Thanks for the nice comments, everyone! I made this but didn't expect to see it here.

As people have noticed, the spinning diagrams are done with CSS, which was fun.

Basically it's just an `animation: linear infinite;` from `transform: rotateY(0turn);` to `transform: rotateY(1turn);`

(source here https://github.com/hrldcpr/poole/blob/master/_sass/_latex3d.... )

To keep the numbers facing forward, they're all also rotating, but in the opposite direction :p

And all of the numbers' `translate3d(...)` coordinates are generated by a Python script because I didn't want to do that by hand...