(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[rn][ro][qp][qq][pr][rr][os][ps]AB[po][qo][pp][oq][pq][rq][mr][or][ns]C[Does White need to defend the corner?]
(;B[rp]C[If Black plays this atari...]
;W[qr]
;B[sr]
;W[sp]C[... then White simply connects and Black gets nothing.])
(;B[qs]C[This atari is harder to read out....]
;W[qr]
;B[sr]
;W[rs]
;B[rp]
;W[sp]C[... but again Black gets nothing.])
(;B[qr]C[White should have defended the corner, as Black can start with the throw-in.]
(;W[qs]
;B[rp]
;W[qr]
;B[sr]C[Now White is short of liberties and gets captured.

])
(;W[rp]C[So White has to give up three stones.]
;B[rs]C[Black doesn't capture them but traps them with this atari creating a snapback shape.]
(;W[sq]C[If  White needs eyes he could take the stone, but
this leaves a ko shape.]
;B[sr]
;W[ss])
(;W[sr]C[This avoids the ko, but White may have to defend again to ensure two eyes.])
(;W[qs]
;B[qr]C[This shows the snapback.]))))
