Help For the Game Of Jade


Welcome to the network Jade server. The rules of Jade are given below. The Jade challenge command is described here. Other commands are the same for all pbmserv games.

jade challenge [-size=rowsxcols] [-first=player] userid1 userid2

Start a new game between userid1 and userid2

The -size parameter sets the overall board size. rows and cols must each be a number, bigger than 2, but not too big (the default size being 9x11).

The -first parameter determines who plays first. player must be either "Cross" or "Parallel", the default is "Cross".


Two players, Cross and Parallel, take turns placing either an 'x' or an 'o' at a vacant board point. Cross wins by connecting all four sides with either a chain of 'x's or a chain of 'o's. Parallel wins by connecting either the top and bottom or left and right sides with both a chain of 'x's and a chain of 'o's. Draws are not possible.

If the board is a rhombus, the size is odd, and Cross plays first then Cross is not allowed to make his first move on the short diagonal.

If the board has one even side and Cross plays first then Parallel's first move is not allowed to by symmetric of the opposite color to Cross' first move. Here symmetric means "rotated through 180 degrees".

Jade looks like just another Hex variant until you've made a few moves, work out what's really going on, and your brain has a hernia.

Example Games

A number of completed 7x7 games are shown by way of example.

     . . . x . . .       . . . . . . o
      . . x . o o o       . . . . . o .
       . . x o x x x       . . . . o . .
        . o x x o o .       . . . o . . .
         . x o x x . .       . . o . . . .
          x o o o x . .       . o . . . . .
           . . . . x . .       o . . . . . .

            Cross wins          Cross wins

     . . . . . . .       o . . . . . x
      . . . . . . .       o . . . . x .
       . . . . . . .       o . . . x . .
        o o o o o o o       o . . x . . .
         . . . . . . .       o . x . . . .
          x x x x x x x       o x . . . . .
           . . . . . . .       o x . . . . .

            Parallel wins       Parallel wins


The move syntax is:

    F6o     Place an 'o' piece at coordinate F6, which must be empty.
    A4x     Place an 'x' piece at coordinate A4, which must be empty.

References and History

Jade was invented by Mark Thompson in 2001. If he wasn't such a nice guy I'd describe it as the product of a brilliant but twisted mind.

The original rules had each player placing both an 'x' and an 'o' each turn (presumably only one on the first move). Claude Chaunier later suggested the current rule of placing only one symbol of the player's choice per turn.

At first, boards always had the same number of rows and columns. Cross then has the easier task as he is able to choose which colour to align with at any move. Many brilliant and not so brilliant rules were suggested and tried in order to fix this problem. Finally Mark Thompson (again) realized that it helps Parallel if the board has more columns than rows (say). The bigger the discrepancy the better for Parallel. It isn't yet known which size exactly balances out Cross' advantage but it does give a very natural way of getting a more even game.

There exists certain symmetry strategies by which certain players can win on certain sized boards. Again various rule changes were suggested until Bill Taylor pointed out that the first move restrictions above is the minimal restrictions needed to prevent the known symmetry strategies. It makes for a good puzzle to rediscover the symmetry strategies given the first move restrictions!

Jade rules copyright (c) 2001 Mark Thompson.

Various improvements to the original rules suggested by Cameron Browne, Claude Chaunier and Bill Taylor.

Implementation and help file by Cameron Browne and Paul van Wamelen, last change October 2003.