(;GM[1]FF[4]SZ[19]AP[SmartGo:0.8.12]CA[UTF-8]GN[187ex]AB[oo][op][oq][po][qo][qp][pq]AW[on][pn][qn][rn][no][np][nq][nr][ro][or]
(;B[rp]C[Any blocking move allows White to jump in the other side and stop the second eye.];W[qr];B[rr];W[rs];B[sr]
;W[sp]C[No corner eye.])
(;B[rr]C[This is the correct first move.];W[rq];B[sr];W[qr];B[rp];W[sp]
(;B[sq]C[Black must play here.]
(;W[rs]C[If White plays here Black must take on the edge.];B[so]
;W[qq]C[White cannot save the cutting stone];B[pr])
(;W[so]C[If White connects, Black must make the eye in the corner.]
(;B[rs]C[White cannot save the cutting stone.])
(;B[pr]C[This is wrong.];W[rs];B[qq]
;W[ps]C[White can get a ko.]))
(;W[pr]C[Black again makes the corner eye if here.];B[rs]))
(;B[pr]C[Mistake by Black.];W[rs];B[qq]
;W[ps]C[This is a ko.])))
