Yes, that's because when your focus is not your browser, Greenfoot would slow down the speed automatically. Then the "timeSpace" in WorldX would get too big for intersection detecting. After all, it works good on Android.

Just write something about how to use it. From downloading Eclipse or dropbox to how to do the convert. You know, the first step out from Greenfoot could be tough to new learners.

Would you introduce my Greenfoot4Android? For it's very like Greenfoot. As you are my first user, you may share your experience with others.

So did you want any pics anymore. I think your method has great fun. BTW I have already collected some pics for the board in wooden style.