By the way, so far we've been speaking only about finite configurations. But there's another problem of at least theoretical interest: Does there exist a planar pattern (i.e., a map Z^2 ->{0,1}) that has every reasonable planar pattern as a descendant? Perhaps reasonable can be defined as those planar patterns each having arbitrarily long lines of ancestors. Or, what is a priori a different condition, maybe reasonable should mean those planar patterns each having at least one infinite line of ancestors. --Dan ________________________________________________________________________________________ It goes without saying that .