FA-82687 / Chess move legality / Member archive

Chess960 king moved two squares as in standard chess · case 02

King b1 castling kingside is treated as landing on d1, so attacks on g1 are never checked.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Input: {"board", "side", "wing", "king_from", "rook_from"}; rights are assumed held. Chess960 castling: the king ends on g (kingside) or c (queenside) and the rook on f or d; the kingside rook must be on the king's h-side and the queenside rook on its a-side. Every square from the leftmost to the rightmost of king start, king end, rook start and rook end must be empty apart from the castling king and rook, and no square the king stands on or passes through (start to end inclusive) may be attacked.

Why this case matters

Chess960 castling generalizes standard rules; standard-chess shortcuts break it.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
rook destination occupied	`true`	`false`	Failed

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