(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]RU[Japanese]SZ[19]KM[0.00]PB[Black to play and live]AW[nn][on][pn][mo][qo][ro][kp][lp][mp][op][rp][kq][oq][rq][sq][jr]
[lr][mr][ns][os][qs]AB[no][oo][po][np][qp][lq][mq][nq][pq][qq][kr][nr][or][rr][sr]
(;B[pr]C[It may look like Black should connect and peep at 
the gap in White's stones.];W[qr]C[However White has this tesuji, and it is self-atari for Black to play either side.]
(;B[ps];W[pp])
(;B[rs];W[ss]))
(;B[qr]C[Black could try this connection.];W[rs]
(;B[ss]C[Black fails after this.];W[ps]
;B[pr]C[Self-atari.];W[pp])
(;B[pr];W[ps]
;B[ss]C[Again self-atari])
(;B[ps]C[Black will have to start a ko to get away.];W[pr]C[But Black has to find the first ko threat 
There is one ko threat locally.];B[pp]
(;W[ps]C[This fails for White.];B[ss])
(;W[oq]C[This is the correct answer to the ko threat.];B[ps]C[White now has to play a ko threat elsewhere, but Black
can do better than this.])))
(;B[rs]C[This is the correct first move. Making the eye in the corner looks stupid, as White can immediately atari it.]
(;W[qr]
(;B[ps]C[However Black now plays this wedge.]
(;W[ss];B[ms];W[ks]
;B[pr]C[Black has two ways to make a second eye.]
(;W[ns];B[rr];W[sr];B[rs])
(;W[rr];B[ns]))
(;W[pr];B[ps])
(;W[ms];B[ls]))
(;B[pr]C[This fails.];W[ss]
;B[ps]C[Self-atari]))
(;W[ps]C[This also fails for White.];B[pr])
(;W[pr]C[This is atari.];B[pp]
(;W[qr]C[It is self-atari for White to play here.];B[ps])
(;W[ps]
;B[qr]C[Two eyes.]))))
