Christmas Puzzle Contest 2005 – solutions February 13, 2005
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Our puzzle contest ended on January 23. There were five problems to solve, with the winners being drawn from readers who solved – or plausibly attempt to tackle – at least two problems. We decided to award an additional prize for the best solution that caught our eye.

We apologize for the delay in publishing the solutions. The reason is simple: it is a daunting task to scan almost two thousand messages! We actually did this, in order to extract feedback, which we give you at the bottom of the page. But before we proceed to that, here are the solutions.

Puzzle 1 – Dec. 27

Richard Muller, Rochade 1985

Proof game 4: Position after White’s 7th move

In this example it is important to remember that the position must arise after White's seventh move (there are a number of solutions after Black's seventh). Cayley Robinson of Gainesville, Florida, reasoned as follows: "Your analysis showed that White cannot capture the two missing black units with his f1-bishop, which I quickly confirmed. The placement of the missing units was quite suspicious – diagonally connected to each other and one of them being on b7, they were easy prey for the missing a2-pawn. After promoting on a8, this pawn would be able to "replace" a victim of the c8-bishop (which is obviously the piece that captured White's missing men). It takes five moves for the pawn to reach a8 and two to reach d1 from there – perfect, so the pawn will probably promote to a queen (which will be the piece that is captured by Black)." Kari Heber of Silverdale, WA wrote: "I initially tried to kill the two absent pawns with the bishop and/or the queen. That caused no end to my frustration. After about an hour, I realized that promotion to queen to replace the captured queen was the key. As soon as that idea entered my mind the solution came quickly."

Solution: 1.a4! d6 2.a5 Bg4 3.a6 Bxe2 4.axb7 Bxd1! 5.bxa8Q Bg4 6.Qf3 Bc8 7.Qd1. There are two alternative tries which fail: 4...Bg4 5.bxa8Q Bh3 6.Qb7 Bg4 7.Qc8 Bxc8; and 4...Bf3 5.bxa8Q Bxa8 6.Qe2 Bb7 7.Qd1 Bc8. In each case the position arises after Black's 7th move, i.e. one ply too late. [Click to replay]

Puzzle 2 – Dec. 30

The French Revolution grandfather's dream puzzle was solved by a large number of readers. Many expressed disbelief at anyone not being able to see the solution intantaneously; but when they tried it on friends they discovered that indeed there are many who cannot see the logical error in the narrative.

We also received a number of wrong solutions, which were often quite convoluted. For instance the following: "If someone is sleeping, their heart beats at a slow rate. A pinch will not instantly influence the action of a beating heart, not do people with heart attacks die instantly. So I'm skeptical that the shock of the pinch could result in an instant heart attack death. If this is not close to the solution of the problem, I can not possibly see what it might be."

No, not even close. Remember that the we know for certain that the story is not true, as told to us by the friend. This is because it contains a glaring logical error. Once you hit upon that you know the correct solution of our puzzle – and you know for certain that you have found the solution.

So what is the solution already? Unfortunately (for a few) we cannot bring it over ourselves to reveal it. As we mentioned before, an easy way to solve the problem is to give it to ten friends or acquaintances. About five of them will give you the correct solution.

If for some reason that does not work, you may want to read the feedback section below quite carefully. Maybe the solution has inadvertently slipped in somewhere. But then again, knowing us, it may not have done so. If you become really desperate you can write to us, using the feedback button on the top left. Change the subject to "Dream puzzle", and also assure us that your friends were unable to help. We warn you, there will be negotiations and some groveling required before we email you the solution.

Puzzle 3 – Dec. 30

Hans Gruber, Schach-Echo 1983-4

Proof game 7: Position after Black’s 8th move

"More difficult than puzzle 1," wrote Johan Ostergaard of Copenhagen, Denmark. "But I quickly realised that one of the points had to be that white had not really castled though he appeared to. It was also clear that the black queen had to do the elimination of white's pieces, since the knights would not have time. So since the king had to maneuvre away from the slaughter on g1 and f1 and didn't have time to go via d2, the only possible option left was to let him go to h2."

Licai Yeo of Singapore sent us solutions to each problem in rhyme. Of this problem he wrote:

White has castled, at first glance,
but no, his bishop is imprisoned.
so Black must have captured it,
though how, is beyond my wit.
What unfathomable dance,
that will befuddle any reason?
Lets try some moves with Black's queen,
Ah! With some trial and error seen,
for the opposing royal pair,
to traipse around the White lair.

Solution: 1.f3 c6 2.Kf2 Qb6+ 3.Kg3 Qxg1 4.h3 Qxf1 5.Kh2 Qe1 6.Rf1 Qxd2 7.Kg1 Qa5 8.Nd2 Qd8. Amazing that it is this exact sequence of moves that works. [Click to replay]

Puzzle 4 – Dec. 31

Joachim Iglesias, after Pascal Wassong, France-Echecs, 2004

Proof game 8: Position after Black’s tenth move

Michalis Kaloumenos of Kallithea, Greece called this "the brave soldier who wanted to become a Bishop (and finally made it)." According to him this was the most difficult puzzle. "I needed five moves to reach gxh1, but the promoted piece on its way home and the original piece sacrificed on h3 was a real trouble. I spent a lot of time on the queen, the only piece that can return home after f3 is played, but I counted 12 black moves, which was disappointing. Then I tested the bishop: d5 and Bh3 are two moves, but after gxh1, all White squares are covered with pawns which should not be taken. So, f3 should be played after the promoted bishop starts the journey back home: with Be4-f5-c8, I could count ten black moves. The white ones were a more difficult problem. With f3 delayed, White has not many moves available. Before I understood the mechanism and the necessity of the Rh1 maneuver, I tried to play with the Ng1, but usually ended with a black bishop on h1 and a white knight either on g1 or h4 which had to move again, to f3 for example, closing the way back home for Bh1. It took me more than two hours and many tests to find the exact and only correct sequence". Licai Yeo put it more poetically:

White has taken on h3,
Black has a full back rank.
Promotion must be the key!
Only bishop can walk the plank,
for naught else can return in time.
White plays gxh3,f3,Kf2,
the other seven how does he lose?
No knight can go home in seven moves,
nor bishops, queen, and king.
The queen rook! That must be the thing!
A forced sequence, a peculiar dance,
a rook's retreat before a pawn's advance!

Solution: 1.Nf3 d5 2.Rg1 Bh3 3.gxh3 g5 4.Rg3 g4 5.Rg2 g3 6.Rg1 g2 7.Rh1 gxh1B 8.Ng1 Be4 9.f3 Bf5 10.Kf2 Bc8. This is the most complex position we included in our Christmas puzzles. Replacing the bishop on c8 requires a switchback by White’s king’s knight and an extraordinary manoeuvre by the king’s rook in order to lose a tempo. [Click to replay]

Puzzle 5 – Dec. 31

W. Pauly, 1913

White to play and mate in two (white pawn missing)

In the above position there is a white pawn missing. You were required to replace it and mate in two moves. We mentioned the fact that there are four different solutions, each with its own little point. 12-year-old Cayley Robinson of Gainesville, Florida immediately smelled the rat: "First of all, there are four solutions. Second of all, a pawn is being added to the board. So, could it be that the solutions involve four different promotions – specifically, one to a rook, one to a bishop, one to a knight, and one to a queen?" Leonidas E. de la Rosa of Cali, Colombia, admitted: "I took some time with the board in front of me, but after finding one or two then the whole logic kicks in. Beautiful problem. If you hadn't said four, I probably would've found one solution, felt good about myself and left it at that." Jarle, Kvåle of Askøy, Norway, wrote: "This was cute, but not among the hardest I've seen. 'Allumwandlung' is always a funny thing in puzzles." Licai Yeo:

Oh curious puzzle, that I must place
a pawn, and mate in two.
but yet I got a little clue,
that there are four different ways.
Could it be? Four promotions,
each to a different piece.
Why yes, it is!
Queen, Rook, Bishop, Knight,
each sealing Black's plight.

• Click here for a printer-friendly version of the contest problems

The winners of our Christmas Puzzle Contest will be contacted by email individually, and will receive personalised prizes after the Linares tournament. After that their names will be published.

Frederic Friedel

Feedback

The following are a few (!) excerpts of the flood of messages we received. They were scanned semi-automatically and the selection of the ones we are quoting was conducted on very vague criteria. Please do not be offended if your comments were not included, even if they were clearly superior to some of those included in the following collection.

David Manning, Los Angeles, CA USA
I want to take a moment to congratulate you on your Christmas puzzles for 2004. The proof games provided me with hours of bewilderment, entertainment, and joy (when the answers finally came to me!). It was far and away your best selection of Christmas puzzles yet (I've been doing them since 2000). Please don't be shy about throwing us an occasional proof game or two to solve in the future!

Markus Bindig, Reinsdorf, Germany
When I saw the proof games the first time, I didn't really like them... mainly because I couldn't solve them. However, you soon get used to it and start to spot the relevant manoeuvres, even in very complicated positions. I was astonished to discover how a position can tell you so much about the way the game went before. I also think it's nice that you should include a puzzle that has nothing to do with chess at all every year.

Martin Baumung, Stutensee, Germany
I'd like to thank you a lot for the very refreshing problems of this year's Christmas puzzle contest. I've never been into shortest proof games before, but I became a real fan :-)

Charlie Linford, Brighton, England
At last! Having been denied access to the Chessbase site yesterday due to the vast numbers already logged in, and having checked the main page at least twenty times today, I can finally send in my answers, having lapped up the problems from the preceeding week. Having (for once!) successfully answered all the problems, I was beginning to test myself on the final puzzles from years past (I solved the courier problem, the game ending in 6.gxf8=N#, but had to trawl Slashdot archives for the answer to the NxR# -at least I was in good company), but I'm relieved to see that I needn't have worried.

Philip Griffin, Jamesville, USA
The proof puzzles were fun. Personally I found them much easier than regular chess puzzles. I’m grateful to John Nunn for introducing this kind of problem. Incidentally I played in the British under 14 Championship the year that John Nunn won. I also played the following year when it was won by Tony Miles and the year after that when it was won by Jon Speelman. Looking back I don’t feel too upset that I was never able to get my hands on the trophy!

Anthony Stebbings, London, England
I have an anecdote to tell about John Nunn. In May 1964 nine years old John played at the Ilford chess congress in the Junior "G" section. He lost his first game to a twelve years old school friend of mine, Stephen Pierce. After the game John Nunn's father asked Stephen if his son was too weak to be playing in the tournament and received the modest reply that John could still come second. That is exactly what happened, as both won all their remaining games and John won second prize.

David Dawnay, Barcelona, Spain
Well I'm glad to say that I'm in the 50% that got the grandfather's dream puzzle almost immediately for a change! This problem reminds me of several typical sleight of hand card tricks that deceive by misdirecting the solver's attention away from the crux of the issue. If it's any consolation to anyone, it's often those people with the most methodical and rational brains that are most easily deceived by this type of thing!

Marc Boulé, Montréal, Canada
The Chessbase Christmas puzzles are quickly becoming one of the holiday traditions I look the most forward to. Being more of a programmer than a chess player, I solved the proof games with my home-made chess-puzzle-solving program (kind of like I did for the 1999 and 2000 xmas puzzles). Only this time, the evaluation function was modified to look for a match with the final position in the puzzle statement. Chess instincts were still required in order to program move-constraints and to pin-down pieces which I thought would not participate in the solution. This was useful to bring down the branching factor and allow 20-ply solutions (proof game 8) to be computed in reasonable time. Once I programmed aggressive constraints customized for each puzzle, the computer found the correct line in a matter of seconds. A nice mix of chess instincts and technology at work. Unfortunately, my program was of no use for the guillotine puzzle! (Wow, that solution really hits you like a ton of bricks.) Thanks go to yourself and Mr. Nunn for making the holiday season even more enjoyable.

Lloyd Gallant, Barrie, Ontario
This year's puzzles are a major disappointment. I don't believe that "proof games" are an exercise in the art of chess in any form but merely a useless mental engagement with no redeeming qualities that happens to take place on a chessboard. Knights, bishops and countless pawns are beginning to turn up at shelters all over the world with heartbreaking stories of pointless abuse at the hands of their owners. Studies and problems expose the solver to unique and often beautiful themes aimed at winning or drawing a chess game and these ideas are often new to many players. The result is a better understanding and appreciation for the game of chess and a higher level of play. Don't you think that's a better use of time and space?

Richard Ashwell, Aurora, IL US
Wow, #8 was ingenious! I was almost ready to write out this long drawn out proof about how it was impossible when I uncovered the latest finesse. Purely awsome. A couple of points I would like to make. First it appears to me interesting that these problems which are right at the opening position have a lot of endgame value as far as understanding tempi and delay moves etc. I mean I never even thought until this very problem that a knight can't leave and return to it's square in an odd number of moves. My second point is composing these problems must get VERY difficult as they get longer in terms of moves, (i.e. verifying that there is only a single unique solution, and that it is the shortest solution). Bravo to Nunn and thanks to Frederic and ChessBase for offering them up for us.

Paul Cornelison, Boulder, Colorado, USA
I am just one of the many thousands of amateur chess players who visit your site. I achieved a FIDE rating and once thought I might become a good player.... but now I'm old, and for me chess has become just a hobby. I can't begin to describe the joy your company brings to me almost every day. If this was even ten years ago (and I remember that far back) I would never have had the daily opportunity to bang out a few games against good players and to keep up with all of the current gossip. I can sometimes even follow the moves of the new chess prodigies in real time. The point of life is different for many people... and even for the same person, what brings happiness is different at different times of their life. Chess is an unlimited spring of happiness for me. The internet has brought many possibilities for all of us to enjoy our passions, but for those possibilities to become reality the work of real people dedicated to providing information and value is required. I really want to express my gratitude to all of you at ChessBase for your work. You all should be very proud of the service that you provide and the happiness that you bring to the many thousands of us chess players every day.

Derek Grimmell, Clinton, Iowa, USA
I thought these proof games were enormous fun! The most enjoyable to me was the third above, with the eight-move solution where the crux is recognizing the unusual "castling by hand." And thank you for printing the answer to the only one that stumped me. I was convinced it was an odds game in which Black gave Knight and move, because I couldn't solve it any other way. Now I see why, and am kicking myself. Pass on to Dr. Nunn the possibility of publishing a book of such puzzles – - or of puzzles in general; he has a knack for them.

Michael Halperin, Nahariya, Israel
Amazing, absolutely amazing – that's all I could say for a few minutes just after I finally figured out the solution for the proof game #8. There is probably no better feeling than successfully accomplishing some enormously difficult task and that's exactly how I felt after an hour of eventful nonstop thinking with only 2 hours left of the 2004 year. It started so different, though... After a few minutes of thinking I came up to the conclusion that there must be a mistake – it was clear that white must take on h3 with its 'g' pawn at some stage, and I wished white rook could get to h3 to be taken by black's g4 pawn, but there was physically no way for the poor rook to get through the barricades created by white's own kingside pawns. I enjoyed solving previous proof games puzzles, and none of them required more than 10 minutes – but here I was dealing with completely different level of problem. Slowly, it became more and more evident that white's h1 rook must find its "death" in some other way. The idea of making a run by black's 'g' pawn up to g2 came into my mind no earlier than I realized that something (most likely queen) should be sacrificed on h3 to make the path clear. "Nice", I thought to myself – "now just like in the game #7 all that is left is to find the shortest path by black queen from h1 back home to d8". But then I couldn't find anything better than h1-g2-g3-d6-d8 manoeuver , which was way too slow. Here I got stopped for some 20 minutes. No, it doesn't work, however promoting g pawn into the bishop on h1 (after sacrificing bishop on h3, instead of the queen) looked no better either as black bishop couldn't find it's way to c8 fast enough with white pawns on f3 and h3. But wait, white can move f3 just after Bishop moves to e4 and then we have Bf5 followed by Kf2 and Bc8! Yes , I did it- this is definitely a solution ! So the only thing left was to find the first 8 moves by white,as all 10 moves by black were resolved by now. But then I noticed that simply moving the knight g1 back and forth to f3 doesn't help. It could have been done in numerous ways (which by itself meant that it couldn't be a solution) but even more so in the end I needed the knight to be on g1 just before black taking the rook on h1 and I couldn't get it there. Wow, so close but still not there... So what can be done with that spare tempo ? Switching the knights g1 and b1 doesn't work, too slow. Making some tricks with the bishop, like Bf1-g2-e4-f3-g2-f1 provided no result either. I was getting a bit annoyed – I thought I've already found the solution a long ago with a very nice play for black pieces and now I've got stacked again. Ahh, maybe moving the h1 rook before it actually disappears from the board will be good enough ? No, Rh1-g1-f1-h1 does not help me to lose the tempo as I would have liked – not enough time to do this before the black pawn arrives. However, the next second I got it. Yes, incredible Rh1-g1-g3-g2-g1-h1 manoeuver by the rook makes all the difference. Fantastic ! Brilliant ! Delightful !

I admit this was one of the better puzzles I've ever came to solve, not neccessarily chess-related. And then, there were almost no limits to my delight for quite some time in the end,I could only hope to experience more moments like this in 2005. Thank you very much !

Mark Zand, Boston, USA
First, thanks for the puzzles, they were fun to solve. Second, your contest conditions are unfair: almost anyone can solve 2 out of 5. I think fair conditions mean requiring 5 out of 5 correct solutions, otherwise it's not a contest, just a random drawing. Third, in puzzle 5 you should have stated that white pawn may replace any black pawn, it was not clear at all (to me), so I had to eliminate all other possibilities to arrive at this strange "rule". In addition, puzzle 5 (position 4) has a duplicate solution, which is not acceptable.

J. Franklin Campbell, Mason, Michigan (USA)
I'm disappointed that your contest is so undemanding and is based largely on the luck of the draw. However, I can still hope to win. BTW, these "Proof games" are sensational puzzles! Many kudos to you and John Nunn for bringing them to us as a special Xmas present. I couldn't rest till I have them all solved, and they were simply delightful challenges.

It is a prize for participation, not for solving skill. After receiving a number of such letters we added one special prize for excellence of the solution presented.

David Or, London UK
I've only recently arrived in the UK for university from Hong Kong and because of this most of my friends are away in some distant land celebrating X'mas while I was stuck in a deserted uni hall. These puzzles (and instant noodles) helped me make it through this long holiday. Thanks loads, you guys never fail to keep the unruly mob entertained.

Kerem Yunus Camsari, Ankara, Turkey
I solved the dream problem instantaneously, in fact I had already thought "Total nonsense!" when I read the next sentence stating the story could not be true. In fact I thought more than 50% of the people would just solve this problem instantaneously but I got very surprised to find out that it's not the case! I've asked this to many friends and I really think it was not easy for them as it was to me, and it's really interesting because the problem is so very simple.

Kari Heber, Silverdale, WA, USA
The dream puzzle was easy; sort of like "whose buried in Grant's tomb?" or "How many of each animal did Moses take with him into the ark?"

Thomas Zaugg, Ypsilanti Michigan, U.S.A.
Thank you for a fine set of puzzles and an enjoyable holiday. I found all the solutions. I guess I have a mind made for solving proof games. For each proof game, I found that as I was able to eliminate possible approaches, the approach remaining, no matter how obscure, had to be correct. Isn't that how Sherlock Holmes solved mysteries? It was also helpful to tally up the moves that are unavoidable (such as moving pawns to their final locations) to see how many moves were left to accomplish the necessary tasks.

Reegan Milne, Rockhampton Australia
I would like to thank the chessbase for selecting a group of puzzles that are difficult but solveable and give a double "thanks you" to who ever decided to put those two help mates as part of the contest. A thank you also to the person who displayed Steven Monarrez suggestion of sleeping on it, two naps later and i solved "H. Mattison, Atputa 1930" "Lasker,Em – Loman, 1913" if only i could sleep between moves in OTB matchs, i would be a GM for sure

Dion Cassio, Lillington, USA
Hello, happy holidays, and a hearty thanks for the puzzles. Proof games are indeed are fun field of problems, and as you said, it is quite astonishing how the solutions can remain unique given the number of moves involved. I couldn't imagine the task it is to compose one.

Carlos Pérez Quintana, Segovia, Spain
It already is like a tradition... I like to begin the year with a music concert and the concert of talent of ChessBase. I happily congratulate to Frederic Friedel by his good humor and his annual installment. I confess that we have worked much and we have amused ourselves. Happy New Year 2005.

Bernhard Skritek, Vienna, Austria
I love proof games... A friend of mine called me so that I would help him. At the time he called me I was in the train going to the mountains, hiking. I tried to solve the puzzle in the train with my chessboard (always with me), but I wasn't able to find the correct solution. When I got out of the train, and started to move, I had the solutions without board in a couple of minutes. It reminded me of the report I read on chessbase, of the grandmaster (or even world champion) who always goes for a stroll in the park, when he has to solve a puzzle and is stuck. Exercise really helps your brain! Thanks a lot for all the great stories, reports and puzzles.Ein schoenes neues Jahr – in the language that "Zeitnot" and "Zugzwang originate from...

Alex Nikouline, Winnipeg, Canada
I do not belong to those 50% of population who solves the Puzzle 2 instantly. So I was pleased to read that somebody with rating well above 2700 could not solve it. Thanks!

Henrik Karlzén, Mölndal, Sweden
Thank you and thank you John Nunn for providing chess aficionados all over the world with interesting and beautiful chess puzzles from Yule-tide to the New Year. I also liked the fact that it was hard to use a computer to solve the puzzles, although I'm sure a skilled programmer would not have too great difficulties having a machine answer even the intriguing proof games.

Arjon Severijnen, Lepelstraat, the Netherlands
I would like to start with wishing everybody from the Chessbase team a very healthy and good 2005! It's always a pleasure to visit the website and use the chessbase programs. Also the playing-site Playchess is great and I'm spending a lot of hours there, having fun. This year it's the first time I had a look at the Christmas Puzzles. It's very nice to read the little stories and after that trying to solve the puzzles. So before I give my answers, I'd like to thank Frederic Friedel in special for this work done by him.

Dang Bich Ngoc, Hanoi, Vietnam
Honestly speaking, I was really surprised and excited when I first saw the puzzles. This reminded me of one puzzle that I had seen in Chessbase before. I think it is also a kind of proof games, that is White begins with e4 and the last position is knight takes rook mate in the fifth move. I spent hours trying to solve that game but couldn't, and sometimes I thought that it was really unreal and unsolvable. These Christmas puzzles 2004 also give me such feelings in the first place. However, fortunately, after some mintues analyzing, I solved one! This brings confidence to me and I solved more puzzles! But there's still one thing that make me not totally satisfied, that is I could not solve the first position (I think it is the simplest one because of the sequence). I really can't understand myself! Sorry for talking so much digressions.

Steven Bass, Plano, TX, USA
Thank you for the great puzzles this year! First off, I need to stress that I loved all of the proof games. Only one of them gave me fits – the very first one! I tried for an entire day and failed. I finally gave up, and moved on to number 2. I solved that one in about 10 minutes, and then proceeded to solve the second day proof in about 2 minutes. I was hoping my success with the 1b and 2 proofs would put me in the right frame of mind for the 1a. NOPE! Still took another hour or two, and getting the solution was more blind luck than anything. I was able to solve all of the other proof mates (including the contest ones) in less than 3 minutes each. Here are my answers to the contest puzzles, with one unrelated (to the contest) complaint at the end.

Shashikant Sahasrabudhe, Mumbai, India
I am thankful to ChessBase for all the problems set for solving from 25th December 2004 onwards. I liked most the Proof Games and request you to soon publish on your home page all the known Proof Games. I also liked the two-mover which required the solvers to add a White Pawn and, in effect, on 4 different squares so as to effect in each, the appropriate promotion and the consequent mate.

Equitable Brown, Kingston, Jamaica
These puzzles are fantastic. I find the Proof Games to be absolutely amazing and definitely the most thrilling to solve. Those are my favourite; I now feel I can do any such puzzle in the world!! My congratlations to the "GM GM" John Nunn; his puzzles demonstrate remarkable ingenuity, especially in the fact that each of them has only one solution. Thank you very much to Chessbase for your Christmas treat of puzzles. They were truly delightful (although of course a few of them took me a few hours to solve!!) Happy New Year!! (and of course, I hope I win.)

Brian Zhang, Stanford, CA, US
I am convinced that puzzle 4 of the ChessBase Christmas Puzzle Contest 2004 is impossible. In order for the g-pawn to get to h3, it must have taken the black g-pawn, which must have taken the white rook to get there. However, the white rook would have no way to get to h3 because it is being blocked by a row of pawns. Help me! [Solved two days later]

Jürgen Glatz, Ingolstadt, Germany
Thanks for this beautiful, refreshing and entertaining puzzles that distracted me from work and kept me twisting my mind at home, too. In case you're interested, I'm a 20 year old club player with a DWZ (some kind of German ELO) of 1450. Recently I've improved a lot and play much stronger, and most of the credit for that goes to Chessbase.

Pável Piña Milián, Camagüey, Cuba
Como han podido apreciar he sido breve en mis explicaciones para no cansarlos, además son tantos los factores que se deben tener en cuenta para resolver estos ejercicios que no se puede explicar todo de forma escrita. Es necesario utilizar mucho la lógica para salir airoso. Les puedo confesar que los pude resolver descartando posibilidades y quedando con la única posible. No sé si es el método más racional, pero para mí resultó ser muy efectivo. Un saludo desde Cuba para todos y muchas gracias.

Mansoor Peerbhoy, Pune, India
Puzzle 4 (Dec 31) has to be one of the most amazing chess problems I've ever seen! At first glance, it seems impossible, because the white rook is missing, which means a black piece must have captured it. Then again, the only black piece missing is the g-pawn, so that must have been captured at h3. But what did the black pawn capture on h3? (the only white piece missing is the rook!). And then, how did the white rook get out before the white g-pawn moved? Such were my initial thoughts. But then, I was struck with an insane possibility. Supposing the black g-pawn had not been captured at all? It could have promoted to something, and then gone right back to where the missing black piece was originally. Well, after I worked on that line, it became apparent that the black piece was the Queen Bishop, since nothing else could first sac itself on h3, and then get back so soon after promoting. So when all the excitement died down (I was not too worried about white's sequence of moves, since that didn't seem too important !). So surprise, surprise, when I realize that white's moves couldn't have been inconsequential Knight moves out-and-in! This was because, white made 10 moves (an even number of moves), and if you discount the 3 "obvious" moves that white has made (gxh3, f3, and Kf2), that leaves you with 7 knight moves to make, while coming back to the initial square, which as we know is impossible, since 7 is an odd number. Well, the only thing then seemed to be that the king must have done some sort of triangulation to get to f2 in an even number of moves. But then even that was impossible, since f3 had to be played "after" the promoted bishop got out of the white camp. (Otherwise the promoted bishop cannot escape). And then there are too few moves left for the King to dance around. So, after all that, that only left the White Rook, and then after working out the solution (a pretty dance), I got the full meaning about your clue "If you can reach the same position in a different sequence, then your answer is wrong".

Jason Rihel, New York, USA
I loved the proof puzzles at first, but once I solved one or two and realized there is always a visual "trick" (for example, the castled position is via the long path "by hand", the pawn captures and underpromotes, only to return to that piece's originial square, the symmetrical pawn structure could not happen by symmetrical moves of the pawns, etc.), coupled with the rule that there is only a single unique move order, they became fairly easy. I agonized over the first few for nearly an hour each, but by the 3rd or 4th proof puzzle, I was solving them in just a few minutes, even on the first attempts.

Faisal Mattoo, India
In my opinion creating proof problems is more difficult than solving them so I think we should appreciate John Nunn for providing these beautiful problems.

Michalis Kaloumenos, Athens, Greece
Happy New year Frederic and all of you guys working for ChessBase. You make my happy, you help my effort to understand chess a little deeper, and make me hope, that I'll be able to teach chess to my three little children.

George, Chen, Vienna, USA
Congratulations on another installment of Christmas Puzzle well done! The very first proof puzzle (which is not part of the contest) was actually the one I stuck quite a bit on. I pondered on it on and off for a few days and finally decided to make a formal prove that it can't be done – and of course that's when I found the elegant solution! In fact very early on I had thought about putting the White Bishop in another black piece's starting position for it to be taken, but somehow I missed the almighty King. That was a good hunt. I am proud to report that after this puzzle, none of the other proof puzzles stood a chance against my sharpened wits – each of them was solved within three minutes. :-) Again, thanks for these joyful puzzles.

Faisal, India
Since submitting my entry to your Christmas puzzle contest, I found some time to check on your previous contests, most notably the previous year's. I can honestly say that I am terribly disappointed.in the way you conduct and award prizes in these contests. I thought you would give some credit to how many correct answers had been given while choosing prize winners. But looks like everyone is in the same boat as regards the prize winning is considered, whether he has correctly replied to 2 or all 5 problems. I don't think this is advisable considering proof problems cannot be solved with computers and this should be done to encourage people to solve the problems themselves. Somebody would spend about half an hour with the last problem putting pawns all over the board in his chess playing program and come up with the solution. Secondly the grandfather problem has got nothing to do with chess and besides is simple so anyone can solve it ( I took less than 2 minutes) within the time frame. And there you have it a man having rudimentry knowledge of chess can win your contest and get the programs. This man, what does he do with them, the novelty of winning a program will last for maybe 1 week maybe two weeks, after that the dvd will gather dust on this guys cupboard. You are doing a great disservice to the real chess enthusiast with this approach. Every one who is interested in chess cannot afford to buy everyone of your programs and some guys like me cannot even get one ( they are not available where I live even though I have searched high and dry for them). I really think you should give this some serious thought as 2 out of 5 is really low for a contest. Considering the entries you receive my chance of winning will be about 0.001% or even lower, which is not a realistic chance. So, looks like I will have to go back to my cblite and scid for quite some time. But you should really give us problems like these regularly even without contests as they are fun to solve. I don't have time to logon daily but I do when I have time. So here's hoping that you bring us more of those excellent reports and extensive coverages of chess events.

Al, Longakit, Dubai, U.A.E.
Staring at those diagram of yours with a background carol is exhilirating. I found your puzzles very interesting, so I spent 2 sleepless nights (actually less than 4 hours of sleep) and 1 day-off to solve them. Your puzzles defy the power of chess engines. They are just useless in this type of chesspuzzles. I'm a brainteaser freak and a chess addict. While making a balancing act with my career as an avionics technician, I have managed to improve my chess by ardently studying the game. I once thought that chess becomes boring because of hundreds of chess engines that are popping out everywhere, but your puzzles makes me excited again. I'm researching at the moment on how to become a mensa member.

Richard Clark, Tsuchiura Japan
Thank you very much for providing me with some mental exercise as well as fun over the New Year. I nearly gave up on trying the contest puzzles as I found the first two very short problems quite hard, but something seemed to click halfway through the third problem with the errant knight, so I decided to give the contest a try.

Dies Irae, Munich, Germany
Never tried this form of puzzle before. Interesting, and moderately difficult (took me a couple of hours for the two). Reminds me of the book "The Flanders panel" by Perez-Reverte, an intriguing chessic mistery I recommend to anybody who has not read it yet.

Uberto Delprato, Roma, Italy
Thanks again for the nice time you "pushed" me to spend at the chessboard. It is now for me a sort of a tradition to have the Chessbase Puzzle Contest in the Christmas' holidays menu. As usual, the puzzles have been exciting and tough, but, again as usual, the gratification in finding the solutions (at least this is what I hope!) gives you such a good feeling...

Ragunathan, Pattabiraman, Hyderabad, India
I am playing chess for many years, an average player I think. Had I tracked, my elo might be around 1600. Lately, I was losing my interest a bit playing chess. I was beginning to think that it's no creative effort anymore. Having understood basic theory, I could beat any of my friends with no much of effort. At this dry time of my chess, I am very thankful to this year's Chessbase Christmas Puzzles, which helped to satisfy my creative urge. Me and my brother, Ananth, sat together to solve them. Many thanks to John Nunn, for the beautiful Proof Games, and the puzzle team at chessbase.

Pedro Miguel Duro de Deus, Barreiro, Portugal
Well I must say that compared to previous Christmas Contests, this one was very easy. I solved all the puzzles in about 2 hours and a half. Perhaps, it’s because proof games are my thing. :)

Alan Wadsworth, Melbourn, United Kingdom
I am a dormant club strength OTB player and do not normally find the time at Christmas that I require to solve chess problems, even mate-in-two's. However, I was pleasantly attracted by the simplicity of John Nunn's proof problems (did he invent the idea?) – maybe because the start position is so well known!!

The knowledge that there was only one unique solution was a big help. After spending upto an hour over my chess set familiarising myself with the proof problem at hand, I usually failed to find the solution. I found, however, that while waking from sleep next morning, while not exactly dreaming (and not having a heart attack!!), the solution usually 'popped' into my thoughts as I pondered the previous day's challenge.

The practice of mentally visualising chess positions is well exemplified by the masters of blindfold chess. From my experience, I wonder whether proof problems by their very nature may be more readily resolved by an 'away-from-the-board' experience. I found it made me concentrate on the white move sequence separately from the corresponding black one. For example, in problem three, any moves by a black knight to remove the immovable white king's bishop would take at least eight moves to return home again, leaving no time for pawn to c6 – hence one can quickly conclude that the solution must involve the black queen.

As the problems became more complicated during the week, it soon became clear that each problem had one or more beautiful finesses to be found – so looking for these finesses (e.g. promotion to a bishop in problem four) speeded up finding the solution. The second finesse in problem four was finding the only piece that could make an odd number of 'time wasting' moves. A very nice touch!

Simon Rubinstein-Salzedo, Sunnyvale, California, USA
I really enjoyed solving these proof game puzzles. It was very nice to have these over the winter break, which was otherwise rather boring for me. #1 was the most difficult for me. I kept expecting the a-pawn to promote to a bishop on c8 (although in retrospect it's obvious that something like this cannot possibly work). Where can I get more of these? Thanks!

Joe Chapman, Fair Oaks, CA, U.S.
This reminded me of a few other logic riddles: A plane crashes exactly on the border of the U.S. and Canada. Where were the survivors buried? Two fathers and two sons go duck hunting. They each get one duck, but only 3 ducks are brought back. What happened to the fourth duck? A doctor and a nurse have a baby boy. However, the doctor is not the boy's father and the nurse is not the boy's mother. Who are the boy's parents?

Or the case of two boys being born on the same day of the same year, within ten minutes of each other, of the same mother. But they are not twins. How come?

Yassen Bogoev, Sofia, Bulgaria
I liked the proof games – an interesting break from the regular chess problems. As to the puzzle with the French Revolution I must admit that actually initially I also fell for the idea with the height of the lever only later to realize my mistake.

Cayley Robinson, Gainesville, Florida, U.S.A.
I came across your site a few months ago, and since then it has been a main source of puzzles and compositions for me. Unfortunately, the day before the competition (December 24th) I got a fever, and a couple of days later my temperature was 105 degrees (not because of the puzzles!). However, I didn't want to miss my first Christmas Competition, and as a matter of fact I was still able to solve (and enjoy!) all five competition puzzles (and many of the others). I have separated my submission into three parts: this introduction; next, my solutions; and finally, the reasoning behind my solutions. P.S. I am only twelve years old, so I don't really have a professional status!

Umesh Nair, Wilsonville, Oregon, USA
It is a pity that all problems are not included in the contest. I had solved every one of them. The hardest for me was the Proof of Game Six on Dec 29. I solved it only after solving everything else. This is the first time I am solving any "Proof of Game" puzzles. It was very enjoyable. Thanks a lot!

Leonidas E. de la Rosa, Cali, Colombia
I discovered your website earlier this year after developing a taste for the chess problems in 'die Zeit.' I have enjoyed your puzzle section a lot, and chessbase is where I found out about and followed the Kramnik-Leko match. My success rate with your puzzles is probably around .5, but I surprised myself and believe I was able to solve all the problems in this year's christmas puzzle contest. I think not having the solutions means you can't give up prematurely, so your head doesn't give up too quickly. I enjoyed the proof games (I had never seen those before); the deduction has a Sherlock Holmes taste sometimes. The grandfather story: I was one of the *didn't get it* people. But since you said some people get it immediately all I had to do was tell the story to a friend and he told me the solution pretty quickly.

Stephane Harvey, Quebec,Canada
Happy new year and congrats for your good work to all the team of Chessbase, also to Mr Nunn and Friedel for this always amazing puzzle contest. See you next year for the puzzle contest!

Nicolas, Croad, Wellington, New Zealand
I greatly enjoyed the Christmas Puzzles Series so thank you for running it. If I do say so myself I think I had a reasonable success rate as well. Anyway when I checked today I noticed you had eliminated one of the puzzles which was causing me great pain.

Ron Fenton, Yellow Springs, Ohio USA
I look forward to the Chessbase Christmas Puzzles with great anticipation and once again, they did not disappoint. This year, I was introduced to proof games, some clever endgame studies and a logic problem. Here are a few comments...

Roberto Stelling, Niteroi, Brazil
This is the first time I've heard about your Christmas Puzzle Contest. Please keep on doing your great job!!! I'm a diehard fan of John Nunn ("Solving in Style" is by far the best book on Chess Problems Solution! I carry it everywhere I go!) and was pleased to read his texts and find some of his problems here. Cheers from Brazil!

Shridhar Deuskar, Cupertino, CA, USA
I would like you to know that I had never seen Proof games before and Dr Nunn's puzzle on Dec 25 was my first encounter with this type of a problem. Interestingly I was unable to solve the sample problem given by Dr Nunn in his introduction and it was only after I saw his solution a couple of days later that I realised the "thought process" required to solve these problems. Armed with this process, I was able to solve your first two proof problems in a matter of minutes !

Jorge Bates, Mexico City, Mexico
So I could finally solve the last two problems of the puzzle. I must say that the proof games were a discovery for me. Usually discouraged by my own inability to solve chess problems, I've found this kind of problems incredibly amusing and entertaining, and I discovered a hidden talent of myself to find these kind of solutions which, however difficult they seem in the beginning, when found, they happen to be rather logical and "easy". This was really, really, very fun.

Jaywant Pai, Mimbai, India
A glance at Puzzle 4 – Dec 31, was sufficient to send shivers down the spines of the stoutest and the toughest in the land. What say with all the Black pieces in their allotted slots and yet have White with a double pawn on the h-file? "Ho", I said to myself, as I spat on my hands and got down to the business of cutting this little chap down to size. Hours pass. Days pass. This nut is proving to be real tough to crack. Fortunately, the fog cleared a bit -just a bit, as I later realized – to enable me catch a glimpse of the pawn–queening theme, or rather to be more precise as in this case, "the pawn- bishoping" theme.

"The black pawn advances down the g-file, takes the rook on h1, bishops itself and then scrams back to square one." I said to myself, clapping my hands with glee. The celebrations proved to be a little too premature. This nasty little chap was made of sterner stuff and was not going to give up so easily. No matter what tricks and permutations and combinations I tried with white’s kingside pieces, I simply could not time the evacuation of the white knight off the f3 Square for black’s promoted bishop squeak through.

It was getting hopeless. I was on the verge of giving it all up when suddenly and to my great surprise, I found the white rook on h1 (whom, sadly, I had ignored all along) winking wickedly at me with a devilish sort of grin on his face. The nasty little chap's game was up and he met with a neat little ending.

The euphoria and the momentum generated by this victory were such that the rest of the problems were simply wiped off the board. Puzzle 3 – Dec 30, fought valiantly but in vain. After a brief resistance, his defenses crumbled and he too was forced to sign the peace treaty.

Licai Yeo, Singapore

I caught a cold after New Years Day,
and quite distraught was I,
that I should spend my day in bed
doing nothing, with a sigh.
But wait, there's something on Chessbase,
some puzzles to be done!
Despite the fact I lost my sense of taste,
I really could have fun!

I would like to thank Chessbase and Dr John Nunn for his fabulous puzzles, for keeping me sane throughout those very sick nights. Luckily for me I heard puzzle 2 before, but I admit I got stumped by it the first time. The proof games are fun! I enjoyed it very much, and I like the very neat and unique ideas that went in all of them.

Matti Israel, Tel-Aviv, Israel
I have succeeded to solve all 5 of your "Christmas Puzzle Contest 2005". Each time I solved one of these puzzles, a smile appeared on my face (as you said). It was very enjoyable and pleasing to solve the puzzles. Thank you for a very interesting and fun columns and puzzles. Keep on the good work! Furthermore, I would like to take advantage of this opportunity, to tell you how much I enjoyed your Christmas columns (especially the one with the French Revolution puzzle). During the whole Christmas time I found myself looking forward each for your daily column, and, indeed, my anticipating was worthwhile. Believe it or not, when I solved the French Revolution puzzle, I found myself not belonging to any of the groups you have mentioned in your column: neither to those who solve it immediately nor to those who put their efforts on it for hours. I must say that only after the 3rd or 4th time I was analyzing the puzzle, I suddenly realized I how utterly clear and simple it is. It is just an astounding puzzle. When I brought the puzzles to some of friends, most of them solved it instantaneously (as you said), but others just couldn’t have found the solution.

Henryk Kalafut, Garfield, NJ, USA
Thank you very much for very interesting chalenge. I have seen a lot chess problems including some amazing from retrograde chess but no from retro time as in 2nd puzzle. These puzzles are great!!!

Ihsan Haluk Akin, Istanbul, Turkey
First of all please forgive me because of my english. After several years later I have decided to spend some time at chess. Now at age 29. I found your site very good designed especially the parts puzzle and tactics. This year you gave us an interesting type of question, at least for me, the proof problems. As a mathematician I quite enjoyed them. This problems contains no meaningfull movements that is, at first, challenged me very much. I had totally enjoyed when get the solutions, since I'm totally satisfied that I've found the solution.

Alexander Thompson, Toronto, Ontario
I must mention that your site is one of excellence. There is a great mixture of actual chess study, games and news. I must admit that chessbase is indeed responsible for my favorite "chess moments" when not at the checkered board. Keep up the fantastic work!

Incidentally: the background music on this page is an imaginative improvisation on the famous "Blue Danube" waltz by Johann Strauss; or, more specifically, it is the 5th Waltz, Opus 314 "An der schönen blauen Donau", composed in 1867 by Johann Strauss II ("The younger", 25.10.1825 – 3.6.1899, Vienna, Austria). Not satisfied? Okay, it is an Arabesques on themes in the Blue Danube by Adolf Schulz-Evler (1852-1952).