function Puzzle(div, dim) {
	this.div = div;
	this.cellSize = div.offsetWidth / dim;
	this.empty = dim * dim - 1;
	var item = {};
	for (var i = 0, n = dim * dim; i < n; i++) {
		var newItem = new PuzzlePiece(this, i, dim, i == n - 1);

		item[i] = newItem;
		div.appendChild(newItem.div);
	}
}