rules --- Anchor

1. Anchor is a game for two players, Black and White, who alternately put stones of their color on the board. Once placed, stones do not move. (But those which die are removed at game's end, prior to counting territory.)

2. The board is a base-8 hexagon, as shown in Diagram 1. (Note that the corners are marked alternately with black and white anchors. Corners with anchors of a player's own color are his "home corners," and corners with anchors of his opponent's color are "away corners.") At the beginning the board is empty, with play taking place on the points.

Diagram 1 --- the board for playing Anchor

3. A corner point is considered to belong to both edges that meet there.

4. It is permissible to pass. If both players pass consecutively, the game concludes.

5. It is not permissible to "mirror" the opponent's moves ten or more turns in succession.

6. The beginning of the game is governed by a "refined" pie rule. Player 1 plays two moves for Black and one move for White. Player 2 then decides which side to take, with White to move. Note that the standard pie rule is encapsulated within the refined rule, because it is permissible to pass a turn. (I.e., Player 1 could play one move for Black, then pass for White, then pass for Black.)

7. A group is an anchor if it touches three or more sides of the board. If a group touches just two sides, it is an anchor only if these two sides do not meet at an away corner. Diagram 2 shows some examples of anchors. The large black group is an anchor, touching four sides of the board --- the stone at O8 is considered to belong to two sides. The large white group is an anchor, touching three sides of the board. Black has an anchor in the upper left, since the two sides touched do not meet at an away corner (they meet at a home corner). The single white stone at the top is an anchor for exactly the same reason.

Diagram 2 --- anchors

In Diagram 3 there are some more examples of anchors. Black and White have large anchors touching two sides which do not meet at an away corner. Black has a small anchor at the bottom, and White has a small anchor on the right --- note that the stones at A1 and H1 are both considered to belong to two sides which meet at a home corner.

Diagram 3 --- more anchors

In Diagram 4 are some examples of groups which are not anchors. The white group at the upper left does not touch any sides and therefore is not an anchor. Neither the black group at the upper right nor the large black group is an anchor, since each touches only one side. The white group at the bottom is not an anchor, since the two sides it touches meet at an away corner. The same goes for the solitary black stone.

Diagram 4 --- non-anchors

8. The game concludes when both players pass consecutively. (At this stage there are no more profitable moves to be made.) Any group that is not an anchor is ruled dead and is removed from the board. Each player then figures his score, which is the sum of his territory (vacant surrounded points) plus dead stones of his opponent. Note that there may be a number of empty points which are neutral --- that is, they aren't part of anyone's territory and their occupation would be useless. These points can be quickly filled in by either player (or just left empty, it makes no difference).

Diagram 5 shows a position just after both players have passed. The following groups are ruled dead and removed from the board: the three-stone black group at the top, the six-stone white group on the left, the three-stone black group in the center, the solitary black stone on the right, the six-stone white group at the bottom, and the two-stone black group at the bottom. All other groups are anchors and are alive. (Please note that it is unwise to rescue dead stones within your own territory --- the stones are saved, true, but you lose the territory they would yield plus the number of stones played in order to save them. In this situation Black could save the dead stone at K5 by playing at any of the six surrounding points, but he would actually lose a point for his trouble. Black could also save the two stones at the bottom by playing at A1 but would again net a one-point loss.) The points marked in orange are all neutral points which will have no bearing on the score. Black's total score is 55 (43 points of territory plus 12 dead white stones), and White's total score is 23 (14 points of territory plus 9 dead black stones).

Diagram 5 --- both players pass

Anchor can be easily played with pen-and-paper. Simply mark an open circle for White and a closed circle for Black. Dead stones can be marked with an "X." Diagram 6 shows a completed pen-and-paper game. Black has won by a score of 42 (33 plus 9) to 31 (27 plus 4).

Diagram 6 --- a completed pen-and-paper game

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