It's still somewhat on the back burner, but I've been working on a
library to allow you to drag and drop irregularly shaped objects (esp.
circles and polygons) while preventing interpenetration. It's a
surprisingly hard problem and I'm reading a lot of computational
geometry papers to find an algorithm to solve it.
This is a subproject/distraction from my game, PEN (puzzles from the
engineer's notebook) which was loosely inspired by the incredible
machine: http://sourceforge.net/projects/pen/. You can see a buggy,
circles-only version of the dragging problem in the code there if you're
curious. I'm hoping a library would be something useful to other game
designers. What do you think?
--Mike