| Instead of playing their moves, the players indicate only the square (free or occupied) where they intend to move to ; of course, there must be at least one of their pieces which is able to move on that square. Then it is the opponent who choose which one of the possible pieces will move to that square. If only one can, the opponent has nothing to choose and the move can be played at once. No check or checkmate, the goal of the game is to capture the opponent's king.
When a pawn is promoted, the promoted piece is chosen by the opponent of the pawn's owner (as it is considered that every promotion is a different move to the same square).
Castling is forbidden.
Note 1 :
One can also equivalently play with the checkmate rule, which translates as follows : a mate is a check that cannot be parried, when the three possible ways to parry a check are :
- Take the checking piece (if it is the only checking piece).
- Move the king to a square where it is not under check, and where no friendly piece can move to (otherwise, the opponent would make that piece play instead of the king, leaving the king in check).
- Block the check by moving a piece to the checking line, but at least two squares away from the king (otherwise the opponent would make the king play to that square instead), and when no pinned piece can play to the same square (otherwise the opponent would make the pinned piece move, again leaving the king in check).
In this case, the stalemate=draw rule can also be adopted (but in the original rules, a stalemate is a win for the stalemating player, because the opponent is forced to suicide his king).
Note 2 :
When using a chess clock, it is recommended to use the following procedure : one plays moves normally and press the clock ; if other pieces could move to the same square, the opponent can (on his thinking time) undo the move and bring another of those pieces to the same square, before playing his own move.
Note 3 :
A move on a square where only one piece can go does not leave any choice to the opponent and is called an unambiguous move ; a move leaving the opponent which a choice of the piece to move is called an ambiguous move.
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