Things I like:
1. It's obvious where sections begin and end.
2. PLENTY or margin and padding. I know some people try to cram as much info on a single line as possible. My old eyes prefer spacing; it helps them track the text.
3. With one exception (mentioned below) the font sizes seem to "look good."
Things I might suggest are improvable:
1. It's not obvious what the show/hide button at the top of the page does at first glance. The button is at the top of the page and its effects are seen at the bottom of the page. Maybe put another copy of the button immediately above the answer section?
2. Continuing the show/hide theme, the per-answer-section show/hide button hides the content, but maintains the blank space in the document. That seems "wrong" to me since I have to scroll past complete blank areas when looking at it on my phone. And I think we could have no end of discussion whether those buttons should be at the top or bottom of the section that gets hidden. I'd just suggest trying putting them at the top and see if they look better to you.
3. The "Objective", "Question", "Result", "Answer" sub-section headers seem like they should be a little bigger.
I don't know if you tested some of these options, and completely defer to you if you tested them and they look even weirder. Just my $0.02. Mostly looks great.
Otherwise, looks quite nice!
Little Schemer was instantly appealing because it starts so simply:
I came to your page wanting to learn P5.js, but it started a little too involved.Consider starting with a few simpler questions and answers like this, which also helps just teach the format and interface, before asking the reader to work their brain much harder.