This is a weird weekend project that ended up producing some nice animations. :)

The cells in this game act independently and only see cells in the surrounding area. Cell types are encoded by color here.

If the structures move, they mostly do it by creating cells from which they repulse. These are left as "garbage" cells (green in these animations). Garbage cells have a low overpopulation threshold, so they disappear quickly.

To create this, I used PyGame (based on libSDL). The animation is done by dumping images to a temporary directory and later combining them with the gifsicle tool.