(;
GM[1]
SZ[19]
AW[fc][fd][ge][he][hd][md][cn][ch]
AB[dp][pd][pp][dd][df][fe][ff][gf][gd][pf][fp]
LB[df:4][ch:7][cn:5][fp:6][fc:3][fd:9][gd:8][hd:13][he:15][ge:11]
LB[fe:10][ff:12][gf:14][md:1][pf:2]
C[Problem 135. Black to play.  

How should Black continue after White connects with 15 ? ]
(;B[ck]
TE[2]
C[Correct Answer.  

Now is the time to invade the left side because Black is thick above and also strong below. ]
;W[ei]
C[White jumps into the center with the knight's move of 2, keeping away from Black's thickness. ]
;B[ek];W[gi]
C[After White 4, ... ]
;B[co]
C[... Black exchanges 5 ... ]
;W[dn]
C[... for 6 to make White heavy, ... ]
;B[gk]
C[... then jumps to 7. White's two groups on the left side are in trouble; even if she saves one of them, the other could die. <= ]
)
(;B[hf]
C[How the game continued.  

Black increased his thickness with 1, but this move had no severe follow-up at the top, so ... ]
;W[dk]
C[... White was able to secure her stones on the left with 2. Black lost his chance to take a decisive lead. <= ]
)
)