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One-Eyed Go
    Keywords: Rules, Theory

One of the great properties of Go is that its rules are so simple that it is tempting to believe there can't be any game with simpler rules. Unlike other go variants, this page does not try to enhance Go by inventing new rules, but rather investigates if Go can be further simplified, and how its character changes in the process.

One-Eyed Go follows the same rules as go (e.g. Japanese Rules) with the exception that it is never allowed to place a stone such that your own group has no liberties[3]. (Not even when the stone captures another stone.) This renders the ko rule superfluous.

So how do these rules change the game? Obviously, there is no ko nor snapback[2]. But in other respects, One-Eyed Go remains remarkably close to Go. There are alive structures, which, however, require only one eye to live - hence the name. Counting of liberties and even many shape preferences remain the same. As unkx80 pointed out, there even can be oiotoshi[1]. Originally, I intended One-Eyed Go as an easier version of Go, to be taught to beginners before they learn all the rules. It came as a surprise to me that the game actually did not get significantly easier. The biggest surprise (although understandable in hindsight) was that there were many more seki situations than in regular Go.[2]

Here's a little sample game:

[Diagram]
A little Game

W4 and W6 form a living one-eye.

B7 takes W2 and forms two living one-eyes.

W8 does not threaten to take B1 since White can not play inside the eye.

Black's move 11 could be at a or b. -- Sebastian 2003-09-21,22

[1] unkx80's example for oiotoshi:

[Diagram]
Oiotoshi.



[2] Example for Seki

Karl Knechtel: Interestingly enough, when I was reading the introduction to this page I was thinking "there must be a lot more seki positions this way" a couple sentences ahead. I wouldn't have found it surprising at all. DominGo allows for a lot of seki positions for similar reasons.

[Diagram]
Seki - no Snapback here

This diagram is similar to "a little Game", with the exception that White has a ponnuki. It is a nice example for seki and snapback:

B1 is a mistake - she should have played at a.

W2 does not set up a snapback, because White can not fill the one-eye at a. Moreover, BC is safe because White can not fill at b, either. Nevertheless, B1 was a mistake because her eastern group now only lives in seki.


[Diagram]
After black 7.


[3] Thanks to DougRidgway for pointing out the misleading wording.


Discussion

(History: unkx80 pointed out that in my discussion of the diagram "A little Game" I overlooked that W2 was taken. I sneakily corrected it by introducing the alternative example "Seki - no Snapback here". I probably should have made it clear that the latter is not a sequence to the former. -- Sebastian)

unkx80: My point is:-

B7 takes W2 and forms two living one-eyes.

W8 does not threaten to take B1 since White can not play inside the eye.

[Diagram]
After black 11.

Isn't the position after B11 the one shown in this diagram?

Sebastian: Yes, it is the one in "a little Game", but not the one in "Seki - no Snapback here". Sorry about the confusion.

unkx80: I see, thanks.



This is a copy of the living page "One-Eyed Go" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.