(;FF[4]
CA[UTF-8]
GM[1]
GN[Becoming 9 Kyu - Lesson 27]
PC[https://online-go.com/review/416688]
PB[Black]
PW[White]
BR[2d]
WR[2d]
OT[Error: time control missing]
RE[?]
SZ[19]
KM[6.5]
RU[Japanese]

;B[pd]
;W[dc]
;B[pq]
;W[cq]C[Hi! Let's focus on how to play on the side. The players have occupied the four corners. Now enclosing, approaching, and invading the corners is important.]
(;B[qk]C[Instead of all that, Black can also extend along the right side. I suppose you've seen this kind of extension many times. This formation is called the "Chinese Opening."]
)(;B[pk]C[This is the High Chinese Opening.]
;AE[pk]
;AB[qk]C[And this is the Low Chinese Opening. There are white stones on the 3-4 and 3-3 points. But instead of securing the corner, why can Black extend like this? It has a lot to do with opening trends. When this opening was popularized, professional players tended to focus more on the sides and center than before. This doesn't mean the corner was unimportant. They just emphasized other parts of the board more than before. Modernly, professional players have started to emphasize the corners again. But this opening is still popular.]
(;W[qo]C[If White approaches here, Black can use the stone on the side to help attack.]
;B[qp]
;W[po]
;B[np]C[This is Black's intention.]
)(;W[de]C[Because of that, White can enclose the upper left corner.]
(;B[mc]C[After that, Black encloses toward the upper side, which is very big. Since the two corners at the top are facing each other, this kind of enclosure is huge because it reduces the potential of White's enclosure.]
(;W[qc]C[Suppose White invades now.]
;B[qd]C[Black would certainly block on this side of White, pushing White into the other black stone.]
;W[pc]
;B[oc]C[Black would bend here, and]
;W[ob]
;B[nb]
;W[od]
;B[nc]C[White trades an atari here, because why not?]
;W[rd]C[Then White plays here to live.]
;B[re]C[Black must block.]
;W[rc]C[After White defends, Black could kill White by Q18, but the cutting point at R15 is too painful.]
;B[qf]C[So Black should defend here with a tiger's mouth shape.]
;W[pb]C[Finally, White blocks this side to make life in the corner.]
;B[jd]LB[od:A]C[Now, extending to the upper side is very big. It further reduces the potential White projects from the upper left enclosure. It also reduces the value of White's cutting stone at A, which is a lot harder to move out now.]
)(;W[fp]C[Since playing in the upper right is early, in response to Black enclosing the corner, White can also enclose a corner. This reflects the modern emphasis on corners.]
(;B[po]C[Probably this move is the most likely continuation, because it's the last unenclosed corner. And we're modern professional players. We love enclosed corners.]
)(;B[ck]C[Another move worth consideration is a move to split the side area on the left, which has large potential thanks to White's dual enclosures. One point higher at C10 can work, too. This move is on the third line rather than the fourth line because it's in White's area of influence, and it's easier to make a base for your stones on the third line than the fourth line.]
(;W[ci]
(;B[do]LB[cn:A]C[Now Black would play either this or a simple base at A.]
(;W[dp]
;B[co]C[Aiming at this.]
)(;W[bo]
;B[dq]
)(;W[dm]
(;B[cm]
;W[dl]
;B[cl]
(;W[dk]
;B[cj]
;W[dj]
;B[bi]
)(;W[co]
))(;B[dq]
)))(;B[cn]
;W[lq]C[Finally, White can extend along the side once more to settle the lower side area.]
))(;W[cm]C[If White plays here,]
;B[ch]LB[be:A]LB[cf:B]C[It pushed Black into White's fourth-line enclosure. This lets Black slide under at A later, and White B is too small now.It pushed Black into White's fourth-line enclosure. This lets Black play slide under at A later, and White B is too small now.]
))(;B[jp]TR[hq]C[Be a little careful with this kind of move. One of the vital points in White's shape is marked. But later it will have a kind of awkward relation to the K4 stone.te's shape is marked. But later it will have a kind of awkarward relation to the K4 stone.]
))(;W[jp]C[In earlier times, White would have extended here instead of enclosing. It's just a different trend. I'm not prepared to say one move is better for you than another.]
))(;B[jd]C[When the Chinese opening was popularized, professional players would often extend along the side like this. The theory was that because you wanted to reduce White's potential, you don't want to play too close to your corner, as White could still extend there after the enclosure. But modern players emphasize the corners more nowadays, and this move is considered to leave the 3-3 point invasion open. So Black avoids this recently.]
)(;B[nc]C[The small enclosure is also fine.]
;AE[nc]
;AB[mc]C[In response, White also wants to limit Black's potential on the lower side.]
))(;W[qc]
)))