did it in 1 sec first piece I looked to move was the right one
The most difficult (?) mate in one move

Took me a couple of minutes since I kept considering the "natural" moves that go towards the center/towards the King. I also fell for the f2 pin for a moment before seeing the actual solution. Very good! It reminds me a little of another mate in 1 problem that also involves an unintuitive solution.
Yitzd "5 seconds. What did you mean, this is hard? It's obvious."
Are you sure you found the real solution ? I don't believe someone below 1000 can solve it in 5 seconds... You probably saw an illegal move like Rf5 or a refuted move. 5 secs is actually the time MVL spent... but some 24+ have spend more than 1 min
Please post your approximative rating and resolution time but not the solution.
Took me about forty seconds. I think I was a bit lucky. I just started considering checks and asking myself if it was mate. The fourth one was. Rating here, 1450ish for blitz, 1550ish for standard. And I'll echo others, it's quite a nice composition.
Oh, wait...my solution was illegal due to a pin. About 3 minutes (computer verified solution) ... not counting the 20 minutes it took me to notice the first one was illegal.