Reconnaissance Blind Chess 1.0

The Reconnaissance Blind Chess (RBC) variant, introduced in 2015 at Johns Hopkins University Applied Physics Laboratory, serves as a platform for the exploration of artificial intelligence applications within chess. This variant introduces elements of imperfect information, strategic depth, and individual observations, which significantly deviate from traditional chess dynamics.

In RBC, players are unable to see their opponent's pieces; instead, they can gain information through private sensing actions. This introduces a layer of uncertainty that challenges conventional chess strategies.

Game formats include unranked and ranked play. In unranked games, players utilize guest accounts, choose their opponents from a list of available bots, and select their starting color. Notably, these matches do not influence player ratings. Conversely, ranked games require players to log in with their credentials; opponents and colors are assigned randomly, impacting the player's rating and resulting in a brief waiting period for match confirmation.

Game Rules:

• RBC is designed to maintain traditional chess integrity while incorporating distinct uncertainties and explicit sensing features.
• Players do not have visibility of adversarial pieces.
• Before making a move, a player selects a 3×3 board region to "sense" the arrangement of pieces within that area. The true configuration is revealed to the sensing player while the opponent remains unaware of this action.
• Upon capturing an opponent’s piece, the player is informed that a capture has occurred but not which piece was taken.
• If a player's piece is captured, they receive notification of the capture without knowing the identity of the capturing piece.
• The concepts of check and checkmate are not applicable, as the players cannot reliably assess these relationships.
• A player wins by capturing the opponent's king or causing time to expire for their opponent. Each player is allocated a cumulative 15-minute time limit for all moves.
• When attempting to move a sliding piece through an opponent's piece, that piece is captured; the moving piece halts on the square of the capture. Both players are notified accordingly.
• Illegal moves (e.g., moving a pawn diagonally onto an empty square) result in failure notifications, ending that player’s turn. However, castling through check is permissible since check itself is not in effect.
• A "pass" option allows players to forgo making a move on their turn if desired.
• Players may access reserve pieces to manipulate and visualize potential board states based on their assumptions about opponent positions.
• A turn tracker keeps players informed of whose turn it is to sense and move.