The rubric says if you can do it in 3 minutes then you're a shodan.
Again, it should not take more than a second to see that 1 is a likely vital point.
$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . . O X . . . . .
$$ | X 1 . X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . . O X . . . . .
$$ | X 1 . X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .[/go]
You can gain that sort of superficial "instinct" for the vital point through "force feeding", as I've said above. But it's only good up to a certain point.
Let's look a bit deeper:
If connects, then Black notices a problem: he cannot directly create a dead internal shape:
$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . . O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . . O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .[/go]
$$B Page 25, Problem No. 4: White creates a seki (Black cannot give atari without granting four-in-a-row)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 3 4 O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25, Problem No. 4: White creates a seki (Black cannot give atari without granting four-in-a-row)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 3 4 O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .[/go]
Therefore, Black has to find another way:
$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . 3 O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . 3 O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .[/go]
And now Black threatens to almost fill with bulky five, leaving White with ko as the only resistance:
$$B Page 25, Problem No. 4: Book solution - ko
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 4 3 O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25, Problem No. 4: Book solution - ko
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 4 3 O X . . . . .
$$ | X 1 2 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .[/go]
But here is the thing: as I considered this position, I thought that I could make out the potential for two other fundamental ideas: the farmer's hat and shortage of liberties.
$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . . O X . . . . .
$$ | X 2 1 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | . . O X . . . . .
$$ | X 2 1 X . . . . .
$$ | O . O X . . . . .
$$ | . O O X . . . . .
$$ | . X X X . . . . .[/go]
Surely now White has got two problems on her hands: that a Black stone on X would be occupying the vital point of the farmer's hat, while the other stones would be caught in a shortage of liberties:
$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | M . O X . . . . .
$$ | X 2 1 X . . . . .
$$ | @ . @ X . . . . .
$$ | . @ @ X . . . . .
$$ | . X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25, Problem No. 4: Black to make ko (kill?)
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | M . O X . . . . .
$$ | X 2 1 X . . . . .
$$ | @ . @ X . . . . .
$$ | . @ @ X . . . . .
$$ | . X X X . . . . .[/go]
Black plays at the marked point, and the shortage of liberties seems to be White's downfall when trying to make a second eye:
$$B Page 25: White cannot play 4 at X because of shortage of liberties
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 3 4 O X . . . . .
$$ | X 2 1 X . . . . .
$$ | O . O X . . . . .
$$ | M O O X . . . . .
$$ | 5 X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25: White cannot play 4 at X because of shortage of liberties
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 3 4 O X . . . . .
$$ | X 2 1 X . . . . .
$$ | O . O X . . . . .
$$ | M O O X . . . . .
$$ | 5 X X X . . . . .[/go]
When White captures, Black simply plays atari on the three stones, leaving the eye false:
$$B
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | 6 O O X . . . . .
$$ | . O O X . . . . .
$$ | . O 1 X . . . . .
$$ | O . O X . . . . .
$$ | 7 O O X . . . . .
$$ | X X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | 6 O O X . . . . .
$$ | . O O X . . . . .
$$ | . O 1 X . . . . .
$$ | O . O X . . . . .
$$ | 7 O O X . . . . .
$$ | X X X X . . . . .[/go]
$$B
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | 6 O O X . . . . .
$$ | . O O X . . . . .
$$ | . O 1 X . . . . .
$$ | O . O X . . . . .
$$ | 7 O O X . . . . .
$$ | X X X X . . . . .
- Click Here To Show Diagram Code
[go]$$B
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | 6 O O X . . . . .
$$ | . O O X . . . . .
$$ | . O 1 X . . . . .
$$ | O . O X . . . . .
$$ | 7 O O X . . . . .
$$ | X X X X . . . . .[/go]
Am I missing something?
Could it be that White can play a hane and make a "Hail Mary" sort of ko?
$$B Page 25: White cannot play 4 at X because of shortage of liberties
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 3 6 O X . . . . .
$$ | X 2 1 X . . . . .
$$ | O . O X . . . . .
$$ | 7 O O X . . . . .
$$ | 4 X X X . . . . .
$$ | 5 . . . . . . . .
- Click Here To Show Diagram Code
[go]$$B Page 25: White cannot play 4 at X because of shortage of liberties
$$ ------------------
$$ | . . . . . . . . .
$$ | X X X . . . . . .
$$ | O O X . . . . . .
$$ | . O O X . . . . .
$$ | 3 6 O X . . . . .
$$ | X 2 1 X . . . . .
$$ | O . O X . . . . .
$$ | 7 O O X . . . . .
$$ | 4 X X X . . . . .
$$ | 5 . . . . . . . .[/go]
Black would get to play first, and the ko would be very heavy for White.
Whether or not I am missing something, I feel, again, I have learned something from this, because I have been able to practise the following points:
1) vital point
2) spotting potential bulky 5
3) spotting potential four-in-a-row
4) using ko to prevent bulky 5
5) shortage of liberties
6) noticing the potential for a farmer's hat
7) Using hane to increase the "stickability" of a group, in this case by setting up a rather desperate ko