Kee Rules Of Go / Example 2x 1

Sub-page of KeeRulesOfGo

2x1 board

[Diagram]

2x1 board

Question: Starting from an empty board, can Black do better than a draw?

[Diagram]

2x1 board (cont.)

B1 = fighting stone play

Suppose Black starts by occupying the left intersection at B1.

W2 = fighting stone play

White responds by W2, occupying the right intersection which captures the black stone.

B3 = primary pass play

Black 3 cannot occupy the left intersection immediately, because it would be classified as a fighting stone play and it repeats the board position encountered by White before White played W2. Within this cycle, Black has only one play as a fighting stone play, so such play is prohibited by Fighting Situational Super Ko (FSSK). Black 3 can thus only be a pass play.

W4 = primary pass play

White is satisfied with the current board position, so White 4 is a pass play.

[Diagram]

2x1 board (cont.)

B5 = reviving stone play

B5 now recaptures the right white stone. Like a stone play in Black 3, it also repeats the board position encountered by White before White played W2, but since B5 is played after two consecutive pass plays, it is classified as a reviving stone play rather than fighting stone play. Within this cycle, Black has two plays - one is a primary pass play (Black 3) and one is a reviving stone play (B5), so there is no prohibition.

W6 = primary pass play

Similar to Black 3, White 6 cannot occupy the right intersection immediately, so it can only be a pass play.

B7 = primary pass play

Black is satisfied with the current board position, so Black 7 is a pass play.

[Diagram]

2x1 board (cont.)

W8 = reviving stone play

W8 now recaptures the left black stone. Similar to B5, it is classified as a reviving stone play and there is no prohibition.

B9 = primary pass play (mandatory)

However, Black 9 does not have any legal play. If he occupies the left intersection and captures the right white stone immediately, it would repeat the board position encountered by White before White played W8 and become a fighting stone play, which results in FSSK. If he passes, it repeats the board position encountered by White before White made his pass play in White 4. Within this cycle, the first Black play was B5 and it was a reviving stone play, and thus Reviving Situational Super Ko (RSSK) would be triggered.

Under Mandatory Pass Rule, Black 9 is a mandatory pass play, and Black can no longer make any stone play in the rest of the game.

W10 = primary pass play

White is satisfied with the current board position, so White 10 is a pass play.

B11 = secondary pass play (mandatory)

Black is not but he has no choice, so Black 11 is a pass play.

W12 = secondary pass play

Again, White is satisfied with the current board position, so White 12 is a pass play.

[Diagram]

2x1 board (ending board position)

Under End of Game Rule, with consecutive secondary pass plays by all players, the game ends with this board position. White wins 2 points under area scoring and territory scoring, or 1 point under stone scoring.

Therefore Black 1 should pass in the first place.

[Diagram]

2x1 board (what if suicide allowed?)

B7 = disturbing stone play

If suicide is allowed, Black 7 can choose not to pass as it can fill up the right intersection to commit suicide instead.

[Diagram]

2x1 board (White still wins)

W8 = fighting stone play

However, it does not alter the outcome because White 8 would then occupy the right intersection. It is here classified as fighting stone play rather than reviving stone play because B7 was here a stone play.

B9 = primary pass play (mandatory)

W10 = primary pass play

B11 = secondary pass play (mandatory)

W12 = secondary pass play

Black 9 still does not have any legal play. In this case, White wins 2 points under area scoring or 1 point under stone scoring, but 3 points under territory scoring.


This is a copy of the living page "Kee Rules Of Go / Example 2x 1" at Sensei's Library.
(OC) 2016 the Authors, published under the OpenContent License V1.0.
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