If it's the first time you've seen it, it's not routine.

I looked at the puzzle, and immediately thought to myself "White doesn't have enough material to mate, therefore he's trying to prevent pawn promotion and a loss. Play for stalemate."

J Nogueiras vs M Gongora Reyes, 2001

<54. Ng4+! Kh1> White blockades the advance of the g-pawn, while forcing the King to h1 and away from h2.

<55. Kf1 h2> With the g-pawn blocked and immobile, White makes an in-between waiting move to force Black to make the h2 pawn advance.

You are quite correct, per the Nalimov tablebases, the best White can do after 53...g4 is a draw after 54.Nf1, 54.Nf5, 54.Nc4, and 54.Nxg4.

Then this morning I read an article at http://www.msn.com/en-us/news/world... about the coming world shortage of chocolate coming by 2020. As a chocolate lover this deeply concerned me, but was of little concern to my wife who can take or leave the stuff. Of course this has always perplexed me, since all of our children and grandchildren love the stuff.

Apparently a fungal disease known as "frosty pod" has greatly reduced supply in West Africa (particularly in Ghana and The Ivory Coast) where 70% of the World's supply of cocoa is produced.

On the demand side is a great increase in the number of people world-wide willing to pay for more of the stuff. Perhaps that's because the world's rising numbers of middle class (now put at 5 Billion) can afford more moderately priced luxury goods like chocolate. Also the increasing popularity of dark chocolate, which contains up to 70% cocoa as compared to milk chocolate with 10% cocoa contributes to the shortage.

On move 77, Carlson had the opportunity to enter a N vs. 2P ending.

He declined.

A very different position. There never was a N vs. 2P ending in Carlsen vs Anand, 2014,. There were rooks on the board so it was properly a R+N vs. R+2P ending, not a N vs. 2P ending. Magnus would have had good chances in a N vs. 2P ending but he couldn't force the exchange of rooks.>

It depends on whether either one of them could have traded down to the ending they wanted.

If Carlsen could have traded down to this ending with White to move he would have won.

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If Anand could have traded down to this ending with Black to move he would have won.

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So let's rewind to see what got us to this pickle. Here's the position after 50. Ne4

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This looks drawn ... and indeed it should be with best play. Black can't get his king off the h file to crown his pawn and white shouldn't have enough material to mate.

But faint heart never won fair maiden and no-one has won a game by accepting a draw offer. Probably.

So black plays the sneaky 50...g5

And now if white plays 51. Nxg5 h2!

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Black willingly stalemates himself. If white moves his king out of the way to anywhere other than f3 we would get 51 K moves Kg1 52. Nf3+ followed by Nxh2 and we only have kings on the board. Even 51. Kf3 is a draw - 51... Kg1 52. Nh3+ and 53. Nf2

Rewind. White can't take the g5 pawn if he wants to win. He probably ought to offer a paw at this point and suggest that they repair to the pub. But white decides to roll the dice with a mini knight tour:

51. Ng3+ Kh2 52. Nf1+ Kh1 53. Ne3

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We've got a similar position to a few moves ago, only this time the white knight and g pawn are one move further down the board. And again black draws by sacrificing his g pawn - 53...g4! 54. Nxg4 h2

But now something odd happens. Black knows how to draw this game by sacrificing the g pawn. He's played that trick already. But for some reason he doesn't play it now. Instead he opts for 53...Kh2? and walks into a rare single knight mate.

Trust we didn't get too far off topic in turning a Tuesday chess puzzle into a discussion of agriculture commodity economics.

The move that turned the draw into a loss was 46...h3??

Black probably still thought he was winning or at least had a chance of winning, and forgot there was even a possibility of losing against a solo knight.