White 281 vs Black 502
White starts from setup 281 (NRKBBNRQ), Black from setup 502 (RQBNKBNR). 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 #502 R Q B N K B N R
King on the e-file, rooks on a, h, queen on the b-file; no 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 502 gives White +0.21 (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 -8 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 281 gives White +0.16 and setup 502 gives White +0.21: 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 f4; the alternatives are slightly weaker but keep the game level.
Along the engine's main line (30 moves) the evaluation stayed within ±20 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.
| Stage | Nodes | Depth | Eval, cp | Main line |
|---|---|---|---|---|
| S0 | 100 000 | 17 | -8 | 1. e4 e6 2. f4 b5 3. Bf3 a5 4. O-O-O b4 |
| S1 | 500 000 | 18 | +4 | 1. f4 c6 2. f5 d5 3. g4 e5 4. e4 d4 |
| S2 | 2 000 000 | 23 | +2 | 1. f4 c5 2. g3 b5 3. e4 e5 4. Ne3 c4 |
| S3 | 8 000 000 | 26 | +18 | 1. f4 c6 2. f5 h5 3. g4 hxg4 4. Bg3 d6 |
| S4 | 32 000 000 | 32 | +2 | 1. f4 c6 2. f5 h5 3. g4 hxg4 4. e4 e5 |
| S5 | 128 000 000 | 43 | 0 | 1. e4 e5 2. f4 Bc5 3. fxe5 Ne7 4. Nb3 Bxg1 |
| S6 | 400 000 000 | 45 | 0 | 1. e4 a5 2. f4 b5 3. Ne3 b4 4. g3 e5 |
| S7 | 800 000 000 | 51 | 0 | 1. f4 a5 2. e4 e5 3. fxe5 Bc5 4. Ng3 Bxg1 |
| S8 | 1 600 000 000 | 58 | 0 | 1. f4 a5 2. e4 e5 3. fxe5 Bc5 4. Ng3 Bxg1 |
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: 0
- Lc0 0.32.1: -6
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 +17, difference +16. 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.
| # | Eval, cp | Depth | Main line |
|---|---|---|---|
| 1 | 0 | 40 | 1. f4 c6 2. f5 d5 3. g4 Qe5 4. c3 h5 5. Bc2 hxg4 |
| 2 | -22 | 40 | 1. e4 e5 2. f4 Bc5 3. fxe5 a5 4. Ng3 Bxg1 5. Qxg1 Ne7 |
| 3 | -25 | 39 | 1. g4 c5 2. e3 Nc6 3. Ng3 e6 4. c3 d5 5. f4 Bd6 |
Main-line play-out
30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 20 cp, mean 6.0 cp, final 0 cp.
| # | White | cp | Black | cp |
|---|---|---|---|---|
| 1 | f4 | +11 | a5 | +12 |
| 2 | e4 | +7 | b5 | -8 |
| 3 | Ne3 | +10 | a4 | +14 |
| 4 | c3 | +10 | e6 | +18 |
| 5 | g3 | +20 | c5 | +14 |
| 6 | Bf3 | +11 | Ba6 | +15 |
| 7 | d3 | +7 | Ne7 | -3 |
| 8 | Nac2 | -9 | Nec6 | -5 |
| 9 | Bf2 | -3 | b4 | -10 |
| 10 | Nc4 | -5 | Be7 | -4 |
| 11 | O-O | -9 | O-O | -14 |
| 12 | h4 | -6 | Na5 | -13 |
| 13 | e5 | -2 | Ra7 | 0 |
| 14 | N2e3 | +3 | Nxc4 | -10 |
| 15 | dxc4 | 0 | Bb7 | -6 |
| 16 | h5 | -7 | h6 | -14 |
| 17 | cxb4 | -8 | Bxf3 | -17 |
| 18 | Qxf3 | -8 | Qxb4 | -9 |
| 19 | Qe2 | -7 | Nc6 | -7 |
| 20 | Nc2 | -2 | Qb6 | -6 |
| 21 | Rfd1 | -6 | Rb7 | -11 |
| 22 | Qe4 | 0 | Rfb8 | 0 |
| 23 | Na3 | 0 | Nd4 | 0 |
| 24 | Bxd4 | 0 | cxd4 | 0 |
| 25 | Nb5 | 0 | d3+ | 0 |
| 26 | Kg2 | 0 | Qc6 | 0 |
| 27 | Kf3 | 0 | f6 | 0 |
| 28 | Qxc6 | 0 | dxc6 | 0 |
| 29 | Nd4 | 0 | Rxb2 | 0 |
| 30 | Rxb2 | 0 | Rxb2 | 0 |
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 34.7 moves.
Sample game 1 (1/2-1/2)
1. e3 h5 2. f4 a5 3. e4 b5 4. Ne3 Bb7 5. g3 Nf6 6. Bf3 Ng4 7. Nxg4 hxg4 8. Bxg4 Qa7 9. O-O-O Nc6 10. Qg2 a4 11. Bf2 Qa5 12. h4 e6 13. Be2 b4 14. Kb1 Na7 15. Rge1 b3 16. g4 bxa2+ 17. Kxa2 d5 18. f5 O-O-O 19. fxe6 fxe6 20. Bxa7 Qxa7 21. h5 dxe4 22. Bc4 Be7 23. Rxe4 a3 24. b3 Kb8 25. d4 Bxe4 26. Qxe4 Rhf8 27. Qxe6 Bg5 28. Qe5 Bf6 29. Qb5+ Qb6 30. c3 Qxb5 31. Bxb5 c5 32. Bd3 Kc7 33. Nc2 cxd4 34. c4 Be7 35. b4 Rf4 36. c5 Rxg4 37. Nxa3 Rb8 38. Kb3 Bxc5 39. Nb5+ Kc6 40. Rc1 Rg5 41. Nxd4+ Kd6 42. Nf5+
Sample game 2 (1/2-1/2)
1. e4 e5 2. g3 b5 3. c3 Bb7 4. f4 f5 5. fxe5 Bxe4 6. Bf3 Qb7 7. Bg2 d6 8. Ne3 Bxg2 9. Qxg2 Qxg2 10. Rxg2 g6 11. exd6 Bxd6 12. a4 a6 13. Nb3 Nf6 14. Ra1 Rb8 15. axb5 axb5 16. Nc2 O-O 17. Re2 Nc6 18. Ncd4 Ne5 19. Kc2 Rfe8 20. d3 c5 21. Ra6 cxd4 22. Rxd6 Nf3 23. Kd1 dxc3 24. Bxc3 Ng4 25. Rb6 Rxb6 26. Rxe8+ Kf7 27. Rh8 g5 28. Rxh7+ Kg6 29. Rg7+ Kh6 30. Rf7 Kg6 31. Rg7+ Kh6 32. Rf7 b4 33. Bh8 Rd6 34. Ke2 Kg6 35. Rg7+ Kh5 36. Rh7+ Kg6 37. Rg7+ Kh5 38. Rh7+ Kg6
Play it in the CH960 app
Open this page on a phone with the CH960 app installed, or find pair 281 / 502 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): rqbnkbnr/pppppppp/8/8/8/8/PPPPPPPP/NRKBBNRQ w BGah - 0 1
Mirror twin (the same position mirrored): White 585 vs Black 550.