Game of 15

Our Game of 15 is a classic puzzle game (also called 15 puzzle, Gem Puzzle, Boss Puzzle, Mystic Square, ...) with numeric and alphabetic tiles. It is a sliding puzzle that consists of a frame of square tiles in random order with one tile missing. Size of the frame is 4x4. Numeric version of the game have numeric tiles that must be ordered from 1 to 15, alphabetic tiles must be ordered from A to O.