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Standard Castling Rules

Fischer Random castling rules are built on the established castling rules from classical chess. Just as a quick refresher, those four rules are:
1. The king and castling rook cannot have moved before castling.
2. The king cannot castle out of check/checkmate.
3. The king cannot castle through check.
4. The pieces in between the king and rook must move out of the way before castling.

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Fischer Random rules stipulate that the final placement for both the king and rook when castling is constant. 
This means that if White wants to castle kingside, the king must land on the g1 square, and the kingside rook must land on f1. 
Should White want to castle queenside, the king must land on c1, and the queenside rook lands on d1

>>> https://www.chess.com/article/view/how-to-castle-in-fischer-random-chess
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