Starting position #801
Back-rank setup: BRKBQNRN
SP-801 · BastionScout — Off-centre king plus a rim knight (a/h): 168 positions carry this shape.
Move the pieces right on the board — full Chess960 rules, castle by dropping the king on the rook.
Position features
The king starts on c1, the rooks on b1 and g1, the queen on e1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
One second-rank pawn starts with no defender at all: a2.
The setup belongs to the BastionScout family; read right to left it becomes position 155.
The engine's main line opens with f4.
Every sentence here is computed from the setup itself and can be checked on the board.
Balance
MBI 96 Morozov Balance Index: 96 of 100 — class A — most balanced.
- Engine evaluation of the starting position: +11 centipawns for White (depth 42, 400 000 000 nodes).
- Rank 35 of 960 by balance — 1 is the most balanced start.
- In 50 self-play games White scored 51.0% (95% CI 37.6–64.3%).
- Balance band S — slight edge · dynamics along the play-out: stable
- Evaluation along the engine's main line (62 half-moves): +34 → +10 → +17 → +11 → +13
- Deeper check (1 200 000 000 nodes, depth 50): +17 cp, +6 cp against the base run — verified
Position facts
- Mirror twin: position #155
- The king starts on c, the rooks on b and g
- King and rook are neighbours — castling from adjacent squares feels unusual
- It becomes the daily position in 17 days
Puzzles from this position
- Attack on the uncastled king: pawn to f4 (g3·6) — Chess960 specifics · 780
- Attack on the uncastled king: pawn to c5 (d4·4) — Chess960 specifics · 780
- Attack on the uncastled king: rook to b4 (b1·3) — Chess960 specifics · 780
- Attack on the uncastled king: bishop to g7 (a1·7) — Chess960 specifics · 780
- Winning blow: king to c1 (b1·7) — Chess960 specifics · 970
- Winning blow: rook to e5 (d5·3) — Chess960 specifics · 1280
- Mate in 2: queen to b8 (b5) — Chess960 specifics · 1320
- Winning blow: knight to f6 (e4·22) — Chess960 specifics · 1340
- Mate in 3: bishop to e5 (c3·2) — Chess960 specifics · 1630
- Winning blow: pawn to b8 (b7·15) — Chess960 specifics · 2060
This position appears in course day 41
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Commentary
The king already stands on c1, so long castling moves the rook alone; the rooks are on b1 and g1. A bishop holds the corner on a1 with one diagonal to h8; the second bishop is on d1, running to a4 on one side and h5 on the other. On the second rank, a2 is the one that begins without a defender. The queen is on e1, the knights on f1 and h1 — the cornered one has only g3 at the start, which is why the Nf2 of the line arrives after the f-pawn has stepped up. The engine finds almost nothing for White here — +11 centipawns — and the line runs f4 d5 b3 b6 Nf2 e6.
Written from the measured facts above and checked against the board before publishing. All 960 positions have one.