(;GM[1]FF[4]SZ[6]
GN[Surrounding black stones (R.clone().xor(F).neighbors4().expandTo(B))]
PC[http://senseis.xmp.net/?BinMatrix]AP[GoWiki:2009]
DT[2012-08-19]
C[Diagram from http://senseis.xmp.net/?BinMatrix

Surrounding black stones (R.clone().xor(F).neighbors4().expandTo(B))]
PL[B]

AB[aa][ca][bb][cb][fb][ac][bc][fc][ad][fd][ae][ce][ee][fe][af][bf][df][ef]


;
)
