid.rows) continue;
					if (grid.canPlace(dragBlock, cx, cy)) {
						// Prefer the closest cell to pointer
						var dist = Math.abs(dx) + Math.abs(dy);
						if (dist < minDist) {
							minDist = dist;
							bestCell = {
								x: cx,
								y: cy
							};
						}
					}
				}
			}
			if (bestCell) foundCell = bestCell;
		}
	}
	if (foundCell) {
		// Place block
		grid.placeBlock(dragBlock, foundCell.x, foundCell.y);
		dragBlock.animatePlace();
		dragBlock.hideGhost();
		if (dragBlock.parent) dragBlock.parent.removeChild(dragBlock);
		var idx = trayBlocks.indexOf(dragBlock);
		if (idx >= 0) trayBlocks.splice(idx, 1);
		LK.getSound('place').play();
		// Clear lines
		var cleared = grid.clearLines();
		if (cleared > 0) {
			updateScore(score + cleared * 10);
			LK.getSound('clear').play();
		} else {
			updateScore(score + 1);
		}
		placed = true;
		// If tray empty, refill
		if (trayBlocks.length === 0) {
			refillTray();
		}
		// Check for game over
		if (!grid.anyValidPlacement(trayBlocks)) {
			LK.getSound('fail').play();
			LK.effects.flashScreen(0xff0000, 800);
			LK.showGameOver();
			return;
		}
	}
	if (!placed) {
		// Snap back to tray
		snapBlockToTray(dragBlock);
		dragBlock.hideGhost();
	}
	// Animate down
	tween(dragBlock, {
		scaleX: 1.1,
		scaleY: 1.1
	}, {
		duration: 80,
		easing: tween.easeOut
	});
	dragBlock.isDragging = false;
	dragBlock = null;
};
// --- Game update loop ---
game.update = function () {
	// No per-frame logic needed for now
};
// --- Start game ---
updateScore(0);
refillTray();

===================================================================
--- original.js
+++ change.js
@@ -234,22 +234,22 @@
 /**** 
 * Initialize Game
 ****/ 
 var game = new LK.Game({
-	backgroundColor: 0xffffff
+	background: 'Background'
 });
 
 /**** 
 * Game Code
 ****/ 
-// Block shapes definition
+// --- Game variables ---
 /*
 We use only shapes for blocks and grid cells. Each block color is a unique asset.
 Block shapes: 1x1, 1x2, 2x1, 2x2, 1x3, 3x1, L-shape (2x2 with one missing), etc.
 Colors: blue, red, green, yellow, purple, orange.
 Grid cell: light gray.
 */
-// --- Game variables ---
+// Block shapes definition
 var BLOCK_SHAPES = [
 // Each shape: {cells: [[x,y],...], size: [w,h]}
 {
 	cells: [[0, 0]],