Phantom Go is a variant of Go for two players and a referee. The players each have their own board, set up so that they can't see the other player's board. The referee has a board of his own. The players play stones on their own board and the referee then copies the move made on his own board, after checking whether the move is legal (i.e. does not try to occupy an intersection on which the opponent has already played or is committing suicide). The referee tells the players what the result of the move was.
If the move could be performed normally he says: 'Black has moved'
If the move was illegal he says 'Illegal move' (but not whether the move was illegal due to a stone already being present or because of the suicide rule).
If the move leads to capture, the referee says 'Black has captured the following stones ...' after which he points out exactly which stones where captured to the White player (and to Black should that be necessary).
To give fair warning to the players the referee also warns when groups are first put into atari.
A snapback sounds like this:
Black plays and puts a white group into atari. White captures one stone and puts himself into atari. Black captures seventeen stones.
For speed, the game is best played on a 13x13 board.
Bill: I have played a form of this game, which we called Kriegspiel Go, after the similar chess variant. The referee only informed the players when it was their turn, prevented illegal moves (the opponent could hear him do that), and removed captured stones. A 9x9 board was large enough. ;-)
Jan: I've also played it that way, but the information about ataris tends to speed up the game and provides some extra confusion... I'm the second best Phantom Go player in Utrecht, by the way :-)
Go Spiel is named from the chess Kriegspiel and is the go equivalent. Two players sit with their backs to each other and each has a board and full set of stones of each colour. A referee is placed so that they can see both boards. An audience is highly desirable also, as this is most definitely a spectator sport.
Black places a stone on his board and the referee says "white to play". White then places a stone on her board and the referee say "black to play". If at some time a player tries to play where the other player has already played then the referee says "you cannot play there" and so the player knows to put a stone of the opponents colour on that point. Sometimes this is a mistake because it might have been suicide that prevented it. In some countries rules (e.g. New Zealand) suicide is allowed.
When a move results in the capture of stones the referee says for example "three white stones are captured" and indicates to white which three. White then knows to place black stones on all the liberties of that group.
Go speil is a surprisingly skillful game as well as highly entertaining. It can be played on a 13x13 board or a full board.
The referee should always consider the position of the black stones on black's board and white stones on white's board as correct as the players are free to put opponents stones on their own board wherever they think that they are.
Gospeil was played in New Zealand from about the late 1970s but I don't know if we invented it or not.
kritz A computer playing the referee and GNUGO would be cool.
Phelan: I had read the article before, and it seems to disregard the fact that the computer player would be much better at keeping the board in memory. It just needs to record the result of its moves to get a picture of the board. A human would have to deal with faulty memory. It would at least require much more memorization skills than usually, probably comparable to the efforts of blind go players.
If i understand correct, then the point is to find a position where either enemy stone is present, or if it's not, it's good place to play. Thus it might be good to try and check as many positions in a move as possible. Unless a failure durng piece placement means you pass a turn. This already, in an elegant way, introduces a common factor of "fog of war" games - deception. I can place my pieces in a way that would be most foolish in ordinary Go, but it will trick my oponnent into expecting one of several other formations. He should be then tricked into placing a stone in position favorable for me. -- e7th04sh