Show[NeighborsPicture[TwoD[{10,10}]]];
NestList[UStep[exrule,#]&,TwoD[{4,4}],4];
Show[GraphicsColumn[NeighborsPicture/@%]];
Show[GraphicsColumn[NeighborsPicture[#,{8}]&/@%209]];
NestList[UStep[exrule,#]&,TwoD[{6,6}],20];
Show[NeighborsPicture[#]]&/@%212;