Can you find the tesuji I missed on OGS?

Uberdude · #1

Here is a position from a recent OGS game of mine where my opponent found a devastating tesuji that I had totally overlooked. Can you find it too?

I was black and had just killed the white stones on the lower side, and had ignored his move at tengen to close the top right corner as a "please resign, the game is simply over now" move. The joy of killing had gone to my head and I was feeling a bit cocky in ignoring his maybe-sente peep at tengen. How to punish me?

Click Here To Show Diagram Code: [go]$$Wc White to play and save the lower side stones $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . 2 . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . 1 . . . . . , . . . | $$ | . X . . . O . O . . . X X . . . . . . | $$ | . . . O . . . . X X . X O . . . O . . | $$ | . . X O . . X . X O O O X X . . . . . | $$ | . . X . . . . . . O X X O X . . . . . | $$ | . . . . O O X X O . X O O O O O . . . | $$ | . . O O . X O . O X . X O X O , O . . | $$ | . . X X . X O . O . X . X X . X O . . | $$ | . . . . . . X . . . . . . . X . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Answer:

Splatted · #2

My answer before looking at Uberdude's.

Edit: Not even close. XD

Uberdude · #3

@Splatted

Amelia · #4

I think rather than trying to solve the problem, I'll try to understand the solution, and if I manage even that I'll be quite happy with myself :mrgreen:

jts · #5

So as I understand it, this :w7:

is the tesuji:

And I was looking at that, but what is wrong with connecting?

Click Here To Show Diagram Code: [go]$$Wc White to play and save the lower side stones $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . 2 . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . 1 . . . . . , . . . | $$ | . X . . . O . O . . . X X . . . . . . | $$ | . . . O . . . . X X . X O . . . O . . | $$ | . . X O . . X . X O O O X X . . . . . | $$ | . . X . . . . . . O X X O X . . . . . | $$ | . . . . O O X X O . X O O O O O . . . | $$ | . . O O . X O 4 O X . X O X O , O . . | $$ | . . X X . X O 5 O 9 X 0 X X . X O . . | $$ | . . . . . 6 X 3 . . 7 8 . . X . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

The liberty situation:

Click Here To Show Diagram Code: [go]$$Wc White to play and save the lower side stones $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O . 3 2 X X . . . . . . | $$ | . . . O . . 7 . X X 1 X O . . . O . . | $$ | . . X O . . X . X O O O X X . . . . . | $$ | . . X . . . . 6 5 O X X O X . . . . . | $$ | . . . . O O X X O . X O O O O O . . . | $$ | . . O O . X O X O X . X O X O , O . . | $$ | . . X X . X O O O O X X X X . X O . . | $$ | . . . . . X X O . 4 W X . . X . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Ah, okay. That's nasty.

Uberdude · #6

jts wrote:

So as I understand it, this :w7:

is the tesuji:

Splatted · #7

Uberdude wrote:

@Splatted

jts · #8

Uberdude · #9

@jts

Heh, I didn't notice my move didn't take a liberty so white can just easily capture. So instead 3 at a or indeed 4 as you say, all have the same approach liberty problem. I wouldn't want to let black connect under as it is free points and also then b4 is definitely not sente on the lower left corner. I don't understand what you mean by "lock in". You can surely read both work and one is unconditionally better so why choose the inferior one?

jts · **#10**

Uberdude wrote:

@jts

Heh, I didn't notice my move didn't take a liberty so white can just easily capture. So instead 3 at a or indeed 4 as you say, all have the same approach liberty problem. I wouldn't want to let black connect under as it is free points and also then b4 is definitely not sente on the lower left corner. I don't understand what you mean by "lock in". You can surely read both work and one is unconditionally better so why choose the inferior one?

Well, it's embarrassing to say, but to my mind 4 liberties to 4 liberties is a settled capturing race, beyond question, whereas 4 liberties to 3 liberties plus two approach moves is something that I might have misread.

Bill Spight · **#11**

Click Here To Show Diagram Code: [go]$$Bcm8 Black to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O 6 O X X X . . . . . . | $$ | . . . O . . O 8 X X O X O . . . O . . | $$ | . . X O . 2 X 1 X O O O X X . . . . . | $$ | . . X . . . 0 X O O X X O X . . . . . | $$ | . . . . O O X X O . X O O O O O . . . | $$ | . . O O . X O X O X . X O X O , O . . | $$ | . . X X . X O O O O X X X X . X O . . | $$ | . . . . . X X O 9 X W X . . X . X . . | $$ | . . . . . . 5 3 4 . 7 . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Bcm8 Black to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O . O X X X . . . . . . | $$ | . . . O . . O . X X O X O . . . O . . | $$ | . . X O . 3 X 1 X O O O X X . . . . . | $$ | . . X . . . . X O O X X O X . . . . . | $$ | . . . . O O X X O . X O O O O O . . . | $$ | . . O O . X O X O X . X O X O , O . . | $$ | . . X X . X O O O O X X X X . X O . . | $$ | . . . . . X X O . X W X . . X . X . . | $$ | . . . . . . . 2 . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Bcm8 Black to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O . O X X X . . . . . . | $$ | . . . O . . O . X X O X O . . . O . . | $$ | . . X O . 3 X 1 X O O O X X . . . . . | $$ | . . X . . . . X O O X X O X . . . . . | $$ | . . . . O O X X O . X O O O O O . . . | $$ | . . O O . X O X O X . X O X O , O . . | $$ | . . X X . X O O O O X X X X . X O . . | $$ | . . . . . X X O . X W X . . X . X . . | $$ | . . . . . . 7 . 2 6 4 5 . . . . . . . | $$ ---------------------------------------[/go]

drmwc · **#12**

What is worng with these ideas?

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

W will need to find a semeia aginst the lower B group. This may be plausible for for W - there is a line with both living, for example.

So maybe my second idea is better:

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

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

B seems to win this semeai. Other move orders are possible, but everyhting seems to converge on this diagram eventually. Edit:

ACtually, W will probably play this:

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

and will live. SO maybe it doesn't work for B after all...

Here's another semeai from the first variation:

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

Click Here To Show Diagram Code: [go]$$Bc Idea 1 fight! continued $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O . . . X X . . . . . . | $$ | . . . O . . . . X X X X O . . . O . . | $$ | . . X O . . X . X O O O X X . . . . . | $$ | . . X . . . . . 1 O X X O X . . . . . | $$ | . . . . O O X X O 2 X O O O O O . . . | $$ | . . O O . X O X O X 3 X O X O , O . . | $$ | . . X X . X O O O . X X X X 0 X O . . | $$ | . . . . . X X O . O O O O X X . X O O | $$ | . . . . . . . 4 X 7 . 6 5 8 9 . . X . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Bc Idea 1 fight! moar continued $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O . . . X X . . . . . . | $$ | . . . O . . . . X X X X O . . . O . . | $$ | . . X O . . X . X O O O X X . . . . . | $$ | . . X . . . . . X O X X O X . . . . . | $$ | . . . . O O X X O O X O O O O O . . . | $$ | . . O O . X O X O X X X O X O 4 O . . | $$ | . . X X . X O O O 1 X X X X O X O . . | $$ | . . . . . X X O 6 O O O O X X 2 X O O | $$ | . . . . . . 5 O X X . O 7 O X 3 . X . | $$ ---------------------------------------[/go]

and I think B wins the ko. W has one ko therat (taking the two stones) but needs 2.

Obviously, I may have misread a stack of things here.

Uberdude · **#13**

Variation for 10: bigger eye better, no?

Click Here To Show Diagram Code: [go]$$Bc Idea 1 fight! continued $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O . . . X X . . . . . . | $$ | . . . O . . . . X X X X O . . . O . . | $$ | . . X O . . X . X O O O X X . . . . . | $$ | . . X . . . . . 1 O X X O X . . . . . | $$ | . . . . O O X X O 2 X O O O O O . . . | $$ | . . O O . X O X O X 3 X O X O , O . . | $$ | . . X X . X O O O 0 X X X X . X O . . | $$ | . . . . . X X O . O O O O X X . X O O | $$ | . . . . . . . 4 X 7 . 6 5 8 9 . . X . | $$ ---------------------------------------[/go]

drmwc · **#14**

Can B change the order:

Click Here To Show Diagram Code: [go]$$Bc Idea 1 fight! continued $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . O . . . . . . . O . . O . . . . . | $$ | . X . O . O . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X O . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . O . . . . . , . . . | $$ | . X . . . O . O . . . X X . . . . . . | $$ | . . . O . . . . X X X X O . . . O . . | $$ | . . X O . . X . X O O O X X . . . . . | $$ | . . X . . . . . . O X X O X . . . . . | $$ | . . . . O O X X O 2 X O O O O O . . . | $$ | . . O O . X O X O X 3 X O X O , O . . | $$ | . . X X . X O O O 1 X X X X . X O . . | $$ | . . . . . X X O . O O O O X X . X O O | $$ | . . . . . . . 4 X . . . 5 . . . . X . | $$ ---------------------------------------[/go]

and it's the same as the line I gave?

Can you find the tesuji I missed on OGS?

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