This is very cool and having stalemate is nice, however how much space would it take to implement the full ruleset? As you write: not implemented: castling, en

This is very cool and having stalemate is nice, however how much space would it take to implement the full ruleset? As you write: not implemented: castling, en passant, promotion, repetition, 50-move rule - those are all required to call the game being played modern chess. I could see an argument for skipping repetition and 50-move rule for tiny engines, but you do need castling, en pessant and promotion for pretty much any serious play. https://en.wikipedia.org/wiki/Video_Chess https://en.wikipedia.org/wiki/Video_Chess fit in 4k and supported fuller ruleset in 1980 did it not? So I would ask what is the smallest fully UCI (https://www.chessprogramming.org/UCI https://www.chessprogramming.org/UCI) compliant engine available currently? This would be a fun goal to beat - make something tiny that supports full ruleset. PS my first chess computer in early 1980s was this: https://www.ismenio.com/chess_fidelity_cc3.html https://www.ismenio.com/chess_fidelity_cc3.html - it also supported castling, en pessant, not sure about 50 move rule.