Chess Variants/Cylinder Chess

Introduction
Cylinder Chess (also known as Cylindrical Chess) is a variant that alters the geometry of the board, turning it from a flat plane into a cylinder. This altered geometry allows for pieces to make sneaky surprise attacks and enriches the tactical opportunities chess offers.

History
Cylinder chess is a rather old variant. In 947 CE the Arabic historian Ali al-Masudi wrote a chess book that described six different variants of chess (then known as shatranj), and cylinder chess was amongst the variants described. The variant's unique board geometry has also been used in chess problems.

Rules
Cylinder chess is played using the exact same starting position and rules as the standard game, with one key difference - the board is assumed to be a cylinder, with the a- and h- files connected. If a piece moves off the edge of the board, it loops around to the other side and may keep moving. So for instance, a rook on a3 could move to h3 even if there was a piece on b3, since the rook could loop around the board to get to h3.

Usually, it is forbidden to make a move that would leave the board position unchanged, such as moving a rook across an empty rank to the square where it started. Also, pawns can capture en passant over the board edge (e.g. if White has a pawn on h5 and black a pawn on a7, then if Black plays 1... a5 White can capture with 2. axh6).

There are two different version of the castling rules in Cylinder chess:


 * One version outright eliminates castling altogether. The proponents of this version state that the altered board geometry makes all of the files equivalent, defeating the purpose of castling.
 * The other version allows the king to castle like normal, but allows it to castle with the wrong rook, over the board edge, if the player so wishes. So for instance the king could castle kingside with the queen's rook, moving the king from e1 to g1 and the queen's rook from a1 over the board edge to f1.

Sub-variants

 * Horizontal cylinder chess turns the board into a horizontal cylinder, with the first and eighth ranks connected. Due to this, a different starting position is used so the kings do not check each other at game start.
 * Toroidal chess combines both standard cylinder chess and horizontal cylinder chess, with both files and ranks connected. Due to this, a different starting position is used so the kings do not check each other at game start.