Cuarenta, by Mark Thompson

Cuarenta (from the Spanish for “40”) is a chess variant played on the board shown at right.  I conceived of it as an entry to the Chess Variant Pages’ contest for a chess variant on a board of 40 squares; it occurred to me one could use a 9x9 board and restrict all the pieces to squares of one color.  You will have to judge the result for yourself.

Pieces start in the positions shown.  Their names are the King, Bishop, Camel, Vao (2) (looks like a cannon), Guard (2), Frog (2), and Pawn (4).

The King is royal (for those unused to chess variant language, that means the object is to checkmate it); and it moves and captures to any diagonally adjacent square (marked in red), and it can move -- but not capture -- to the adjacent square either straight forward or backward (marked in blue).

The Bishop (not illustrated separately) moves diagonally any number of squares, just as in chess, and captures by occupying an enemy piece’s square.

The Vao moves (without capturing) the same as a Bishop to the squares marked blue.  But to capture it can and must jump over exactly one piece (called the “screen”) in between its starting square and that of its victim.  The screen can belong to either army, and the captured piece can be any number of squares beyond it.

The Vao resembles the “Cannon” in Xiangqi (Chinese Chess), except that it moves diagonally instead of orthogonally.

The Guard moves diagonally either one or two spaces, and can jump an intervening piece.  It captures the same way.

The Camel moves to the square in the opposite corner of any 2x4 rectangle, something like a chess Knight only longer.  (The Camel is a familiar piece to Chess Variant fans.)

Castling:  In a special castling move, the King and (unpromoted) Camel may trade places.  A player may castle only when neither his King nor his Camel has moved yet.  White may not castle until Black has either castled or otherwise moved his King and Camel.  Castling when in check is allowed.

The Frog moves and captures to the nearest light square in any orthogonal direction.  It may also jump to the next square over a line of any number (greater than zero) of friendly pieces, in any orthogonal or diagonal direction; the square may be vacant or occupied by an enemy piece, which is captured.

Finally, the Pawn moves and captures either to a forward-diagonally adjacent squares, or to the light square directly on either side.  A Pawn may not capture another Pawn.  When the Pawn moves to a square in the last three ranks, it may promote to a Camel; or if it moves to a square in the last rank it may promote to either a Camel, Frog, Guard, Vao, or Bishop.  A Pawn can remain unpromoted on the last rank, and promote on some later move (since it still can move to either side).  Of course, if a Pawn promotes to a Camel before the last rank, it is no longer a Pawn and so cannot promote further.