[ymimwzuf] Chess proof

If someone claims that a certain position is mate in N, the proof is in general quite large, needing to exhaustively enumerate all defender tries.

The best one can do to shorten it is to give the best attacker response for each position that can be reached, similar to how alpha-beta improves minimax.  Given a data limit on the number of "hints", give all the best attacker moves to some shallow depth, or perhaps along the main line.