• curve_horn_*: actually combine geometry properly.

• Look at everything in README.md in automata_scratch.

• Implement some of the tougher examples from the above too, e.g. the triple nested spiral

• Lots of Rust-kosher refactoring (once I understand Rust better)

• Grep for all TODOs in code, really

• Actual Rust-style docs!

• Fix links in tri_mesh docs that use relative paths & do a PR?