Ha, yes, I was being nosy. It was quite easy to spot as it's the only XHR/Fetch request.

I was intrigued what you had used to build it, and if you had built your own solver (which you have), and what editor you used (Code Mirror) so went looking at the code. Interesting to see you left the source maps for production, made it easy for my sleuthing...

I experimented with a similar idea last year, but used ProseMirror/TipTap as the editor to enable rich text editing, and the MathJS (https://mathjs.org) solver. I also combined it with PouchDB and Yjs for offline editing and syncing between devices. Never finished it though, you have kept your nice and simple!