States and Finite State Automata

These binary CAs can implement states.
If a CA is firing, that state is active.
It's a relatively simple thing to keep a system of states so that only one state is active at a time.
When inputs arrive, that can also be represented by binary CAs, they cause the system to transition to a new state.
That's all you need for a finite state automata (FSA).
We've been using these FSAs for quite some time now.
They're a nice way to implement regular languages and simple agents,
but they can also be used to represent rules.