Fifteen puzzle

The 15-puzzle is a sliding puzzle that consists of a frame of numbered square tiles in random order with one tile missing.
The object of the puzzle is to place the tiles in order by making sliding moves that use the empty space.
The score is based on the time and how many times you move the tiles.

There are 5 different puzzles and levels.
You can also take a picture and use that image as your puzzle.

Enjoy !

For the geeks out there:
The n-puzzle is a classical problem for modelling algorithms involving heuristics.
Commonly used heuristics for this problem include counting the number of misplaced tiles and finding the sum of the Manhattan distances between each block and its position in the goal configuration.
Note that both are admissible, i.e., they never overestimate the number of moves left, which ensures optimality for certain search algorithms such as A*."