(;
AB[dd][dc][fd][fe][df][pd][nd]
AW[ec][fc][gd][kc]
TR[kc]
LB[jc:A]
C[Normally, White extends to A, instead of the marked play.  What is Black's response now?

Source
    Go World #14, p. 42
    Practical Tactics and Tesuji
    Rin Kaiho 9P];
B[ic]
C[The time to invade is now, before Black loses the chance.

The outcome will favor Black, but Black cannot be careless.]
(;
W[id]
C[One possible response.];
B[hc];W[hd];B[gc];W[jc]
(;
B[gb]
C[A tesuji and the best move.  Black takes a large profit capturing the 2 stones.]
)
    (;
    B[fb]
    C[Inferior.];
    W[ib]
    C[White forces here.]
    (;
    B[gb]
    C[And Black has to connect to take a small endgame loss.]
    )
        (;
        B[hb]
        C[Defending here makes matters much worse.];
        W[ha];B[gb];W[eb];B[jb];W[ja]
        C[White makes a big ko.]
        )
    )
)
    (;
    W[jd]
    C[Another possibility, but ...];
    B[gc]
    LB[hc:A][gb:B]
    C[... after Black cuts, neither White A or B works well.]
    )
    (;
    W[ge]
    C[White could also ignore a direct response by extending here, but ...];
    B[ie]
    C[... Black simply jumps out.];
    W[gg];B[ke]
    TR[kc]
    C[Although the marked stone still has some potential, Black can hardly complain.]
    )
)

