Black has set up a fairly decent position, and White approaches with . The play at a feels like the right response, if passive. In the game, I played b, anxious about seizing this big point (my opponent immediately played in between b and my enclosure, aggravating me to no end). So. Is a the proper response? Is there anything better?
Alex Weldon: My rank's actually only about the same as yours (currently fluctuating between 13k*-15k* on IGS) but it seems to me that your shimari is stronger than the two white stones already present and much stronger than the white stone he played between the shimari and the extension. Surely if he plays there you can arrange a powerful splitting attack against the two groups? If, on the other hand, he ignores your extension and slides in at a, or one below, you get good thickness from your shimari and use it to build a big moyo on the bottom side.
Anyway, a looks overconcentrated to me. I would have played the extension like you did, or maybe one further to the left, but like I said, I'm a weak player, so don't take me too seriously. I'm just trying to get some discussion started, to hopefully entice one of the stronger players to say something so deep and meaningful that we'll both instantly become two stones stronger upon reading it. :)
HolIgor: Why did you play this kind of high shimari? Perhaps, to become stronger in the center. So, the lower side should be the direction of your play. The move at b is a little bit too close, perhaps since it is not at the optimal position with respect to the future kakari of the bottom left corner. The move at a has the advantage that it takes away a good point from the white group at the right side. It is a good move, not immediately though.
As for the opponent playing between your shimari and the extension, that kind of play is very scattered and you should be able to get good result attacking that stone. A fight this early is in Black's favour.
Alex Weldon: Wow. I'm pleased. From what Holigor said, I actually sort of gave the right answer. One question, though, for Holigor, or whoever else... I was right to think that b is too close an extension. I said one to the left, but is that still too close? How far should one extend from a small high shimari like this?
adamzero The three moves that I would consider would be the side star, the point below it, and the point one to the left of the point below the side star.
I would decide which one to play depending on the following: If it seemed like other areas of the board were hot enough to prevent my opponent from playing on the bottom side soon, I would play the high extension, hoping to be able to make a kakari against White's star and then complete my framework when she responded. If White's corner were stronger, I would play the low extension, hoping later to play a one-space jump above it to form a box moyo, or simply the tent point in between my shimari and extension if White had developed a strong center.
The farthest extension I would find the most questionable, unless White's corner were weak and I had some more strength over the white group on the right side which would make it more unreasonable for her to invade the bottom side. That said, I wouldn't even consider a unless by doing so I would be far more seriously threatening White's side group than I am in the present case, and I would dismiss b as too short unless White had played a four-space extension from his corner -- which would be a very unusual extension.
Yilun Yang's lectures say a five-space extension is good for development, a two-space for stability, and three and four are generally inferior half-measures, though I see so many three-space extensions in pro games that, in my arrogance, I doubt that much of his wisdom. So that is how I would think through this position. Hope it helps.
Velobici: I believe that the guidelines that you quoted are general guidelines without reference to specific positions. The three-space extension can be a good move. It must be used in a context where it makes sense and its inherent weakness is not a burden. One example is when the three-space extension is also a pincer or attack on the opponents stones. Please note that I am 9k on KGS so this may be mistaken.
Bill: Although it is a narrow extension, I think that is quite playable. The point is not so much that it protects the corner -- simply protecting the corner is too small at this point -- as that it attacks the white group on the side, which is not quite settled.
White threatens to play at a, reducing Black's corner while stabilizing the White group. If White does not respond to , Black b knocks White's socks off.
Bob McGuigan: I agree with Bill. The white knight's move on the right side is too narrow. It does peep in at the weak side of Black's high enclosure but it doesn't help much in giving White a base on the right side. Consequently the White stones are heavy and a good target for attack.
If Black wants to play on the lower side the extension should be to the star point or the point below the star point. b in the first diagram is too close to the corner enclosure, i.e. it's inefficient. If White invaded into such a narrow space, with no support to the left it would only create a target for attack. Such an invasion is annoying if you don't have confidence in your attacking skills but it's actually something to be happy about in this case.
How does white make anything out of playing at a in the last diagram?
Bill: He makes a base for his weak group. It is now hard for Black to mount an effective attack against it. At the same time he reduces Black's corner. To evaluate the play you have to compare the position after it with the one after .
krv 4k: I think that when four star points are not occupied there is no need to worry about enclosures. Any of star points (may be include tengen) would be better.
bud1027: in my view,,,three points r considerable moves,,,,Black-a, Black-b, Black-c, but!!!,..um..im not sure which is best...it is TOO hard for me to conclude...!!!!.,,,err...
anyway,,,concerning Black-a move, two things are my troubles.
First : in my feeling, by playing Black-a move, the shape of bottom-right corner is obvious overconcentration...
Second : let assume that black plays Black-a. what's the response of white? probably,,,White may respond with white-b (low side move). He will not defend his stones of right side. At least, if i were white, i would have played white-b.
then...the follwing question is my trouble. there is any effective and severe move that attack white stones of right side???
hard for me to find such a move. of course, it might be cuz im too weak ... anyway, this is my trouble when i consider Black-a move.
what i mean is...If black can't find a good attacking move against right-side white group, that will end up being quite favorable to white, probably. this is my trouble@@@.
bye...have a good day@@@
Bill: If B a were not a dual purpose move, it would be bad, not even worth considering.
tderz: That is correct. It is just that bud1027 analyzed all other purposes apart from protecting corner territory in endgame fashion and found them inferior to moves as b and c.
No misunderstanding, if they (moves b, c) were not available (anymore, e.g. in endgame), a is a fine move in itself.
Bill: You are confusing me. We are talking about the opening and not the endgame. The point is that B a attacks the White stones on the right side by preventing a large White move that would make a base for them. That is what makes it playable now.
As for bud1027's general assessment above, he and I agree. a, b, and c are all big moves. He doesn't know which is best, and I do not, either. We also agree about the fact that a is not a severe attack, although I did not mention that before.
tderz (...confused?) Exactly! This is the opening stage and I am quite convinced that you are fully aware of the common opening priciples, as e.g. given in this link here:
Excerpt of Yilun Yang's : "Fundamental Principles in Go" - Ranking the big opening moves: http://www.slateandshell.com/pdf/ssyy005.pdf.
Another aspect not yet mentioned by bud1027 or any of us is the answer to the following question:
"Is there a white continuation after in below diagram?" If not, is it not so urgent for white to move there (now) for herself. The white position is open at the skirt (m), defending there would induce strengthening black's upper right corner etc.
, on the other hand is , what Yilun Yang (and many other) calls a "Second class move" (disons Cru bourgeois - after occupying corners) and equivalent to making shimaris or approaching corners. Afterwards I would like to grab any of the points p, q, r, s and be convinced that Black's position is not bad.
Perhaps it boils down to the point that is not urgent either for white, nor for black, because Whites is so light and flexible with her stones. The added value of seems so small in comparision with traditional moves. I do not grudge White the pleasure of making another move on the 2nd line in that area at all. It would strengthen Black's moyo -.
I have to admit that I misunderstood bud1027's comment
"of not being sure". I did not read carefully. I thought that he firstly related only to the evaluation of moves b and c, leaving out a totally, and was doing an understatement as about his rank. in his diagram a  puts even more eggs in one basket (the right side).
As White - I am only a weak 3dan (EUR) and not good in any fuseki - I would ignore (which I find a very nice move BTW)and grab another big point - either sanren sei c or remaining side hoshi d.
If Black then attack the 2 white stones directly (mistake I guess) I would be delighted and grab further big points.
Therewith White relies on shinogi and sabaki and the conviction that 2 light stones with good shape (redundancy here) don't simply die. Even with 1 or 2 more black moves there, white has many possibilities. Of course these questions must include the evaluation of collateral dammage. Black should not attack too tight, I guess.
If Black wants to postpone the direct attack he must also wait for the leaning attacks, because there is not much of white positions at this moment which have to be defended in one way (thereby gaining strength to attack W). If black waits too long with either, the question of "is a good move - how can I use it" becomes more and more urgent (like playing a tengen as 1s move - not bad at all, rather it must put to use in special ways).
I think that b leads to an easier game (for both?) than in .
In conclusion, and with circular reasoning, I find b or c are better than a.
I think I herewith ran out of arguments and rest my case.
bud1027: bill, let assume this result. this is good for black? in my view(or feeling), no. this fuseki is not good for black. the reasons why i think so r followings.
First : at now, the shape of the white group in right side is light and flexible. i mean, it is NOT so easy to attack this group at now.
Second : let see..., how many black stones r there in right side? six. and,,,all of black stones r in right side. This look like a black's overconcentration in right side. In addition, one stone(black 3) is at second line (too low position)
Third : i dont think that white's 2 extention in low-side is not worth considering. to be sure, this move is valuable move. now, white 2 move is blocking the development of bottom-right black corner - black's shimari(?) - which is very strong base.
anyway, i have two plans as black.(diagram a, diagram b) although im not sure which is better.
bye@@@ have a good tea@@@.
Bill: Well, my opening style is fleet footed, so I would tend to extend on the bottom, myself. However, I do believe that the kosumi in the bottom right corner is playable, and it is the kind of play that gets overlooked, because of its flaws.
As for in the Early attack diagram, it seems premature.
Earlier, it looks like this was the position and Black extended to a. That looks bad to me for two reasons. First, it is premature. is light. The right side is non-urgent. Second, if Black does play on the right side, 'b' or 'c' is better, as it makes more secure territory or a bigger moyo. It is also closer to .
tderz This explanation follows common (or better good) Go sense. It follows actually the same arguments 1-2-3 as the Korean 6dan bud1027 has given above. In a rapid development opening style ("fleet footed") a in diagram  would not be considered, because one wants to take the big points b, c (fast) before the (seemingly) urgent points (a).
Bill: Perhaps the nub of our (minor) disagreement (I think we would make pretty much the same plays as Black), is the assessment of and here. per se is light. (In fact, I would probably tenuki as White after .) However, after the exchange, - , I think that White has become somewhat heavy. It will now be hard to give up these stones, which as yet lack a base.
To put it a bit too strongly, Black's bottom right corner may be inefficient, but, looking at White's group on the right, why did White play there at all?
Imagist: White's attack doesn't seem urgent to me, as it only stands to gain a small amount of territory compared to the amount of territory that black can gain by placing elsewhere. If you really feel the need to defend the corner territory, A is a relatively efficient way of doing it, but it seems to me that it would be better to play the wedge at B, or my personal favorite, an at C to threaten the corner and then expand back to enclose the bottom edge.
AJP: If you want to get in a black play on the bottom, why not induce white to make you get that play? The white group is still not fully settled. is clearly bad. I would say should have been at a. This setup looks like "black cruises to victory" to me.
Bill: (Aside.) Reviewing earlier discussion, I think I should avoid expressing opinions of the also playable kind, when I think that another play is (probably) better. It tends to make for confusion.
makes the bottom side quite big. Surely White will reply at or around .
Imagist: is a good way of crippling the white group by blocking the direction of play, but it seems unlikely to be able to kill the white group, and the stone is in a vulnerable position for counterattack at A, so the effort of defending it isn't likely to be worthwhile.