White 63 vs Black 105

The two setups

White: setup #63 N N R Q K R B B

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 63 gives White +0.23 (Morozov Balance Index, 400M nodes).

Black: setup #105 Q N R B B N K R

King on the g-file, rooks on c, h, queen on the a-file; no bishop starts in a corner; the knights start on central files. The king already stands on a castled square, so one of the castlings moves only the rook. In ordinary symmetric play setup 105 gives White +0.35 (Morozov Balance Index, 400M nodes).

Why the pair is balanced

At the deepest rungs (400M, 800M, 1.6B nodes) the evaluation never left ±1 centipawns of equality, reaching search depth 59.

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 -13 and +16 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.

For comparison, in symmetric play setup 63 gives White +0.23 and setup 105 gives White +0.35: 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 f4, and 3 first moves are within 10 cp of it.

Along the engine's main line (30 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 1, drawn 8, Black won 1 (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: -2
• Lc0 0.32.1: +5

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 +30, Black +45, difference -15. A balanced pair needs White's setup to be weaker by about the price of the first move.

Extended self-play: 10 games, 1 White wins, 8 draws, 1 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| 26 cp, mean 8.9 cp, final 0 cp.

Engine self-play

10 games at 500 000 nodes per move: White won 1, drawn 8, Black won 1 — White scored 50.0%. Average length 48.3 moves.

1. f4 b5 2. Be3 e6 3. a4 bxa4 4. g3 d5 5. c4 Bf6 6. Nc3 Bc6 7. cxd5 exd5 8. d4 h5 9. Nc2 a5 10. O-O Nbd7 11. Ne1 Nb6 12. Bf2 Be7 13. Nd3 Rh6 14. Ne5 Nfd7 15. Bg2 Bb4 16. Rc2 Bb7 17. Nxa4 Nxe5 18. Nxb6 Nf3+ 19. Bxf3 cxb6 20. Rxc8+ Qxc8 21. Qb3 h4 22. g4 Bd2 23. f5 Qe8 24. Ra1 h3 25. Be1 Bg5 26. Kf1 Rc6 27. Qd3 Qc8 28. Bxd5 Ba6 29. Qxh3 Rc2 30. Bf3 Rxb2 31. Bf2 Qe8 32. Kg1 Bxe2 33. Re1 Qb5 34. Be4 Rb3 35. Qg2 Rc3 36. Bd5 Qe8 37. Be4 Qb5 38. Bd5 Qe8 39. Be4

1. g3 c5 2. c3 d6 3. f4 Bc6 4. Bxc6 Nxc6 5. e4 Nd7 6. Bf2 b5 7. O-O O-O 8. d4 e6 9. Qe2 cxd4 10. cxd4 Bb6 11. Nb3 a6 12. Nc3 Na5 13. e5 dxe5 14. fxe5 Rc4 15. Rcd1 Nxb3 16. axb3 Rc7 17. d5 Qb7 18. Qe4 Bxf2+ 19. Rxf2 Nc5 20. Qb4 h6 21. h4 exd5 22. Nxd5 Rcc8 23. Qg4 Rfd8 24. Kh2 Ne6 25. Nf6+ Kf8 26. Ne4 Rxd1 27. Qxd1 Qxe4 28. Qd7 Rc7 29. Rxf7+ Kg8 30. Qe8+ Kh7 31. Qxe6 Rxf7 32. Qxf7 Qxe5 33. Qf2 a5 34. Qc2+ Kg8 35. Qc8+ Kh7 36. Qc2+ Kg8 37. Qc8+ Kf7 38. Qb7+ Kf6 39. Qc6+ Ke7 40. Qb7+ Ke6

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 63 / 105 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): qnrbbnkr/pppppppp/8/8/8/8/PPPPPPPP/NNRQKRBB w CFch - 0 1

Mirror twin: White 896 vs Black 857 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 277.