Definitions

Two adjacent cells, and any pieces on them, are linked if their shared edge segment does not contain a wall.

A group is a piece along with all other like-colored pieces one could reach from it through a series of steps between linked pieces of its color.

A liberty of a group is an empty cell linked to at least one piece in that group.

Similarly, a territory is an empty cell along with all other empty cells one could reach from it through a series of steps between linked empty cells. You own a territory if all pieces linked to cells in that territory are of your color.

Play

Black plays first, then turns alternate. On your turn, you must pass or place a piece of your color on an empty cell without causing any edge segment on the board to contain more than one wall, not even momentarily during the move.

After a placement, remove all enemy pieces in groups without liberties. After all removals, the following conditions must be met:

• Your newly placed piece must be part of a group with at least one liberty.
• The cell on the other side of the wall of your newly placed piece must not contain an enemy piece.
• The current board position, ignoring walls, must be different from the board positions at the end of all your previous turns.

Otherwise, your placement is illegal.

The game ends when both players pass in succession. The player with the higher score in the final position wins. A player's score is the number of pieces of their color on the board, plus the number of cells in their territories, plus a komi in the case of White. The button is used to avoid ties.

Komi and button

The komi is the whole number of points which is added to White's score at the end of the game as a compensation for playing second. Before the game starts, the first player chooses the value of komi, and then the second player chooses sides. Alternatively, experienced players may agree on a standard value for all games.

The button is a special token which is placed next to the board at the start of the game. On your turn, if neither player has taken the button yet, you may not pass, but you may take the button instead of making a board play. At the end of the game, a half point is added to the score of the player who has taken the button. When checking for repetitions, two identical board positions are still considered different if the button had already been taken in one of them but not in the other.

Notes

Like its companion game Keil, Bargo aims to preserve crosscuts and ko from Go by reducing the natural connectivity of the hexagonal grid.

-description from designer