Kill Box Mate Intermediate Puzzle (Rated 940): Spot — Mate in 1

This puzzle is a pure forcing finish: the side to move has a direct checkmate available, so there is no need for calculation beyond checking every legal escape square. In classical chess, these moments usually come from a mating net built by active pieces, weak king shelter, and overloaded defenses. The key idea is to recognize when the enemy king is boxed in by its own pieces and pawns, leaving only one decisive tactical shot.