Chess programs are glorified calculators as the game is broken down mathematically, so it's nothing more than numbers to the computer.

I have nothing against <Random Visitor> either, his posts appear sincere, but I feel he, along with many others out there have become, in a way but not entirely by definition, addicted to the chess engine.

Of course it does. But it does not give white a forced mate in 10, as is the case in the capture.

<Sneaky: Now when it comes to 18.Nf6+ Kf8 and 18.Nf6+ Kh8, I don't see any point in looking at these lines any further. When I saw the puzzle I summarized these variations very quickly, thinking this: "If Black has nothing better to do then move his king and surrender the exchange, then the combination is valid." >

Do you also dislike knitting frames ?-)

Are you familiar with the 4-color theorem in graph theory, one of the most famous/celebrated/difficult problems in math? Guess what - the proof involved HEAVY computer use.

Having been involved in software for about 30 years now, I find good software to be as appealing to my aesthetic sensibilities as best art.

BTW, I always try to interpret the computer-generated lines in terms of "what would I need to notice to come up with this idea using just the brain". See the analysis of 34. Be3 move in another puzzle, referenced below.

But the move given by many already -- 19...Bb8 20. Rg3+! is superior. It leads to a forced mate.

The royal fork 18. Ne7+ leads nowhere. The rook takes with knight with no repercussions.

Oh, I'm certain that technology is helpful in so many ways, and the 4-color theorem in graph theory needing a computer to confirm it's analysis is most likely intriguing. I am always impressed with people who can even conceive of such things, but do we start with the 4-color theorem when teaching math? I don't think so.

Learning/teaching/getting an answer are different things. Since you and I are into writing programs I'm certain you've come across many a beginner in your time. Have you ever tried to explain a simple array to that person? Sure, you can just show them how it's done, but explaining how it works is far more effective.

I know, this is chess and seeing the move may feel like an end to a means. Please note the last paragraph of my previous post. I also have a training background, and I don't believe that knowing the move itself truly helps someone grow.

It's possible you haven't reached a level of chess training that allows you to understand the broader concepts involved that the computer is incapable of showing you, thus you may not fully appreciate what I am saying. This too can take us back to the cake and nutrients in my previous post. How many times has a parent told a 6 year old he must eat his broccoli, when all he wants his cake?!

The 6 year old only knows it fills him up, but he doesn't understand that it will not help him grow.

20. Rg3+! Bxg3 21. hxg3 Bh3! 22. Qg6+ Kh8 23. Bxf7 Qf5 24. Qh6+ Qh7 25. Qxf6+ Qg7 26. Rxh3#

I then analyzed Black refusing the ♘, didn't see a mate, but the won exchange together with Black's cramped position should be enough to secure the win.

Example lines:

18. ..Kf8 19. Nxe8 Qxe8 20. Bxe6 Qxe6 21. Qc7 - looks anything but pleasant for Black.

18. ..Kf8 19. Nxe8 Bxc4 20. Nd6 Qc7 21. Rf3 Be6 22. Rd1 also not good for Black.

PS: I immediately saw 20. Rg3+ after 19. ..Bb8 (or ..Bxf2 which I missed) because I had already analyzed 19. ..Bg4 20. h3! with the h file clearance threat. So it was obvious that White can just sac the rook on g3 and proceed to mate. The really interesting question is why Black even accepted the ♘ sac. If he did see up to 20. Rg3+, it makes no sense at all. If he didn't, I would at least have expected him to play on until this move. Probably he missed it at first and then it occurred to him as he was playing 18. ..gxf6 or shortly thereafter.

PPS: Black got his due for allowing White 4(!) pieces in the center ready to attack the almost undefended kingside. And the mating theme with doubled f, pawns, hostile queen on h6 and hostile rook ready to attack on the g file is so common, it should ring all alarm bells. This is probably because the position is straightforward to achieve, and because it's so powerful. With the king on g8 and the enemy queen on h6, the king has no flight squares. Vacating f7 often takes too much time because f6 must be cleared first. And finally the doubled f pawns also make it impossible for Black to assist the king along the 6th and 7th rank. So Black is forced to find a defense on the diagonals - in this case, a rook sacrifice nicely refutes that possibility, too, depriving black of all hope.

[A1] 19.Qxh6 f6>

19. ..f6 is not a legal move in this line.

<dhotts: 19...Bb8 protecting against Rh3+. The right response is 19.Qxh6 Bb8 20. Bxe6!!>

Black has the clearance sacrifice 20. ..Bf4+! 21. Qxf4 Rxe6 and it seems the king can escape, although I think White is still going to win some material and the endgame.

Of course. I don't get angry on internet any more :-)

I'll reply later in the evening to your post. The debate should be probably moved to Kibitzer's Café.

click for larger view

Analysis by Rybka 2.3.2a mp up:

(24-ply)
1. (2.89): 18...Kh8 19.Nxe8 Bxc4 20.Nd6 Bb8 21.e5 Bxd6 22.Qxc4 Bxe5 23.Qxf7 Qf8 24.Rf3 Bf6 25.Qxb7

2. (2.96): 18...Kf8 19.Nxe8 Bxc4 20.Nd6 Qc7 21.Rf3 Be6 22.e5 Qe7 23.Nf5 Bxf5 24.Qxf5 Qg5+ 25.Qxg5

D'oh! It's a deflection sac of course, not a clearance (what was I thinking when I wrote that?).

<MostlyAverageJoe: I disagree. What would be a better indication that Rg3 is the center of the entire combination?>

Hmmm, you do have a point here. But it's not very enlightening on what one might have played if not for Rg3+ at some time.

<fzoozle: How does white mate after 19. ...Bb8 20. Bxe6 fxe6 21. Rh3 Kf7 ?>

Hmmm, maybe 22. Qh7+ Kf8 23. Qg6 Ke7 24. Rd1 Qd7 (..Bd6 25. Qg7+ Kd8 26. Rxd6+ Qd7 27. Qxd7#) 25. Rh7+ Kd8 26. Rdxd7+ Kc8 27. Qxe8#

Of course it does. But it does not give white a forced mate in 10, as is the case in the capture.>

Well, the puzzle's caption doesn't read 'White to move and force a mate in ten,' but simply 'White to move.' I think the puzzle was great - they nearly always are - and as described in the Daily Puzzle F.A.Q. the first move is not necessarily the solution to the puzzle.