Interactions between Persistent Structures in CA Code 20

According to A New Kind of Science, after a few steps class 4 systems typically organize themselves to the point where definite structures become visible. The NKS book discusses such systems starting at page 281 and shows some samples of this behavior using 2-color, next-nearest neighbor, totalistic cellular automaton (CA) code 20.

This Demonstration lets you investigate interactions between two such structures in this CA. Various possibilities arise from this interaction: destruction of one structure, or increasing or decreasing complexity. You can control the interaction by selecting the persistent structures that can be used, mirroring one (or both) structures, or varying the distance between initial conditions to generate a new initial condition for the CA.