Bottleneck Chess is a chess variant designed for the 41 Squares Contest in http://www.chessvariants.com by Koksal Karakus in 2001.
 
Other than that, the only difference from the usual chess is the movement of the pawns. Here the pawns move one square in the NW direction for white or one square in the SE direction for black (diagonally). Pawns can capture one square in the N or W direction for white, or one square S or E direction for black (orthogonally).
 
One thing to note is that Knights cannot jump to a square if all of the three squares between them are outside the board, which for example applies to the inner Knight at the beginning of the game.
 
There is no en-passant rule or castling.
 
The aim is to checkmate to opponent's King.