(;GM[1]FF[3]
RU[New Zealand]SZ[7]HA[0]KM[9]
PW[White]
PB[Black]
GN[White (W) vs. Black (B)]
DT[1996-05-23]
SY[Cgoban 1.4.0]TM[-]
C[In the American GO Journal (vol. 29, number 3, summer '95),
James Davies had this to say:
"On a 7x7 board, Go becomes challenging for even the strongest human players.
The challenge (find the best moves for both sides) was taken up in 1977 by a group
of Japanese amateurs including Kiga Yasuo, Nebashi Teruichi, Noro Natsuo and
Yamashita Isao. In 1989, with some professional help from Kudo Norio and
Nakayama Noriyuki, they reached the conclusion that Black wins by nine points.
What follows is a tip-of-the-iceberg summary of the evidence. It should be added
that the analysis is still somewhat tentative, and future discoveries may lead to
further revisions."
Many other remarks by Davies have been included in the node commentaries.
]
(;B[cc]C[suboptimal
];W[dd];B[cd];W[de];B[dc];W[ec];B[eb];W[ce];B[ed];
W[fc];B[fd];W[fe];B[fb];W[ee];B[gc];W[bd];B[bc];W[be];B[ge];W[gf];
B[ac];W[ad];B[gd];W[ff]C[black loses by 6
])

(;B[dd]
C[On a 7x7 board, Black's best opening is pretty certainly in the center.
]
(;W[ec]C[suboptimal
];B[ed];W[dc];B[cc];W[cd];B[ce];W[bd];B[cb];W[be];
B[fc];W[de];B[ee];W[cf];B[ef];W[bb];B[bc];W[ac];B[ba];W[ab];B[eb];
W[df];B[dg];W[cg];B[eg];W[ad];B[ca];W[aa];B[db]C[black wins by 4
])

(;W[dc]C[White  should reply in contact.
]
(;B[ed]
C[Under AGA rules, Ing rules and Chinese rules, this variation by black is equally good.
Although this move loses by one point under Japanese and Korean rules, it yields him
a jigo under these other rule systems by virtue of getting the last move.
]
;W[cc];B[cd];W[ec];B[bc];W[bb];B[bd];W[fd];B[fe];W[fc];B[ab];W[ge];
B[ff];W[ba];B[gf];W[gd];B[ac];W[cb];B[aa]C[jigo
])

(;B[ec]
C[White can flip a coin to choose between the cross-cut at E4 and the hane at C4.
]
(;W[cd]C[
]
(;B[cc]C[premature
];W[de];B[db];W[ed];B[dc];W[ce];B[fe];W[ef];B[ff];
W[ee];B[fd];W[bc];B[bb];W[ad];B[eg];W[dg];B[fg];W[ab];B[ba];W[ac];
B[aa];W[be])

(;B[de]
C[Black should extend, after which White has another coin-flip: heads for C6,
tails for E6.
]
(;W[eb]C[This triple hane opens the gates to a flood of variations.
]
(;B[cc]C[unique best move
];W[db]
C[Black has four equally good continuations: B4, C3, C6, or F5.
]
(;B[bd];W[ed];B[ee];W[fc];B[cb];W[fe];B[ff];W[gf];B[fg];W[ca];B[ba];
W[da];B[bb];W[ge];B[ef];W[gg];B[ce]C[jigo
])

(;B[ce];W[bd]
(;B[bc];W[bb];B[be];W[ed];B[fd]
(;W[ee]C[too bad
];B[fc];W[fe];B[ff];W[ef];B[ge])

(;W[fc];B[fe];W[cb];B[ad];W[ee];B[ef];W[ec];B[ab];W[gd];B[gf];W[ba];
B[ge];W[gc];B[ac];W[aa]C[jigo
])
)

(;B[fc];W[be];B[bf]
(;W[bb];B[fb];W[af];B[ea];W[cb];B[bg];W[da];B[fa];W[ae];B[cf];W[ag];
B[tt];W[bc]C[jigo
])

(;W[bc];B[fb]
(;W[bb];B[af];W[fa];B[gb];W[ae];B[ga];W[ea];B[tt];W[cb]C[jigo
])

(;W[af];B[ea];W[cb];B[bg];W[da];B[fa];W[ae];B[cf];W[ag]C[jigo
])
)
)
)

(;B[cb];W[ed];B[fc];W[fb];B[ce];W[bd];B[bc];W[ee];B[ef];W[fd];B[ff];
W[be];B[bf];W[cf];B[df];W[af];B[cg];W[ca]
(;B[ba];W[ac];B[da];W[ab]C[oops
])

(;B[ab];W[ba];B[ge];W[gc];B[fe];W[bb];B[ac];W[da];B[ae];W[aa];B[ad];
W[gd];B[ag]C[jigo
])
)

(;B[fc];W[bc];B[ce];W[bd];B[fb];W[be];B[ea];W[cb];B[bf];W[af]
(;B[ae]
(;W[cf];B[ag];W[ad];B[df];W[af];B[cg];W[bg];B[cf];W[fa];B[ga];W[da];
B[fa]
(;W[ae];B[bb];W[ba];B[ab];W[ac];B[ag];W[aa];B[bg]C[black wins by 2
])

(;W[bb];B[ag];W[ed];B[fd];W[bg];B[ee];W[ae];B[ag]
(;W[tt];B[bg]C[black wins by 2
])

(;W[ff];B[bg];W[fe];B[eg];W[fg];B[ef])
)
)

(;W[ad];B[bg];W[da];B[fa];W[ae];B[cf];W[bb];B[ag]C[black wins by 2
])
)

(;B[bg];W[da];B[fa];W[ae];B[df];W[ag]C[jigo
])
)
)

(;B[db]C[Black should resist this temptation.
];W[cc];B[fb];W[ce];
B[df];W[cf]C[Black loses.
])
)

(;W[cc]C[suboptimal
];B[eb];W[ce];B[cf];W[bf];B[df];W[db];B[bg];W[af];
B[da];W[ca];B[ea]
(;W[be];B[cg];W[ag]C[
];B[bb]C[
];W[cb];B[bc]C[Black gets a seki.
])

(;W[bd];B[cg]
(;W[bb];B[ag]C[black wins by 2
])

(;W[ag];B[bb];W[cb];B[ac];W[ad];B[ba]C[
];W[ab];B[aa]
C[black wins by 11
])
)
)

(;W[cb]C[White C6 is simplest.
];B[db];W[cc]
C[It's black's turn to flip the coin to choose E6 or C3. Whichever of these points Black
takes, White will take the other.
]
(;B[eb];W[ce];B[cf];W[bf];B[df];W[bg];B[ca];W[ba];B[da]
(;W[ab];B[cg]C[black wins by 2
])

(;W[cg]C[The key move in this sequence.
]
(;B[dg];W[ab]C[jigo
])

(;B[bb]C[Inviting Black to this ko.
]
(;W[bc]C[not such a good idea for white, because...
];B[aa];W[dg];
B[ac];W[ad];B[be];W[ab];B[af];W[ae];B[ac]C[oops
])

(;W[dg]C[this almost works, but not quite.
];B[ef];W[ff];B[eg];W[ab];
B[aa];W[ed];B[fd];W[ba];B[be];W[ae];B[aa];W[fg];B[ee];W[ba];B[af];
W[bd];B[aa];W[fe];B[ed];W[ba];B[ad];W[ac];B[aa]C[one threat short...
])

(;W[ab]
C[White can barely win this ko, altough the details area bit tricky, to say the least.
]
;B[aa];W[ed]
(;B[fd];W[ba]
(;B[dg];W[bc];B[ee]C[jigo
])

(;B[bc];W[bd];B[aa];W[dg];B[ad];W[be];B[ac];W[ef];B[ee];W[fe];B[ed];
W[gf];B[ae];W[af];B[gd];W[ge]C[black loses by 2
])
)

(;B[be];W[bd];B[ad];W[ae];B[bc]
(;W[ac]
C[Obvious, but bad, since Black gets to win the A7 ko in sente.
];
B[ad];W[ac];B[ff];W[ef];B[ee];W[eg];B[fg];W[dg];B[fd];W[ad];B[ba];
W[ab]C[black wins by 2
])

(;W[be]
C[Now with the ko at A7 still open, Black has to handle E4 as solidly as possible.
]
;B[fd];W[dg];B[ac];W[ef];B[ee];W[fe];B[ed];W[gf];B[gd];W[ge]
C[black loses by 4
])
)
)
)
)
)

(;B[ce];W[eb];B[fb];W[da]
(;B[fc]C[This apparent underplay is the critical move.
];W[be];B[bf];
W[bd];B[af];W[fa];B[ae];W[gb];B[ad];W[ac];B[fe];W[ea];B[gc];W[ga]
C[jigo
])

(;B[fa];W[be];B[bf];W[af];B[bd];W[ad];B[ae];W[fc];B[ed];W[be];B[bg];
W[bc];B[fd];W[ea];B[cf];W[ae];B[ag];W[tt];B[gc]C[jigo
])
)
)
)
)

(;W[ed]
(;B[de]C[
];W[eb];B[fc];W[cc]
(;B[bd];W[fb];B[fd];W[bc];B[be]
C[This is perhaps the only move for which black has any choice, the other choices
being C3 or C4.
]
;W[gb];B[gc];W[cd];B[ce];W[ad];B[ae];W[ac];B[ee]C[jigo
])

(;B[fb]C[optimal only under area rules
];W[be];B[bf];W[ce];B[cf]
(;W[df];B[ef];W[ee];B[dg];W[cd];B[df];W[db]
(;B[ae];W[ad];B[af];W[fa];B[gb];W[bb];B[fe];W[ea];B[ga];W[tt];B[fd]
C[jigo
])

(;B[fa];W[af];B[ea];W[da];B[bb];W[bc];B[ad];W[ae];B[ac];W[bg];B[ff];
W[ba])
)

(;W[cd];B[df];W[db];B[fa];W[af];B[ea];W[da];B[bb];W[bc];B[ad];W[ae];
B[ac];W[ba];B[bg])
)
)

(;B[fc]C[suboptimal
];W[cd];B[de];W[ce]
(;B[cc]
(;W[db]C[suboptimal
];B[cb];W[df];B[ee];W[ef];B[fe];W[bc];B[bb];W[bd];
B[ab];W[ff];B[gf];W[bf];B[ac];W[ad];B[ge];W[fg];B[gg]C[
];W[tt];B[fd];
W[tt];B[eb];W[tt];B[da]C[black wins by 2
])

(;W[df];B[ee];W[bc];B[db];W[bb];B[ef];W[cf];B[dg];W[cg];B[eg];W[cb];
B[da];W[ca];B[dc];W[tt];B[fd]C[black loses by 2
])
)

(;B[df];W[db];B[cc];W[cb];B[cf];W[fd];B[fe];W[fb];B[bc];W[bb];B[gd];
W[eb];B[ee];W[bd];B[be];W[ac];B[ae];W[gb];B[gc];W[ad];B[bf]
C[black loses by 4
])
)
)
)
)
)

(;B[dc]C[suboptimal
]
(;W[de];B[ce];W[dd];B[cd];W[ec];B[eb];W[cc];B[db];W[cf];B[bf];W[df];
B[bc];W[fc];B[fb];W[bg];B[gc];W[fe];B[af];W[gd];B[gb];W[cg];B[be];
W[ag];B[cb]C[black loses by 4
])

(;W[tt];B[de];W[dd];B[cd];W[ed];B[ee];W[ec];B[db];W[fe];B[ff];W[eb];
B[fd];W[fc];B[ge];W[cc];B[cb];W[bc];B[bb];W[bd];B[ce];W[be];B[fa];
W[cf];B[af])
)

(;B[gg];W[dd];B[de];W[ee];B[cd];W[cc];B[ce];W[dc];B[ef];W[fe];B[ff];
W[bd];B[be];W[bc];B[ge];W[fc];B[gc];W[gb];B[gd];W[fd];B[gf];W[ae];
B[af];W[ad];B[bf];W[fb])

(;B[gd];W[dd];B[dc]
(;W[ec];B[ed];W[cc];B[db];W[ee];B[fd];W[cd];B[cb];W[bb];B[fc];W[ca];
B[eb];W[fe];B[ge];W[ff];B[gf];W[fg];B[ba];W[aa];B[da];W[bc];B[ba];
W[ab];B[fa];W[ca];B[de];W[df];B[ba];W[ce];B[ca];W[gg])

(;W[cc];B[ed];W[de];B[ee];W[ef];B[cb];W[ff];B[ec];W[bc];B[bb];W[cd];
B[ac];W[ad];B[ab];W[fe];B[fd];W[ge])
)

(;B[ff]
(;W[dd]
(;B[ee]
(;W[ed];B[fd];W[de];B[df];W[fc];B[ce];W[cd];B[be];W[bd];B[gc];W[fb];
B[ad];W[ac];B[ae];W[bb];B[gb];W[fa];B[gd];W[ga])

(;W[de];B[df];W[ed];B[fd];W[fc];B[ce];W[cd];B[be];W[gd];B[fe];W[bd];
B[ad];W[ac];B[ae];W[bc];B[ge];W[gc])
)

(;B[dc];W[cc];B[ec];W[ed];B[fd];W[cb];B[cd];W[ce];B[bd];W[be];B[de];
W[ee];B[df];W[bc];B[ef];W[ad];B[fe];W[cd];B[db];W[da];B[fb];W[fa];
B[bf];W[cf];B[cg];W[gb];B[gc];W[ea];B[ga];W[ca];B[gb];W[eb];B[fc];
W[af];B[bg];W[ae];B[dg];W[ag])
)

(;W[ee];B[dd];W[de];B[cd];W[ce];B[ed];W[fe];B[fd];W[gd];B[be];W[bf];
B[bd];W[fc];B[af];W[bg];B[eb];W[fb];B[fa];W[ec];B[db];W[dc];B[cc];
W[ge];B[bb];W[gc];B[ae];W[df];B[ga];W[gb];B[ea];W[dg];B[ag])
)

)