White 281 vs Black 306
White starts from setup 281 (NRKBBNRQ), Black from setup 306 (BNQRKBRN). In the encyclopedia since 2026-10-03: neither side starts better.
|cp| ≤ 5 at 400M · 800M · 1.6B · 4B nodes, two independent engines agree
The two setups
White: setup #281 N R K B B N R Q
King on the c-file, rooks on b, g, queen on the h-file; no 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 281 gives White +0.16 (Morozov Balance Index, 400M nodes).
Black: setup #306 B N Q R K B R N
King on the e-file, rooks on d, g, queen on the c-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 306 gives White +0.33 (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 58.
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 -31 and +3 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.
For comparison, in symmetric play setup 281 gives White +0.16 and setup 306 gives White +0.33: 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 h4, and 2 first moves are within 10 cp of it.
Along the engine's main line (30 moves) the largest swing was 40 cp (around move 27), ending at -24 cp — the position stays playable for both sides.
Engine self-play agrees: 10 games, White won 1, drawn 9, Black won 0 (White scored 55.0%).
Verification ladder
Nine independent searches of the starting position, each with a larger node budget. Evaluation in centipawns from White's point of view.
| Stage | Nodes | Depth | Eval, cp | Main line |
|---|---|---|---|---|
| S0 | 100 000 | 14 | -31 | 1. e3 c5 2. Be2 e6 3. d4 cxd4 4. exd4 Ng6 |
| S1 | 500 000 | 17 | -2 | 1. c3 e6 2. Bc2 Ng6 3. O-O-O Be7 4. d4 O-O |
| S2 | 2 000 000 | 23 | -10 | 1. c3 Ng6 2. h4 b5 3. Qh2 e5 4. e3 Bd6 |
| S3 | 8 000 000 | 27 | -26 | 1. c3 Ng6 2. h4 b5 3. Qh2 e5 4. e3 Bd6 |
| S4 | 32 000 000 | 31 | -18 | 1. h4 b5 2. Qh3 e6 3. h5 f6 4. c3 Nf7 |
| S5 | 128 000 000 | 38 | +3 | 1. h4 c5 2. c3 Ng6 3. h5 Nf4 4. g3 Ne6 |
| S6 | 400 000 000 | 42 | 0 | 1. h4 c5 2. h5 b6 3. c3 g6 4. e3 Nc6 |
| S7 | 800 000 000 | 54 | 0 | 1. h4 c5 2. h5 b6 3. c3 g6 4. Bc2 Qa6 |
| S8 | 1 600 000 000 | 58 | 0 | 1. h4 c5 2. h5 b6 3. c3 g6 4. Bc2 Qa6 |
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.
| Nodes | Eval, cp |
|---|---|
| 4 000 000 000 | not checked |
| 8 000 000 000 | not checked |
| 16 000 000 000 | not checked |
This pair held exactly 0.00 up to 1 600 000 000 nodes.
Independent engines, run on the same position:
- Berserk 14: +6
- Lc0 0.32.1: +7
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 +33, Black +51, 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, 1 White wins, 9 draws, 0 Black wins, White scored 55.0%.
Best first moves
The 3 best first moves for White, searched together at 400 000 000 nodes.
| # | Eval, cp | Depth | Main line |
|---|---|---|---|
| 1 | 0 | 39 | 1. h4 c5 2. h5 b6 3. c3 g6 4. Bc2 Qa6 5. Ne3 Qxe2 |
| 2 | -3 | 39 | 1. g4 c5 2. h4 Nc6 3. c3 d5 4. h5 d4 5. Bc2 g6 |
| 3 | -20 | 38 | 1. c3 Ng6 2. h4 b5 3. Qh2 e5 4. e3 Bd6 5. h5 Ne7 |
Main-line play-out
30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 40 cp, mean 23.6 cp, final -24 cp.
| # | White | cp | Black | cp |
|---|---|---|---|---|
| 1 | c3 | -21 | Ng6 | -7 |
| 2 | h4 | -23 | b5 | -24 |
| 3 | d4 | -26 | c5 | -19 |
| 4 | Qh2 | -16 | e6 | -21 |
| 5 | h5 | -29 | Ne7 | -28 |
| 6 | dxc5 | -26 | d6 | -27 |
| 7 | Bc2 | -26 | dxc5 | -32 |
| 8 | f3 | -20 | b4 | -28 |
| 9 | Ne3 | -39 | Nd5 | -25 |
| 10 | Nxd5 | -26 | Bxd5 | -24 |
| 11 | Bh4 | -22 | Bd6 | -16 |
| 12 | Bg3 | -11 | Be7 | -15 |
| 13 | Bh4 | -14 | Bxa2 | -14 |
| 14 | O-O-O | -12 | bxc3 | -19 |
| 15 | bxc3 | -13 | Bd5 | -16 |
| 16 | Ba4+ | -15 | Bc6 | -16 |
| 17 | Bxe7 | -15 | Kxe7 | -16 |
| 18 | Nb3 | -24 | f6 | -29 |
| 19 | Qf4 | -19 | Kf7 | -21 |
| 20 | Bxc6 | -23 | Nxc6 | -23 |
| 21 | Qc4 | -27 | Ne5 | -24 |
| 22 | Qa4 | -17 | Qc7 | -30 |
| 23 | Kc2 | -25 | Rb8 | -32 |
| 24 | Ra1 | -32 | Nd7 | -25 |
| 25 | g3 | -31 | h6 | -31 |
| 26 | Qf4 | -36 | Ne5 | -29 |
| 27 | Qa4 | -19 | Rgd8 | -40 |
| 28 | Rgd1 | -28 | Rxd1 | -35 |
| 29 | Rxd1 | -29 | Kg8 | -39 |
| 30 | Ra1 | -25 | Qb6 | -24 |
Engine self-play
10 games at 500 000 nodes per move: White won 1, drawn 9, Black won 0 — White scored 55.0%. Average length 46.2 moves.
Sample game 1 (1/2-1/2)
1. c3 b5 2. Bc2 Ng6 3. O-O-O c5 4. Kb1 e6 5. d4 Nf4 6. Ng3 Na6 7. e3 Nd5 8. Ne2 cxd4 9. Nxd4 b4 10. c4 Qxc4 11. e4 Nb6 12. f3 Nc5 13. Bf2 Be7 14. Nab3 Rc8 15. Rge1 O-O 16. Nxc5 Qxc5 17. Bd3 Qc7 18. Qf1 Na4 19. Nb3 d6 20. Re2 Qb8 21. Bg3 Nc5 22. Nxc5 Rxc5 23. Rc1 Rc6 24. Rxc6 Bxc6 25. Rc2 Bd7 26. Ba6 h6 27. b3 Rd8 28. Qd3 Qb6 29. Bf2 Qa5 30. Bd4 h5 31. Qe2 e5 32. Be3 d5 33. exd5 Qxd5 34. Bd3 Qa5 35. Rc1 g6 36. Qc2 Rc8 37. Qd2 Rxc1+ 38. Qxc1 Kg7 39. Qc2 a6 40. Qd2 Bc8 41. Bh6+ Kh7 42. Be3 Kg7 43. Bh6+ Kh7 44. Be3
Sample game 2 (1/2-1/2)
1. g4 Nc6 2. c3 b5 3. Qd5 b4 4. f4 Ng6 5. Bg3 e6 6. Qh5 Qa6 7. f5 bxc3 8. dxc3 Qb6 9. e3 Nge5 10. Be2 h6 11. Nc2 g6 12. Qh3 gxf5 13. gxf5 Ne7 14. fxe6 Qxe6 15. Qxe6 dxe6 16. Nd4 h5 17. Bxh5 Be4 18. O-O-O Nd3+ 19. Rxd3 Bxd3 20. Nxe6 Rd6 21. Nxf8 Kxf8 22. e4 Ra6 23. a3 f5 24. exf5 Nxf5 25. Nd2 Nxg3 26. hxg3 Rf6 27. Bd1 Rf2 28. Bc2 Bb5 29. Ne4 Re2 30. Nc5 Rg5 31. b4 Ke7 32. a4 Bc4 33. g4 Rge5 34. Kb2 Rh2 35. Nb3 Ree2 36. Nd4 Rd2 37. b5 Kd6 38. g5 Kc5 39. g6 Rdg2 40. Rxg2 Rxg2 41. Ka3 Bd5 42. Bb1 Rg4 43. Bc2 Rg3 44. Kb2 Bg8 45. Nb3+ Kb6
Play it in the CH960 app
Open this page on a phone with the CH960 app installed, or find pair 281 / 306 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): bnqrkbrn/pppppppp/8/8/8/8/PPPPPPPP/NRKBBNRQ w BGdg - 0 1
Mirror twin (the same position mirrored): White 585 vs Black 359.