Well, you said the position was set up correctly, which is misleading.
Most Difficult Mate in 1 ?

Well, you said the position was set up correctly, which is misleading.
Usually it means the pieces are on the right squares. Of course, someone already told you that, yet you ignored it, so I don't expect to fare better. :)

You made an illegal position. Don't take your frustrations out on me.
I am calm and enjoying a nice vacation, actually. Just sit back and watch caveatcanis or another similarly incisive solver show you how it's done.

You made an illegal position. Don't take your frustrations out on me.
I am calm and enjoying a nice vacation, actually. Just sit back and watch caveatcanis or another similarly incisive solver show you how it's done.
It seems like I was the one to truly solve it actually.

I found it amusing to watch the Shahade video and see how many people thought they had found a mate, just like in this forum. The only way I could solve it was to try every legal check (some checks like d8=Q+ are illegal). I count 21 checks White could give, and only one mates. If you play the mating move on the board I provided you will see I typed in the refutation for each of the other 20 checks. (Hopefully I didn't make a mistake.)
I like your problem too BigDoggProblem, which certainly seems harder.
I think it's black's move. Against everything black can play, white has mate in 1.
I realised that eventually, but you beat me to it.
White's last move was hxg3, capturing either a rook or a knight.

What about: d8 with a queen promotion?! You double check black king and he can't take,because your new queen is protected.

Just that the FEN is Q2bRBNN/K1kqRpp1/p1Prp3/p1pp4/6P1/5PP1/2P1Pp2/7n w - - 0 1
The w means white to move.
It's only w because it has to be set to something. But I took pains to make sure there was no caption that said 'white to move'.
Yes, it has to be set to something in order to create a position. You set it to "white to move," so it is white to move. If you would have set it to "black to move," then your argument would be valid.
Besides that major malfunction, the position itself is illegal, as there is no way the White king could have found itself onto a7 in the course of legal play.
I suggest you study how to make compositions. Then, the next time you make a problem, you might actually look clever instead of bone-headed.
Hahaha, troll. You're wrong (naturally) - the position is legal. You're just not clever enough to figure it out. You're also not wise enough to shut up when talking to an expert on a subject you know nothing about.
In a few days, I will post proof that it is legal.

What about: d8 with a queen promotion?! You double check black king and he can't take,because your new queen is protected.
d8 would be mate if it weren't illegal -- you can't expose yourself to check.

The poster of the problem is using deception as a substitute for creativity. Although the position as posted is White to move, the poster is now contradicting the original posting and claiming it is Black to move, thinking he is being a very clever fellow indeed.
Oops, you are not paying attention. I neither composed this nor stipulated the side to move.

I saw this problem in a Jennifer Shadade lecture (around 31:40).
White to play and mate in 1 (White started at the bottom of the board as usual.)
What about Nf6 +
in the original puzzle, isn't d8=Q checkmate?
My answer is the same. But now I realize it is illegal. :(
Aha I found it after systematically eliminating pieces. i.e. Queen on b6 is the only defender of d8, Rook on a7 is only defender of d7, Bishop on h6 is only defender of f8, etc. etc.
I think it's black's move. Against everything black can play, white has mate in 1.
That's probably the idea, but if so it's set up wrong.
I was thinking that "set up wrong" means that the only thing that's wrong is that the pieces are on the wrong squares.
Just that the FEN is Q2bRBNN/K1kqRpp1/p1Prp3/p1pp4/6P1/5PP1/2P1Pp2/7n w - - 0 1
The w means white to move.
It's only w because it has to be set to something. But I took pains to make sure there was no caption that said 'white to move'.