(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[bo][do][cp][ep][eq][er][gr]AB[bp][bq][dq][dr][es]C[This is the problem position. Black to play.]
(;B[bs]C[Sometimes the 2-1 works]
(;W[ar]
(;B[br]
;W[cq]
;B[cr]
;W[ds]C[But black doesn't make two eyes that way])
(;B[ds]C[though black can try this response]
;W[br]
;B[cq]C[And it looks like black will live]))
(;W[cq]C[This is the correct move for white in this shape.]
;B[cr]
;W[ar]
;B[ds]
;W[br]C[And black can't capture the two white stones]))
(;B[cq]C[If black connects...]
;W[ap]C[... then its death in the hane.])
(;B[ar]C[It's the diagonal move that works. The other 2-1 point.
This is the correct answer.]
(;W[ap]
;B[bs]C[If white hanes, black takes the other 2-1 point to
make two eyes.])
(;W[bs]C[So if why tries to stop black with the second 2-1 point.]
;B[ap]
;W[cr]
;B[cq]
;W[ds]
;B[br]
;W[fs]
;B[as]C[It is not a ko as white ends up short of liberties.])))
