(;
AB[bq][ap][cp][dp][eq][fq][gq]
AW[bp][bo][co][do][bn][ep][fp][fn][ck]
PL[W]
C[White plays.

Source:
    From the endgame volume of Gokyo Seimyo, a nearly 200 year old problem set.]
(;
W[cq]
C[OK, the 1st move is easy.];
B[dq];W[cr];B[br]
C[Everything is forced up to here.]
(;
W[ar]
C[Vital point!]
(;
B[dr]
C[Black has nothing better than defending here.];
W[ao];B[cs];W[aq]
C[White successfully reduces the corner.]
)
    (;
    B[aq]
    C[Greedy.];
    W[bs]
    C[White has a picnic ko.]
    )
)
    (;
    W[ao]
    C[Too slow.];
    B[ar]
    C[Having time to take this vital point, Black is at least 3 points better than the main line.]
    )
)
    (;
    W[ao]
    C[Bad timing.];
    B[cr]
    C[Happy to protect the cut here, Black is more than 3 points better than the main line.]
    )
)

