And make it a legal square. I was talking with a 30-something player a while ago and he said that as a kid he played a game in a scholastic tournament where the opponent moved his queen on the diagonal from a light square to the center of a dark square. Rather than claiming an illegal move he simply captured the queen with his dark-squared bishop. The opponent looked confused, but he saw the queen on the dark square prior to the capture and thus knew that the capture was a legal move. Eventually the loss of the queen lost the game (after ten more moves the illegal move is treated as legal). When the capturing player went over the game with his coach later the coach questioned the illegal queen move and the player said that he thought it was better to capture the queen than get two minutes for the illegal move violation.