I had a game that had a nice game ending move.
White does have options, so it’s not a Mate-in-X, but I couldn’t find anyway for white to salvage his position.
White is on top, Black is on the bottom.
Black moves for decisive advantage
[b]SPOILER ALERT /b TO FOLLOW!
Bill Smythe
[b]SPOILER ALERT /b:
In your earlier version of this post, which you quickly deleted, you hinted that at one point castling would be a crushing move, leading to almost unavoidable mate two moves later.
The first idea, of course, is … Nxe4 followed by … Qh4+, but can’t white then escape (only a pawn down) with Ne4-g3 … ?
Anyway, I can do you one better. In a Florida CCA tournament I directed many years ago, black’s final move was … O-O mate. In the late middle game, white’s king had walked up to f6. … Rf8+ alone would not have been mate, because then white could reply Kf6-g7.
Bill Smythe
Actually, a rather more interesting puzzle would be, how did the diagrammed position (in the top post) come about? In other words, what happened to white’s a-pawn? I think there actually is a solution (jwiewel could probably find it) but it’s highly unlikely to have come up in an actual game.
Bill Smythe
Where did the pawn at a2 go?
The missing “a” pawn is very mysterious. But seriously, sometimes I have to click a square 2 to 5 times for the diagram to put a piece in the square. I just didn’t realize the pawn was missing when I made the diagram. Jinchess.com has always been like that.
Arghh, it’s not a forced mate in 2 after all, but it’s still a crushing move, with zero chance for white to win.
I was thinking of what happened in the game and more focused on the first diagram, rather than the later position. So it’s a bit cooked, but it came from an actual game. 
Here’s the updated diagram.
Black to Move
Here’s the mythical mate-in-2 that doesn’t actually exist, but castling is optional, but feels good.
Black to Move, I thought it was a forced mate-in-2. White did choose the wrong move in the game, so it was mate-in-2 in that respect.
But still crushing.
I’ll post the game soon. I have to transfer it off my cell phone, which is a bit of a hassle.
I still don’t get it. How did the black N at f6 disappear between the first diagram and the second?
I’m guessing there was also a white B at e2. In that case the following sequence could have occurred:
- … Ng4 2. Bxg4 Qh4+ 3. Kf1 Bxg4 4. Nce2 O-O+
– in which case I agree you have a crushing position – either mate next, or you win his Q after he is forced to interpose first his B and then his N at f4.
Instead of clicking, it sometimes works better if you simply drag the piece from the piece list to the desired square.
Bill Smythe
EDIT: After I posted the above, I noticed that your original diagram did have a B on e2. But when you corrected it to add the pawn at a2, you somehow lost the B on e2.
OMG, the dang website to make chess diagrams sucks toad turds.
I just passed a national exam today, after spending months preparing for. I think my mind is a bit preoccupied with celebrating. 
Hmm. I’ve NEVER had any problem whatever with Jinchess. A single click on the piece list, followed by a single click on the desired square, always goes there right away with no problem.
I can even use it to play through a game, simply by dragging the desired piece to the desired destination square. That always works instantly too. But it doesn’t know the rules, which means:
- It will allow an illegal move.
- When castling, I must move both the king and the rook.
- When promoting, I must drag the pawn to the promotion square, then drag the promotion piece from the piece list to the pawn’s new square.
- When capturing en passant, I must drag the capturing pawn to its new square, then drag the captured pawn off the board.
I am wondering what type of computer you are using, what browser, what version of Windows, and how much other stuff you have running at the same time. I use Windows 10 on a desktop using either Internet Explorer or Edge, and it’s fine.
Bill Smythe