So, there's been a 3D aperiodic monotile discovered. I have software for handling aperiodic tilings computationally, but only tested so far in 2D. Can it cope?

My system works in a purely combinatorial manner, not relying on the geometry of the tiling: it only depends on what tiles exist, which are adjacent via what part of their boundary, and which ones are subtiles of which in the hierarchy of substitutions. So it _ought_ to handle 3D tilings as easily as 2D.

This seemed like a good moment to test that claim! Can I write down, or generate, a combinatorial description of the Chair44 substitution system which my code can handle?

I gave this a try, and found that the answer was yes, _eventually_. But I had missed something subtle, and had to fix it, or rather, bodge it.

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