Keys "s"=save "l"=load "b"=back once
You may castle, whether or not you are in check, passing over squares under attack and/or occupied squares, so long as neither king nor rook have been moved and the rook ends up on the far side of the king, not beyond the king's square.
This was the norm in Italy up into the 19th century.
Tim Harding on Free Castling
These are simple illustrations rather than strong opponents.
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