Life In 19x19

Hello everyone,

I won that game by half a point after grinding quite a number of points in yose, mostly thanks to mistakes of my opponent.

The middle game was dreadful, though. Mostly I think I messed up responding to the invasion on the bottom and the approach on the left side. About the left side, I'm pretty sure I know what I did wrong (move 18), but I'm a bit at a loss with the bottom invasion (starting with move 57). Could I have got a better result? Or did it go so wrong because my group on the bottom left was too weak?

Thanks in advance for any advice.

I added some comments and variations.

As usual, my mistakes aren't really where I thought they would. Thanks a lot for looking at the game !

Here is a standard tesuji that is worth learning.

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[go]$$W
$$ . . . . . . . |
$$ . . . . O . . |
$$ . . . . . O 3 |
$$ . . . . O X O |
$$ . . O . O X 7 |
$$ . . . O X 5 X |
$$ . O . O X 6 4 |
$$ . . O X X 2 1 |
$$ . . O . . . 8 |
$$ --------------[/go]

Variation if Black wants to take sente.

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[go]$$W
$$ . . . . . . . |
$$ . . . . O . . |
$$ . . . . . O 3 |
$$ . . . . O X O |
$$ . . O . O X 7 |
$$ . . . O X 5 X |
$$ . O . O X . 4 |
$$ . . O X X 2 1 |
$$ . . O . . . 6 |
$$ --------------[/go]

Toge, this is the vital point, isn't it?

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[go]$$W
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X . . |
$$ . . O X X a . |
$$ . . O X . . . |
$$ --------------[/go]

If I play there first:

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

And this:

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[go]$$W
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X 4 . |
$$ . . O X X 3 2 |
$$ . . O X . 1 . |
$$ --------------[/go]

Am I correct?

Bill, thank you for the tesuji. I'll learn it, this shape comes up so often in my games.

You found it Amelia. In the second diagram black can turn the position into ko by throwing in at T2 and white can turn it into ko by playing T1. The ko is risky for black, but if the game is close, opting to choose seki here can be enough. In the second diagram black must play T1 to prevent ko. If white wants to just get seki, then playing move 3 at T2 makes that happen.

Amelia wrote:

$$W
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X . 3 |
$$ . . O X X 1 . |
$$ . . O X . 2 . |
$$ --------------

Click Here To Show Diagram Code

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

And this:

$$W
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X 4 . |
$$ . . O X X 3 2 |
$$ . . O X . 1 . |
$$ --------------

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[go]$$W
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X 4 . |
$$ . . O X X 3 2 |
$$ . . O X . 1 . |
$$ --------------[/go]

Am I correct?

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[go]$$W Typical
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X . . |
$$ . . O X X 1 3 |
$$ . . O X . 2 . |
$$ --------------[/go]

This sequence would be usual with White playing first.

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[go]$$W Seki
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X 4 . |
$$ . . O X X 1 3 |
$$ . . O X . 2 . |
$$ --------------[/go]

can make seki.

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[go]$$W 10,000 year ko
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X . . |
$$ . . O X X O O |
$$ . . O X . X 1 |
$$ --------------[/go]

If Black plays elsewhere, can make a 10,000 year ko. (The name implies that the ko is never converted into a direct ko for the corner. But normally White should convert the ko or threaten to do so. It all depends on the rest of the board, of course. )

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[go]$$W Black lives
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X O |
$$ . . . O O X O |
$$ . . . O X X X |
$$ . . O O X . 4 |
$$ . . O X X 2 3 |
$$ . . O X . 1 . |
$$ --------------[/go]

is a mistake. lives. If , preserves two eyes.