Comment by returningfory2

I've been building a bunch of UIs for my project Texcraft: https://hyphenate.dev and https://ligkern.dev.

Texcraft is an attempt to re-implement TeX with a modular/LLVM software architecture. These UIs take the same code in Texcraft that has identical behavior to TeX, and illustrates some of the inner workings of TeX. The lig/kern one is missing instructions :)

I have also found at least one bug in Knuth's TeX recently and am currently writing it up.