[whatever_yeah]

Very cool stuff, and great work. Minor UI nitpicks (my personal bugbear):

- Lesson content section has unnecessary horizontal scrollbar visible

- No visual distinguishing or handling for scrollable area (vs the finished display area) had me trying to scroll with my mouse hovering on the lefthand side often, and momentarily confused why it wouldn't go. Make the whole main body section scroll the content, ideally.

[HunorBorbely]

Yes, I was thinking of fixing the second point, but then I was annoyed with it and left it like that. If I knew that it blows up here on Hacker News I would have fixed it.

I'm not sure where you see horizontal scrollbars though. Are you on Windows?