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Highest priority:

• If my closure_try2 branch seems to be working: start converting other things and cleaning everything up. (twist is still ugly. Look at all my TODOs in it.)
• See automata_scratch/examples.py and implement some of the tougher examples.
  • spiral_nested_2 & spiral_nested_3 (how to compose efficiently?)
  • twisty_torus
  • ram_horn_branch - Can I pass depth via a closure?

Important but less critical:

• Elegance & succinctness (my recent closure work may help with this):
  • Why must I repeat myself so much in these definitions?
  • What patterns can I factor out? I do some things regularly, like: the clockwise boundaries, the zigzag connections, the iterating over a Vec<Vertex> to transform each element and make another vector.
• Docs on modules
• Grep for all TODOs in code, really.
• Look at performance. Can I save on copies of geometry by using Rc<OpenMesh> or the like? In many cases I have nothing but copied geometry. Can I pre-allocate vectors instead of extending/appending?
• Look at everything in README.md in automata_scratch.

If I'm bored:

• Fix links in tri_mesh docs that use relative paths & do a PR?
• Look in https://www.nalgebra.org/quick_reference/# for "pour obtain". Can I fix this somehow? Looks like a French-ism that made its way in.
• Multithread! This looks very task-parallel anywhere that I branch.