How is this a castling move ?

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Avatar of CaydesSix
I’m in a standard 1 day game, the opponent had the king at g8 and a rook at h8. The game said he made a short castling move O-O on his turn by moving the rook to f8. How is this possible ?
Avatar of Staerex

It is possible because the game you are talking about is Chess960 variant and the starting square of the King can vary.

https://support.chess.com/article/347-chess960-fischer-random-chess

Avatar of CaydesSix
I see. Thanks !