Ambiguous Chess

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.