White 161 vs Black 283

The two setups

White: setup #161 B N R B N K Q R

King on the f-file, rooks on c, 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 161 gives White +0.06 (Morozov Balance Index, 400M nodes).

Black: setup #283 N R K N B R Q B

King on the c-file, rooks on b, f, queen on the g-file; one bishop starts in a corner; the knights start away from the centre. The king already stands on a castled square, so one of the castlings moves only the rook. In ordinary symmetric play setup 283 gives White +0.27 (Morozov Balance Index, 400M nodes).

Why the pair is balanced

At the deepest rungs (400M, 800M, 1.6B, 3.2B nodes) the evaluation is exactly 0.00 each time, reaching search depth 61.

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 agreed early: from 100 thousand to 128 million nodes the evaluation never left ±9 cp.

For comparison, in symmetric play setup 161 gives White +0.06 and setup 283 gives White +0.27: 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 b4, and 2 first moves are within 10 cp of it.

Along the engine's main line (30 moves) the largest swing was 33 cp (around move 20), ending at 0 cp — the position stays playable for both sides.

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 stays within the ±5 cp corridor up to 16 000 000 000 nodes.

Swap the two setups, giving White the black back rank and Black the white one, and the evaluation jumps to +148. The same two armies dealt the other way round are no longer balanced at all: that is how precisely this pair pays for the first move.

Independent engines, run on the same position:

• Berserk 14: 0
• 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 +61, Black +106, difference -45. A balanced pair needs White's setup to be weaker by about the price of the first move.

Extended self-play: 160 games, 0 White wins, 156 draws, 4 Black wins, White scored 48.8%.

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| 33 cp, mean 11.7 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 52.0 moves.

1. b3 Nc6 2. f4 O-O-O 3. Qf2 f5 4. O-O d6 5. c4 Kb8 6. e3 Nb6 7. Bf3 e5 8. Bxc6 Bxc6 9. fxe5 dxe5 10. Bxe5 Nd7 11. Bc3 Nf6 12. Bb4 Ne4 13. Qe2 Nd6 14. Nf3 g5 15. Nd4 Bxd4 16. exd4 Rfe8 17. Qh5 Ne4 18. d5 Bd7 19. Qh6 Qh8 20. Bc3 Nxc3 21. Nxc3 Rg8 22. Rce1 Qd4+ 23. Rf2 Rde8 24. Rxe8+ Rxe8 25. Kf1 f4 26. Re2 Rxe2 27. Nxe2 Qxd2 28. Qxg5 a5 29. Qg8+ Bc8 30. Qxh7 b5 31. Qe4 Qxa2 32. Nd4 Qa1+ 33. Kf2 a4 34. bxa4 bxa4 35. Nc6+ Ka8 36. c5 Bd7 37. d6 Qb2+ 38. Kf3 Qc3+ 39. Kxf4 Qc1+ 40. Kf3 Qa3+ 41. Ke2 Qb2+ 42. Ke3 Qa3+ 43. Ke2 Qb2+ 44. Ke3 Qc1+ 45. Kf3 Qc3+

1. b3 Nc6 2. f4 O-O-O 3. Qf2 f5 4. O-O d6 5. c4 Kb8 6. e3 Nb6 7. Bf3 e5 8. Bxc6 Bxc6 9. fxe5 dxe5 10. Bxe5 Nd7 11. Bc3 Nf6 12. Bb4 Ne4 13. Qe2 Nd6 14. Nf3 g5 15. Nd4 Bxd4 16. exd4 Rfe8 17. Qh5 Ne4 18. d5 Bd7 19. Qh6 Qh8 20. Bc3 Nxc3 21. Nxc3 Rg8 22. Rce1 Qd4+ 23. Rf2 Rde8 24. Rxe8+ Rxe8 25. Kf1 f4 26. Re2 Rxe2 27. Nxe2 Qxd2 28. Qxg5 a5 29. Qg8+ Bc8 30. Qxh7 b5 31. Qe4 Qxa2 32. Nd4 Qa1+ 33. Kf2 a4 34. bxa4 bxa4 35. Nc6+ Ka8 36. c5 Bd7 37. d6 Qb2+ 38. Kf3 Qc3+ 39. Kxf4 Qc1+ 40. Kf3 Qa3+ 41. Ke2 Qb2+ 42. Ke3 Qa3+ 43. Ke2 Qb2+ 44. Ke3 Qc1+ 45. Kf3 Qc3+

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 161 / 283 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): nrknbrqb/pppppppp/8/8/8/8/PPPPPPPP/BNRBNKQR w CHbf - 0 1

Mirror twin: White 795 vs Black 577 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 35.