(;
AB[pn][po][qo][qp][rp][sp][jq][pq]
AW[qq][rq][pr]
C[Black plays.]
(;
B[oq]
C[Normally, Black might have to give way here, in order to avoid a White atari on this point.  But ...];
W[or]
C[... White is happy to extend.];
B[nr]
(;
W[rr];B[rs];W[qs];B[sr]
C[Black can start a ko, but ...];
W[os]
C[... White not only takes the ko 1st, but also has local ko threats and aji starting with A.

This result is not ideal for Black.]
LB[nq:A]
)
    (;
    W[rs]
    C[Note that taking the vital 1-2 point is even worse.];
    B[sr];W[sq];B[ps]
    C[Black threatens a double atari at A.]
    LB[qr:A];
    W[qs];B[rr];W[qr];B[os];W[ns];B[os]
    C[White is in big trouble.]
    )
)
    (;
    B[or]
    C[Good move that works in this shape.];
    W[oq];B[nq];W[op];B[nr]
    C[Black has time to connect.];
    W[pp]
    C[To have any chance to live, White must prevent Black from connecting here.];
    B[no]
    C[The killing move.  White's corner is a dead shape, and White does not have a good outside cut.]
    )
)

