General

P (at least 2) players play the game with stones and a board. Each player uses his own stone colour. The board is a grid of lines and their intersections. As a default, the game starts from the empty board that is a grid of 19 horizontal and 19 vertical lines forming 361 intersections. Two intersections can be adjacent along a line.

Stones of the same colour are connected if they are adjacent or if there is a chain of adjacent stones of their colour between them. Likewise, empty intersections are connected if they are adjacent or if there is a chain of adjacent empty intersections between them.

A region consists of an intersection and any intersections connected to it.

The position is the distribution of stones with their colours and no stones on all the unique intersections of the grid. For a play, this is given after all its removals.

The score of each player is the number of all intersections a) with stones of his colour, and b) of the empty regions that are adjacent only to intersections with stones of his colour.

Game

The P players move successively in the order of their numbers. Player 1 moves first and succeeds player P.

A move is either a play of one's own stone on an empty intersection, or a pass.

A play removes stones of every region without adjacent empty intersection, first every such opposing region and then any such own region.

A play may not recreate a previous position from the game.

Successive moving ends with P successive passes.

The winners are the players with the greatest score of the final position.