A constantly evolving procedural map generated by Langston's ant, implemented in SpriteKit. Basically: there are three "ants" on a map, one that leaves behind lava, and two that leave behind water. Lava creates land that evolves over time (from lava, to rock, to dirt, then to either sand or grass), and water washes away sand, slowly eroding the land. If you let it run long enough, you get some pleasing shapes that look vaguely like landmasses.
If you think this is neat, wait til you see Life Saver!
