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Rybka 3:

<[-1.25] d=23 13.a4> Ba6 14.Ng4 Bd3 15.Nxf6+ Qxf6 16.Qb3 Qa6 17.e5 Rxe5 18.Rxe5 Bxe5 19.Nf3 Bc4 20.Qc2 Bg7 21.Be3 Bd5 22.Rd1 c6 23.Bd4 Re8

After making sure it was indeed White's move, Nxf7 seemed like the obvious choice, followed by Qb3+ winning the bishop. Then, I saw that Black could play Qd5, and, because White's king pawn is pinned by the threat of a backrank mate, Black's queen cannot be captured except by the White's queen. Therefore, White loses a knight for a pawn and his position is even worse.

13. Nef3 followed by (in no particular order) b3, e5, Bb2, Qc2 consolidates White's position. The problem is that Black has plenty of counterplay while this is going on. Black has the bishop pair and a more open position (i.e. tempo), but White has the central pawn and a half open c-file. Slight advantage to Black.

Seeing as it's a puzzle, I'll bet White plays the Nxf7 foray. If so, only two questions remain, 1) does Black find Qd5?, and if so, 2) when does White resign?

But of course I missed Qd5 - it looks so unnatural putting the Queen where a pawn can take it. Normally pattern recognition helps chessplayers, but here it has claimed numerous victims!

13.Nxf7 appears to be white's best chance. 13.Qb3? Rxe5 14.Nf3 Rh5 or Qe8 should win handily for black. Grabbing the knight does not appear to be the best option for black:

A) 13... Kxf7 14.Qb3+ Kf8 15.Qxb5 gives up the bishop pair and leaves the black king exposed.

For black, I prefer an active continuation that keeps the bishop pair:

B) 13... Qd3! (to draw the R from the undefended back rank) 14.Re3 Qd7 15.Qb3 Kf8 16.Nf3 (e5 Nd5 looks strong for black) Ba6 17.N7g5 h6 18.Nh3 Ng4 and black looks better.

I discarded 13.Nxf7 Kxf7 14.Qb3+ not because I did find 14... Qd5, but just because It was only an exchange (B+P x N), that would not put white in advantage, so I gave up the puzzle.

The one thing that really bothers me about this is, "Would I fall for this OTB?" It is very possible! The problem is tricky, but what's trickier is how to avoid this in the future.

Whenever I miss a key move in a puzzle or actual game, the first thing I try to answer is, "Why did I miss it?" Answering questions like this is important feedback in improving one's thought process. Part of the problem may be that this is a puzzle and we expect a solution, but there may be a more serious side which suggests there is a flaw in our thought process or at the very least--a hole in our logic.

The problem is directly related to the mental process of candidate move selection. Qd5 did not even pop up on the radar screen for me, so it could be that I'm not considering every interposition. For some of you, it could be that d5 did not look safe so you dismissed Qd5 before you could even examine the follow-up. Or it could be that since it's a puzzle and a solution is expected to be there, you considered it "solved"-- after all, there couldn't be anything else so Nxf7 must be the solution!

There is another possible reason for missing this. The "solution" matched a given pattern we've seen too often before and without doing a "sanity check", we assume the pattern works. Puzzles seem to condition us into thinking the pattern always works, but it takes spoilers like this to wake us up occasionally.

Whatever the reason may be, if you want to improve, you must figure out why you missed the key move and become aware of the problem so it can be corrected. Otherwise you will be stuck repeating the same mistake.

That's a nice way to improve, and I always ask myself why did I miss, too!

In this case, I came to the conclusion that Qd5 could be spotted in two ways. Just to mention, I did spot Qd5, but it passed through my sanity check, because I was rushing up a little bit, and it was late at night(good excuse :D)

The two ways are:

1 - When giving a fork with a check, can a piece block the check and defend the other piece at the same time? If you think like this, Qd5 kind of moves will always appear into your mind. And after seeing that the queen is hanging, you would ask, what happens after that?

2 - And when you ask this, You'd probably notice that there is a back-rank problem, and the pawn that would get his queen is pinned! So you will conclude that the move is not possible, and you would forget about it.

I did spot this two things, but I couldn't match them together very well. Sometimes I was looking at back rank problems after I take the bishop, and sometimes I was thinking at interpositions that could defend the bishop.

How are you supposed to spot 14...Qd5? Those of you who saw it - how and why did it occur to you?>

After discovering the cute trap, 13.NxP/f7?, KxN/f7; 14.Qb3+, Qd5!; I decided that ... A.) I could find nothing really good for White.
B.) This was a Sunday Puzzle, accidentally given today. C.) That I was losing my chess abilities, surely there was some basic tactic that I was missing.