If anyone is still interested in this kind of project, I could lend the Mr Beanbag engine towards it. In fact if someone could provide me with the graphics and some music mods, I could probably make Mr Beanbag run round a sonic zone in next to no time. He wouldn't be able to go round loops and stuff unfortunately (that was actually planned for Mr Beanbag in the early stages but I dropped the idea pretty soon as I couldn't think of a neat way to do it. The Beanbag II engine, if I ever get round to it, will have much better physics which will allow this sort of thing.)