Royal Shuffle nomenclature
Our naming for Chess960, built only on facts you can verify on the board. Every one of the 960 starting positions belongs to exactly one family; a position and its mirror twin always share a family.
Position families
ThroneGuard (204 positions)
King on a central file (d/e) with both knights on inner files — the classic-type setup.
ThroneScout (204 positions)
King on a central file (d/e) with a knight starting on the rim (a/h).
BastionGuard (168 positions)
King off-centre on c or f with both knights on inner files.
BastionScout (168 positions)
King off-centre on c or f with a knight starting on the rim (a/h).
RampartGuard (144 positions)
King on the wing (b/g) with both knights on inner files.
RampartScout (72 positions)
King on the wing (b/g) with a knight on the rim (a/h) — the rarest family.
Mirror twin
MirrorTwin — The mirror twin of a position is found by reversing its back-rank piece order and looking up the resulting setup. It is a perfect pairing over all 960 positions with no position paired to itself (480 twin pairs); e.g. #518 ↔ #534.
Shuffle Rating
ShuffleRating — A deterministic difficulty score for a puzzle (scale 600–2400), computed by engine self-analysis — not a player rating. Base comes from mate distance or the search depth at which the key move is found, plus adjustments for extra moves, quiet first moves and sacrifices.
Shuffle Rating · TargetRating
TargetRating — The planned difficulty target of a course day — a curve rising over the 1000-day course with periodic deload days. Puzzles on a day are chosen so their Shuffle Rating sits near this target.
Key-square tag (square·N)
KeySquareTag — A tie-breaker in puzzle names, written (square·N): when two puzzles share a title, the departure square of the key move distinguishes them; a further clash appends an occurrence number N. It is a naming tag, not a board coordinate system.
Dataset
The full position → family table, byte-reproducible: