White 66 vs Black 880

The two setups

White: setup #66 B N N R K B Q R

King on the e-file, rooks on d, h, queen on the g-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 66 gives White +0.22 (Morozov Balance Index, 400M nodes).

Black: setup #880 B B R Q K R N N

King on the e-file, rooks on c, f, queen on the d-file; one 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 880 gives White +0.63 (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 60.

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 same corridor is required at every deeper budget (8 G, 16 G) at which the pair has been evaluated.

The shallow rungs wandered between -12 and +18 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.

For comparison, in symmetric play setup 66 gives White +0.22 and setup 880 gives White +0.63: with both sides on the same rank the first move is worth something. In this pair Black's own setup absorbs that edge completely.

White is not forced into a single path: the best first move is b3, and 2 first moves are within 10 cp of it.

Along the engine's main line (30 moves) the largest swing was 61 cp (around move 5), ending at 0 cp — the position stays playable for both sides.

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 stays within the ±5 cp corridor up to 4 000 000 000 nodes.

Independent engines, run on the same position:

• Berserk 14: -3
• Lc0 0.32.1: -1

Independent confirmations: 3 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 +19, Black +128, difference -109. 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| 61 cp, mean 22.1 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 37.6 moves.

1. b3 f6 2. g3 c5 3. f4 b6 4. Bg2 Bxg2 5. Qxg2 d5 6. O-O e5 7. fxe5 fxe5 8. Nd3 Nf7 9. c4 d4 10. Nf2 Nf6 11. d3 O-O 12. Bb2 Nd6 13. Rde1 Qd7 14. Nd2 Nf5 15. Nd1 Rf7 16. Bc1 Re8 17. Ne4 Nxe4 18. Qxe4 h6 19. Nf2 Nd6 20. Qd5 Qb7 21. Qxb7 Rxb7 22. Kg2 Rd7 23. h4 Rf7 24. h5 Ref8 25. g4 Bc7 26. e3 Bd8 27. Nh3 Bh4 28. Rxf7 Nxf7 29. Re2 dxe3 30. Rxe3 Ng5 31. Rxe5 Nf3 32. Rd5 Ne1+ 33. Kh2 Rf3 34. Bd2 Nxd3 35. Ng1 Rg3 36. Ne2 Rf3 37. Kg2 Rf2+ 38. Kh3 Rxe2 39. Rxd3 Bg5 40. Bxg5 hxg5

1. b4 Nf6 2. g3 O-O 3. Bg2 e6 4. f4 d5 5. c4 b6 6. cxd5 Nxd5 7. Nc3 c5 8. bxc5 bxc5 9. Qf2 f6 10. O-O Nf7 11. d3 Nxc3 12. Bxc3 Bxg2 13. Kxg2 e5 14. Nb3 Re8 15. e4 exf4 16. gxf4 c4 17. dxc4 Qc7 18. Rd4 Nd6 19. Nd2 a5 20. Qf3 Ba7 21. Bxa5 Qxa5 22. Rxd6 Rcd8 23. Rxd8 Rxd8 24. Nb3 Qxa2+ 25. Kh1 Rb8 26. Ra1 Qc2 27. Rxa7 h6 28. Qg3 Qxe4+ 29. Kg1 Qb1+ 30. Kg2 Qe4+ 31. Kg1 Qb1+ 32. Kg2 Qe4+

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 66 / 880 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): bbrqkrnn/pppppppp/8/8/8/8/PPPPPPPP/BNNRKBQR w DHcf - 0 1

Mirror twin: White 887 vs Black 79 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 296.