(;
AB[rr][qr][qq][pq][pp][po][on][nn][no]
AW[rq][rp][qn][pn][oo][op][nq][or][pr][kq]
C[Black plays.]
(;
B[oq]
C[A mistake.];
W[np]
C[Black strengthens White on the outside.];
B[mr]
C[Now this placement is too late.];
W[nr]
C[Black can no longer cut off White's stones.];
B[lp];W[lq];B[mq];W[mp]
C[Black has nothing.]
)
    (;
    B[mr]
    C[The only move!]
    (;
    W[mq]
    C[The obvious defense is to block here, but ...];
    B[oq]
    C[... Black simultaneously threatens the 2 stones above and below.];
    W[np];B[nr];W[lr];B[os]
    C[Black has enough room to make 2 eyes at the bottom.]
    )
        (;
        W[np]
        C[The toughest defense.];
        B[nr];W[oq];B[lp]
        C[A nice net tesuji!  White cannot escape with the 7 stones.];
        W[mp]
        C[For example ...];
        B[mo];W[lq];B[mq]
        C[Black wins the semeai.]
        )
    )
)

