I have just studied the following position and I discovered ( ) my intuition was not that good. I imagine that some of you might also be wrong and that is the reason why I show you this semeai for analysis.

Click Here To Show Diagram Code

[go]$$B Black to play - What is the best black move?
$$ ------------------
$$ . . X . . . . . |
$$ . . X X X O . . |
$$ . . . . X O O . |
$$ . . . . X X O . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . , O O . |
$$ . . . . . . O . |
$$ . . . . . . O O |
$$ . . . . . . . . |
$$ . . . . . . . . |
$$[/go]

I think it is like this. I recall having something similar in a game recently but I played too quickly then. Hope I'm not posting too quickly

S19 is a common tesuji to reduce liberties quickly in this kind of corner shape.

That's the intuition part - which is probably wrong:) I look forward to seeing the definitive analysis in due course.

At least you confirm it is a rather common semeai!

It seems white has not find the best move in your main sequence:

The known moves for black to handle this corner are the following ones (a to e)

Click Here To Show Diagram Code

[go]$$B Black to play - What is the best black move?
$$ ------------------
$$ . . X . . a b . |
$$ . . X X X O . c |
$$ . . . . X O O . |
$$ . . . . X X O d |
$$ . . . . . O X e |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . , O O . |
$$ . . . . . . O . |
$$ . . . . . . O O |
$$ . . . . . . . . |
$$ . . . . . . . . |
$$[/go]

But which one is the best and why? OC you have to find the best black and white moves.

Pure shape intuition. Don't know and haven't tried to read it out.

Quite good lightvector. It is a big progress because you prove black can kill white unconditionnally. Unfortunately your moves are not all the best one to reach the best score. Some more work is still needed.

Click Here To Show Diagram Code

[go]$$B Black to play - What is the best black move?
$$ ------------------
$$ . . X . . . . . |
$$ . . X X X O . . |
$$ . . . . X O O . |
$$ . . . . X X O . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . , O O . |
$$ . . . . . . O . |
$$ . . . . . . O O |
$$ . . . . . . . . |
$$ . . . . . . . . |
$$[/go]

After two months it's time to give you the answer to this problem.

First of all the wrong answer:

Click Here To Show Diagram Code

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

After black territory will be only 12 points.

Click Here To Show Diagram Code

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

With this above the final black territory will be 13 points!

The only issue with this is to verify that black can kill the corner unconditionnaly.

Here is the proof:

Click Here To Show Diagram Code

[go]$$B at
$$ ------------------
$$ . . X 7 4 9 5 8 |
$$ . . X X X O 6 1 |
$$ . . . . X O O 2 |
$$ . . . . X X O . |
$$ . . . . . O X 3 |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . . O X . |
$$ . . . . , O O . |
$$ . . . . . . O . |
$$ . . . . . . O O |
$$ . . . . . . . . |
$$ . . . . . . . . |
$$[/go]

Click Here To Show Diagram Code

[go]$$Bcm9 at
$$ ------------------
$$ . . X X 2 3 9 O |
$$ . . X X X O O . |
$$ . . . . X O O O |
$$ . . . . X X O . |
$$ . . . . . O X X |
$$ . . . . . O X . |
$$ . . . . . O X 8 |
$$ . . . . . O X 5 |
$$ . . . . . O X 4 |
$$ . . . . , O O 6 |
$$ . . . . . . O . |
$$ . . . . . . O O |
$$ . . . . . . . . |
$$ . . . . . . . . |
$$[/go]

and white is dead

Not that easy is it?