Both black and white should play b. Black would get a point at a and white playing there would prevent black from getting this point. Was this the other good thing about ? It enables this extra point (assuming white decides to play elsewhere)?

Yep.

Since we don't know the rest of the board, we don't know who will get to play at "b", we count the point at "a" as 1/2 point for Black.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Next question:

Click Here To Show Diagram Code

[go]$$W
$$ . . . . O O O O O O . .
$$ . , . . O X O X X X . .
$$ . . . X X X O . . . X .
$$ . . X . 4 3 O O X X X .
$$ . . X 6 5 1 X O O O X .
$$ . . X . . . 2 X X . X .
$$ . . X X X X X X X X X .
$$ . , . . . . . , . . . .[/go]

Does Black have a better play than ?

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Click Here To Show Diagram Code

[go]$$W
$$ . . . . O O O O O O . .
$$ . , . . O X O X X X . .
$$ . . . X X X O . . . X .
$$ . . X . . 2 O O X X X .
$$ . . X . . 1 X O O O X .
$$ . . X . . . . X X . X .
$$ . . X X X X X X X X X .
$$ . , . . . . . , . . . .[/go]

White would have to capture the stone or risk being cut off..

Click Here To Show Diagram Code

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

That is very interesting. The possibility of sacrificing the stone to gain more territory hadn't actually occurred to me before.

Bravo!

BTW, in a real game, after is so small by comparison with - that White will probably have a bigger play somewhere else, and will not play right away. In fact, Black will probably be able to play there with sente.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Awesome. Thanks. It is interesting to note how focusing on preserving my territory rather than just getting offending and trying to block my opponent makes a difference.