Fifteen Puzzle is a free, mind-bending puzzle game for S40 phones. The object of the game is to rearrange the numbered tiles so that they run in sequence from 1 to 15, by swapping them with the conjoining tiles.
The aim is to make as few moves as possible. There is an online leaderboard in Fifteen Puzzle where you can pit yourself against other players of the game from around the world.
The presentation of Fifteen Puzzle is a bit drab but it's a riveting puzzle game that will keep your attention.