Puzzle 15 (also called gem puzzle, boss puzzle, game of fifteen, mystic square and many more) is a sliding puzzle consisting of 15 square tiles, numbered 1 to 15, in a frame 4 tiles high and 4 tiles wide leaving one unoccupied. tile position. Tiles in the same row or column of an open position can be moved by sliding them horizontally or vertically, respectively. The goal of the puzzle is to place the tiles in numerical order.