Entries by nabla

Author: nabla

Extinction Chess (official rules here) is one of the most fascinating chess variants. It comes from a very natural enhancement of the goal of the chess game, in that one wins by extincting one species in the opponent's pieces - for instance capturing both knights. With such a phrasing, standard chess can be defined as a kind of restricted Extinction Chess, where only the king's species is taken into account - you certainly know that the goal of chess is to extinct the opponent's king ! This variant manages to be in the same time different enough from standard chess in order to produce a lot of new ideas, but close enough as to keep the most positional features of chess, like pawn structures and space. A game where the chess skills are highly transposable, yet where it is vital to stay fully aware of the additional dangers.

Although it is not only a deep game, but also a very fun game, Extinction Chess is less popular on Brainking that I would have expected. I don't know the reason why, and am taking profit of this column to advocate this variant by annotating in detail one of the two best games I ever played. My opponent played it very well too, equalizing as Black, and then only failing to risk himself into an unpredictable position and falling into a passive one as the result of that choice. The game illustrates how easily an Extinction Chess is unbalanced, and how hard it is to overcome the slightest inaccuracies.

Remark about the notation

Although the rules of Extinction Chess state that there is no check or checkmate, I still find it to be a big help to add the check (+) and checkmate (#) symbols to the game notation, with the meaning that :

• A check is a threat to one of the opponent's pieces, which is the last of its kind - such a piece is to be considered as a royal piece as its loss would lose the game.


• A checkmate is an unstoppable such threat. Typical Extinction checkmates are double attacks on two last pieces (those are called forks), and attacks on one last piece, whose move would uncover another last piece (those could be called pins, but I prefer to call them skewers). And it is of course also possible to mate a piece in the good old-fashioned way, attacking it in such a way that it has no retreat.

Author: nabla

When seeking for a subject of my next chess article, I was thinking of how I could maximize my potential readership, and found out that problem was not so easy. Indeed, one of the great things about the community of chess players is its variety. We have veterans and youngsters, intellectuals and manuals, bankers and tramps, artists and competitors, and since a short time we even have men and women.

Isn't there one common denominator ? Fortunately there is one : we all love queen sacrifices. Ahah, say no more, I have found my theme ! Here are three of the finest chess studies ever composed on the theme of the queen sacrifice. I would even like to issue a poll about which one you will like best.

Author: nabla

An introduction to equity

If you have ever played backgammon, you are very likely to have encountered what we call beginner's luck. Your opponent plays a move which seems just terrible to you, leaving two vital blots when he could have left only one. And of course, you roll a double of the very number which would have hit if your opponent had played the correct move, but which now misses the two blots and loses the game outright. Well, a bit frustrating maybe, but luck is a part of the game, you think, and if your opponent plays such blunders you are very likely to do better in the next game. However you can't resist the temptation to explain him the mistake he did and how lucky he has just been. Now here is the big mistake of yours !

Your opponent bitterly disagrees with you ! What is that advice that you are trying to give him ? That he should have played the move which would have allowed you to hit, and filling your last gaps in the same time ? He is not that dumb ! It is absolutely obvious that his move was much better, as a simple look at the current position tells. From now on, he would very much appreciate if you could keep your comments for yourself.

What can go wrong when discussing checker play can get even worse when discussing cube decisions. The doubling cube is sometimes seen as a gambler's device, with cube decisions as well motivated as by "I was feeling lucky" or "What could I do but reject ? I know it is not my day". There is certainly no evil in resorting to such guesses if you don't mind winning or losing, but assuming that you prefer to win, couldn't your decision making be backed up by something slightly more solid ?

Author: nabla

Ambiguous Chess is a chess variant that I invented in January 2005, and which has been introduced on BrainKing in June 2006. It is nothing more than a very simple idea that anybody could have thought of, but the game seems to work very well, and unlike many inventions in the field, I have a good hope that it will last. For the moment, I enjoyed seeing it become one of the most popular chess variants on BrainKing : there are actually more than 400 games running, and 80 players are taking part to this prize tournament.

Rules of Ambiguous Chess

1. Instead of playing a move on the board, the player points at the square he intends to move to. The opponent then chooses which one of the possible men will indeed move to the square.
2. Winning is by capturing the opponent's king. It remains possible to announce checks and checkmates, but the rules do not take them into account. That means that you have the right to choose for your opponent a move that allows you to capture his king, and that a stalemate position wins for the stalemating player.
3. When a pawn is promoted, the promotion piece is chosen by the opponent of the pawn's owner.
4. Castling is forbidden.

For instance, if at move one White points to the e4 square, Black has no choice but to accept the move 1.e2-e4. But if White had pointed at the f3 square, Black could have chosen between 1.Ng1-f3 and 1.f2-f3.

Simple ideas don't necessarily arise in a simple way. Ambiguous Chess derives from a variant I invented as Unambiguous Chess, a notation-independent form of the existing but very confidential game of "Unambiguous Three-symbol Chess". In the latter game, the only possible moves are those which can be written using only three symbols in the English notation. In my Unambiguous Chess, the move must be deducible from the arrival square only : it is allowed to play a man to a square only when no other of the player's men can reach this square.