[Causal networks for] mobile automata

The special structure of mobile automata of the type used here leads to several special features in the causal networks derived from them. One of these is that every node always has exactly 3 incoming and 3 outgoing connections. Another feature is that there is always a path of doubled connections (associated with the active cell) that visits every node in some order. And in addition, the final network must always be planar—as it is whenever it is derived from the evolution of a local underlying 1D system.