Interchange Chess

After inventing Palindromic Chess, I play-tested the game with Fergus Duniho. Our finding was that the game is not very playable, due to problems identifying illegal positions, and as Fergus commented, "the game plays like a marriage where neither side ever fights". So, after some thought, Fergus suggested some changes to the rules, which after trying out the resulting game, seemed to resolve any playability problems. So, Interchange Chess is the result.

In Palindromic Chess, Alexandre Muñiz suggested that players move one of their own pieces and also one of the opponent's pieces. That rule still makes sense here, so I'm keeping it. In fact, the rule adds some zest to the game because you are allowed to mess up your opponent's carefully planned moves.

The object of the game is to get as many of your own pieces to their destination squares (on the other side of the board) as possible. There are no illegal positions to worry about.

Initial Array

   +---+---+---+---+---+---+---+---+
 8 |lr | n | b | k | q | b | n | rr|  Ortho-chess setup except:  
   +---+---+---+---+---+---+---+---+  
 7 | p | p | p | p | p | p | p | p |  1. Black King and Queen positions are switched.
   +---+---+---+---+---+---+---+---+  2. Left-Handed Rooks on a8 and h1.
 6 |   |   |   |   |   |   |   |   |  3. Right-Handed Rooks on a1 and h8.
   +---+---+---+---+---+---+---+---+
 5 |   |   |   |   |   |   |   |   |
   +---+---+---+---+---+---+---+---+
 4 |   |   |   |   |   |   |   |   |
   +---+---+---+---+---+---+---+---+
 3 |   |   |   |   |   |   |   |   |
   +---+---+---+---+---+---+---+---+
 2 | P | P | P | P | P | P | P | P |
   +---+---+---+---+---+---+---+---+
 1 |RR | N | B | Q | K | B | N | LR|
   +---+---+---+---+---+---+---+---+
     a   b   c   d   e   f   g   h

Rules

Ortho-chess rules, except:

No capturing is allowed.
All pieces must move forward (except the rooks, which may move sideways).
Pawns move one square forward orthogonally or diagonally (same as the King).
A player's turn consists of two actions. The first action is for the player to move one of their own pieces. The second action is for the player to move an opponent's piece. If a player has to pass on moving their own piece because no legal move is available, they still may move an opponent's piece (and vice-versa).
There is no check or checkmate. See below for winning conditions.
Castling is not allowed.
Initial orthogonal two-square move for pawns is allowed. Pawns cannot move to the last rank, nor can they promote.
RR is a Right-handed Rook. When this rook moves sideways, it must move to the (player's) right. LR is a Left-handed Rook. When this rook moves sideways, it must move to the (player's) left. Fergus suggests using an inverted Rook for the Left-handed Rook (the up-right Rook is then the Right-handed Rook).

Winning Conditions

Players continue to move until no legal moves are left. Pieces move until they reach one of their destination squares, or it is no longer possible for them to make a legal move. At the end of the game, the winning player is the one who has moved more of their pieces to their destination squares. If both players have achieved the same number, then the game is a draw.

Note that the destination square of a piece is the starting square of the same type of opponent's piece. So the pawn on a2 has a destination of any of the squares on the 7th rank. Right- and Left-handed Rooks are considered to be different types.

In the above example, the game is over since neither side can move. White has won since there are 11 white pieces on their destination squares, and black only has 10.

Notes

The game is easily implemented in Zillions-of-Games Rules, except for the winning condition, which looks like it may be difficult.

Variations

Instead of counting the number of pieces that end up in their destination squares, add up their values. Player achieving the higher sum wins. Pawns = 1, Knights & Bishops = 3, Rooks = 5, Queens = 9, Kings = 3.
Players cooperate to see if they can get all their pieces to their destination squares. This may or may not be difficult.

Written by David Howe. Game designed by David Howe, Fergus Duniho and Alexandre Muñiz. Diagrams created using Chess Captor.

WWW page created: February 19, 2000.