Trilobite and crab, tiles and puzzle

This Thing constructs trilobite-and-crab tilings. They are described in [The Trilobyte and Crab: A Full Explanation, by Chaim Goodman-Strauss](https://arxiv.org/abs/1608.07167). These tiles can be assembled into patterns that fill the entire plane, but no such pattern can have a translational symmetry. This Thing contains three versions:
* A pair of tiles that have markings on top. A proper tiling matches these markings, and the markings illuminate the non-periodic but systematic structure of a