White 15 vs Black 203
White starts from setup 15 (QNNRKRBB), Black from setup 203 (QNRKBNRB). In the encyclopedia since 2026-10-21: neither side starts better.
|cp| ≤ 5 at 400M · 800M · 1.6B · 4B nodes, two independent engines agree
How to play with different setups
White sets up the pieces by position No. 15, Black by position No. 203, mirrored on their own side; the pawns stand as usual.
Moves as usual: White starts; everything else follows the Chess960 rules.
The two setups
White: setup #15 Q N N R K R B B
King on the e-file, rooks on d, f, queen on the a-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 15 gives White +0.27 (Morozov Balance Index, 400M nodes).
Black: setup #203 Q N R K B N R B
King on the d-file, rooks on c, g, queen on the a-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 203 gives White +0.43 (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 51.
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 -20 and +23 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.
For comparison, in symmetric play setup 15 gives White +0.27 and setup 203 gives White +0.43: 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 d4, and 3 first moves are within 10 cp of it.
Along the engine's main line (30 moves) the largest swing was 32 cp (around move 19), ending at 0 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 | +23 | 1. g3 d6 2. d4 g5 3. a4 c5 4. dxc5 Rxc5 |
| S1 | 500 000 | 18 | +1 | 1. d4 b6 2. f4 d6 3. Be3 g5 4. g3 Bc6 |
| S2 | 2 000 000 | 23 | +7 | 1. g3 c5 2. d4 cxd4 3. Nb3 d6 4. Nxd4 g5 |
| S3 | 8 000 000 | 26 | -20 | 1. g3 c5 2. c3 d6 3. d4 cxd4 4. cxd4 Bc6 |
| S4 | 32 000 000 | 35 | +11 | 1. d4 b6 2. f4 d6 3. d5 Qb7 4. g3 c5 |
| S5 | 128 000 000 | 38 | +9 | 1. f4 d6 2. d4 b6 3. d5 g5 4. fxg5 Rxg5 |
| S6 | 400 000 000 | 44 | +1 | 1. d4 b6 2. f4 d6 3. d5 g5 4. fxg5 Rxg5 |
| S7 | 800 000 000 | 51 | 0 | 1. d4 b6 2. f4 d6 3. d5 g5 4. fxg5 Rxg5 |
| S8 | 1 600 000 000 | 51 | 0 | 1. d4 b6 2. f4 d6 3. d5 g5 4. fxg5 Rxg5 |
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 | 0 |
| 8 000 000 000 | not checked |
| 16 000 000 000 | not checked |
This pair stays within the ±5 cp corridor up to 4 000 000 000 nodes.
Independent engines, run on the same position:
- Berserk 14: +1
- Lc0 0.32.1: +6
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 +11, Black +25, difference -14. 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 | 42 | 1. d4 b6 2. f4 d6 3. d5 c5 4. g3 g5 5. fxg5 Rxg5 |
| 2 | 0 | 42 | 1. g3 c5 2. f4 d6 3. a3 g6 4. Qa2 a5 5. Nc3 Ne6 |
| 3 | -5 | 41 | 1. f4 c5 2. d4 cxd4 3. Nb3 Nc6 4. Nxd4 Nxd4 5. Bxd4 Ne6 |
Main-line play-out
30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 32 cp, mean 12.1 cp, final 0 cp.
| # | White | cp | Black | cp |
|---|---|---|---|---|
| 1 | g3 | -12 | c5 | -17 |
| 2 | c3 | -12 | d6 | -13 |
| 3 | d4 | -22 | cxd4 | -26 |
| 4 | cxd4 | -16 | Bc6 | -8 |
| 5 | d5 | 0 | Bd7 | 0 |
| 6 | f4 | -4 | Bh3 | -4 |
| 7 | Rf3 | -3 | g6 | -6 |
| 8 | Ra3 | -6 | Na6 | 0 |
| 9 | Nc3 | 0 | Nd7 | 0 |
| 10 | Bd4 | 0 | Bxd4 | 0 |
| 11 | Rxd4 | -21 | O-O | -18 |
| 12 | Bf3 | -13 | Qb8 | -13 |
| 13 | Nd3 | -11 | Nb6 | -5 |
| 14 | b3 | -9 | Bf5 | -22 |
| 15 | e4 | -22 | Bd7 | -26 |
| 16 | Qb2 | -27 | Qc7 | -22 |
| 17 | Ne2 | -24 | e6 | -25 |
| 18 | dxe6 | -20 | fxe6 | -29 |
| 19 | e5 | -32 | d5 | -27 |
| 20 | Qd2 | -22 | Nb8 | -26 |
| 21 | Rxa7 | -23 | Nc6 | -24 |
| 22 | Ra3 | -22 | Be8 | -19 |
| 23 | Bg4 | -7 | Bf7 | -13 |
| 24 | Ra5 | -12 | Nd7 | -19 |
| 25 | Rb5 | -8 | Na7 | -2 |
| 26 | Ra5 | -7 | Nc6 | -4 |
| 27 | Rb5 | 0 | Nxd4 | 0 |
| 28 | Nxd4 | 0 | Rfe8 | 0 |
| 29 | Rb4 | 0 | g5 | 0 |
| 30 | Nb5 | 0 | Qb6 | 0 |
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 41.0 moves.
Sample game 1 (1/2-1/2)
1. f4 d6 2. a4 g5 3. fxg5 b6 4. Be3 Bc6 5. Nd3 Ne6 6. O-O-O Bxg2 7. Bxg2 Qxg2 8. Rxf7 Qe4 9. Qa2 Kd7 10. Rf3 Rcf8 11. Rg3 Nc6 12. Rdg1 Rf5 13. Nc3 Bxc3 14. bxc3 Qh4 15. Kb2 Rgf8 16. Ne1 Qxh2 17. R1g2 Qh4 18. Nf3 Qe4 19. Rg4 Nf4 20. Bxf4 Rxf4 21. d3 Rxg4 22. dxe4 Rxg2 23. Qc4 e5 24. Qb5 Re8 25. a5 a6 26. Qc4 Nxa5 27. Qf7+ Re7 28. Qf5+ Kd8 29. Qf8+ Kd7 30. Qf5+ Kc6 31. Qf6 Nc4+ 32. Kb3 Na5+ 33. Kb2 Nc4+ 34. Kb3 Na5+
Sample game 2 (1/2-1/2)
1. f4 g5 2. fxg5 b6 3. Be3 d6 4. Nd3 Bc6 5. O-O-O Bxg2 6. Bxg2 Qxg2 7. Rxf7 Kd7 8. a3 Ne6 9. Qa2 Qe4 10. Nc3 Bxc3 11. bxc3 Nc6 12. Rf3 Na5 13. Rg3 Rcf8 14. Rdg1 Nc4 15. a4 a6 16. Kb1 b5 17. Nb2 Nxe3 18. Rxe3 Rxg5 19. Rxe4 Rxg1+ 20. Nd1 Rxd1+ 21. Kb2 Nc5 22. Rb4 bxa4 23. d4 Rff1 24. dxc5 a3+ 25. Kxa3 Ra1 26. cxd6 Rxa2+ 27. Kxa2 cxd6 28. Rh4 Rf7 29. Kb3 Kc6 30. Ra4 Kb5 31. Rb4+ Kc5 32. Rc4+ Kd5 33. Ra4 Rf2 34. Rh4 Rf7 35. Ra4 Rf2 36. Rd4+ Kc6 37. Rh4 Rf7 38. Rc4+ Kd7 39. Rh4
Play it in the CH960 app
Open this page on a phone with the CH960 app installed, or find pair 15 / 203 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): qnrkbnrb/pppppppp/8/8/8/8/PPPPPPPP/QNNRKRBB w DFcg - 0 1
Mirror twin: White 944 vs Black 657 — a different position (castling squares are fixed), not evaluated by the search.
Current place in the live balance rating: 121.