Life In 19x19

shapenaji wrote: ...
Black to play and kill (ko is not acceptable)

I llllove this kind of one move "blind spot" problems. So obvious, but not obvious...

Please more !!!

Joaz Banbeck wrote:At move 69, play S9. ......

You prefer this over 67 at T7?

@entropi: Love them also. Especially after solving!
@Leyleth: Very good to have spotted this! Really on your way to shodan!

cyclops wrote:

Joaz Banbeck wrote:At move 69, play S9. ......

You prefer this over 67 at T7?

I could have suggested a better move 67, and minor improvements on a handful of other moves. But I don't want to bury the OP. I wanted to offer him the most basic, fundamental advice that I could.
With that goal in mind, I chose to mention the throw-in. I consider it 'more fundamental' than the encroachment at T7, because it shows up in both variations - move 67 at T7 or at T9.

This throw-in wrecks the eye after 67 at T9:

Click Here To Show Diagram Code

[go]$$B
$$ . . . . . . |
$$ . . . . . . |
$$ . . . . X . |
$$ . X X X O 2 |
$$ . O O O 3 1 |
$$ . . . X O . |
$$ . . . X O . |
$$ . . X X X . |
$$ . . . X . . |
$$ . . . . . . |[/go]

This kills the eye too:

Click Here To Show Diagram Code

[go]$$B
$$ . . . . . . |
$$ . . . . . . |
$$ . . . . X . |
$$ . X X X O 3 |
$$ . O O O 2 1 |
$$ . . . X O . |
$$ . . . X O . |
$$ . . X X X . |
$$ . . . X . . |
$$ . . . . . . |[/go]

If he plays 67 at T7, he may still need to do a throw-in. Move 3 is elsewhere, but after 4, throw-in at 'a' is needed.

Click Here To Show Diagram Code

[go]$$B
$$ . . . . . . |
$$ . . . . . . |
$$ . . . . X . |
$$ . X X X O 4 |
$$ . O O O a . |
$$ . . . X O 2 |
$$ . . . X O 1 |
$$ . . X X X . |
$$ . . . X . . |
$$ . . . . . . |[/go]

I figure that it is best to give him a technique that appears in multiple lines rather than a technique that shows up in one. Indeed, 'a good move showing up in lots of variations' may be the very definition of 'fundamental'.

To the OP: As Cyclops says, at move 67, T7 is best. But once you have missed it and played T9, you still have a chance to destroy his eye with S9.
Note that they are different techniques. One pushes in from the outside to restict eyespace, the other destroys the eye from the inside.
The general pattern will be to employ the outside squeeze first, the throw-in second. ( FWIW, the throw-in is often combined with vital point placements. There are exceptions. It can get tricky. )

You guys are missing that white can't make an eye on the right edge of the board after , period. Thus, any move by black on the right edge of the board is about as good as passing.

cyclops wrote:

Joaz Banbeck wrote:At move 69, play S9. ......

You prefer this over 67 at T7?

I would prefer 67 at K7

HermanHiddema wrote:
I would prefer 67 at K7

K7 is just all-around better, still leads to ko though,

BK7 WR11 leads to ko. EDIT: Scratch that, hallucinating

shapenaji wrote:

HermanHiddema wrote:
I would prefer 67 at K7

K7 is just all-around better, still leads to ko though,

BK7 WR11 leads to ko. EDIT: Scratch that, hallucinating

Is this the sequence you mean?

67 B k7
68 W r11
69 B r12
70 W s12
71 B t11
72 W t10 (atari)
73 B q11 (capture)
74 W t7 -> second eye


If black wants to avoid unconditional life for white, he can probably capture at q11 on move 71 (instead of blocking at t11). But then white would play t11 himself, leading to a ko?

entropi wrote:

shapenaji wrote:

HermanHiddema wrote:
I would prefer 67 at K7

K7 is just all-around better, still leads to ko though,

BK7 WR11 leads to ko. EDIT: Scratch that, hallucinating

Is this the sequence you mean?

67 B k7
68 W r11
69 B r12
70 W s12
71 B t11
72 W t10 (atari)
73 B q11 (capture)
74 W t7 -> second eye


If black wants to avoid unconditional life for white, he can probably capture at q11 on move 71 (instead of blocking at t11). But then white would play t11 himself, leading to a ko?

Doesn't work though, black can just fill the ko and let white connect underneath and there's no way to get another eye on the bottom

shapenaji wrote: Doesn't work though, black can just fill the ko and let white connect underneath and there's no way to get another eye on the bottom

Amazing! Indeed no room for another eye on the right side even if white goes out. But at least white can get a big(ger) portion of the upper right corner using the remaining aji Surely not enough compensation for the loss of the group but ...