The Stockfish chess engine: https://github.com/official-stockfish/Stockfish https://github.com/official-stockfish/Stockfish I learned a ridiculous amount from

The Stockfish chess engine: https://github.com/official-stockfish/Stockfish https://github.com/official-stockfish/Stockfish I learned a ridiculous amount from reading the source code to TeX (https://www.amazon.com/Computers-Typesetting-B-TeX-Program/dp/0201134373/ https://www.amazon.com/Computers-Typesetting-B-TeX-Program/d...) but it is written in a very 1970s style.