One of my favourite sites! and an interesting example of that class of sites which are book made into sites with animations/interaction --- the another classic and notable example is:
https://mathcs.clarku.edu/~djoyce/java/elements/elements.htm...
Really wish that the folks doing the 507 Mechanical Movements would finish the balance of the animations.
Curious if folks are aware of other similar text/website combinations which are still extant (many others such as Bembo's Zoo are no longer available, and of course at one point in time, this sort of thing was the province of CD-ROMs such as Leonardo).
If you haven't checked it out before, Nicholas Rougeux often does these types of modernization conversions for older printed content: https://www.c82.net/
e.g. here's a very beautiful reproduction of Euclid's elements https://www.c82.net/work/euclid