Very cool how on move 1, black's g-pawn block's his king's escape hatch, either way he chooses to advance. Then white slams the door with an interpose checkmate.

Yes, I noticed the hint, which as you say practically gives it away, and having seen it I could not unsee it. I wish the creator had not felt the need to give that hint, as it takes away much of the challenge of solving the problem.