(;
AB[sq][rq][rp][qp][pp][pq][pr][np][nq][nr][oo][no]
AW[qr][ps][os][or][oq][po][qo][ro][so][sp][op][pm]
C[Black plays.]
(;
B[qs]
C[A throw-in like this move is often the correct move, but ...];
W[rs]
LB[sr:A]
C[... after capturing, White threatens A to kill the corner.];
B[sr]
C[Black must make another move to ensure seki, but ends in gote.  Black can do better!]
)
    (;
    B[rr]
    C[No better.];
    W[rs]
    C[After White simply blocks here, ...];
    B[sr]
    C[... again Black has to fill in here for a gote seki.  Otherwise, White has the option of playing here to make the corner a ko.]
    )
    (;
    B[rs]
    C[The best move.];
    W[rr]
    C[White cannot let Black play here.];
    B[qs];W[ss];B[qs];W[rs];B[ns];W[qs]
    C[After these forcing moves, Black again has a seki, but this time in sente!]
    )
)

