I really like your approach of pushing as far as you can just to learn more. I do the same thing here on FCC!
Having said that though: it can be quite easy to over do something. Knowing when something is too complicated or even confusing is just as valuable as learning complicated techniques, imo.
I like the way your content is set up. The warning boxes, headers, font choice, subtle button on the bottom-right, are all easy on the eye and it is very organized! Easy to read and understand.
This is why the navigation negatively stands out to me, it seems overcomplicated for this page while the rest is quite neat and tidy. The main issue is that thetransition from icon -> text is confusing. I couldn’t figure out if my cursor was on the same item before and after I hovered over it. This is due to two effects:
the transition should be instant or very smooth (it is now in between - not enough time to watch what happens, but also not quick enough to make it immediately obvious that the same items are displayed)
during the collapse/expand of the menu, the text is first pushed onto the next line, which draws your eye away from the navigation itself. I would make it so that the text appears after the div has completely expanded.
Another option would be to put small icons in front of the text so that it is easier to see that they refer to the same thing!
Hope this feedback helps you, good luck!