(;
GM[1]
SZ[19]
AW[kc][rc][qd][qe][pf][pg][qh][pp][qo][nq][bp][cn][ck]
AB[dc][ce][ic][qb][qc][oc][pd][pe][of][jq][dp][cq][fq]
TR[kc]
C[Problem 16. Black to play.  

How can Black use his wall on the right side to attack the marked white stone ? ]
(;B[je]
TE[2]
C[Correct Answer.  

The knight's move of Black 1 is the most effective way to attack. The white stone at the top is now in a pinch. ]
(;W[ke]
C[Trying to break out into the center with White 2 seems reasonable, but ... ]
;B[kf];W[le];B[lf];W[ne];B[oe];W[mf];B[mg];W[ib];B[hb];W[jb];B[hc]
C[... Black can confine White to the top with the sequence to 13. ]
;W[mc];B[nb];W[mb]
LB[mc:14]
C[White barely lives in gote with 14 and 16, but ... ]
;B[dj]
C[... Black can now build a moyo in the center with the shoulder hit of 16. <= ]
)
(;W[le]
C[Variation.  

Against the knight's move of White 2, ]
;B[ld]
C[... Black attaches at 3. He then ... ]
;W[kd];B[ke];W[md];B[lf];W[lc];B[mf]
LB[dj:A]
C[... sacrifices this stone and confines White to the top with the sequence to 9. The white stones are alive, but just like in the Correct Answer, Black gets a thick wall and he can then create a moyo by attacking the white stone on the left with a shoulder hit at A. <= ]
)
(;W[jd]
C[Variation.  

The diagonal attachment of White 2 is not good. After ... ]
;B[id];W[ke];B[kf];W[jf];B[ie];W[lf];B[kg];W[le];B[lg]
C[... Black 11, White can't live because there are no defects in Black's position to exploit. <= ]
))
(;B[ie]
C[Failure.  

Jumping out into the center with Black looks like a normal move, but it is slack. ]
;W[ke]
C[White jumps to 2, and Black doesn't have a good follow-up, so White's stones have escaped. <= ]
)
(;B[jd]
C[Failure.  

The diagonal move of Black 1 is also slack. ]
;W[le];B[jf];W[lg]
LB[le:2]
C[After 2 and 4, White's stones are out in the center. ]
)
(;B[ke]
C[Failure.  

Capping is another common attacking technique, but, after Black caps with 1, ... ]
;W[jd]
C[... White escapes ... ]
;B[if];W[je];B[jf];W[hd];B[hc];W[gd];B[gc];W[hf];B[hg];W[gf]
LB[kf:A]
C[... with the sequence to 12. Black has failed to make any significant gains, and White has the cut at A to exploit. <= ]
)
)