(;
GM[1]
SZ[19]
AW[bd][cf][ci][qf][pj][jb]
AB[cc][dd][fd][jd][nd][pd]
LB[jb:1]
C[Problem 63. Black to play.  

White invades at 1. Although on the second line, it is a vital point of this formation. How should Black respond ? ]
(;B[jc]
TE[2]
C[Correct Answer.  

Black 1 is the vital point. ]
(;W[hc]
C[If White jumps to 2, ... ]
;B[kb]
C[... Black will block off the territory at the top right with 3. ]
;W[he]
C[White then escapes into the center with 4, ... ]
;B[ff]
C[... and Black follows suit with 5. Black gets territory and White is still under attack. <= ]
)
(;W[ib]
C[Variation.  

If White extends to 2, ... ]
;B[kb]
C[... Black still blocks at 3. ]
;W[hc]
C[After the exchange of White 4 ... ]
;B[hd]
C[...for Black 5, White can live, but this time Black gets both territory at the top right and thickness in the center. <= ]
))
(;B[kc]
C[Failure.  

The diagonal move of Black 1 is lukewarm. ]
;W[kb]
C[White first pushes into Black's side with 2, ... ]
;B[lc];W[hc]
C[... then jumps to 4. ]
;B[hd]
C[After Black attaches with 5, ... ]
;W[gc];B[gd];W[eb]
LB[gc:8]
C[... White easily lives with 6 and 8. <= ]
)
)