Futility Closet posted a chess puzzle that claims, “White to mate in half a move”.
There’s an obvious mate at Qb7, but no “half” moves that I can see. When someone says half a move, I immediately think of the two-part movement of castling, but that’s not happening here.
My instinct aimed at 1. cxb6 e.p. +, but that’s no checkmate (1. … Rxb6).
I wrestled with the idea that the board displays a piece half-way through a move But white’s pawns can not proceed further, and have no where to go if you flip the board 180. Knight has no mating squares except xb5, but where would it come from? c7? That would suggest it’s already in the air.
Speaking of which, it’s one thing to lift a piece to reveal a checkmate, but it wouldn’t be fair to have an unknown piece already hanging in the air…
The last idea I have is that “half a move” refers merely to white’s “half” (or, ply) of a two-part turn, and thus my first move stands.
So what’s the answer? I hate to wait until tomorrow, but hate more not figuring this out on my own.
Update: Chris Lott saw through this almost immediately, recognizing that the white queen could be representing the default choice of a promoted pawn–just prior to choosing the knight which cinches a checkmate. Nice brain on that guy, eh?
Futility Closest just posted the solution, and I was disappointed.
The move is the xb6 e.p., but just the first half: move the white pawn without removing the captured black pawn, which remains to block the rook.
That’s cheating, isn’t it? I vote for Chris’s solution. Even my semantic solution was better than the e.p.