Advanced Game Rules

How Important are these Rules?

With the exception of Promotion, most of these rules are only used in games between highly skilled players. Even computerized Chess games rarely, if ever, have their AI players perform Castling or En Passant.

But, while many players aren't likely to encounter these rules in casual play, it can be useful to understand them.

	Castling
Castling is a defensive move that allows a player to hide their King and expose a Rook on the same turn. To Castle, the King moves two spaces towards their Rook, and the Rook moves to the opposite side of the King. However, Castling is only permitted if the following conditions are met: The King has not moved yet. The Rook has not moved yet. There are no pieces blocking the path between the King and the Rook. None of the spaces between the King and its new position are threatened.

	En Passant
When a Pawn is first moved, it may move one or two spaces forward. Moving two spaces can be an advantage sometimes, but En Passant provides the other player a way to counter this. If a Pawn moves two spaces on its first turn, and this places it next to an enemy Pawn, the enemy Pawn may move diagonally (as if attacking an empty space) to capture the first Pawn. In other words, the enemy Pawn may capture the first Pawn "in passing", which is the meaning of En Passant.

	Promotion
You might have noticed that Pawns will not be able to move if they reach the far side of the chessboard. Promotion solves this dilemma by allowing the player to replace the Pawn with a new piece of their choosing (usually a Queen, for obvious reasons).