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Offline jlt
 Post subject: Shapes to remember (SDK level)
Post #1 Posted: Fri Aug 30, 2019 2:49 am 
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In this thread I will post a few positions that occurred in my games, in which the best move (according to LZ) doesn't require reading to be found, but didn't cross my mind (I am 4k on KGS and on Fox).

Here, White should play at "a". If White doesn't, Black has some forcing moves that threaten to surround White while building influence.

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . a O . . . |
$$ | . . . . . . . . . . . . . . . X O O . |
$$ | . . . O . . . . . , . . . X . X X O . |
$$ | . . . . . X . . . . . . . . . X O O . |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Here, Black is surrounded. Playing at "a" secures the group while building a large corner.
Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . X O O . . |
$$ | . . . . . . . X . . . . . X . X O . . |
$$ | . . . X . . . . . O . X . . . X O O O |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . O . . O . . O . . . . . . . . . |
$$ | . . . . O . . . . . . O . . . O . X . |
$$ | . . . X X X . . . . . . . . . . X . . |
$$ | . . X . . . . X X X X . . . . O O X . |
$$ | . . . , O X X O O O O O . . . O X . . |
$$ | . . X O . O O X . . . . . . . O X . . |
$$ | . . . a . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

This post by jlt was liked by: Bill Spight
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Offline Uberdude
 Post subject: Re: Shapes to remember (SDK level)
Post #2 Posted: Fri Aug 30, 2019 3:04 pm 
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I'm guessing in the first diagram black's previous move was approach at bottom left, and it should have been a? But o4 is not efficient then...
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #3 Posted: Sat Aug 31, 2019 1:48 am 
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The previous move was indeed approach on the bottom left. Instead of that move, LZ157's main line is the following, but I don't understand the purpose of the exchange :b1: :w2:.

Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . 1 . . . |
$$ | . . . . . . . . . . . . . . . O 2 . . |
$$ | . . . . 9 . . . . . . . . . . X O O . |
$$ | . . . O 7 6 . . . , . . . X . X X O . |
$$ | . . . . 8 3 . 4 . 5 . . . . . X O O . |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
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Offline gennan
 Post subject: Re: Shapes to remember (SDK level)
Post #4 Posted: Sat Aug 31, 2019 3:27 am 
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It's similar to peeping a tiger mouth: having a black stone here for free gives black better options later while not helping white much.

Forcing moves are an advanced concept. SDK players tend to play many sente moves, because they see them as forcing moves and thus good. But often they are aji-keshi and thus bad.
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Offline Bill Spight
 Post subject: Re: Shapes to remember (SDK level)
Post #5 Posted: Sat Aug 31, 2019 5:24 am 
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jlt wrote:
The previous move was indeed approach on the bottom left. Instead of that move, LZ157's main line is the following, but I don't understand the purpose of the exchange :b1: :w2:.

Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . 1 . . . |
$$ | . . . . . . . . . . . . . . a O 2 . . |
$$ | . . . . 9 . . . . . . . . . . X O O . |
$$ | . . . O 7 6 . . . , . . . X . X X O . |
$$ | . . . . 8 3 . 4 . 5 . . . . . X O O . |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


It's a case of get it while you can. If Black waits until White plays at a, White will not respond at :w2: to :b1:. In fact, Black will not play at 1 in that case.

The exchange, :b1: - :w2: is also why White does not play :w4: at a. It does not accomplish so much, now.

I would be happy to find :b1: in this position. :)

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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #6 Posted: Sun Sep 01, 2019 11:30 am 
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Position 3 : this one should have been obvious, and yet I missed it :oops:. White to play.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O . . . . . . . . . . . . . . |
$$ | . . . . X X . . X . O . X . . X O . . |
$$ | . . O O O . . . . , O . . . . X O . . |
$$ | . . X . . X . X . O . . . . . X . . . |
$$ | . . X O O O . . . . . . . . . . . O . |
$$ | . . . X X O O . O . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . X . . . |
$$ | . . X O O O . . . , . . . . . , X . . |
$$ | . O O X X X O . . . . O . . O . . . . |
$$ | . X X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]



Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 1 O . . . . . . . . . . . . . . |
$$ | . . . . X X . . X . O . X . . X O . . |
$$ | . . O O O . . . . , O . . . . X O . . |
$$ | . . X . . X . X . O . . . . . X . . . |
$$ | . . X O O O . . . . . . . . . . . O . |
$$ | . . . X X O O . O . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . X . . . |
$$ | . . X O O O . . . , . . . . . , X . . |
$$ | . O O X X X O . . . . O . . O . . . . |
$$ | . X X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


(and not D17, otherwise F18 would be sente. Then maybe Black is dead ?)
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Offline dfan
 Post subject: Re: Shapes to remember (SDK level)
Post #7 Posted: Sun Sep 01, 2019 1:09 pm 
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Yay, I got one! Further discussion hidden so as not to spoil.
By the way, this sort of pulling back to make a hane-connection one point (or more) farther back but with much better shape is something that I was never really taught explicitly, but often shows up in make-the-proper-move problems.

That is,
Click Here To Show Diagram Code
[go]$$Wc
$$ --------------
$$ | . . . . . .
$$ | . . . 1 O .
$$ | . . 3 2 X X
$$ | . . O O O .
$$ | . . X . . X[/go]

instead of
Click Here To Show Diagram Code
[go]$$Wc
$$ --------------
$$ | . . . . . .
$$ | . . . . O .
$$ | . . . 1 X X
$$ | . . O O O .
$$ | . . X . . X[/go]

Here it's pretty clear why it's better for tactical reasons, but even when there isn't a clear tactical refutation to the greedier move, the shape move is generally much better.
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #8 Posted: Fri Sep 06, 2019 9:02 am 
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Black to play.

Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . O X . . . |
$$ | . . O X . X . . . O . . . O . . X X . |
$$ | . . O O . . . . . , . . O X X X O . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . X X O . . |
$$ | . . . . . . . . . . . . . . . O X O . |
$$ | . . . . . . . . . X . . X X . . X O . |
$$ | . . . . . . . . . . . . . O X . X O . |
$$ | . . . , . . . . . , O . O . . X O . . |
$$ | . . . . . . . . X . O . . . X O O . . |
$$ | . . O . . . . . . X X O O . O X O . . |
$$ | . . . . . . . . . . . . . . . X O . . |
$$ | . . X . . . . . . . X . O . . X . . . |
$$ | . O O . O O . . . . X O . . X X . . . |
$$ | . X O O . X X . . , . X O O X , X . . |
$$ | . X X X . . . . . . X . O . O X O . . |
$$ | . . . . . . . . . . . O . . O X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Hint:
Where to invade on the left side?

Answer:
Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . O X . . . |
$$ | . . O X . X . . . O . . . O . . X X . |
$$ | . . O O . . . . . , . . O X X X O . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . X X O . . |
$$ | . . . . . . . . . . . . . . . O X O . |
$$ | . . a . . . . . . X . . X X . . X O . |
$$ | . . . . . . . . . . . . . O X . X O . |
$$ | . . 1 , . . . . . , O . O . . X O . . |
$$ | . . . . . . . . X . O . . . X O O . . |
$$ | . . O . . . . . . X X O O . O X O . . |
$$ | . . . . . . . . . . . . . . . X O . . |
$$ | . . Y . . . . . . . X . O . . X . . . |
$$ | . O O . O O . . . . X O . . X X . . . |
$$ | . X O O . X X . . , . X O O X , X . . |
$$ | . X X X . . . . . . X . O . O X O . . |
$$ | . . . . . . . . . . . O . . O X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The answer is to invade at :b1:. I invaded at "a", thinking that the upper group is weaker than the lower one, but this is wrong because of the stone :bt: that can help the invading stone.
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #9 Posted: Sun Sep 08, 2019 11:28 am 
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Position #5: LZ proposes several moves but I didn't find any of them. White to play.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . O . X X . O X X O . |
$$ | . . . . . . . . X . O . O O . X O O . |
$$ | . . . X . . . . . , . . . . . X X O . |
$$ | . . . . . . . . . . . . . . X . X O . |
$$ | . . . . . . . . . . . . . . . X O O . |
$$ | . . . . . . . . . . . . . . X . X O . |
$$ | . . . . . . . . . . X X X . X . X O . |
$$ | . . . . . . . . O O O O O O O X . X O |
$$ | . . . , . . . . . X O . O X X X O O . |
$$ | . . . . . . . . . X X O X X O O X X O |
$$ | . . . . . . . . . X O O . O O X X . . |
$$ | . . . . . . . . . . X . O O X . X O O |
$$ | . . X . . . . . . . . . O X X X X . . |
$$ | . . . X . . X . . . . . O O X O X X . |
$$ | . . O O X X O X X X . . X O O O O O . |
$$ | . . . . O O O O . . . . X O X X X . . |
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The upper white group can't escape easily. Better extend eyespace with sente moves first, and then
capture the two black stones.
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . 3 1 O . X X 5 O X X O . |
$$ | . . . . . . 4 2 X . O . O O . X O O . |
$$ | . . . X . . . . . , . . . . . X X O . |
$$ | . . . . . . . . . . . . . . X . X O . |
$$ | . . . . . . . . . . . . . . . X O O . |
$$ | . . . . . . . . . . . . . . X . X O . |
$$ | . . . . . . . . . . X X X . X . X O . |
$$ | . . . . . . . . O O O O O O O X . X O |
$$ | . . . , . . . . . X O . O X X X O O . |[/go]


Another sequence considered by LZ: sacrifice the group to get moves in the center.
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 O . X X . O X X O . |
$$ | . . . . . . . . X 6 O 9 O O . X O O . |
$$ | . . . X . . . . . 5 4 8 . . . X X O . |
$$ | . . . . . . . . . 1 7 . . . X . X O . |
$$ | . . . . . . . . 3 . . . . . . X O O . |
$$ | . . . . . . . . . . . . . . X . X O . |
$$ | . . . . . . . . . . X X X . X . X O . |
$$ | . . . . . . . . O O O O O O O X . X O |
$$ | . . . , . . . . . X O . O X X X O O . |[/go]

This post by jlt was liked by: Bill Spight
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #10 Posted: Sun Sep 29, 2019 4:11 am 
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I got 11 wins and 6 losses at 3k level on Fox, so got promoted to 2k, then went back to IGS to check if my 7k rank is still valid. So far I got 2W and 2L, so maybe the answer is yes but I will see after more games.

The next position is from a 7k game on IGS. It requires a bit of reading, but the first move should be intuitive.

Position #6: Black to play.
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O . . |
$$ | . X X O X O . O X . . . . . X . . . . |
$$ | . . O O O . O . O X . . . . . . X O . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The wrong answer I chose was R3, but there was a better one:

Click Here To Show Diagram Code
[go]$$Bc
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O 7 . |
$$ | . X X O X O . O X . . . . . X 6 . 1 . |
$$ | . . O O O . O . O X . . . . . 2 X O 3 |
$$ | . . . . . . . . . . . . . . . 8 5 4 9 |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wcm10
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O X . |
$$ | . X X O X O . O X . 8 6 2 . X O . X . |
$$ | . . O O O . O . O X 7 1 3 4 . O X . X |
$$ | . . . . . . . . . 9 . . . 5 . O X . X |
$$ ---------------------------------------[/go]


So White lives but the central group is floating and Black is connected and has sente.
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Offline EricBackus
 Post subject: Re: Shapes to remember (SDK level)
Post #11 Posted: Sun Sep 29, 2019 8:42 am 
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jlt wrote:
Position #6: Black to play.
The wrong answer I chose was R3, but there was a better one:

Click Here To Show Diagram Code
[go]$$Wcm10
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O X . |
$$ | . X X O X O . O X . 8 6 2 . X O . X . |
$$ | . . O O O . O . O X 7 1 3 4 . O X . X |
$$ | . . . . . . . . . 9 . . . 5 . O X . X |
$$ ---------------------------------------[/go]


So White lives but the central group is floating and Black is connected and has sente.

What about B11 at O2? I think that kills the white group on the right, though it does let the center white group connect.
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Offline Bki
 Post subject: Re: Shapes to remember (SDK level)
Post #12 Posted: Sun Sep 29, 2019 9:43 am 
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EricBackus wrote:
jlt wrote:
So White lives but the central group is floating and Black is connected and has sente.[/hide]

What about B11 at O2? I think that kills the white group on the right, though it does let the center white group connect.


I was thinking the same. Killing the bottom right is at least 25 points. It feels better than a speculative attack against the center group which has enough space that it isn't going to die. But that's because :w10: might be incorrect. Instead, white can play this way (which still isn't good enough) :

Click Here To Show Diagram Code
[go]$$Wcm10
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O X . |
$$ | . X X O X O . O X . . 6 4 . X O . X . |
$$ | . . O O O . O . O X 7 5 1 2 . O X . X |
$$ | . . . . . . . . 8 . . . . 3 . O X . X |
$$ ---------------------------------------[/go]


:b17: doesn't look like sente against the bottom sadly, but the capture at H2 might be, and in anyway it nicely disconnect white.
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #13 Posted: Sun Sep 29, 2019 11:12 am 
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EricBackus wrote:
What about B11 at O2? I think that kills the white group on the right, though it does let the center white group connect.


There are many variations, but it seems that :b11: at O2 leads to a ko which is good for White, for instance:
Click Here To Show Diagram Code
[go]$$Wcm10
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O X . |
$$ | . X X O X O . O X . . . . 8 X O . X . |
$$ | . . O O O . O . O X . 1 5 2 7 O X . X |
$$ | . . . . . . . . . . . . 4 3 6 O X . X |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wcm18
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O X . |
$$ | . X X O X O . O X . 2 4 . X X O . X . |
$$ | . . O O O . O . O X . O O X O O X . X |
$$ | . . . . . . . . . 5 . 3 X 1 . O X . X |
$$ ---------------------------------------[/go]
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Offline kvasir
 Post subject: Re: Shapes to remember (SDK level)
Post #14 Posted: Sun Sep 29, 2019 12:42 pm 
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jlt wrote:
The next position is from a 7k game on IGS. It requires a bit of reading, but the first move should be intuitive.


You don't have to play the best move.

I think you are excused if your are not able to kill white in a game on igs. It looks like it works judging from the variations posted but it takes 18 moves to figure out if white can connect under and there is a game deciding ko at the end. I would just play on the outside.

"killing" is not that big if it is not clean and with blacks potential on the outside it doesn't look like white has time to reinforce.

:b1: builds a roof on your house, a is coming soon. You can go for the LR corner if white catches up. Also ask white if his center group is OK.

If you can read how to kill white, that everything works out and it is clear to you then you just do that but it doesn't look so easy.

Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . a . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . 1 . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . X . . X . O . . . X X . . |
$$ | . . . . . X . . . . . . . O X X O . . |
$$ | . . . X . . O . X . . O . . X O O . . |
$$ | . . . . . . . . . . X O . . X X O . . |
$$ | . . . X X . O . X , . O . . X O O . . |
$$ | . X X O X O . O X . . . . . X . . . . |
$$ | . . O O O . O . O X . . . . . . X O . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #15 Posted: Sat Oct 05, 2019 2:36 pm 
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I won 14/22 games at IGS 7k level, so got promoted to 7k+. Since some losses were due to lack of concentration, I decided to focus more. I then won 7/7 games and am now 6k. The last game was a 2-stone handicap game.

Position #7: White to play.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . , . . . . . X . . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . O . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Clearly the stone :bc: is misplaced, but I couldn't see a good way to exploit the cut, so I played K17, which is a -17% mistake after a few thousand playouts according to LeelaZero. If :bc: were at C12, then :w15: at K17 would have been a good move, but in the present position, LZ wants to cut:

Click Here To Show Diagram Code
[go]$$Wcm15
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . 0 . . . . . X . . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . B 1 2 . . . . . . . . . . . . . . . |
$$ | . . 3 4 . . . . . . . . . . . . . . . |
$$ | . . 5 6 . . . . . , . . . . . , X . . |
$$ | . . 7 8 . . . . . . . . . . . . . . . |
$$ | . . 9 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . O . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Then make a 3-3 invasion and let Black build a huge moyo...

Click Here To Show Diagram Code
[go]$$Wcm25
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . 0 9 . . . |
$$ | . . O X . . . . . . . . . . . 2 1 . . |
$$ | . . O X . . . . . X . . . . . X 3 . . |
$$ | . O X . . . . . . . . . . . 8 7 5 . . |
$$ | . O X . . . . . . . . . . . . 6 4 . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . X O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . O . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Which can be invaded thanks to the weak point E14!
Click Here To Show Diagram Code
[go]$$Wcm35
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . X O 1 . . |
$$ | . . O X . . . . . . . . . 2 . X O . . |
$$ | . . O X . . . . . X . . . . . X O . . |
$$ | . O X 4 . . . 5 . . . . . . X O O . . |
$$ | . O X . 3 . . . . . . . . . . X X . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . X O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . O . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


I would find pretty scary to invade deeply like that. Maybe I should try anyway.

This post by jlt was liked by 2 people: Bill Spight, xela
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Offline Bill Spight
 Post subject: Re: Shapes to remember (SDK level)
Post #16 Posted: Sat Oct 05, 2019 5:25 pm 
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Congratulations! :clap: :clap: :clap:

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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #17 Posted: Mon Oct 07, 2019 5:01 am 
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Position #8: White to play. This is from a Fox 2k vs. 2k game.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X O . . . . . . . . . . . . . . |
$$ | . . X O . O . . . X X O . X . . . . . |
$$ | X . X O . . . O . O . . . . . , X . . |
$$ | . X O X . . . . . . . O . X . . . . . |
$$ | . O O . . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . O . O . O . . |
$$ | . . X . X . . . . . . X X O . . . . . |
$$ | . . . , . . . . . , . . . X O O . . . |
$$ | . . . . . . . . . . . X X X X X O . . |
$$ | . X X . X . . . . . O O X O . . . . . |
$$ | . O X . . . . . . . . . O O X X X . . |
$$ | . O O O . . . . . . O . . . . O . X . |
$$ | . . . . . . . . . X O . . . . . O O O |
$$ | . . . O . X . . . , X O O O O O X X . |
$$ | . . . . O X . . . . X X O X X X X . . |
$$ | . . . . . . . . . . . . X . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


This is the move suggested by LeelaZero. It occurs frequently in invasion sequences, and yet it is still not obvious to me. Instead I played "a" and let Black connect underneath, which is a -17% mistake.
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X O . . . . . . . . . . . . . . |
$$ | . . X O . O . . . X X O . X . . . . . |
$$ | X . X O . . . O . O a W . . . , X . . |
$$ | . X O X . . . . . . . O . X . . . . . |
$$ | . O O . . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |[/go]


The cut at "a" does not work :

Click Here To Show Diagram Code
[go]$$Bcm2
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X O . . 9 8 . 0 . . . . . . . . |
$$ | . . X O . O . 7 6 X X O . X . . . . . |
$$ | X . X O . . . O 3 O 1 W . . . , X . . |
$$ | . X O B . . . . 5 4 2 O . X . . . . . |
$$ | . O O . . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |[/go]


However the stone :bc: starts to be problematic, even if Black's winrate at that stage is about 15%.

Black may also want to live on the top:

Click Here To Show Diagram Code
[go]$$Bcm2
$$ ---------------------------------------
$$ | . . . . . . . . . . . 9 . . . . . . . |
$$ | . . X X O . 5 . . . . 7 8 . . . . . . |
$$ | . . X O . O 6 . 3 X X O . X . . . . . |
$$ | X . X O . . . O 4 O 1 W . . . , X . . |
$$ | . X O X . . . . . . 2 O . X . . . . . |
$$ | . O O . . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |[/go]

but this is even worse for Black because it hurts the upper right corner:

Click Here To Show Diagram Code
[go]$$Wcm11
$$ ---------------------------------------
$$ | . . . . . . . . . . . X 3 . . . . . . |
$$ | . . X X O . X 2 . 4 . X O . . . 5 . . |
$$ | . . X O . O O . X X X O 1 X . . . . . |
$$ | X . X O . . . O O O X W . . . , X . . |
$$ | . X O X . . . . . . O O . X . . . . . |
$$ | . O O . . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |[/go]

This post by jlt was liked by: Bill Spight
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #18 Posted: Wed Oct 30, 2019 3:14 pm 
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Position #9 : White to play.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . . X O . O . . . . . . . . . . . . |
$$ | . . . X O . X . O O X . . . . X O . . |
$$ | . . X O . . . . O X . . . . . X O . . |
$$ | . . X O . . . . O . X . . . . . X O . |
$$ | . . X O . . . . . . . . . . . . X O . |
$$ | . . . O . . . . . . . . . . . . X O . |
$$ | . . . . . . . . . . X . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O O O O O . . . . . . . |
$$ | . . X . . . O X X X X . . . O . O O . |
$$ | . . . . . . . . O . . X . O . X O X . |
$$ | . X . O . O X X . , . . . . . O X X . |
$$ | . . O . . . O . X . . X X O . O X . . |
$$ | . . . . . O . X . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . . X O . O . . . . . . . . . . . . |
$$ | . . . X O . X . O O X . . . . X O . . |
$$ | . . X O . . . . O X . . . . . X O . . |
$$ | . . X O . . . . O . X . . . . . X O . |
$$ | . . X O . . . . . . . . . . . . X O . |
$$ | . . 1 O . . . . . . . . . . . . X O . |
$$ | . . . . . . . . . . X . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


This is sente because if Black plays elsewhere then Black cannot save all his corner...

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . 6 4 X O . O . . . . . . . . . . . . |
$$ | . 5 3 X O . X . O O X . . . . X O . . |
$$ | . 7 X O . . . . O X . . . . . X O . . |
$$ | . . X O . . . . O . X . . . . . X O . |
$$ | . . X O . . . . . . . . . . . . X O . |
$$ | . . 1 O . . . . . . . . . . . . X O . |
$$ | . . . . . . . . . . X . . 2 . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


So loses part of it, and barely lives in gote.
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . 7 X X O . . . . . . . . . . . . . |
$$ | . 6 5 X O . O . . . . . . . . . . . . |
$$ | . 4 3 X O . X . O O X . . . . X O . . |
$$ | . . X O . . . . O X . . . . . X O . . |
$$ | . . X O . . . . O . X . . . . . X O . |
$$ | . . X O . . . . . . . . . . . . X O . |
$$ | 0 8 1 O . . . . . . . . . . . . X O . |
$$ | . 9 . . . . . . . . X . . 2 . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


Click Here To Show Diagram Code
[go]$$Wcm11 :b20: at :w11:
$$ ---------------------------------------
$$ | . 9 O . . O . . . . . . . . . . . . . |
$$ | . X O . O . O . . . . . . . . . . . . |
$$ | 6 X O . O . X . O O X . . . . X O . . |
$$ | 3 4 X O . . . . O X . . . . . X O . . |
$$ | 1 2 X O . . . . O . X . . . . . X O . |
$$ | 7 8 X O . . . . . . . . . . . . X O . |
$$ | X X O O . . . . . . . . . . . . X O . |
$$ | 5 O . . . . . . . . X . . X . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


I often fail to see these kinds of moves because I forget that cutting stones, even if eventually captured, can help to provide sente moves.

This post by jlt was liked by: Bill Spight
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #19 Posted: Sat Nov 16, 2019 6:28 am 
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Position #10: a move that both players (KGS 3k and 4k) failed to see during most of the game. Black to play.

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O O . . . . . . . . . . |
$$ | . . . O O O . X . . . . . . . . . . . |
$$ | . . O X X X X . . , . . . . . X . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 8 3 6 . . 5 O O . . . . . . . . . . |
$$ | . . 1 O O O 7 X . . . . . . . . . . . |
$$ | . 2 O X X X X . . , . . . . . X . . . |
$$ | . 4 X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

White has been cut in sente.

Of course, :w6: cannot be at :b7:

Click Here To Show Diagram Code
[go]$$ This is even worse for White
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . 7 5 O O . . . . . . . . . . |
$$ | . . 1 O O O 6 X . . . . . . . . . . . |
$$ | . 2 O X X X X . . , . . . . . X . . . |
$$ | . 4 X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


Another variation:
Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . 8 . . . . . . . . . . . . |
$$ | . . 3 . . 6 5 O O . . . . . . . . . . |
$$ | . . 1 O O O 7 X . b . . . . . . . . . |
$$ | . 2 O X X X X . . , . . . . . X . . . |
$$ | . 4 X . . . . . . . . . . . . . . . . |
$$ | . 0 9 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . a . . . . . . . . . . . . . . . . |[/go]


Then Leelazero hesitates between a and b. Both are good for Black.

This post by jlt was liked by: Bill Spight
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Offline jlt
 Post subject: Re: Shapes to remember (SDK level)
Post #20 Posted: Mon Nov 25, 2019 7:00 am 
Lives in sente
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Posts: 747
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Position #11.

No-komi game against a Fox 3k, I am white. What to do of the marked stones?

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . O O X . . . . . |
$$ | . . . X X O . . . O O . O X X X . . . |
$$ | . . X X O . O X X X X O O X O X . . . |
$$ | . X O O O . . X O O O O O O O , X . . |
$$ | . X . . . . . . X . X . X X X X . . X |
$$ | . . X . O . . X . . . . X O O O X X O |
$$ | . . . . . . . . . . . . . . O . O O O |
$$ | . . . . O O . X . . X . . O . O O X X |
$$ | . . X X X O . . . . . . . . O X X X . |
$$ | . . X W W X . O . , . . . . . O X . O |
$$ | . . W X W . . . . . . . . . . O O X . |
$$ | . . W X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . O O . . |
$$ | . . O O O . . . . , . . . . . , X . . |
$$ | . . X X X O O O . . . . . X . X . . . |
$$ | . . . . . X X O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


It's hard to save both groups. Better sacrifice the one on the edge and build a strong center
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . O O X . . . . . |
$$ | . . . X X O . . . O O . O X X X . . . |
$$ | . . X X O . O X X X X O O X O X . . . |
$$ | . X O O O . . X O O O O O O O , X . . |
$$ | . X . . . . . . X . X . X X X X . . X |
$$ | . . X . O . . X . . . . X O O O X X O |
$$ | . . . . . . . . . . . . . . O . O O O |
$$ | . . . . O O . X . . X . . O . O O X X |
$$ | . . X X X O . . . . . . . . O X X X . |
$$ | . . X O O X . O . , . . . . . O X . O |
$$ | . . O X O . . . . . . . . . . O O X . |
$$ | . . O X . 1 . . . . . . . . . . . . . |
$$ | . . . 2 . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . O O . . |
$$ | . . O O O . . . . , . . . . . , X . . |
$$ | . . X X X O O O . . . . . X . X . . . |
$$ | . . . . . X X O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The above move :w1: is sente, since it threatens to save the two white stones, so Black responds with :b2:. Then White can play elsewhere.

I've seen this kind of shape before, like in move 8 of this joseki
Click Here To Show Diagram Code
[go]$$B san-san invasion joseki
$$ +--------------------
$$ | . . . . . . . . . .
$$ | . . . . . 1 2 . . .
$$ | . . X X 3 O . . . .
$$ | . . O O 5 4 . . . ,
$$ | . 8 . 7 6 . . . . .
$$ | . . . 9 0 . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]


but it's not yet natural for me.

The next move is not easy to find. Katago suggests


Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . O O X . . . . . |
$$ | . . . X X O . . . O O . O X X X . . . |
$$ | . . X X O . O X X X X O O X O X . . . |
$$ | . X O O O . . X O O O O O O O , X . . |
$$ | . X . . . . . . X . X . X X X X . . X |
$$ | . . X . O . . X . . . . X O O O X X O |
$$ | . . . . . . . . . . . . . . O . O O O |
$$ | . . . . O O . X . . X . . O . O O X X |
$$ | . . X X X O . . . . . . . . O X X X . |
$$ | . . X O O X . O . , . . . . . O X . O |
$$ | . . O X O . . . . . . . . . . O O X . |
$$ | . . O X . 1 . . . . . . . . . . . . . |
$$ | . a . 2 . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . 3 . . . . . . . . . . . . . O O . . |
$$ | . . O O O . . . . , . . . . . , X . . |
$$ | . b X X X O O O . . . . . X . X . . . |
$$ | . . . . . X X O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


It seems that this move threatens "a" which saves the two stones, and "b" which seems to kill the corner by ko if I am not mistaken.

Click Here To Show Diagram Code
[go]$$Wcm3
$$ | . 1 . . . . . . . . . . . . . O O . . |
$$ | . . O O O . . . . , . . . . . , X . . |
$$ | . 3 X X X O O O . . . . . X . X . . . |
$$ | 5 4 . 6 . X X O . . . . . . . . . . . |
$$ | . 7 8 . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
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