Nice that it detects valid moves, But it doesn't know about checkmate? https://chess.maxmcd.com/r1b1kRnr/p1ppB2p/n2P2p1/8/7P/1p6/PP... Should say checkmate?
Ideally every page needs to include a string summarizing every preceding board state leading up to it, so you can search for a current board state plus ‘checkmate white’ to find every possible way to win from a given board state.
Then all that remains to turn Google into the ultimate chess oracle is to persuade your opponent to make all the moves you found.