(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[]PB[Black to Play]C[Just play through the moves to move 30 which is the problem
position. These do not represent a game sequence!]
;B[dp]
;W[bp]
;B[do]
;W[co]
;B[en]
;W[bn]
;B[fo]
;W[cm]
;B[fp]
;W[dm]
;B[eq]
;W[em]
;B[cq]
;W[fm]
;B[br]
;W[bq]
;B[fr]
;W[gr]
;B[]
;W[gq]
;B[]
;W[gp]
;B[]
;W[go]
;B[]
;W[fn]
;B[]
;W[fq]
;B[]
;W[dr]C[This is the problem position. Black to play
and live his group.]
(;B[er]C[CORRECT: Connecting at 1 seems fairly
obvious. The stone nearer the corner has a 
better chance of surviving because of the special
liberty property of the corner.]
(;W[cr]
(;B[bs]C[This descent is the move that uses that special
liberty property.]
(;W[ar]
;B[ds]C[White cannot approach on either side as both are
self-atari.])
(;W[ep]C[This is a tricky response from white.
Black musn't get too greedy.]
(;B[eo]
;W[dq]
;B[cp]
;W[dn]C[FAILURE: black runs out of liberties if he
tries to save the two stones.])
(;B[dq]
;W[eo]
;B[ar]C[SUCCESS: Giving up the two stones alows black
time to make a second eye in the corner instead.])))
(;B[ar]
;W[bs]C[FAILURE: If black extends this way, now it is the
special liberty property of the corner that is helping
white. ]))
(;W[ar]C[This attack does not work for white.]
;B[ds]
;W[cr]
;B[bs]
;W[eo]
;B[ep]
;W[dn]
;B[fs]))
(;B[cr]C[FAILURE : This connection doesn't use the special
liberty property of the corner.]
;W[er]
;B[ar]
(;W[ep]C[Whilst making an eye in the corner black loses
his one in the middle. In fact white 
does not need to play the move - the eye
is already lost.])
(;W[]
;B[dq]
;W[eo]
;B[ep]
;W[dn]C[The eye is clearly false.]))
(;B[dn]C[FAILURE: Securing the two point eye is not fast enough]
;W[er]
;B[cr]
;W[ar]C[Still only one eye]))
