Yesterday I watched an FFmpeg podcast video Link where someone mentioned writing assembly on his phone while watching his children at the playground. As someone who doesn't really care about the hype that programming is already solved, I really like it.
Last year, I stumbled upon this dude somehow writing a SQLite parser by hand in Rust: Turso PR. Parsing probably sounds scary if you come from a high-level language, but the TL;DR is simple: parsing just generates the AST structure from tokens/code. As always in CS, the devil is in the details—so I decided to write my own parser.