It's probably not quite true to say that this is the only move, but it's certainly the one that is simple and clean and avoids future complications. My lower-right group is getting a little constricted, but still has space for two eyes. I'm still not really sure why 1986 is playing this out - does he really think he has a chance to live? I think the game is close, despite me having gained quite a few points over recent moves, so why not make moves in unfinished parts of the board rather than waste ko threats over here?

Indeed, robinz's 151 capture was better than (a) throw-in,
but 153 should be at :

Click Here To Show Diagram Code

[go]$$B
$$--------------+
$$ . . . . . . . |
$$ X X X . . . . |
$$ O O O O O O . |
$$ O X X X X O . |
$$ X O . . X X X |
$$ O . O X O O . |
$$ . . . X X X O |
$$ . . B . X O . |
$$ . X . X O O . |
$$ X . X X X O . |
$$ X O O O X O . |
$$ O X X O O a . |
$$ . O X O X O O |
$$ . O X X X X W |
$$ O X . . . . . |
$$ . . . X . 1 . |
$$ . O . . X . . |
$$ . . . O . . . |
$$ . . . . . . . |
$$----------------[/go]

Re: 152 = another aji keshi move to help B.

The more you play at that dead group the less you will get out of them.

lets caputure this one stone, and go from there, 
i dont think this is sente so its on him now ...
*the anticipation is killing me*

I thought me might get that move in at some point - it's been there for most of the game. But I get to block in sente - if he captures, I'll probably finally play R2, to make my corner group absolutely 100% alive, and also, of course because it's fairly big (and sort-of sente). I don't really expect 1986 to play the obvious reply, though, on recent evidence

lets keep on pushing on this bottom corner, 
he's running short on liberties, and eye space

OK, that's a slightly strange order of moves, but no harm done. I honestly didn't even have to think about this move - I'm just being consistent with my previous play and making my group secure while making sure his can't get any additional eyespace.

Click Here To Show Diagram Code

[go]$$B
$$. X . X X X O . |
$$. X O O O X O . |
$$O O X X O O . . |
$$. . O X O X O O |
$$. . O X X X X O |
$$. O X O X . X W |
$$. . . . X . . . |
$$. . O . . X . . |
$$. . . . O 1 . . |
$$. . . . . . . . |
$$-----------------[/go]

Continuing my attack on this conrner

robinz needs to be careful and read out the variations,
thanks to the "no thinking" 157 (there are more):

Click Here To Show Diagram Code

[go]$$B
$$ . X . X O O . |
$$ X . X X X O . |
$$ X O O O X O . |
$$ O X X O O . . |
$$ . O X O X O O |
$$ . O X X X X O |
$$ O X O X . X O |
$$ . . . X . X . |
$$ . O . . X . . |
$$ . . 3 O 1 O . |
$$ . . . . 2 . . |
$$---------------+[/go]

Click Here To Show Diagram Code

[go]$$B (a) and (b) are miai
$$ . X . X O O . |
$$ X . X X X O . |
$$ X O O O X O . |
$$ O X X O O . . |
$$ . O X O X O O |
$$ . O X X X X O |
$$ O X O X . X O |
$$ . . . X . X 6 |
$$ . O 4 5 X 7 8 |
$$ . . 3 W 1 O b |
$$ . . . 9 2 a . |
$$---------------+[/go]

Click Here To Show Diagram Code

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

Click Here To Show Diagram Code

[go]$$B (c) and (d) are miai
$$ . X . X O O . |
$$ X . X X X O . |
$$ X O O O X O . |
$$ O X X O O . . |
$$ . O X O X O O |
$$ . O X X X X O |
$$ O X O X . X O |
$$ . . . X . X 6 |
$$ . O 5 . X 4 7 |
$$ . . 3 O 1 O d |
$$ . . . . 2 c . |
$$---------------+[/go]

This is what I'd always planned in response to that particular white move. But it turns out that I'd read it rather superficially before, and I've just discovered more interesting tactics lurking in the position that I previously thought.

For a start, if white just blocks, I need to find a throw-in in order to win the ensuing capturing race:

Click Here To Show Diagram Code

[go]$$Bcm159 Prisoner Count
$$ +---------------------------------------+
$$ | . . . . . . . . . . . O . . . . . . . |
$$ | . . . . . . . O X . . O X X X . . . . |
$$ | . . . . O X . O X . X X O O O O O O . |
$$ | . . . O . X . . . X X O O X X X X O . |
$$ | . . . . . . . O . . O X X O . . X X X |
$$ | . . O . O . . . . O . . O . O X O O . |
$$ | . . O X . . . . . . . . . . . X X X O |
$$ | . O X O O O O . . . . . . . X . X O . |
$$ | . O X X . X X X . . . . . X . X O O . |
$$ | . . X , X . . . . , O . X . X X X O . |
$$ | . . X X X . . . . . . . X O O O X O . |
$$ | . . . O . . . . . . . O O X X O O . . |
$$ | . . O . X X X X . X . . . O X O X O O |
$$ | . O O . X O O X O . . . . O X X X X O |
$$ | X X O X . . . O X X . . O X O X . X O |
$$ | . . X O O O . . O , . . . . . X . X . |
$$ | X X X O X O . . . . O . . O 4 5 X . . |
$$ | . . . X X O . . . . . . . . 3 O 1 O . |
$$ | . . . . . . . . . . . . . . 9 6 2 7 8 |
$$ +---------------------------------------+[/go]

(Yes, I know, this is such basic stuff even a DDK should be able to find it - my point is just that it was only just now that I found it myself, having realised I couldn't simply atari )

Secondly, with S2 on the board, white can push at T4 to much better effect that he could before. But on reflection, I'm not worried about this - there are no eyes for him in the corner (I can play S3 in sente), and I can play P2 whenever the time is right. And, if I've missed something and my group gets in trouble, I can always as a last resort play O4 to guarantee a second eye at P4. (But of course the most important thing is to keep white's group from getting a second eye - living with my group is only important to this end.)

Seems like this turns into a ko?

Click Here To Show Diagram Code

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

5 at 6 is sometimes the move to avoid the ko, but here it seems to not work since white can just ruin black's eyes and win the race instead

Ok I played around with this move last night,
I just wanted to make sure it's cut proof and I'm pretty confident
I can Handel blacks resonse

OK, I'm officially an idiot

For some reason, it was only after seeing my opponent's move, and being about to play the planned O2, that I noticed the blindingly obvious ko I was walking into:

Click Here To Show Diagram Code

[go]$$Bcm161 Prisoner Count
$$ +---------------------------------------+
$$ | . . . . . . . . . . . O . . . . . . . |
$$ | . . . . . . . O X . . O X X X . . . . |
$$ | . . . . O X . O X . X X O O O O O O . |
$$ | . . . O . X . . . X X O O X X X X O . |
$$ | . . . . . . . O . . O X X O . . X X X |
$$ | . . O . O . . . . O . . O . O X O O . |
$$ | . . O X . . . . . . . . . . . X X X O |
$$ | . O X O O O O . . . . . . . X . X O . |
$$ | . O X X . X X X . . . . . X . X O O . |
$$ | . . X , X . . . . , O . X . X X X O . |
$$ | . . X X X . . . . . . . X O O O X O . |
$$ | . . . O . . . . . . . O O X X O O . . |
$$ | . . O . X X X X . X . . . O X O X O O |
$$ | . O O . X O O X O . . . . O X X X X O |
$$ | X X O X . . . O X X . . O X O X . X O |
$$ | . . X O O O . . O , . . . . . X . X . |
$$ | X X X O X O . . . . O . . O 2 3 X . . |
$$ | . . . X X O . . . . . . . . 1 O X O . |
$$ | . . . . . . . . . . . . . . 4 . O . . |
$$ +---------------------------------------+[/go]

After looking at this for a while, I realised that my initial instinct was correct: that I can't possibly win this ko. White has at least 2 unignorable ko threats to live on the right (as well as a couple of unrelated but huge ones on top). While I have a number of ko threats to make 2 eyes or escape with my lower right group, white can happily ignore any of these, win the ko, and connect out with his group by playing H4 - and then I can resign.

So I must go back and stop this connection - and accept that I can never get two eyes for this group if my opponent doesn't want me to have them; I have to win the capturing race instead. Fortunately, while it's difficult for me to read, I'm pretty sure I should do so. My choice of move was between this and S3 - I quite liked S3 at first because it gave me more of the corner, assuming I win the capturing race, and takes a liberty away from S2 which might be important in some lines. But it removes a liberty from my group, as well as allowing white a further ko threat. H4 is the most direct move to achieve my goals, so I've made it. Of course, my last move is now just huge aji keshi, and I've also given up several points in the corner - but I am still back in the game and able to fight over the remaining undecided areas.

This is assuming I'm right that I will win this capturing race, of course

(It's not all bad though - if white ignores, I can still play O4 to live; and what's more, now I've walled off the right for good, the ko looks distinctly playable for me. But white has ways to prevent both, notably P3.)

this stops him from playing n7, however its not sente
so its back on him now...

Very natural now? Then, (a) and (b) seem perfect local threats for B:

Click Here To Show Diagram Code

[go]$$B
$$. . . X . X O O . |
$$O . X b X X X O . |
$$. . X O O O X O . |
$$. O O X X O O a . |
$$. . . O X O X O O |
$$. . . O X X X X O |
$$. . O B O X . X O |
$$. . . W . X . X X |
$$O . . O 2 3 X . . |
$$. . . . 1 O X O . |
$$. . . . 4 5 O . . |
$$------------------+[/go]

There goes the second eye, so the semeai it is! It's times like this I really wish I could read properly

It's possible that I've missed some tesujis, or better move sequences, here, but if not, I think the situation is as follows. Both sides have one eye (neither being a "big eye") and there are no shared liberties, so it comes down to who takes the fewest net plays to capture the opponent's stones. I can capture white in 5:

Click Here To Show Diagram Code

[go]$$Bc Prisoner Count
$$ +---------------------------------------+
$$ | . . . . . . . . . . . O . . . . . . . |
$$ | . . . . . . . O X . . O X X X . . . . |
$$ | . . . . O X . O X . X X O O O O O O . |
$$ | . . . O . X . . . X X O O X X X X O . |
$$ | . . . . . . . O . . O X X O . . X X X |
$$ | . . O . O . . . . O . . O . O X O O 7 |
$$ | . . O X . . . . . . . . . . . X X X O |
$$ | . O X O O O O . . . . . . . X . X O 5 |
$$ | . O X X . X X X . . . . . X . X O O 9 |
$$ | . . X , X . . . . , O . X 3 X X X O a |
$$ | . . X X X . . . . . . . X O O O X O b |
$$ | . . . O . . . . . . . O O X X O O 1 2 |
$$ | . . O . X X X X . X . . . O X O X O O |
$$ | . O O . X O O X O . . . . O X X X X O |
$$ | X X O X . . . O X X . . O . O X . X O |
$$ | . . X O O O . . O , . . . O . X . X X |
$$ | X X X O X O . . . . O . . O . . X . . |
$$ | . . . X X O . . . . . . . . . O X O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ +---------------------------------------+[/go]

- here is at , and and are at a and b. Seven plays for me, 2 for white - so 5 net plays.
For white to capture me, is ... 4 net plays

Click Here To Show Diagram Code

[go]$$Wc Prisoner Count
$$ +---------------------------------------+
$$ | . . . . . . . . . . . O . . . . . . . |
$$ | . . . . . . . O X . . O X X X . . . . |
$$ | . . . . O X . O X . X X O O O O O O . |
$$ | . . . O . X . . . X X O O X X X X O . |
$$ | . . . . . . . O . . O X X O . . X X X |
$$ | . . O . O . . . . O . . O . O X O O . |
$$ | . . O X . . . . . . . . . . . X X X O |
$$ | . O X O O O O . . . . . . . X . X O . |
$$ | . O X X . X X X . . . . . X . X O O . |
$$ | . . X , X . . . . , O . X . X X X O . |
$$ | . . X X X . . . . . . . X O O O X O . |
$$ | . . . O . . . . . . . O O X X O O . . |
$$ | . . O . X X X X . X . . . O X O X O O |
$$ | . O O . X O O X O . . . . O X X X X O |
$$ | X X O X . . . O X X . . O . O X 9 X O |
$$ | . . X O O O . . O , . . . O 7 X 6 X X |
$$ | X X X O X O . . . . O . . O . 3 X 5 1 |
$$ | . . . X X O . . . . . . . . . O X O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ +---------------------------------------+[/go]

I couldn't find any alternative plays for me in the above sequence which work out any better. So much for my previous statement that I would win the semeai.

But I think I'm OK if I try to increase my liberties first. Well, actually, this doesn't really increase my liberties so much as cause a shortage of liberties for white as he tries to capture me. An example:

Click Here To Show Diagram Code

[go]$$Bcm163 Prisoner Count
$$ +---------------------------------------+
$$ | . . . . . . . . . . . O . . . . . . . |
$$ | . . . . . . . O X . . O X X X . . . . |
$$ | . . . . O X . O X . X X O O O O O O . |
$$ | . . . O . X . . . X X O O X X X X O . |
$$ | . . . . . . . O . . O X X O . . X X X |
$$ | . . O . O . . . . O . . O . O X O O . |
$$ | . . O X . . . . . . . . . . . X X X O |
$$ | . O X O O O O . . . . . . . X . X O . |
$$ | . O X X . X X X . . . . . X . X O O . |
$$ | . . X , X . . . . , O . X . X X X O . |
$$ | . . X X X . . . . . . . X O O O X O . |
$$ | . . . O . . . . . . . O O X X O O . . |
$$ | . . O . X X X X . X . . . O X O X O O |
$$ | . O O . X O O X O . . . . O X X X X O |
$$ | X X O X . . . O X X . . O . O X . X O |
$$ | . . X O O O . . O , . . . O . X . X X |
$$ | X X X O X O . . . . O . . O . 5 X 2 3 |
$$ | . . . X X O . . . . . . . . 6 O X O 1 |
$$ | . . . . . . . . . . . . . . . . O 4 . |
$$ +---------------------------------------+[/go]

- and now I have 5 liberties with a further approach move required from white, for 6 effective liberties.

Oh well, I've probably missed something - but this is what I'm playing.

Why didn't I see all this way back when I thought white had just killed himself in gote?