A "Pro-Level" Tsumego

[ethanb]

@ethanb:

$$Bc
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | . . O O . O X . . , . . . . . , . . . |
$$ | . . . O X X . X . . . . . . . . . . . |
$$ | . 2 . O X . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Bc
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | . . O O . O X . . , . . . . . , . . . |
$$ | . . . O X X . X . . . . . . . . . . . |
$$ | . 2 . O X . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Looks like this white lives, but black has lots of sente endgame. I'd be ok in most real games with this if I couldn't find the kill.

How does white respond to this black move:

$$Bc
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | . . O O . O X . . , . . . . . , . . . |
$$ | . . . O X X . X . . . . . . . . . . . |
$$ | 3 2 . O X . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

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

By throwing the board, I think. That is a NICE tesuji.

[hiyayang]

@ethanb:

How does white respond to this black move:

$$Bc
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | . . O O . O X . . , . . . . . , . . . |
$$ | . . . O X X . X . . . . . . . . . . . |
$$ | 3 2 . O X . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

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

By throwing the board, I think. That is a NICE tesuji.

And that would make it an interesting tsumego too.

For those who are wondering about the status of the white corner after , here is a diagram to show it is dead:

$$Bc white dies
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | . 7 O O . O X . . , . . . . . , . . . |
$$ | 4 5 . O X X . X . . . . . . . . . . . |
$$ | 3 2 . O X . . . . . . . . . . . . . . |
$$ | 6 . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Bc white dies
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | . 7 O O . O X . . , . . . . . , . . . |
$$ | 4 5 . O X X . X . . . . . . . . . . . |
$$ | 3 2 . O X . . . . . . . . . . . . . . |
$$ | 6 . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

It would not work if black switched the order of and above, like this:

$$Bc white lives
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | 6 4 O O . O X . . , . . . . . , . . . |
$$ | . 3 . O X X . X . . . . . . . . . . . |
$$ | 5 2 7 O X . . . . . . . . . . . . . . |
$$ | . 8 9 0 . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Bc white lives
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | 6 4 O O . O X . . , . . . . . , . . . |
$$ | . 3 . O X X . X . . . . . . . . . . . |
$$ | 5 2 7 O X . . . . . . . . . . . . . . |
$$ | . 8 9 0 . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

White group has enough outside liberties to kill the black inside, even though the latter has an eye. Note that black at doesn't connect. (If black plays instead of , white plays and the result would be the same as the diagram below.)

Other black moves like the below would also allow white to live:

$$Bc white lives
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | 9 X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | 7 6 O O . O X . . , . . . . . , . . . |
$$ | 3 5 8 O X X . X . . . . . . . . . . . |
$$ | 4 2 . O X . . . . . . . . . . . . . . |
$$ | . . . 0 . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Bc white lives
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | 9 X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O . O . . . . . . . . . . . . . |
$$ | 7 6 O O . O X . . , . . . . . , . . . |
$$ | 3 5 8 O X X . X . . . . . . . . . . . |
$$ | 4 2 . O X . . . . . . . . . . . . . . |
$$ | . . . 0 . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

When white corner lacks outside liberties (e.g., the 'a' spots are taken by black), below is another way to kill white corner, but it doesn't work in this case (because doesn't put itself in atari):

$$Bc white lives
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O a O . . . . . . . . . . . . . |
$$ | 7 6 O O a O X . . , . . . . . , . . . |
$$ | 9 5 0 O X X . X . . . . . . . . . . . |
$$ | 8 2 . O X . . . . . . . . . . . . . . |
$$ | . . 4 3 . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Bc white lives
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . X X X . . . X . . . . . . . . . . . |
$$ | 1 O X O a O . . . . . . . . . . . . . |
$$ | 7 6 O O a O X . . , . . . . . , . . . |
$$ | 9 5 0 O X X . X . . . . . . . . . . . |
$$ | 8 2 . O X . . . . . . . . . . . . . . |
$$ | . . 4 3 . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

[gonut]

hiyayang,

Doesn't White have a better response to your Black A5 attack?
I would answer this question myself, but I still miss bulky fives.

(;AB[co][cn][bn][dn][dl][fm][hn][gp][hq][fq][eq][er][ao]AW[dr][dq][dp][do][cp][bo][fp][fo]SZ[19]C[White's response to the marked stone?]
TR[ao]
;W[bq]C[White's toughest defense?]
(;B[br]C[Best attack?];W[ar];B[cr];W[bs];B[cs]C[Black only has a ko.])
(;B[cr]C[Inferior?];W[ds];B[ar];W[bp];B[br];W[bs]C[Seki])
(;B[ar]C[Inferior?];W[bp];B[ap];W[aq];B[cr];W[ds];B[br];W[bs]C[Seki])
(;B[aq]C[Bad?];W[ar];B[cr];W[bs]C[White lives with territory.]))

[hiyayang]

hiyayang,

Doesn't White have a better response to your Black A5 attack?

Correct. White has better responses than B2. I was just expanding on ethanb's post. I think white B4 would be OK too.