I completed a pc game with the same concept and started looking for something similar on Pocket PC and found this. It works fine on WM5 (I have a x51v).
It's a real brain buster, makes my bus rides seems like 5min instead of 25min as it's quite a challange and requires a lot of logic thinking :)
There is a free demo at the following link:
http://www.twilightgames.com/pda/ppc...argon_info.htm