CHECKERED CROWN ORIGINAL COMPOSED-POSITION ANALYSIS ORIGINAL-WORK CALCULATION NOTE — NOT WHOLE-ARTICLE RELEASE APPROVAL Prepared by Checkered Crown’s AI-assisted studio workflow. These composed teaching examples and finite calculations are original-work evidence, not external independent corroboration or examples supplied by FIDE/Chess.com. Library-generated move legality and material bookkeeping are distinguished from editorial review. Originality here describes the retained workflow, not a worldwide novelty or legal ownership certification. C011: SPOT CHESS FORKS Material values P=1, N=B=3, R=5, Q=9, K=0. Gains are changes from each initial position, not evaluations. Exhaustive means all immediate Black replies and all next Black replies after the specified target captures only; not all White strategies or a full game tree. No engine search, forced-win, unique-best or full-history reachability finding. knight: Nc7+; 5 legal replies; representative Nc7+ Kd7 Nxa8; representative material change 5; minimum best local material change 5. pawn: e5; 19 legal replies; representative e5 Nde4 exf6 Nxf6; representative material change 2; minimum best local material change 2. queen: Qd5+; 4 legal replies; representative Qd5+ Kh7 Qxa8; representative material change 5; minimum best local material change 5. defense: Nc7+; 5 legal replies; representative Nc7+ Qxc7; representative material change -3; minimum best local material change None. SUMMARY [ { "id": "knight", "fen": "r3k3/8/8/1N6/8/8/8/6K1 w - - 0 1", "move": "Nc7+", "legal_replies": [ "Kf8", "Kf7", "Ke7", "Kd7", "Kd8" ], "representative": [ "Nc7+", "Kd7", "Nxa8" ], "representative_final": "N7/3k4/8/8/8/8/8/6K1 b - - 0 2", "representative_gain": 5, "minimum_best_local_gain": 5, "scope": "Every legal reply to the check allows Nxa8 on the next move; rook capture only, no game-result claim." }, { "id": "pawn", "fen": "7k/8/3n1n2/8/4P3/8/8/6K1 w - - 0 1", "move": "e5", "legal_replies": [ "Kh7", "Kg7", "Kg8", "Nb7", "Nc8", "Nde8", "Nf7", "Nf5", "Nde4", "Nc4", "Nb5", "Nd7", "Nfe8", "Ng8", "Nh7", "Nh5", "Ng4", "Nfe4", "Nd5" ], "representative": [ "e5", "Nde4", "exf6", "Nxf6" ], "representative_final": "7k/8/5n2/8/8/8/8/6K1 w - - 0 3", "representative_gain": 2, "minimum_best_local_gain": 2, "scope": "Every immediate legal Black reply allows at least one pawn capture of a knight; enumerate next Black recaptures and worst local exchange. Not an engine evaluation or proof of a won game." }, { "id": "queen", "fen": "r5k1/8/8/8/8/8/8/3Q2K1 w - - 0 1", "move": "Qd5+", "legal_replies": [ "Kh8", "Kh7", "Kg7", "Kf8" ], "representative": [ "Qd5+", "Kh7", "Qxa8" ], "representative_final": "Q7/7k/8/8/8/8/8/6K1 b - - 0 2", "representative_gain": 5, "minimum_best_local_gain": 5, "scope": "Every legal reply to the check allows Qxa8 on the next move; rook capture only, no game-result claim." }, { "id": "defense", "fen": "r2qk3/8/8/1N6/8/8/8/6K1 w - - 0 1", "move": "Nc7+", "legal_replies": [ "Qxc7", "Kf8", "Kf7", "Ke7", "Kd7" ], "representative": [ "Nc7+", "Qxc7" ], "representative_final": "r3k3/2q5/8/8/8/8/8/6K1 w - - 0 2", "representative_gain": -3, "minimum_best_local_gain": null, "scope": "Existence of one legal refutation is enough to disprove a guaranteed rook win; queen captures the checking knight, not the king or rook." } ] RETAINED RAW RESULT Original raw result SHA256 b0bec3f35bd440252479f06fc91570c3727f8b08d66378bbf36dc65be0d5d903 The single internal absolute modulePath field is omitted below; every other field is unchanged. This redacted presentation has a different file hash. chess.js 1.4.0 is the move-generation dependency (BSD-2-Clause software; no library code distributed here). { "status": "COMPLETED_CHESS_JS_FALLBACK_NOT_PYTHON_CHESS", "module_sha256": "76c7c34f0e2e9ab076521a5d6fe786a9cce537bb1b6f29d32a9c9970b5b232d2", "node": "v26.12.1", "examples_sha256": "b37e12c449c505f1ae646899d117cfe977d427db0628c849213a7be591521300", "convention": "Material values pawn=1 knight=bishop=3 rook=5 queen=9; kings excluded. Local net captured material, NOT game evaluation.", "scope": "All legal replies after each fork plus all one-ply Black replies after each candidate target capture. No engine, tablebase or full-game minimax. FEN validity here is library load plus move legality, not a proof of historical reachability.", "results": [ { "id": "knight", "fen": "r3k3/8/8/1N6/8/8/8/6K1 w - - 0 1", "move": "Nc7+", "attacker": "c7", "targets": [ "e8", "a8" ], "capture": "Nxa8", "min_immediate_gain": 5, "representative": [ "Nc7+", "Kd7", "Nxa8" ], "scope": "Every legal reply to the check allows Nxa8 on the next move; rook capture only, no game-result claim.", "first_move": "Nc7+", "after_fen": "r3k3/2N5/8/8/8/8/8/6K1 b - - 1 1", "legal_reply_count": 5, "branches": [ { "reply": "Kf8", "fen": "r4k2/2N5/8/8/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Nxa8", "fen": "N4k2/8/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Kg8", "fen": "N5k1/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg7", "fen": "N7/6k1/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf7", "fen": "N7/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke7", "fen": "N7/4k3/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke8", "fen": "N3k3/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] }, { "reply": "Kf7", "fen": "r7/2N2k2/8/8/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Nxa8", "fen": "N7/5k2/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Ke8", "fen": "N3k3/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf8", "fen": "N4k2/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg8", "fen": "N5k1/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg7", "fen": "N7/6k1/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg6", "fen": "N7/8/6k1/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf6", "fen": "N7/8/5k2/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke6", "fen": "N7/8/4k3/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke7", "fen": "N7/4k3/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] }, { "reply": "Ke7", "fen": "r7/2N1k3/8/8/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Nxa8", "fen": "N7/4k3/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Kd8", "fen": "N2k4/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke8", "fen": "N3k3/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf8", "fen": "N4k2/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf7", "fen": "N7/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf6", "fen": "N7/8/5k2/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke6", "fen": "N7/8/4k3/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kd6", "fen": "N7/8/3k4/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kd7", "fen": "N7/3k4/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] }, { "reply": "Kd7", "fen": "r7/2Nk4/8/8/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Nxa8", "fen": "N7/3k4/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Kc8", "fen": "N1k5/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kd8", "fen": "N2k4/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke8", "fen": "N3k3/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke7", "fen": "N7/4k3/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke6", "fen": "N7/8/4k3/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kd6", "fen": "N7/8/3k4/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kc6", "fen": "N7/8/2k5/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] }, { "reply": "Kd8", "fen": "r2k4/2N5/8/8/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Nxa8", "fen": "N2k4/8/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Ke8", "fen": "N3k3/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke7", "fen": "N7/4k3/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kd7", "fen": "N7/3k4/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kc8", "fen": "N1k5/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] } ], "representative_final": "N7/3k4/8/8/8/8/8/6K1 b - - 0 2", "representative_gain": 5, "minimum_best_local_gain": 5 }, { "id": "pawn", "fen": "7k/8/3n1n2/8/4P3/8/8/6K1 w - - 0 1", "move": "e5", "attacker": "e5", "targets": [ "d6", "f6" ], "capture": null, "min_immediate_gain": 3, "representative": [ "e5", "Nde4", "exf6", "Nxf6" ], "scope": "Every immediate legal Black reply allows at least one pawn capture of a knight; enumerate next Black recaptures and worst local exchange. Not an engine evaluation or proof of a won game.", "first_move": "e5", "after_fen": "7k/8/3n1n2/4P3/8/8/8/6K1 b - - 0 1", "legal_reply_count": 19, "branches": [ { "reply": "Kh7", "fen": "8/7k/3n1n2/4P3/8/8/8/6K1 w - - 1 2", "options": [ { "capture": "exd6", "fen": "8/7k/3P1n2/8/8/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kg8", "fen": "6k1/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh8", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh6", "fen": "8/8/3P1n1k/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg6", "fen": "8/8/3P1nk1/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg7", "fen": "8/6k1/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nd7", "fen": "8/3n3k/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne8", "fen": "4n3/7k/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng8", "fen": "6n1/7k/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nh5", "fen": "8/7k/3P4/7n/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng4", "fen": "8/7k/3P4/8/6n1/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne4", "fen": "8/7k/3P4/8/4n3/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nd5", "fen": "8/7k/3P4/3n4/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 3 }, { "capture": "exf6", "fen": "8/7k/3n1P2/8/8/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kg8", "fen": "6k1/8/3n1P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh8", "fen": "7k/8/3n1P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh6", "fen": "8/8/3n1P1k/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg6", "fen": "8/8/3n1Pk1/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nb7", "fen": "8/1n5k/5P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nc8", "fen": "2n5/7k/5P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne8", "fen": "4n3/7k/5P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf7", "fen": "8/5n1k/5P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf5", "fen": "8/7k/5P2/5n2/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne4", "fen": "8/7k/5P2/8/4n3/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nc4", "fen": "8/7k/5P2/8/2n5/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nb5", "fen": "8/7k/5P2/1n6/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 3 } ] }, { "reply": "Kg7", "fen": "8/6k1/3n1n2/4P3/8/8/8/6K1 w - - 1 2", "options": [ { "capture": "exd6", "fen": "8/6k1/3P1n2/8/8/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kf8", "fen": "5k2/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg8", "fen": "6k1/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh8", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh7", "fen": "8/7k/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh6", "fen": "8/8/3P1n1k/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg6", "fen": "8/8/3P1nk1/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kf7", "fen": "8/5k2/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nd7", "fen": "8/3n2k1/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne8", "fen": "4n3/6k1/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng8", "fen": "6n1/6k1/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nh7", "fen": "8/6kn/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nh5", "fen": "8/6k1/3P4/7n/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng4", "fen": "8/6k1/3P4/8/6n1/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne4", "fen": "8/6k1/3P4/8/4n3/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nd5", "fen": "8/6k1/3P4/3n4/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 3 }, { "capture": "exf6+", "fen": "8/6k1/3n1P2/8/8/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kf8", "fen": "5k2/8/3n1P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg8", "fen": "6k1/8/3n1P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh8", "fen": "7k/8/3n1P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh7", "fen": "8/7k/3n1P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh6", "fen": "8/8/3n1P1k/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg6", "fen": "8/8/3n1Pk1/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kxf6", "fen": "8/8/3n1k2/8/8/8/8/6K1 w - - 0 3", "gain": 2, "captures_attacker": true }, { "san": "Kf7", "fen": "8/5k2/3n1P2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 2 } ] }, { "reply": "Kg8", "fen": "6k1/8/3n1n2/4P3/8/8/8/6K1 w - - 1 2", "options": [ { "capture": "exd6", "fen": "6k1/8/3P1n2/8/8/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kh8", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kh7", "fen": "8/7k/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg7", "fen": "8/6k1/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kf7", "fen": "8/5k2/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kf8", "fen": "5k2/8/3P1n2/8/8/8/8/6K1 w - 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- 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf6", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 3 } ] }, { "reply": "Nh5", "fen": "7k/8/3n4/4P2n/8/8/8/6K1 w - - 1 2", "options": [ { "capture": "exd6", "fen": "7k/8/3P4/7n/8/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kh7", "fen": "8/7k/3P4/7n/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg7", "fen": "8/6k1/3P4/7n/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg8", "fen": "6k1/8/3P4/7n/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf6", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng7", "fen": "7k/6n1/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng3", "fen": "7k/8/3P4/8/8/6n1/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf4", "fen": "7k/8/3P4/8/5n2/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 3 } ] }, { "reply": "Ng4", "fen": "7k/8/3n4/4P3/6n1/8/8/6K1 w - - 1 2", "options": [ { "capture": "exd6", "fen": "7k/8/3P4/8/6n1/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kh7", "fen": "8/7k/3P4/8/6n1/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg7", "fen": "8/6k1/3P4/8/6n1/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg8", "fen": "6k1/8/3P4/8/6n1/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne5", "fen": "7k/8/3P4/4n3/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf6", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nh6", "fen": "7k/8/3P3n/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nh2", "fen": "7k/8/3P4/8/8/8/7n/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf2", "fen": "7k/8/3P4/8/8/8/5n2/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne3", "fen": "7k/8/3P4/8/8/4n3/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 3 } ] }, { "reply": "Nfe4", "fen": "7k/8/3n4/4P3/4n3/8/8/6K1 w - - 1 2", "options": [ { "capture": "exd6", "fen": "7k/8/3P4/8/4n3/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kh7", "fen": "8/7k/3P4/8/4n3/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg7", "fen": "8/6k1/3P4/8/4n3/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg8", "fen": "6k1/8/3P4/8/4n3/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nc5", "fen": "7k/8/3P4/2n5/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nxd6", "fen": "7k/8/3n4/8/8/8/8/6K1 w - - 0 3", "gain": 2, "captures_attacker": true }, { "san": "Nf6", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng5", "fen": "7k/8/3P4/6n1/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ng3", "fen": "7k/8/3P4/8/8/6n1/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf2", "fen": "7k/8/3P4/8/8/8/5n2/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nd2", "fen": "7k/8/3P4/8/8/8/3n4/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nc3", "fen": "7k/8/3P4/8/8/2n5/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 2 } ] }, { "reply": "Nd5", "fen": "7k/8/3n4/3nP3/8/8/8/6K1 w - - 1 2", "options": [ { "capture": "exd6", "fen": "7k/8/3P4/3n4/8/8/8/6K1 b - - 0 2", "gain": 3, "black_replies": [ { "san": "Kh7", "fen": "8/7k/3P4/3n4/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg7", "fen": "8/6k1/3P4/3n4/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Kg8", "fen": "6k1/8/3P4/3n4/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nb6", "fen": "7k/8/1n1P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nc7", "fen": "7k/2n5/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne7", "fen": "7k/4n3/3P4/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf6", "fen": "7k/8/3P1n2/8/8/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nf4", "fen": "7k/8/3P4/8/5n2/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Ne3", "fen": "7k/8/3P4/8/8/4n3/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nc3", "fen": "7k/8/3P4/8/8/2n5/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false }, { "san": "Nb4", "fen": "7k/8/3P4/8/1n6/8/8/6K1 w - - 1 3", "gain": 3, "captures_attacker": false } ], "worst_next_reply_gain": 3 } ] } ], "representative_final": "7k/8/5n2/8/8/8/8/6K1 w - - 0 3", "representative_gain": 2, "minimum_best_local_gain": 2 }, { "id": "queen", "fen": "r5k1/8/8/8/8/8/8/3Q2K1 w - - 0 1", "move": "Qd5+", "attacker": "d5", "targets": [ "g8", "a8" ], "capture": "Qxa8", "min_immediate_gain": 5, "representative": [ "Qd5+", "Kh7", "Qxa8" ], "scope": "Every legal reply to the check allows Qxa8 on the next move; rook capture only, no game-result claim.", "first_move": "Qd5+", "after_fen": "r5k1/8/8/3Q4/8/8/8/6K1 b - - 1 1", "legal_reply_count": 4, "branches": [ { "reply": "Kh8", "fen": "r6k/8/8/3Q4/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Qxa8+", "fen": "Q6k/8/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Kh7", "fen": "Q7/7k/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg7", "fen": "Q7/6k1/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] }, { "reply": "Kh7", "fen": "r7/7k/8/3Q4/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Qxa8", "fen": "Q7/7k/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Kh6", "fen": "Q7/8/7k/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg6", "fen": "Q7/8/6k1/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg7", "fen": "Q7/6k1/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] }, { "reply": "Kg7", "fen": "r7/6k1/8/3Q4/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Qxa8", "fen": "Q7/6k1/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Kh7", "fen": "Q7/7k/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kh6", "fen": "Q7/8/7k/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg6", "fen": "Q7/8/6k1/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf6", "fen": "Q7/8/5k2/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf7", "fen": "Q7/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] }, { "reply": "Kf8", "fen": "r4k2/8/8/3Q4/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Qxa8+", "fen": "Q4k2/8/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Kg7", "fen": "Q7/6k1/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf7", "fen": "Q7/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke7", "fen": "Q7/4k3/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 5 } ] } ], "representative_final": "Q7/7k/8/8/8/8/8/6K1 b - - 0 2", "representative_gain": 5, "minimum_best_local_gain": 5 }, { "id": "defense", "fen": "r2qk3/8/8/1N6/8/8/8/6K1 w - - 0 1", "move": "Nc7+", "attacker": "c7", "targets": [ "e8", "a8" ], "capture": null, "representative": [ "Nc7+", "Qxc7" ], "scope": "Existence of one legal refutation is enough to disprove a guaranteed rook win; queen captures the checking knight, not the king or rook.", "first_move": "Nc7+", "after_fen": "r2qk3/2N5/8/8/8/8/8/6K1 b - - 1 1", "legal_reply_count": 5, "branches": [ { "reply": "Qxc7", "fen": "r3k3/2q5/8/8/8/8/8/6K1 w - - 0 2", "options": [] }, { "reply": "Kf8", "fen": "r2q1k2/2N5/8/8/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Nxa8", "fen": "N2q1k2/8/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Qe8", "fen": "N3qk2/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qe7", "fen": "N4k2/4q3/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qf6", "fen": "N4k2/8/5q2/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qg5+", "fen": "N4k2/8/8/6q1/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qh4", "fen": "N4k2/8/8/8/7q/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd7", "fen": "N4k2/3q4/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd6", "fen": "N4k2/8/3q4/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd5", "fen": "N4k2/8/8/3q4/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd4+", "fen": "N4k2/8/8/8/3q4/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd3", "fen": "N4k2/8/8/8/8/3q4/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd2", "fen": "N4k2/8/8/8/8/8/3q4/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd1+", "fen": "N4k2/8/8/8/8/8/8/3q2K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qc7", "fen": "N4k2/2q5/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qb6+", "fen": "N4k2/8/1q6/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qa5", "fen": "N4k2/8/8/q7/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qc8", "fen": "N1q2k2/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qb8", "fen": "Nq3k2/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qxa8", "fen": "q4k2/8/8/8/8/8/8/6K1 w - - 0 3", "gain": 2, "captures_attacker": true }, { "san": "Kg8", "fen": "N2q2k1/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kg7", "fen": "N2q4/6k1/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Kf7", "fen": "N2q4/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke7", "fen": "N2q4/4k3/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Ke8", "fen": "N2qk3/8/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false } ], "worst_next_reply_gain": 2 } ] }, { "reply": "Kf7", "fen": "r2q4/2N2k2/8/8/8/8/8/6K1 w - - 2 2", "options": [ { "capture": "Nxa8", "fen": "N2q4/5k2/8/8/8/8/8/6K1 b - - 0 2", "gain": 5, "black_replies": [ { "san": "Qe8", "fen": "N3q3/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qf8", "fen": "N4q2/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qg8+", "fen": "N5q1/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qh8", "fen": "N6q/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qe7", "fen": "N7/4qk2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qf6", "fen": "N7/5k2/5q2/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qg5+", "fen": "N7/5k2/8/6q1/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qh4", "fen": "N7/5k2/8/8/7q/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd7", "fen": "N7/3q1k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd6", "fen": "N7/5k2/3q4/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd5", "fen": "N7/5k2/8/3q4/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd4+", "fen": "N7/5k2/8/8/3q4/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd3", "fen": "N7/5k2/8/8/8/3q4/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd2", "fen": "N7/5k2/8/8/8/8/3q4/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qd1+", "fen": "N7/5k2/8/8/8/8/8/3q2K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qc7", "fen": "N7/2q2k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qb6+", "fen": "N7/5k2/1q6/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qa5", "fen": "N7/5k2/8/q7/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qc8", "fen": "N1q5/5k2/8/8/8/8/8/6K1 w - - 1 3", "gain": 5, "captures_attacker": false }, { "san": "Qb8", "fen": "Nq6/5k2/8/8/8/8/8/6K1 w - 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