White 213 vs Black 731

The two setups

White: setup #213 N Q B B R K N R

King on the f-file, rooks on e, h, queen on the b-file; no bishop starts in a corner; the knights start away from the centre. Castling follows the Chess960 rule: king and rook end on the classical squares. In ordinary symmetric play setup 213 gives White +0.28 (Morozov Balance Index, 400M nodes).

Black: setup #731 R K N Q B N R B

King on the b-file, rooks on a, g, queen on the d-file; one bishop starts in a corner; the knights start on central files. Castling follows the Chess960 rule: king and rook end on the classical squares. In ordinary symmetric play setup 731 gives White +0.31 (Morozov Balance Index, 400M nodes).

Why the pair is balanced

At the deepest rungs (400M, 800M, 1.6B nodes) the evaluation is exactly 0.00 each time, reaching search depth 56.

Admission rule: |cp| ≤ 5 at four budgets up to 4 billion nodes, no one-sided drift along the ladder, and confirmation by two independent engines — Berserk and Lc0 — each below its own median on symmetric positions.

The shallow rungs agreed early: from 100 thousand to 128 million nodes the evaluation never left ±11 cp.

For comparison, in symmetric play setup 213 gives White +0.28 and setup 731 gives White +0.31: with both sides on the same rank the first move is worth something. In this pair Black's own setup absorbs that edge completely.

The engine's first choice for White is e4; the alternatives are slightly weaker but keep the game level.

Along the engine's main line (23 moves) the evaluation stayed within ±26 cp the whole way: the balance holds as the pieces come out, not only on move one.

Engine self-play agrees: 10 games, White won 0, drawn 9, Black won 1 (White scored 45.0%).

Verification ladder

Nine independent searches of the starting position, each with a larger node budget. Evaluation in centipawns from White's point of view.

Deep verification

The search ladder reaches 1.6 billion nodes; admission needs a 4-billion rung and two further engines on top of that. Beyond even that, every pair was re-checked at budgets up to ten times larger and in thousands of self-play games. This section shows what each check returned for this pair.

This pair held exactly 0.00 up to 1 600 000 000 nodes.

Independent engines, run on the same position:

• Berserk 14: 0
• Lc0 0.32.1: -13

Independent confirmations: 2 of 3. An engine counts as confirming when its reading of the pair is closer to equality than its own reading of a typical symmetric Chess960 position (+10 for Berserk, +18 for Lc0). Where only one engine confirms, the pair is balanced according to that engine alone, and this page says so.

Own weight of each setup, measured against the classical array: White +78, Black +96, difference -18. A balanced pair needs White's setup to be weaker by about the price of the first move.

Extended self-play: 10 games, 0 White wins, 9 draws, 1 Black wins, White scored 45.0%.

Best first moves

The 3 best first moves for White, searched together at 400 000 000 nodes.

Main-line play-out

23 moves, 5 000 000 nodes per half-move. Largest |evaluation| 26 cp, mean 6.2 cp, final 0 cp.

Engine self-play

10 games at 500 000 nodes per move: White won 0, drawn 9, Black won 1 — White scored 45.0%. Average length 44.0 moves.

1. e4 e5 2. d3 f5 3. exf5 g6 4. Nf3 d6 5. fxg6 Bxg6 6. c3 Qd7 7. O-O Ne7 8. Bb3 Ne6 9. Nh4 d5 10. Nxg6 Nxg6 11. Kh1 Nh4 12. Rg1 O-O-O 13. Bd1 Rdf8 14. Qc2 a5 15. Qe2 Kb8 16. Nc2 Rf6 17. d4 Qf7 18. Ref1 exd4 19. Nxd4 Nxd4 20. cxd4 Nf5 21. Qd3 h5 22. h3 Qh7 23. Be2 Rff8 24. Bf4 Bxd4 25. Qd2 Bb6 26. Qxd5 Nd4 27. Bc4 Ne2 28. Bxc7+ Qxc7 29. Bxe2 Qc5 30. Qe6 Re8 31. Qb3 Rg5 32. Bf3 Re7 33. Qd3 Ka7 34. b4 Qxb4 35. Rb1 Qd4 36. Qxd4 Bxd4 37. Rgf1 h4 38. Rbd1 Bb6 39. Rd2 Rf5 40. Rb1 Bc5 41. Rc2 b6 42. Kg1 Rf4 43. Kf1 Ka6 44. Rbc1 a4 45. Rc4 Ref7 46. Rxf4 Rxf4 47. Ke2 Rb4 48. Rc2 Bd6 49. Ke3 Bf4+ 50. Ke2 Bd6 51. Bd5 Ka5 52. Ke3 b5 53. Be4 Rb1 54. Kf3 Re1 55. Re2 Rxe2 56. Kxe2 b4 57. Bc2 b3 58. Bxb3 axb3 59. axb3 Kb4 60. Kf3 Kxb3 61. g4 Kc4 62. Ke4 Bb4 63. f4 Bc3 64. Kf5 Kd4 65. Kg6 Bb4 66. f5 Ke5 67. g5 Bd2 68. f6 Kf4 69. f7 Bb4 70. Kh5 Kf5

1. e4 f5 2. c3 fxe4 3. Qxe4 g5 4. d4 a5 5. Nf3 h6 6. O-O Ng6 7. Nc2 Ra6 8. c4 d5 9. Qxd5 Qxd5 10. cxd5 Nf4 11. Bxf4 gxf4 12. Ne5 Rd6 13. Re4 Rf8 14. Bf3 Nb6 15. Rd1 Rxd5 16. Nd3 Bg6 17. Re2 Rb5 18. b3 Bxd3 19. Rxd3 Bf6 20. a4 Rf5 21. Be4 Rh5 22. Rf3 e5 23. dxe5 Rxe5 24. Kf1 Rfe8 25. Bd3 Nd5 26. g4 fxg3 27. hxg3 Rxe2 28. Bxe2 Bg7 29. Bc4 Nb6 30. Ne3 Rf8 31. Kg2 Nd7 32. Bd3 c6 33. Bc2 Rd8 34. Nc4 Ne5 35. Nxe5 Bxe5 36. Bd3 Kc7 37. Bc4 Rd6 38. Rf7+ Rd7 39. Rf5 Bc3 40. Kh3 Rd6 41. Rf7+ Rd7 42. Rf3 Be1 43. Rf6 Rd6 44. Rf7+ Rd7 45. Rf5 Bc3 46. Rf3 Be1 47. Kg2 Bb4 48. Rf5 Bc3 49. f4 Rg7 50. Kf3 Be1 51. g4 Bc3 52. Kg3 Be1+ 53. Kf3 Bc3 54. Rf8 Rd7 55. Rg8 Rg7 56. Re8 Rd7 57. f5 Bf6 58. Rf8 Be7 59. Rg8 Bg5

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 213 / 731 in the app's encyclopedia, then choose how to play.

• Local game — two players on one device, with a clock.
• With a mentor — a clearly labelled training bot with hints, at your level.
• Challenge a friend — an online game by link; both players get the same pair, colours swap on rematch.

Play this pair against the computer, right here Play a friend

FEN (Shredder, castling rights by rook files): rknqbnrb/pppppppp/8/8/8/8/PPPPPPPP/NQBBRKNR w EHag - 0 1

Mirror twin (the same position mirrored): White 650 vs Black 417.