The rules of chess are followed, but with the following difference: each move, a player also gives one move that his opponent is not allowed to play in his next move.
When a player mates his opponent, he gets one point. However, there is an additional way to win a `minor victory': when a player is in check, and there is only one way out of check, and the opponent forbids this way out of check, the opponent wins the game and gets 3/4 point, the losing player receives 1/4 point (this is called a No-chess mate. When a player is stalemated (i.e., he is not in check but has no legal move), his opponent receives 3/4 point, and he receives 1/4 point. However, when a player has only one legal move in a position and this move is forbidden by the opponent (a No-chess stalemate), then both players receive 1/2 point.
Promotion to different pieces are seen as different moves. Thus, white could forbid a pawn on a2 to move to a1 and become a queen; black then can decide to promote the pawn to e.g. rook.
For instance, white can start with: e2-e4 forbid e7-e5. Now black must play a move, different from e7-e5.
Here is an interesting position: White: King c5, Queen c3; Black: King a4, Rook b1. White can get 3/4 point by playing Qc3-a3+ (if forbidden Qc3-b4+), and forbidding in both cases the one legal move out of check. But, can white get 1 point?
Written by Hans Bodlaender and Zoltan Blazsik.
WWW page created: April 21, 1997. Last modified: October 14, 2002.