Substitution Systems for Elements of Two Kinds
This Demonstration shows a substitution system that displays evolutions for substitutions of two kinds, namely, a gray or black cell can go to either a single gray cell, a black cell, or to any combination of two gray or black cells. The rule icon for the system is located at the top left. The evolutions only go up to 10 steps, since some of the rules cause the evolution to grow very quickly.
The substitution system for elements of two kinds is described in S. Wolfram, A New Kind of Science, Champaign, IL: Wolfram Media Inc., 2002 p. 82.