Instead of at
, Black can also play the more severe move
shown here.
In most cases the intention is to get sente, in which Black succeeds in this diagram. is forced; White cannot allow a black capture at that spot.[1] Black in turn should not omit
and
, or White can come out too easily.
Grech: What if White plays at
? This also ameliorates the threat of capture from
, and puts White ahead of Black on the third line.
What if White plays at a? Can Black still take the corner back if the left side is not interesting?
lavalyn: If White plays at
in the above, Black can take the corner as in the variation below, but also gets a four-stone wall instead of three.
becomes close to a wasted move relative to the variation below.
Black can take the corner by playing here, but giving White this ponnuki is not good in most cases.
aLegendWai (9k? KGS): I deem most cases here may mean 80-90% of all cases.
If so, I don't think so. First the diamond shape (or ponnuki) [2] is at the second line. Its influence is somewhat, not to say greatly, reduced. It is better if it occurs at higher lines (eg fourth line) Second if B emphasise more on the corner, it is applicable. Third, If B has surrounding stones around (eg at "a"), B may force W to escape and play good forced moves.
By the way, this variation is also one of the joseki.
White will most likely continue with these moves. In most cases, when White invades at the 3-3 point, Black has stones on both sides, at or around the places shown here. Black's left side stone has lost much of its value after this sequence.
aLegendWai (9k? KGS): When B gets good control on the outer areas, it should play the standard 3-3 invasion joseki (ie the non-hane one) in the first place.
And note that it is not uncommon 3-3 invasion occurs in early stage. Giving B good influence in early stage may not be bad. First W can prevent B from making good use of its influence (if situation favors). Second, W mostly gets sente in the 3-3 invasion
Black would probably like to play the double hane of in this diagram, but the marked white stones have too much aji for Black to do so. White can retake the corner - or worse.
If Black plays the double hane at , Black has to be prepared for this
. White intends to give up the corner in exchange for a position on the top.
After in the previous diagram,
is the joseki move, reaffirming the unity of the black stones. After
, White can secure a base with a move like a or play tenuki.
is vulgar, and White gets a relatively large corner. Still, if the upper side is important this might be playable.
at
is sometimes possible, depending on the position on the top side.
aLegendWai (9k? KGS): may not be vulgar (bad). Click [3] for details.
[1]
This is too dogmatic: the connection may be honte, but in many pro games not connecting has been tried.
[2] Some people consider ponnuki and diamond shape / diamond different. Click on their names for details.
[3] Charles Matthews This comment has gone unchallenged since the initial version of the page; but it's misleading. This atari play is recognised as joseki, but is highly sensitive to stones on the upper side, for example at a or b in this diagram.
These plays occur in pro games. When Black plays , White will eventually have to live at e. Before that White has a chance of pulling out the marked stone with White c, Black d and White continuing on the third line for a while. The books teach that this is good for White if Black has a stone at b, but poor if Black has a stone at a.
If White lives immediately at e and Black tidies up by capturing at c, Black will be thick anyway (possibly slightly overconcentrated).
There's an early example in Chapter 1 of Beauty and the Beast.
Rich: Moved the discussion on the dead stone activation to the Discussion page.