Blindfold chess (also known as sans voir) is a form of chess play wherein the players do not see the positions of the pieces or touch them. This forces players to maintain a mental model of the positions of the pieces. Moves are communicated via a recognized chess notation.
Blindfold chess was considered miraculous for centuries, but it is now accepted that any strong player today can play blindfolded, and many can keep track of more than one simultaneous blindfolded game. In simultaneous blindfold play, an intermediary usually relays the moves between the players.