It was custom made for the tutorial. I didn't release it yet because I mostly focused on polishing the tutorial itself and not the code for the interface. Do you think people would be interested in the interface by itself?

Yes, 100%.

The tutorial on git is super cool, but for me the thought of constructing my own tutorials using a framework that got you here is even cooler.

Definitely! It is so well done at first I though I was on a MOOC site and navigated to the home to figure out if there were more tutorials :)

I would certainly take a look. It would be amusing if you released it using the interface itself.

Literal programming from Knuth's WEB adapted to modern web ;)

I was wondering the same, this format feels extremely intuitive for the material it explores. Looking at the HTML and the CSS class names I'd assume it was handmade, but it seems like standardizing this format or even generating this webpage format from a repo would be a useful tool. The comment left at the end is ambiguous as to whether it refers to the tutorial or the website as a whole.