What do you mean by 'it starts accumulating' in this context? Are you talking about the fact that numbers gain decimal places? Or the fact that using a number between 0 and 1 will make your values diverge to infinity? Either way, it's just mathematics for you, I'm afraid, and there's little Python can do about it. ;)
Which part of the code issues the overflow error? I'm guessing it's the draw.point() call since that's the only bit I can't test. -- Ben Sizer -- http://mail.python.org/mailman/listinfo/python-list