Chipmunk Physics

I'm almost ready to release my new game that uses the chipmunk engine, it will be cross platform but I'm going to release it for the mac a week or so before windows to make the process easier. The game is an original puzzle game, and you can download the mac demo here - http://nuclearnova.com/temp/liquiddefense.zip . Here is a screenshot from a few weeks ago,

Any feedback is welcome and VERY MUCH appreciated. If anyone has a PPC mac I would appreciate a test just to see if it runs, and a crash report if it doesn't. There is a serial number in the download, but please try the demo first.