Simplify the following text for a Grade 6 native English-speaking person.
Original: A player who performs a forbidden castling must return the king and the rook to their original places and then move the king , if there is another legal king move , including castling on the other side .
Simplified: In castling , the king is moved two squares toward the rook , and the rook moves past the king to the square right next to where the king has moved . Castling takes one move , and is the only way for a player to move two of his own pieces on the same move .