Cho U's bite-sized tsumego.

[Solomon]

Found this on Twitter; Cho U has released some very cute (I think it's the blue and the pink stones that sold me) 4x4 tsumego, and you can find a handful here: http://photozou.jp/photo/list/1009326/2724169

Here's one taken from the album, blue to move:



If anyone knows Japanese and can provide a fuller description/objective of the problem, that'd be great . I want to assume that the 2.5/3 stars is a difficulty rating, similar to the star ratings he provided in one of his tsumego books.

[Kirby]

A translation should be something like this:

Yose Technique

<Problem picture>

The yose problems are continuing to "level up". First setup a ko, and then at the end, let's fire off a spectacular move (I put "spectacular move" for 妙手. Senseis talks about it here: http://senseis.xmp.net/?ExcellentMove).

[emeraldemon]

$$B
$$-----------
$$| . 4 6 O |
$$| X X 5 O |
$$| 3 O 2 O |
$$| . 1 . O |
$$-----------

Click Here To Show Diagram Code

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

Is this a win for black, using territory scoring? I've heard japanese rules don't count points in seki, but this is a slightly unusual situation.

[Bill Spight]

(;FF[4]CA[ISO8859-1]ST[2]AP[GOWrite:2.2.21]GM[1]SZ[4]PM[2]AB[ab][bb]FG[259:]GN[ ]PB[ ]PW[ ]AW[da][db][dc][dd][bc]
;B[cc]
;W[cb]
;B[bd]
;W[cd]
;B[ac]
;W[ad]
;B[ca]
;W[ba]
;B[bd]
)

Err, that is,

$$B Ko
$$ ----------
$$ | . 8 7 O |
$$ | X X 2 O |
$$ | 5 O 1 O |
$$ | 6 3 4 O |
$$ ----------

Click Here To Show Diagram Code

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

takes ko.

[Harleqin]

$$Bc
$$-----------
$$| . 4 6 O |
$$| X X 5 O |
$$| 3 O 2 O |
$$| . 1 . O |
$$-----------

Click Here To Show Diagram Code

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

Is this a win for black, using territory scoring? I've heard japanese rules don't count points in seki, but this is a slightly unusual situation.

Territory scoring, yes. A1 is obviously a point.

Japanese scoring contains (I believe) a misunderstanding that has gone mainstream. In the following situation, the free points count for no-one:

$$B
$$ -------------
$$ | . X X X X |
$$ | O O O O . |
$$ -------------

Click Here To Show Diagram Code

[go]$$B
$$ -------------
$$ | . X X X X |
$$ | O O O O . |
$$ -------------[/go]

In an attempt to be concise, one could say, looking at such a situation, that "there are no points in seki".

The misunderstanding is in applying that "proverb" to the following:

$$B
$$ -----------
$$ | . X X . |
$$ | X X O O |
$$ | . O O . |
$$ -----------

Click Here To Show Diagram Code

[go]$$B
$$ -----------
$$ | . X X . |
$$ | X X O O |
$$ | . O O . |
$$ -----------[/go]

Here, the upper right and lower left are no points, but the upper left and lower right are. However, the misapplication of above proverb nullifies the latter points.

This misunderstanding has subsequently been codified in several japanese rule sets. It is neither necessary nor useful for territory rules, however.

So, your situation does not count as a win in japanese rules, even though it is one under territory rules.