Fifteen - a puzzle, which is 15 square tiles with applied numbers from 1 to 15. All the knuckles are enclosed in square of 4x4 (side of the square is four times longer than that of the knuckles). Thus when placing the tiles in a square is one empty space the size of a domino that can be used to move the tiles. The goal - to streamline the placement of numbers, placing them in ascending from left to right and top to bottom, beginning with the knuckle with the number 1 in the upper left corner and ending with an empty space in the bottom right corner. You can select the background color of the game and knuckles. Good Luck !!!