White 273 vs Black 611

The two setups

White: setup #273 B N R B K N R Q

King on the e-file, rooks on c, g, queen on the h-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 273 gives White +0.46 (Morozov Balance Index, 400M nodes).

Black: setup #611 B R N Q K R N B

King on the e-file, rooks on b, f, 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 611 gives White +0.15 (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 55.

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 wandered between -21 and 0 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.

For comparison, in symmetric play setup 273 gives White +0.46 and setup 611 gives White +0.15: 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 b3; the alternatives are slightly weaker but keep the game level.

Along the engine's main line (30 moves) the evaluation stayed within ±25 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 10, Black won 0 (White scored 50.0%).

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: -7
• Lc0 0.32.1: +9

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 +65, Black +72, difference -7. 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, 10 draws, 0 Black wins, White scored 50.0%.

Best first moves

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

Main-line play-out

30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 25 cp, mean 9.1 cp, final 0 cp.

Engine self-play

10 games at 500 000 nodes per move: White won 0, drawn 10, Black won 0 — White scored 50.0%. Average length 40.5 moves.

1. b3 e6 2. h4 f5 3. g4 b6 4. Qh2 fxg4 5. h5 Nd6 6. Ne3 Nf6 7. c4 Qe7 8. Nxg4 g6 9. Nxf6+ Bxf6 10. Bxf6 Qxf6 11. c5 bxc5 12. Rxc5 Rb4 13. f3 Rh4 14. Qe5 Qxe5 15. Rxe5 Rf5 16. hxg6 hxg6 17. Re3 Ra5 18. a4 Rah5 19. Nc3 Ke7 20. Rxg6 Nf5 21. Re5 Rh1+ 22. Kf2 R1h2+ 23. Ke1 Rh1+ 24. Kf2 R1h2+ 25. Ke1

1. c4 g6 2. d3 Nd6 3. Nfd2 f5 4. e3 b5 5. cxb5 Nxb5 6. h4 Nh6 7. Qh3 O-O 8. O-O e6 9. Bf3 Bd5 10. Bxd5 exd5 11. Nc3 Nxc3 12. bxc3 Ng4 13. Nf3 Rb6 14. c4 Bxa1 15. Rxa1 dxc4 16. dxc4 Nf6 17. Qg3 d6 18. Qf4 Ne4 19. Ng5 Qe7 20. Nxe4 fxe4 21. Qg4 Rc6 22. Rad1 Rxc4 23. Rd5 Rc2 24. Ra5 Qf7 25. Rxa7 Rxf2 26. Rc1 Rf1+ 27. Rxf1 Qxf1+ 28. Kh2 Qc1 29. Qxe4 Rf1 30. Ra8+ Kg7 31. Qe7+ Rf7 32. Qe8 Qc4 33. Ra4 Qd5 34. a3 c5 35. Rf4 Rxf4 36. exf4 c4 37. Qe7+ Kg8 38. Qe8+ Kg7 39. Qe7+ Kh6 40. g4 Qd2+

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 273 / 611 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): brnqkrnb/pppppppp/8/8/8/8/PPPPPPPP/BNRBKNRQ w CGbf - 0 1

Mirror twin (the same position mirrored): White 587 vs Black 243.