Sokoban is a fun game. Try to push the boulders onto the diamonds.

You cannot pull the boulders, so be careful that you don't push them too far.
The buttons are as follows:
Move Sokoban with the arrow keys
'<' - Go back a level
'>' - Go Forward a level
'X' - Restart a level
'U' - Undo the last move

You cannot save your game, but you can Go Forward to the level you were working on.
There are 103 levels in all, So there's plenty here to keep you busy!