(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]RU[Japanese]SZ[19]KM[0.00]PW[Chris Oliver]PB[DDK]LB[dd:1][ed:2][fd:3][de:4][ee:5][fe:6][df:7][ef:8]
(;B[dd]
;AE[dd]AW[ih][ii][hj][ij][kj][lj][mj][hk][il][im][in]AB[jh][ji][jj][ik][kk][fl][gl][hl][jl][kl][jm][jn];W[jk]LB[ik:1][jk:2]C[Diagram 1 - An improbable ko.

Black cannot play 3 at 1, and so must find a "threat" - a move elsewhere that White feels compelled to respond to.];)
(;B[ed]
;AW[dc][ad][bd][cd][ed][fd][ce][de][ee]AB[ca][bb][db][eb][ac][bc][cc][ec][fc]LB[dc:1]SQ[dd]C[Diagram 2

A "minimal ko".

This is often referred to as the "half point ko", although its value in miai counting is actually one third of a point.])
(;B[fd]
;AW[ea][ga][ka][ma][oa][qa][bb][eb][gb][kb][mb][ob][qb][ec][gc][kc]
[mc][oc][qc][rc][dd][ed][gd][kd][md][od][qd][ae][be][ce][ee][ge]
[he][ie][je][ke][me][ne][oe][qe][re][se][cf][df][ef]AB[ca][da][fa][la][pa][db][fb][lb][nb][pb][ac][cc][dc][fc][ic][lc]
[pc][sc][ad][bd][cd][ld][pd][fe][le][pe][ff][gf][hf][if][jf][kf]
[lf][mf][nf][of][pf][qf][rf][sf]LB[bb:1][nb:3][ic:2][sc:4]C[Diagram 3

Which is the real ko threat? 1, 2, 3 or 4?]
(;W[ib];B[hb];W[hc]
(;B[jb];W[ia];B[jc]
;W[id]C[Even if White plays the less easy option of j18 instead of J16, it shouldn't be too hard to live here.])
(;B[id];W[ia]))
(;W[ig]LB[ig:T]
(;B[ib];W[id];B[hc]
;W[jc]C[One eye beats no eye.

This is unconditionally alive.])
(;B[hb];W[id];B[jb]
;W[hc]C[Resoundingly alive];B[jc]C[White doesn't even have to respond to this.]))))
