FYI: more state of the art

[kirby urner]

Here's a link to some Youtubes showing a state-of-the-art geometric exploration tool (flat universe, a flat land), written in Python:

http://www.youtube.com/user/fbasegmez#p/a/u/2/K1pdoLi6UPc

The first Youtube is specifically mathematical and demonstrates using scales (as in "weighing machine") to compare area.

This is not open source or free, but much of the best stuff is like that.

http://www.mekanimo.net/downloads/

And now for something completely different (or not completely):

http://www.4dsolutions.net/synergetica/eja1.html  (because today is Buckyball Day -- check Google).

Kirby