By choosing appropriate rules, it is possible to achieve many forms of synchronization within cellular automata. One version, known as the firing squad synchronization
problem, was introduced by J. Myhill in 1957, although the first published reference
did not appear until five years later (Moore 1962). The firing squad synchronization
problem seeks to determine a rule in which all cells in a region go into a special
state after the same number of steps. The problem was first solved by Moore (1962).
A solution using six colors and a minimal number of steps, illustrated above, was
subsequently discovered by Mazoyer (1988), who also determined that no similar four-color
solutions exist (Wolfram 2002, p. 1035).
