Martian Chess is an abstract strategy game for two to six players invented by Andrew Looney. It is played with Icehouse pieces on a chessboard or checkerboard; to play with a number of players other than two or four, a small distorted board is available which can be tiled to produce a board of the required size.


Rules

Initial setup
Each player starts with nine pieces: three small, three medium, and three large. The color of the pieces is irrelevant; for reasons given below, a mix of colors should be used.

In a two-player game, only half the board is used; a folding checkerboard is useful. The pieces are placed in the corners of the board as shown:



The players decide who moves first by a random method or by agreement. Play passes to the left after each move.


Movement and capturing
The red lines in the diagrams indicate notional canals that divide the board into territories. At any given time a player controls only those pieces that are in his or her territory.

The pieces may be moved as follows:

small pieces (pawns) move one space diagonally (unlike chess pawns, they may move backwards) 
medium pieces (drones) move one or two spaces horizontally or vertically 
large pieces (queens) move any distance horizontally, vertically or diagonally, just like a chess queen 
A piece is captured when an enemy piece lands on the square it occupies. The person who moved takes the piece and puts it aside for later scoring.

Since a piece is always owned according to the territory it is in, a player whose piece is captured immediately gains control of the capturing piece. It is easy to forget this if each player's starting pieces are all the same color, so it's better to start with a mix of colors instead (unless you have enough pieces that everyone can use the same color).

Pieces may not jump over other pieces, nor may they end a move on an occupied square except to capture.

The No Rejections rule: in the two-player game, you may not immediately reverse your opponent's last move.


End of game and scoring
The game ends when one player runs out of pieces (i.e., their territory becomes empty). Players then compute their scores by adding up the pips on their captured pieces: 3 per queen, 2 per drone, and 1 per pawn. The player or players with the highest total win.

In a variation of the four-player game, the players form two teams who play for a combined score. Teammates sit at opposite corners. Aside from strategic differences, play is unaffected; it is legal (and sometimes good strategy) to capture your teammate's pieces.


Strategy
Capturing with a queen often allows the opponent to immediately recapture, leading to a back-and-forth battle until one player runs out of pieces in the line(s) of capture. This is more common in two-player games, since other players may interfere in the four-player version. The net point difference is usually minor with two players, but can give the players involved a significant lead over the others in a four-player game.

More generally, remember that any piece used to capture becomes the opponent's, and consider which of your pieces will be vulnerable.

Moving a pawn or drone into enemy territory can be a good move for several reasons:

it can prevent an opponent from capturing the piece from you 
it can ensure that you capture that piece or another piece from an opponent 
it can block an attack from an opposing queen or drone 
If you're in the lead and don't have many pieces left, get rid of them to end the game.