(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Chinese]SZ[19]KM[7.50]
C[Duan Rong 7p Using joseki in real games 3/130
Tianyuanweiqi
围棋 定式在实战中的应用
段嵘
29:53 mm:ss

Translated by Daniel Hu UK 5d
胡怿伦
20190702

Good day to all go players. Welcome the lesson.
]
;B[qd]
(;W[od]
;B[ld]
;W[pg]C[Last week we discussed this large knight's move, the Muramasa sword joseki. 村正妖刀

And discussed the necessity of each move.]
;B[oe]
;W[ne]
;B[of]
;W[pd]
;B[qf]LB[nc:B][md:A]C[Jumping here is joseki. It has a rough connection to the corner stone.

...

If white doesn't push through, then where should white play?

...

The other vital point is how white should protect the cut. Of course, A and B are both ok.]
(;W[pe]C[Of course white can directly capture.

[DH\] This is the famous variation which alphago considers the punishment for the P15 mistake, and is a disaster for black. When previously pros thought this was terrible for white. [/DH\]

...

In other words. For this move, after black cuts ats O16, if white has some stones around that reduce black's influence, then this is entirely playable.

But if black has support, then the power of the influence is too great.]
(;B[pf]
;W[qe]C[But in real games, not many people choose this variation.

Black has two moves here]
;B[nd]C[The main common move is cutting directly]
(;W[nc]C[So white ataris underneath]
;B[md]
(;W[rf]C[and hanes on the second line
black can block or turn]
(;B[rg]
;W[re]
;B[qg]
;W[]
;B[pq]
;W[]
;B[pn]C[When black can made this area territory, then black blocks, stopping white from entering.])
(;B[qg]
;W[pp]
;B[]
;W[qn]C[If this side is white stones, then black doesn't necessarily block and just turns.]
(;AW[re]AB[rg]
;B[ql]C[Because even if black blocks and extends later, there is still not many points])
(;B[oc]C[The advantage of not blocking is that black later has this cut.

If black already blocked, then this cut would be captured in a ladder.]
;W[pc]
;B[ob]
(;W[pb]
;B[nb]C[Black can preserve the opportunity to capture this stone which is advantageous for the top side.])
(;W[nb]C[white can't block]
;B[pb]
;W[qb]
;B[qc]))
(;B[]
;W[rd]C[Probably white has to defend.

...

Although white got a very large corner, and professionals do play this way, black's thickness is also very appealing. The two white stones on the outside are pretty much wasted. So if it works well with the surroudings, this is enough to make up for the loss in the corner. ]
;B[dd]
;W[]
;B[fc]
;W[]
(;B[nb]C[If later black wants to make territory at the top, then the clamp is a good tesuji.]
(;W[ob]
;B[mc]C[Black's way of playing is very active, better than jumping at N18 directly.])
(;W[mc]
(;B[oc]C[If white pushes, on the one hand there is this cut.]
;W[ob]
;B[pc]
;W[qc]
;B[pb]
;W[mb]
;B[oa]
;W[kc]C[Although black has this move, it depends on the situation. Although black can live in gote in the corner, the outside is completely destroyed so it isn't worth it.])
(;B[lc]C[Black's simpler method is to naturally block.]
;W[mb]
;B[lb]
;W[ob]C[Although black gives up a few points, black seals off the top in sente.])))
(;B[]
;W[lb]C[If black doesn't play, white can play a knight's move and it is hard for black to block this off.]))))
(;W[re]C[Or descends]))
(;W[md]C[Atariing down doesn't exist as black can escape and then cut white.]
;B[nc]
;W[mc]
;B[me]))
(;AW[fc][dd][qn][pp]C[white can push through and take territory])
(;AB[pn][pp]C[white doesn't want to push through and cut]))
(;W[qc]C[Hence if white doesn't push through, white can either hane.])
(;W[nf]C[Pushing can also defend the cut as now if black cuts, white can atari down.

...

Or white can play here.

The earliest version of the joseki was to push here first. If black doesn't respond, then white plays P13 in sente, very big.]
(;B[og]C[So black responds]
;W[qc]
;B[qe]C[White basically has two moves]
(;W[rc]C[If white has the ladder white can descend. Let's say simply why.

You also have to pay attention to whether you hane (R17) first or push (O14). We'll discuss this carefully in the next section.

If white descends, then the cut is very dangerous.]
;B[nd]
(;W[md]C[Hence the wedge atari is the only move.]
;B[nc]
;W[mc]
(;B[ob]C[The kosumi is a good move. A tesuji. It is about to cut white (Q17)

...

Tiger's mouth means the corner will die. Playing on the outside means the two stones get cut off. That leaves only one way to get both vital points.]
(;W[oc]C[A crude move to defend the cut in sente]
;B[nb]
;W[mb]C[White seizes the vital point.
Although very crude, it is also very practical.]
;B[pb]C[black extends liberties]
;W[pc]C[Black loses the corner semeai by one liberty.

...

But just because black is behind by a liberty doesn't mean this doesn't work for black.]
(;B[me]C[because there is a cut on the outside.

Now black has lots of sente moves around M14, so black is about to capture white by sticking or clamping (M17 or M18)]
;W[kb]C[white must jump to escape

...

There are all sorts of sacrifice variations and ladder breaker variations that we will start to discuss this week.]
;B[mf]C[Now this depends on a ladder. If black has the ladder, then white has completely collapsed.

But of course, white would only choose S17 when white has the ladder. 

])
(;B[qb]
;W[rb]
;B[ra]C[hane is the vital point for liberties]
;W[na]C[Most sides have four liberties. White wins with this hane]))
(;W[pb]C[If white defends like this, it is a bit problematic.
[DH\] leelazero likes this, but in this case, following the variations, it looks there are a lot of mistakes in it's reading [/DH\]]
;B[mb]
;W[lc]
(;B[lb]C[Black can simply crawl]
;W[kc]
;B[kb]
(;W[jc]
;B[jb]
(;W[ic]
;B[rd]C[Although black crawling on the second line is suffering, when black blocks, white's corner is dead.

If white dies, then the loss is too great. With a relatively simple variation, we can say this doesn't work for white.])
(;W[ib]C[You still can't block]
;B[ic]
;W[hb]
;B[hc]
;W[gc]
;B[gd]
;W[fc]
;B[me]C[white now finds it hard to save both sides.]
;W[jd]C[Obviously white has to save the five stones.]
(;B[lf]C[Black has too many sente moves]
;W[mg]
;B[lg]
;W[mh]
(;B[ie]C[White can't escape])
(;B[lh]C[Even this is sente]
;W[mi]
;B[ie]))
(;B[ke]LB[ie:A][lg:B]C[Black has many ways to capture. This move threatens both A and B to capture one side or the other.])))
(;W[jb]
;B[jc]C[white obviously can't block, there is also a cut at N15. White falls apart.]))
(;B[me]C[[DH\] The cut is very complicated if black has the ladder. But if black has the ladder, white really shouldn't be playing N16. [/DH\]]
(;W[le]
;B[mf]
;W[ng]
;B[kc]
;W[kd]
;B[lb])
(;W[kc]C[[DH\] If white has the ladder this is KO, black collapses [/DH\]]))))
(;B[nb]C[If black just descends]
;W[mb]
(;B[pc]C[There is no cut]
;W[oc]
;B[pb]
;W[ob]C[Black is dead])
(;B[pb]C[Jumping also has a problem]
;W[ob]
;B[oc]
;W[pc]
;B[oa]
;W[ma]
;B[na]
;W[qa]C[Just locally black is also dead])))
(;W[nc]C[If white just ataris from below, this is clearly very submissive. Although white lived with some points in the corner, the two outside stones are wasted.

[DH\] leelazero gives a very similar winning percentage for this move and says S17 is the only move, and this is overall slightly better for white. [/DH\]]
;B[md]C[White completely becomes a weak group and black is relatively strong on both sides. This is unacceptable for white.]
;W[lf]C[[DH\] This is leelazero's move [/DH\]]))
(;W[pb]C[If white doesn't have the ladder, this is a rather good shape. It can both make life in the corner and also defend the cut]
;B[nd]
;W[md]
;B[nc]
;W[mc]C[white can directly capture]))
(;B[nd]
;W[md]))
(;AB[qc]C[We can see that this is a vital point. If black gets this, black's shape is very good with a lot of territory. White is an isolated weak group.]))
(;W[dd]C[There was a real game by China's Wang Yao against Korea's Lee Sedol.]
;B[pq]
;W[dp]
;B[fc]
;W[cf]
;B[kc]
;W[po]
;B[pl]
;W[mp]
;B[oo]
;W[on]
;B[no]
;W[pp]
;B[nq]
;W[qq]C[White haned first. Regarding whether to hane first or press first, we will discuss later.]
;B[oq]
;W[nn]
;B[mo]
(;W[qr]C[Therefore, white wants to take advantage of having the ladder and descends.]
(;B[pn]C[So that is why many professionals choose the cut even when they don't have the ladder.]
;W[pm]C[We've already discussed the necessity of playing here.
[DH\] Leelazero 230 thinks the R6 atari has similar winning percentage [/DH\]]
;B[qn]
;W[qm]
;B[ro]
;W[qo]C[This atari is a very useful practical move.]
;B[rn]
;W[rm]
;B[rp]
;W[qp]
;B[om]
(;W[rk]C[so white has to maintain being able to kill black unconditionally.

...

So this move defends against the first line hane.]
(;B[qk]
;W[rl]C[...

all in all, whether or not this variation is good depends on how powerful the ladder breaker is. If it isn't that powerful, the descending at R2 is a good move.]
(;B[de]C[Black plays a ladder breaker. Black probably already envisioned this variation when black approached the corner.

[DH\] Leelazero gives this variation as even for both sides, which isn't bad for black given that it thinks both Q8 and P5 lost a lot [/DH\]
...

But with the approach exchange, look at how powerful the ladder breaker is.

]
(;W[nm]C[white must atari]
(;B[ce]C[The power of cutting straight through is clearly much greater than just attaching to a star point stone.

So even when black doesn't have the ladder, from a whole board perspective, black can play a ladder breaker in the upper left corner to profit.]
;W[ol]C[In fact, if when black cuts through. If black feels white is too thick after capturing and black feels dissatisfied, then black can still continue.])
(;B[ol]C[black can continue connecting]
(;W[nl]
(;B[nk]
;W[mk]
;B[nj]
;W[ce]C[If black thinks developing the upper side moyo is big, then after white blocks, black can block to continue developing the moyo.]
;B[rq]
;W[rr]
;B[rj])
(;B[ce]C[Alternatively black can treat connecting as a profitable exchange, gaining the S10 sente, and come back here.]))
(;W[ce]C[white can't block]
;B[ml]C[white is captured in a net])))
(;W[ol]C[Or atari])
(;AE[fc][cf]C[Because if it was just a star point stone on its own, a ladder breaker is not so severe.

White can tenuki or even respond for a move.]
;W[ed])
(;W[ce]C[because white can't block]
;B[nm]C[black sets up the ladder]))
(;AE[fc][cf]C[But even when black's ladder breaker is not severe and black doesn't play a ladder breaker, white still has a lot to be careful of]
;B[rq]
;W[rr]
;B[sr]C[black can first short liberties]
;W[sn]C[white certainly shorts liberties]
;B[sm]
;W[sl]
;B[rj]C[this hane changes the liberty situation a bit

...

black is about to sacrifice so how should white deal with it?

...

so white doesn't want to see black sacrifice. What can white do to stop it?]
(;W[so]C[If white is obedient and responds, then ]
;B[pr]C[black blocks]
(;W[sq]C[If white still responds, then the S10 and Q2 move first gain a lot of points. Even though white captured black, white had to retreat for a lot of moves. It can be considered a sacrifice because black got these two profitable moves.

[DH\] Leelazero naturally likes white a lot, but only 80% [/DH\]]
;B[mm]C[Even though black doesn't have the ladder, black can seal white in.]
(;W[]
;B[nm]C[If white doesn't play, then the atari is very comfortable]
;W[sp]C[White's territory is only around 15 points. Black's influence looks very good. So clearly this is a great success for black.])
(;W[nm]C[If white responds]
;B[nl]
;W[ol]
;B[mn]
;W[om]C[Black can tenuki and later choose between extending (O9) or blocking (P9) depending on the whole board.]
;B[fq]C[black can continue expanding over here. We can say black is also not bad. White still only has around 20 points in the corner, and the miserable black stones on the right still have some use to them.

Even after sacrificing, black can be satisfied. White must watch out for this.]))
(;W[nm]C[If you only play the atari, it doesn't help much.]
;B[ol]
(;W[nl]
;B[sq]C[black can continue the semeai]
;W[sm]
;B[ql]C[and kill white]
;W[qj]
;B[ok]
;W[ri]
;B[sj]C[descending is even better]
;W[si]
;B[op]C[and kill white. White's centre four stones aren't healthy and still only has one eye on the right. This isn't good. [DH\] Leelazero gives black 70% [/DH\]])
(;W[sq]C[Of course if white goes back, this is even worse. ]
;B[ml]C[Black completely seals white in. Even if white captures black, white is still unsatisfied.
[DH\] Leelazero gives white 90% [/DH\]]))
(;W[ol]C[what about atari on this side?]
;B[nm]C[black must run out]
;W[mn]C[...

so even though black can capture white, it is in fact loss making, so what can black do?]
(;B[sq]
;W[sm]
;B[ql]C[Black has a self-injuring move.]
;W[qj]
(;B[op]C[White can't short black's liberties on either side. Although black can capture white, but this in reverse becomes white sacrificing stones.]
;W[mm]C[white]
;B[]
;W[nl]C[If black does nothing, then white capture is sente]
;B[qs]C[although black captures, white is clearly too thick. This is unacceptable for black.])
(;B[pk]C[[DH\] leelazero says this horrible shape is best and white is 87%, slightly inferior to capturing the corner [/DH\]]))
(;B[nl]C[black can turn]
(;W[ok]C[If white extends then the situation is totally different]
(;B[sq]
;W[sm]
;B[ql]C[black can play the self-injury move again]
;W[qj]
;B[op]TR[ok][nl]C[as black made a very profitable exchange, black's situation is much better.]
;W[pk]
;B[qs]
;W[ln]C[[DH\] leelazero still gives 88% to white. After all, black lose the R11 atari [/DH\]])
(;B[nk]C[But black has better]
(;W[sq]C[If white goes back to defend then white loses too much on the outside
[DH\] leelazero almost agrees that it is now close to even, but black has to atari at M6 first [/DH\]]
;B[oj])
(;W[ln]C[[DH\] leelazero finds this move after which black collapses [/DH\]])
(;W[oj]C[So if white responds]
;B[nj]C[black can even consider pressing again.

In fact it is already very troublesome for white. Even if black doesn't have the ladder, the atari and net is painful.]
;W[oi]C[If white responds, then the situation is very different]
;B[sq]
;W[sm]
;B[ql]
;W[qj]
;B[op]
;W[pk]
(;B[qs]C[Every pressing move is profitable to black. All white's moves are useless dumb shape. All of black's moves help to fight on the outside.

In other words, white can't extend with P9. Black pushes several times and this is bad for white.])
(;B[ln]C[[DH\] leelazero says atari is critical, still the difference between white collapse and black collapse.]
;W[mm]
;B[lm]
;W[ml]
;B[qs]
;W[ll]C[[DH\] 23% for white [/DH\]]))))
(;W[sq]C[so white can comeback to capture since black always has the way to capture the corner.]
(;B[ok]
;W[ln]C[If black captures, white extends and white is very happy.])
(;B[ln]C[but black has this more active move]
;W[mm]
;B[lk]C[black can even consider not capturing immediately]
;W[lm]
;B[kn]C[this way, black sacrifices the corner to surround the lower side and later can capture at P9.

So does white have any way to deal with black sacrificing the corner?

We'll wait to next week to discuss that. Today we'll finish here.

Thanks for watching!
Goodbye!])))))
(;W[]
;B[pr]C[If black gets to play in the corner]
;W[so]
;B[sq]
;W[sm]
;B[ql]C[black can show this poisonous move. So actually the S10 hane is shorting white's liberties.])))
(;B[sm]
;W[sl]C[Now white can block]
(;B[sn]C[connecting in sente also has no meaning]
;W[qk]
;B[rq]
;W[rr]
;B[sr]
;W[sp]
;B[sq]
;W[rs]C[black loses by one liberty.])
(;B[so]C[of course, if black plays this kind of garbage ko, white can just defend on the outside.

The inside is a multi-step ko, many steps in white's favour]
;W[nm]
;B[rq]
;W[rr]
;B[sr]
;W[sq]
;B[sp]C[Making a multi-step ko or a garbage ko has little point to it.])))
(;W[qk]C[You have to watch out that white must jump on the 2nd line not the 3rd. When this joseki was first being developed, there really were several people who played the jump and got captured by the opponent.]
;B[rq]C[The liberties in the corner are different]
;W[rr]
;B[sm]C[white can't block the hane]
(;W[sl]
;B[ql]C[white only has one liberty]
;W[rl]
;B[rk])
(;W[rk]C[white must leave the liberties loose.]
;B[sr]C[This situation is called two hanes extend a liberty. This has cause black to get an extra liberty.]
(;W[sn]
;B[pr]
(;W[so]C[white can't keep pushing in, this gets captured]
;B[sp])
(;W[sl]C[white still has to come back to capture]
;B[op]C[Then white doesn't have enough liberties. This is unconditionally dead.]))
(;W[sq]C[Of course white still has a tenacious way to play.]
;B[sp]
;W[ss]
;B[rs]
;W[qs]C[White can make a ko. White can't capture black cleanly in the corner. On the outside, black can still play ladder breakers. This doesn't work for white.

[DH\] leelazero considers this almost even with a slight advantage for black. Of course, this is so complicated that it is probably doesn't understand it much better than humans either [/DH\]]))))
(;B[jq]C[Now if black still extends, ]
(;W[qn]C[white defends.

Although white spent an extra move, the  territory is far larger.

...

If black extends and white gets this move, we can say that white is extremely satisfied.]
;B[]
;W[ns]C[And black's territory is reduced by an extra 6 points at least compared to the tiger's mouth. Just looking at territory, the difference is over 10 points. And furthermore the Q9 has become a stone that is too close to white thickness. Its efficiency has become bad.])
(;W[qm]C[[DH\] The leelazero move [/DH\]])))
(;W[rp]C[If white didn't have the ladder, the tiger's mouth is joseki. But even so]
;B[jq]C[black can get a lot of points extending]
;W[]C[Black has lots of ways to take advantage in sente.

In this shape, some professionals don't really like white, feeling that the shape isn't upright enough. It has the feeling of curling inwards. And even after retreating, black can still exploit the cutting aji.]
(;B[mn]C[And later when black turns, white's head is soft])
(;B[ql]C[If black descends, there is also a cut.]))))