(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
AB[aq][bq][cq][dq][eq][fq][gq][hq][iq][jq][kq][lq][mq][nq][oq][pq][qq][rq][sq]
C["Eel's Bed", Takeshiro Yoshikawa's problem.
White to play 1st and live, but White plays 2 stones for every Black stone!

In all variations it is important to note that any black stone not solidly connected to the third line may be killed by white, meaning white may connect as long as black does not get 2 moves in the same column.

There is also no such thing as ko, as white may capture and fill in the same turn.]
;B[]
;W[sr]
;B[]
;W[ar]
(;B[br]
;W[rr]
;B[]
;W[qr]
(;B[pr]
;W[jr]
;B[]
;W[ir]
(;B[kr]
;W[hr]
;B[]
;W[gr]
(;B[fr]
;W[ks]
;B[]
;W[ps]
;B[js]
;W[is]
;B[]
;W[gs])
(;B[ks]C[If black cuts]
;W[fr]
;B[]
;W[er]
;B[dr]
;W[es]
;B[]
;W[js]))
(;B[hr]C[Blocking on the other side does not help]
;W[kr]
;B[]
;W[lr]
(;B[mr]
;W[ms]
;B[]
;W[ps])
(;B[ps]
;W[mr]
;B[]
;W[nr]
;B[is]
;W[js]
;B[]
;W[or]
;B[os]
;W[ns]
;B[]
;W[ls]))
(;B[ps]C[If black cuts the corner white easily lives in the middle.]
;W[hr]
;B[]
;W[gr]
;B[fr]
;W[kr]
;B[]
;W[lr]
;B[mr]
;W[ls]
;B[]
;W[gs]))
(;B[or]C[Playing further does not help black, as it allows white to gain a sente move in the corner, thus gaining an extra stone on the outside.]
;W[ps]
;B[]
;W[ir]
;B[pr]C[Black must play here]
;W[jr]
;B[]
;W[hr]
(;B[gr]
;W[kr]
;B[]
;W[os])
(;B[kr]
;W[ks]
;B[]
;W[os]
;B[gr]
;W[js]
;B[]
;W[hs]))
(;B[nr]C[Any further than p2 allows white to live directly in the corner.]
;W[pr]
;B[]
;W[or]
;B[os]
;W[ps]
;B[]
;W[rs]))
(;B[cr]C[C2 slightly lessens the space white has in the middle, however white still has enough room for the original solution to work.]
;W[rr]
;B[]
;W[qr]
;B[pr]
;W[ir]
;B[]
;W[jr]
(;B[kr]
;W[hr]
;B[]
;W[gr]
(;B[fr]
;W[ks]
;B[]
;W[ps])
(;B[ks]
;W[fr]
;B[]
;W[er]
;B[js]
;W[is]
;B[]
;W[dr]
;B[ds]
;W[es]
;B[]
;W[gs]))
(;B[ps]
;W[hr]
;B[]
;W[kr]
;B[gr]
;W[lr]
;B[]
;W[mr]
;B[nr]
;W[ms]
;B[]
;W[hs]))
(;B[dr]C[D2 is more useful than C2 against the center, however it leaves white the chance to form an eye in the lower left.]
;W[rr]
;B[]
;W[qr]
;B[pr]
;W[ir]
;B[]
;W[jr]
;B[kr]
;W[hr]
;B[]
;W[gr]
(;B[ks]
;W[fr]
;B[]
;W[er]
(;B[js]
;W[es]
;B[is]
;W[ds]
;B[]
;W[br]
;B[cr]
;W[cs]
;B[]
;W[bs])
(;B[es]
;W[fs]
;B[]
;W[js]
;B[hs]
;W[ds]
;B[]
;W[br]))
(;B[fr]
;W[ks]
;B[]
;W[ps]))
(;B[er]C[The usefulness of being able to make an eye in either corner becomes even clearer when black plays E2.]
;W[rr]
;B[]
;W[qr]
;B[pr]
;W[jr]
;B[]
;W[kr]
;B[lr]
;W[ir]
;B[]
;W[hr]
;B[ls]
;W[br]
;B[]
;W[es]
;B[cr]
;W[cs]
;B[]
;W[bs])
(;B[fr]C[F2 makes white's space in the middle start to seem very limited, however there is still enough room to make one eye in the center and miai either another in the corner or a second in the center.]
;W[br]
;B[]
;W[rr]
(;B[qr]
;W[kr]
;B[]
;W[lr]
;B[jr]
;W[mr]
;B[]
;W[nr]
(;B[js]
;W[or]
;B[]
;W[ps]
(;B[qs]
;W[pr]
;B[]
;W[ks])
(;B[pr]
;W[qs]
;B[]
;W[rs]))
(;B[or]
;W[js]
;B[]
;W[fs]))
(;B[pr]C[Playing further than R2 here makes it even easier on white, removing the necessity of threatening to make a second eye in the ceter.]
;W[jr]
;B[]
;W[kr]
;B[lr]
;W[ir]
;B[]
;W[hr]
;B[fs]
;W[ls]
;B[]
;W[ps])
(;B[nr]C[If black plays too far in his attempt to restrict the center, white will live directly in a corner.]
;W[qr]
;B[]
;W[cr]
;B[pr]
;W[dr]
;B[]
;W[er]
;B[es]
;W[ds]
;B[]
;W[bs]))
(;B[gr]C[By the time black reaches G2, he no longer is playing close enough to the corner to prevent white from making miai for living in one corner or the other.

The same sequence that works for this move also may be used for H2, J2, and K2. Beyond that it becomes symmetrical to attempts already shown.]
;W[br]
;B[]
;W[rr]
;B[qr]
;W[cr]
;B[]
;W[dr]
(;B[bs]
;W[er]
;B[]
;W[fr]
;B[fs]
;W[es]
;B[]
;W[cs])
(;B[er]
;W[ds]
;B[]
;W[bs])))
