Twitch - a GPL arcade game by David Clark <silenus@telus.net>.

Twitch is an overhead 2-d shooter, reminiscent of games like Robotron or Tron:
Deadly Disks. The player has entered the fortress of the evil Hippopoticus,
and is trying to rescue the fair Lady Penelope from his clutches. I wrote
Twitch as a proof-of-concept: namely that Python, properly written, is fast
enough to create a playable, cross-platform arcade game.

WWW: http://www3.telus.net/futility/twitch/index.html