This is a version of the classical 15 puzzle, which is a sliding puzzle where you should reorganize the numbers 1 to 15 so that they are ordered from left to right and top to bottom. The game consists of a 4x4 board (frame) with 15 tiles containing the numbers 1 to 15 placed on it, from the start in an incorrect order. There is one tile missing and this free slot can be used to move the other tiles.

The objective is to order the tiles by moving one tile at a time (swapping place with the position of the empty tile) so that they are placed in order. You should aim at finishing the puzzle with as few moves and as possible and as quick as possible. The game is also known as sliding puzzle, gem puzzle, boss puzzle and mystic square.