RTG Problem 4 / Attempts

White first to play.  

To me, seems the best move at Black's vital point. Even so, it seems Black has the chance to live in ko.

Black gets ko, I  

After , doesn't this depend on the ko?

unkx80: Nice try! Unfortunately the correct result is not ko. =)

Another attempt resulting in ko:

Black gets ko, II  

White invades fiercely...

Black gets ko, II - moves 11-13  

But after White 13, Black can again live by winning the ko. White 11 at 12, while tempting (to me, at least), is worse. at gives Black unconditional life.

White fails  

After , I think a and b are miai for life.

unkx80: This statement is somewhat inaccurate. at b, at a, and at c makes a ko.

Brian: Ah, I see. Thank you for the correction.

White fails again  

Now Black can easily get two eyes and live.

unkx80: If is played at , then Black dies. Also, what happens when is played at ?

Brian: Hmm. If is at , then Black cannot split at , or he'll lose . But blocking reduces the eye to three in a row, which White can kill. OK, I see that now.

But when is at ,

A better result?  

White can just extend with , preventing an eye in the corner. Black needs an eye on the left, so . Ah! kills, then, by threatening a white move at . defends, but prevents the eye.

Is this the correct answer this time?

unkx80: What if is played at ?

Brian: If is played at , then played at prevents an eye on the left.

Bill: But then the result is seki.

Important plays  

The situation after .

In my mind, for Black to form an eye at z he needs to occupy one set of: a-b-c-d, a-b-c-e, a-b-d-e, or b-c-d-e.

Alternately, Black could attempt to form an eye at d. This would require points c-z-e.

Since, at best, Black requires three of six points, White can prevent this.

Main line  

Dieter: I have a feeling this is coming pretty close. Just another minute ...

Shortage of liberties  

In a real game I would have gone for ko, I'm afraid. cannot connect at . takes away the second eye.

unkx80: Bingo. =)

Thanks for the hint, unkx80, I had been under the illusion that Black could connect at .