This is technically my second PyWeek, but I never produced an entry for the last one. This time though, I have an idea that will fit and that is within reasonable size for a week:

It's a puzzle game where you move blocks around obstacles, eventually making every block "disappear" by moving it adjacent to its twin. It's more-or-less a remake of an old VB3/win16 game I remember playing but can't find anymore, called "Uz."