Sokoban is a wonderfully addictive little puzzle game. This is an enhanced version of the original version as found on Squeak Map. The original version was published for Squeak by Robert Hirschfeld.
After playing it for a while I made a few enhancements to the game. A lot of the changes were cosmetic. But the most important enhancement is that an undo command was added. The game is a lot more playable. All the original rules about moves and the original puzzle/board configurations are intact. I just added a move stack that allows you to use the "z" key and roll-back any move you had already made. I also added a move that allows the use of the Control key modifier and causes a move to repeat. It's easier to just try it than explain it here.
To see a picture of the game look here: http://squeak.preeminent.org