Upon reading the title, this is one of those "I know that's possible, but I'd never bother to implement it" things, although this particular implementation isn't exactly what I had in mind.

This is amazing. I'm at loss for words.

During my CS years I remember being fascinated by NFA's, as opposed to boring single universe DFA's.

For some reason I internalized that I would never see something like an NFA implemented beyond text books.

Then came Carlini.

I get "illegal move, game over" like 50% of the time, chrome on android.

The technical write up is worth perusing but I played a game before reading and accidentally found a winning strategy immediately. I'm not sure if this is a result of the 2-ply nature of the engine or if the mentioned deficiencies account for this but the computer did not act to prevent checkmate in 1 (without any intervening check); the game I played was (in algebraic notation): 1. e4 e5 2. kf3 kf6 3. kxe5 kxe4 4. d4 kxf2 5. Kxf2 a5 6. Qf3 b5?? 7. Qxf7 1-0

This is absurd. I did not realize you could do nearly this much computation in regex.

2025

This is like a fever dream.