The previous move was indeed approach on the bottom left. Instead of that move, LZ157's main line is the following, but I don't understand the purpose of the exchange
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| Shapes to remember (SDK level) http://www.lifein19x19.com/viewtopic.php?f=48&t=16894 |
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| Author: | jlt [ Fri Aug 30, 2019 2:49 am ] |
| Post subject: | Shapes to remember (SDK level) |
In this thread I will post a few positions that occurred in my games, in which the best move (according to LZ) doesn't require reading to be found, but didn't cross my mind (I am 4k on KGS and on Fox). Here, White should play at "a". If White doesn't, Black has some forcing moves that threaten to surround White while building influence. Here, Black is surrounded. Playing at "a" secures the group while building a large corner. |
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| Author: | Uberdude [ Fri Aug 30, 2019 3:04 pm ] |
| Post subject: | Re: Shapes to remember (SDK level) |
I'm guessing in the first diagram black's previous move was approach at bottom left, and it should have been a? But o4 is not efficient then... |
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| Author: | jlt [ Sat Aug 31, 2019 1:48 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
The previous move was indeed approach on the bottom left. Instead of that move, LZ157's main line is the following, but I don't understand the purpose of the exchange . |
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| Author: | gennan [ Sat Aug 31, 2019 3:27 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
It's similar to peeping a tiger mouth: having a black stone here for free gives black better options later while not helping white much. Forcing moves are an advanced concept. SDK players tend to play many sente moves, because they see them as forcing moves and thus good. But often they are aji-keshi and thus bad. |
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| Author: | Bill Spight [ Sat Aug 31, 2019 5:24 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
jlt wrote: The previous move was indeed approach on the bottom left. Instead of that move, LZ157's main line is the following, but I don't understand the purpose of the exchange .It's a case of get it while you can. If Black waits until White plays at a, White will not respond at to . In fact, Black will not play at 1 in that case.The exchange, - is also why White does not play  at a. It does not accomplish so much, now.I would be happy to find in this position. 
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| Author: | jlt [ Sun Sep 01, 2019 11:30 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Position 3 : this one should have been obvious, and yet I missed it  . White to play. |
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| Author: | dfan [ Sun Sep 01, 2019 1:09 pm ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Yay, I got one! Further discussion hidden so as not to spoil. |
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| Author: | jlt [ Fri Sep 06, 2019 9:02 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Black to play. Hint: Answer: |
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| Author: | jlt [ Sun Sep 08, 2019 11:28 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Position #5: LZ proposes several moves but I didn't find any of them. White to play. |
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| Author: | jlt [ Sun Sep 29, 2019 4:11 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
I got 11 wins and 6 losses at 3k level on Fox, so got promoted to 2k, then went back to IGS to check if my 7k rank is still valid. So far I got 2W and 2L, so maybe the answer is yes but I will see after more games. The next position is from a 7k game on IGS. It requires a bit of reading, but the first move should be intuitive. Position #6: Black to play. |
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| Author: | EricBackus [ Sun Sep 29, 2019 8:42 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
jlt wrote: Position #6: Black to play. What about B11 at O2? I think that kills the white group on the right, though it does let the center white group connect. |
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| Author: | Bki [ Sun Sep 29, 2019 9:43 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
EricBackus wrote: jlt wrote: So White lives but the central group is floating and Black is connected and has sente.[/hide] What about B11 at O2? I think that kills the white group on the right, though it does let the center white group connect. I was thinking the same. Killing the bottom right is at least 25 points. It feels better than a speculative attack against the center group which has enough space that it isn't going to die. But that's because  might be incorrect. Instead, white can play this way (which still isn't good enough) : |
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| Author: | jlt [ Sun Sep 29, 2019 11:12 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
EricBackus wrote: What about B11 at O2? I think that kills the white group on the right, though it does let the center white group connect. There are many variations, but it seems that  at O2 leads to a ko which is good for White, for instance: |
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| Author: | kvasir [ Sun Sep 29, 2019 12:42 pm ] |
| Post subject: | Re: Shapes to remember (SDK level) |
jlt wrote: The next position is from a 7k game on IGS. It requires a bit of reading, but the first move should be intuitive. You don't have to play the best move. |
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| Author: | jlt [ Sat Oct 05, 2019 2:36 pm ] |
| Post subject: | Re: Shapes to remember (SDK level) |
I won 14/22 games at IGS 7k level, so got promoted to 7k+. Since some losses were due to lack of concentration, I decided to focus more. I then won 7/7 games and am now 6k. The last game was a 2-stone handicap game. Position #7: White to play. |
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| Author: | Bill Spight [ Sat Oct 05, 2019 5:25 pm ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Congratulations! 
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| Author: | jlt [ Mon Oct 07, 2019 5:01 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Position #8: White to play. This is from a Fox 2k vs. 2k game. |
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| Author: | jlt [ Wed Oct 30, 2019 3:14 pm ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Position #9 : White to play. |
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| Author: | jlt [ Sat Nov 16, 2019 6:28 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Position #10: a move that both players (KGS 3k and 4k) failed to see during most of the game. Black to play. |
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| Author: | jlt [ Mon Nov 25, 2019 7:00 am ] |
| Post subject: | Re: Shapes to remember (SDK level) |
Position #11. No-komi game against a Fox 3k, I am white. What to do of the marked stones? |
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that can help the invading stone.
doesn't look like sente against the bottom sadly, but the capture at H2 might be, and in anyway it nicely disconnect white.
is misplaced, but I couldn't see a good way to exploit the cut, so I played K17, which is a -17% mistake after a few thousand playouts according to LeelaZero. If 
at K17 would have been a good move, but in the present position, LZ wants to cut:
at 
cannot be at 
is sente, since it threatens to save the two white stones, so Black responds with 
. Then White can play elsewhere.