semantic elements

[SArpnt]

minor complaint but using the details tag would improve accessibility and not need supporting javascript code
already implemented on my website, not entirely sure how styling works for this but i don't think it would be difficult

[SArpnt]

i think this issue should be extended to more elements actually, for example many buttons on the website are divs, which makes them impossible to select with tab (the library buttons seem to have selectable text too), the time counter is a text input and not a number input, and you could probably use some elements like main, aside, article, section, footer, etc.

[SArpnt]

i think the library should use list elements and the info section use paragraphs instead of line breaks

there should also be an aria-label on the code editor and oscilloscope