The famous 15-puzzle (you may know that game under other names Gem Puzzle, Boss Puzzle, Game of Fifteen, Magic Square or Mystic Square) is a sliding puzzle that consists 15 tiles numbered from 1 to 15 that are placed in a 4×4 box leaving one position out of the 16 empty.

The object of the puzzle/game is to reposition the tiles from a given arbitrary starting arrangement by sliding them one at a time into the following order:

This app is designed for both iPhone and iPad:

You can use this free app available in the iTunes App Store: