The rendering is all thanks to KaTeX, which is indeed great! Maybe it's not clear enough from the page, but the page is actually editable -- click anywhere and

The rendering is all thanks to KaTeX, which is indeed great! Maybe it's not clear enough from the page, but the page is actually editable -- click anywhere and start writing. You can add new math by typing an expression like $x+y=z$. The untested bit has to do with math editing on -- there are some issues with moving your cursor around using the arrow keys on FF.