Firstly, job well done. Secondly, what is the motivation of going pure CSS aside from the challenge of it?
I once prefered Pure CSS stuff until I learned Javascript myself. Now I've come to loathe that approach on complex menus and widgets.
Mainly I dislike using them because I have to refactor them to use Javascript so they can be stateful (reacting to an active category or something indicated by the url or querystrings, etc.
To assume those code bases don't contain bugs or go through multiple revisions and iterations is just naive. Just because bugs have not been exposed does not mean they are not present.
Smart contracts have people actively snooping and trying to exploit bugs for gain. Oh, and they are publicly accessible.
I think this is the reason so many are picking up Vue rather than React or Angular these days. Vue offers the component approach and is generally fun to learn IMHO.
...And then subsequently took me several days to get my currentUser state shared with my userIcon component.
The real question should be, how long does it take to learn Redux and react tooling.