At antony's request, I have prepared an analysis of where black's game went off track after a strong opening. Other comments welcome. Pete99
On
2010-07-28 at 01:10,
pete99*
said:
In the game as played, white made some simple opening responses while black carefully built a nice pattern, and white was quickly in trouble -- essentially surrounded by black. White played 7.m12 to try to force a connection to the q13 peg. Black's 8.m16 response was difficult for white to respond to, but it left an opening between m13 and m16 for white to work against. White eventually built a line up the right side 17.r10 by continually threatening to connect to the center white links, until the right side line could stand on its own.
The |8.n15 response creates a link that solidifies black's initial 6.p10 structure.
On
2010-07-28 at 23:12,
Alan Hensel
said:
Antony might have been in good shape as late as move 15: |16.o8, because of the strong 2-5 gap across the top, threatening, for example, 17.o1118.k8. That's not what would have actually happened, however, because what |16.o8 actually says is that the o8 group is connected to the right side, and as for the left side, there's a double threat (k8 to go across the top, or q11 to go across the bottom). I'm sure Pete would have responded to the double threat with a defensive move on the left, though it is messy enough that I cannot predict what it would have been or whether it would have worked. For example, 17.g12. Then maybe 18.j1319.h1020.i8, and there's a big smiley face for Black :-)
On
2010-07-30 at 20:41,
antony
said:
Thanks for the analysis! Alan's move 16.o8, in particular, is the kind of move I still have much difficulty to see at my level. However, one thing I can't understand is that you seem to consider that the right group is connected to the top after 17.r10, but it seemed to me that twixt.wetpaint.com's page on the Achilles defense said otherwise (the diagram says that r10 is one of the last points that can be blocked with an Achilles defense), so that was what I was planning to do, until I discovered that it was too late. So where did I get it wrong?
On
2010-07-31 at 01:46,
Alan Hensel
said:
Well, you might have still been able to win after |17.r10, but it's murkier. I didn't mean to imply that move 16 was your last chance; it's just the last one that I see.
The analysis of the Achilles defense on Wetpaint is better for opening and mid-game moves, or, that is to say, moves when large parts of the board are blank. Surrounding pegs change the analysis. For example, starting with the Achilles defense |18.q6, here are some possible future lines:
And there are many other things that could have happened. So, you have to be careful about applying the Achilles defense analysis from Wetpaint to the endgame.
So what do you do if there are interfering pegs? Feel it out with some possible lines. Since you're facing down a combinatorial explosion, it's best to know the common patterns, so you don't waste time considering bad possibilities. Here, after |18.q6, the first thing I'd look at is 19.p9 -- that's probably the strongest response 90% of the time. I'd only look at other possibilities if that one didn't work.
After 17.r10, then 18.r5, and black secures the right side connection.
For remembering to consider link-back moves like 16.o8, it may help to keep in mind the principle that before16.o8, white had a large and wide open playing space from w2 to b9. However, after16.o8, white was restricted to having two separate and much smaller playing areas (w2 to q10; b2 to n9) to work with -- therefore more difficult to navigate through -- and furthermore, black had an extra advantage within each one by virtue of having the o8-p10 link in place along one edge of the reduced playing area, no matter which one white might choose to attack.
A four-away drop-back move such as 16.p6 might have been equally useful to black in that spot.
On
2010-07-31 at 04:04,
David J Bush
said:
At first I thought black tossed the game on his last move but after
The analysis of the Achilles defense on Wetpaint is better for opening and mid-game moves, or, that is to say, moves when large parts of the board are blank. Surrounding pegs change the analysis. For example, starting with the Achilles defense |18.q6, here are some possible future lines:
19.q8 20.o7 21.u6 22.s7 23.v8 24.t9 25.u11 26.u12 27.v13 28.t10 29.u10 - White win on account of R10-R16 gauntlet. (But: 22.r8 23.t9 24.v6 - win for Black.)
19.o7 20.o5 21.q8 22.n7 23.m8 24.l6 25.j9 26.j7 27.i7 28.h6 29.g6 30.f5 31.e5 32.d4 33.d5 34.e6 35.e7 - White wins because of the c3 peg.
19.p9 20.o7 21.n8 22.m8 23.k8 24.n10 25.o11 - White win on the strength of the K10-K14 group.
And there are many other things that could have happened. So, you have to be careful about applying the Achilles defense analysis from Wetpaint to the endgame.
So what do you do if there are interfering pegs? Feel it out with some possible lines. Since you're facing down a combinatorial explosion, it's best to know the common patterns, so you don't waste time considering bad possibilities. Here, after |18.q6, the first thing I'd look at is 19.p9 -- that's probably the strongest response 90% of the time. I'd only look at other possibilities if that one didn't work.
After 17.r10, then 18.r5, and black secures the right side connection.
For remembering to consider link-back moves like 16.o8, it may help to keep in mind the principle that before 16.o8, white had a large and wide open playing space from w2 to b9. However, after 16.o8, white was restricted to having two separate and much smaller playing areas (w2 to q10; b2 to n9) to work with -- therefore more difficult to navigate through -- and furthermore, black had an extra advantage within each one by virtue of having the o8-p10 link in place along one edge of the reduced playing area, no matter which one white might choose to attack.
A four-away drop-back move such as 16.p6 might have been equally useful to black in that spot.
|20.s7 21.q8 22.q6 23.p6 24.o6 25.t4 26.p4 27.t9 OR
|20.s7 21.q8 22.r5 23.o7 24.n5 25.n6 26.m7 27.m8 OR
|20.s7 21.q8 22.o6 23.s5 white still wins.
So, backing up one more notch, how about
|18.q6 19.q8 20.p4 OR
|18.q6 19.q7 20.r8 21.p9 22.o7 OR
|18.q6 19.o7 20.q8 21.s8 22.s5 23.q7 24.o5 25.m6 26.p6 OR ... what?
Anyway, don't forget the latent N10 threat. So, in reply to your OR ... what? How about this:
|18.q6 19.o7 20.q8 21.s8 22.s5 23.q7 24.o5, like you started out, but then 25.n10 26.o10 27.o8 28.j5 29.l5 30.m6 31.j6 32.i7 33.j4, and it looks like a White win to me. Without N10, it looks like it ends well for Black: 25.o8 26.j5 27.l5 28.m6 29.j6 30.i7 31.j4 32.l8 33.k8 34.n9.
|18.q6 19.o7 20.q8 21.s8 22.s5 23.q7 24.o5 25.n10 26.j5 27.l5 28.n7 29.j9 30.k3 31.g6
But how about
|18.q6 19.o7 20.q8 21.s8 22.s5 23.q7 24.o5 25.n10 26.l6 27.j9 28.h6
If you're looking for a victory for Black after |18.q6 19.o7, how about: 20.o5 21.q8 22.n7 23.m8 24.j5 ?