@danluu I really enjoyed this post. Thank you for putting it together.
I think you might find the new zig standard library documentation web app interesting, since I made the controversial decision to have it fetch all the source code up front and then do all the content rendering locally. In theory, this is CPU intensive but in practice... even those old phones have really fast CPUs!
https://ziglang.org/documentation/master/std/
I'm curious how it fares with those old phones you have.