ChessBase Christmas Puzzles December 25, 2004
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Christmas is here, and we trust all our friends from the ChessBase.com community have survived the commercial anguish of the pre-season days, and are now bravely facing the culinary challenges that await. As in the past we come to you with a set of eight Christmas puzzles, one a day, each hidden behind a festive wreath, to be opened every day between Christmas and the New Year.

But before we come to the thematic puzzles of this year's suite, we would like to wish all the visitors to our site a ...

Note that you can click on each of the figures to switch them on and off.

Assuming you have had as much fun as we did with the above flash animation, let us pause for a moment to remember the man who invented the reindeer character shown in the middle of the picture. In 1939 34-year-old Robert L. May, who worked for the Montgomery Ward department store, was asked to come up with a promotional gimmick for Christmas shoppers. So he wrote a story-poem. It was about an unfortunate reindeer who, because of a physical abnormality, was ostracized by the reindeer community. The abnormality was a large, glowing, red nose. May's boss was initially unimpressed by the narrative, because he associated the red nose with alchohol and drunks. But in the end it was published and distributed to the Montgomery Ward shoppers.

Some time later Robert May slipped into a personal financial crisis as a result of medical bills for his terminally ill wife. As an employee of the company he was not entitled to any royalties derived from the Rudolph character. But in 1947 he managed to convince Montgomery Ward's corporate president to turn the copyright over to him. The story of "Rudolph the Red-Nosed Reindeer" was printed commercially the same year, and in 1949 May's brother-in-law, Johnny Marks, composed a little Rudolph song. This too was initially rejected by music publishers. But Gene Autry recorded it, and two million copies were sold. Since then the song has become the second most successful Christmas seller of all time (after "White Christmas"). The Rudolph story itself has been translated into twenty-five languages and been made into a television movie, narrated by Burl Ives. It has been playing at Christmas time every year since 1964. May's died in 1976, comfortable in the life his reindeer character had provided for him.

Let us turn to chess and to our Christmas chess puzzles. This year our problem expert John Nunn introduces us to a genre that, while not new, is gaining in popularity.

Proof games

By John Nunn

Most chess players are familiar with the traditional types of chess problem, such as mates in two or three moves, and with endgame studies (White to play and win or draw positions). However, there are plenty of other types of chess problem. In the past, the ChessBase website has featured helpmates, which are often popular with over-the-board players.

This year I propose to introduce you to another type of chess problem, the so-called ‘proof game’. This type of problem has several advantages; it is easy to understand, needs no special knowledge and is fun to solve. The basic idea is that you are presented with a position and are told how many moves have been made since the start of the game. What you have to do is reconstruct the game.
Here is an example which was popular amongst over-the-board players several years ago.

Proof game 1: Position after Black’s 4th move

We must find out how this position can arise after Black’s fourth move in a normal game of chess. There are no tricks in this type of problem; they always begin with the normal starting position and all the moves are legal. The moves do not have to be good ones and can be as silly as you like, but they must be legal.

One can immediately see that it is easy to get the above position after Black’s third move by 1 e4 e6 2 Bb5 c6 3 Bxc6 dxc6, but it is much harder to see how it can arise after Black’s fourth move. It is easy for White to lose a tempo (for example, by 1 e4 e6 2 Be2 c6 3 Bb5 pass 4 Bxc6 dxc6) but it is not so easy to provide a pass move for Black.

One useful tool when tackling proof-game puzzles is that the knowledge that the solution must be totally unique, both in terms of the moves played and their order. Thus we can immediately see that the above sequence of moves must be wrong, because instead of 2 Be2 White could just as well play 2 Bd3 or 2 Bc4. The real solution involves a surprising finesse which is quite pleasing when you find it.

Proof game 2: Position after White’s 4th move

Here White has apparently played e4, Black has played ...d6 and the c8-bishop is missing. The problem is the lack of a Black waiting move, for example 1 e4 d6 2 Qe2 Bg4 3 Qxg4 pass 4 Qd1 would solve the problem except that there is no possible pass move.

We know from uniqueness considerations that the above sequence cannot be right (because 2 Qf3 would serve just as well as 2 Qe2). More generally, we can see that White’s 3rd move cannot be the one that captures the bishop because Black must have played 1...d6 and 2...B somewhere for White to take the bishop, and then Black’s 3rd move will disrupt the positioning of his pieces.

We will publish the solutions in our Christmas Puzzle sections in a day or two. We urge you to print out the two positions, get out the trusty old chess set and let the whole family participate in the search for the solutions. They are not too difficult and do not require great chess expertise. Just some lateral thinking.

Merry Christmas, everybody!

Frederic Friedel