(;
AB[ir][jp][jr][kq][lq][mp][no][oo][po][qp][qq][qr][rp]
AW[js][kr][lr][mq][nq][pq][pr][qs][rr]
C[Black plays.

Source:
    Xuan Xuan QiJing, a 700 year old problem set.]
(;
B[np]
C[The only move!

That this move kills is strange enough, but that all the obvious moves fail is even stranger.]
(;
W[nr]
C[The toughest defense.];
B[ms];W[oq];B[os];W[ps];B[ns];W[ks]
C[Even at this point, imagining how Black can avoid giving White a seki is difficult.];
B[mr]
C[The magic begins.];
W[or];B[is];W[ls]
(;
B[ns]
C[The "coup de grace".  White has only one eye.];
W[ms];B[mr];W[lr]
C[And Black has several ways to keep White to only one eye.]
)
    (;
    B[ms]
    C[A careless mistake!];
    W[ns];B[mr];W[lr]
    C[White lives.]
    )
)
    (;
    W[ms];B[nr];W[or];B[ks]
    C[White has only one eye.];
    W[ns];B[ps]
    )
)
    (;
    B[ms]
    C[Bad timing.];
    W[ns]
    C[White has this beautiful defense.];
    B[nr];W[mr];B[os];W[or];B[op]
    C[White has a ko for life.]
    )
    (;
    B[nr]
    C[Even worse.];
    W[or]
    C[Now White has simple forcing moves leading directly to life.];
    B[ns];W[ms]
    (;
    B[ks];W[op]
    )
        (;
        B[op];W[ks]
        )
    )
    (;
    B[ns]
    C[Fails.];
    W[ms];B[nr];W[or]
    (;
    B[ks];W[op]
    )
        (;
        B[op];W[ks]
        )
    )
    (;
    B[op]
    C[Too stylish.];
    W[ms];B[nr];W[ks]
    C[Black has nothing.]
    )
    (;
    B[ks]
    C[Fails.];
    W[nr];B[ms];W[ns]
    )
)

