Fifteen is a well-known puzzle game. The number 15 in the name of the game comes from the number of tiles in the box. Each tile is numbered from 1 to 15. There are 16 cells in the box, one of which is not occupied by a tile. Box size 4x4. The player can move the tiles in the box at the expense of a free cell. The goal of the game is to collect the tiles in a box with numbers in order, using as few moves (movements) as possible. The game is considered over as soon as the goal is reached.