Updated the old tectonics simulation to work on the mostly-hex grid. It was relatively painless: most of the codebase had been written with the idea of "tiles" on a planet just being points on the unit sphere, each with some arbitrary number of neighbors.
The climate model, such as it is, was pretty much hacked in from earlier experimental code that had made more assumptions about data structures, so there was some refactoring to take care of there. But otherwise it seems to work like before, just on a bunch of hexes instead of a bunch of rectangles.
Two sides of a planet: