(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
AW[cp][bq][dq][eq][br]AB[dp][ep][cq][cr]C[Black hasn't got enough liberties to capture the two White stones.]
(;B[fq]
;W[dr]
(;B[ds]
;W[cs])
(;B[cs]
;W[ds]))
(;B[dr]
;W[er]C[White still has more liberties (three to Black's two) and would win a capturing race.])
(;B[co]C[So really he is better off building outside thickness. This is the solution.]
;W[bp]
(;B[bo]C[e.g. if the ladder following a White cut at d5 is OK he can play here.])
(;B[dn]C[If the ladder following a White cut at d5 doesn't work for Black then he could play this.])
(;B[fq]C[However black can force again by playing here....]
;W[dr]
;B[er]C[...and here]
;W[cs]
;B[fo]C[And then make some sort of defending move like this one.]
;W[fr]
;B[gr]
;W[es]
;B[gq]C[If white wants that stone, black gets even stronger.]))
(;B[er]C[This look like a tesuji, but it doesn't work.]
(;W[fq]C[Playing here is risky for white]
;B[dr]
;W[fr]
;B[bp]
;W[co]
(;B[bs]C[Black has a better move than that.]
;W[bo]
;B[ap]
;W[ao]
;B[ar]
;W[aq]
;B[fs]
;W[gs]
;B[es]
;W[cs]
(;B[ds]
;W[cs])
(;B[gr]
;W[ds]))
(;B[bo]
;W[cn]C[Assuming black here would capture white in a ladder
what had better play here.]
;B[bs]
;W[ar]
;B[bn]
;W[cm]
;B[ap]
;W[cs]
;B[ds]
;W[fs]
;B[aq]))
(;W[dr]
;B[fq]
;W[cs]C[Black's wall is very thin and white very strong.])))
