Reconnaissance Blind Chess
Reconnaissance Blind Chess (RBC) was intentionally designed to keep the game as close to traditional chess as possible while adding an appropriate amount of uncertainty and explicit sensing. RBC is like chess but includes the following core differences:
A player cannot see their opponent's pieces.
Prior to making each move, a player selects a 3x3 region of the chess board to “sense” the pieces in that region. The player is informed of the true piece configuration within the sensed 3x3 region. The opponent is not informed about where the player sensed.
When a player captures a piece, they are informed that they made a capture, but they are not informed about what piece they captured.
When a player's piece is captured, they are informed that their piece was captured, but they are not informed about what piece captured it.
There is no notion of check or mate because players may be unaware of a check relationship.
A player wins by capturing the opponent's king or when the opponent runs out of time. Each player begins with a cumulative 15-minute clock to make all their moves, and gains 5 seconds on that clock after each turn.
A game is automatically declared a draw after 50 turns without a pawn move or capture. This mirrors the 50-move rule in chess, except here neither player needs to claim the draw for the game to end.
If a player tries to move a sliding piece through an opponent's piece, the opponent's piece is captured and the moved piece is stopped where the capture occurred. The moving player is notified of the square where the piece landed, and both players are notified of the capture.
If a player attempts to make an illegal move, such as moving a pawn diagonally to an empty square, moving a pawn forward to an occupied square, or a castling through an interposing piece, they are notified that the move did not succeed and their turn is over. However, castling through check is allowed because the notion of check is removed.
There is a "pass" option that a player can select if they prefer to make no move during their turn.