Simulation archive
Run the earlier worlds.
Earlier worlds, original rules. Run the live demos or replay the first recording. All use scripted agents.
Clone an environment and try your own agent →
Chess
October 27, 2026 · Playable game
Standard chess with full FIDE rules, laid out like a lichess board. Play both sides or face the random baseline agent; the same integer action space is what an agent steps.
Click or drag a piece to move. Arrow keys step through the moves, f flips the board.
Environment API
Plain chess, FIDE rules: castling, en passant, promotion, checkmate, stalemate, threefold repetition, fifty-move rule, insufficient material. ChessEnv.reset() and step(action) move one side per step. Actions: from·64 + to (a1 = 0 … h8 = 63) for ordinary moves and queen promotions, 72 under-promotion ids from 4096. Observation: 19 × 8 × 8 planes from the mover's view (own pieces, their pieces, colour, castling rights, en-passant file, fifty-move clock). Reward: 1 for delivering checkmate, 0 otherwise, −1 for an illegal action. Pieces: cburnett set (Colin M.L. Burnett).
Open chess on its own page → · Also run the Target Drift / Mountain Car demo →