 The surprising patterns in the aforementioned classroom example were generated by boxes in a line with just two states and a simple rule. One may wonder how many variations are possible on such a basic framework. To address this issue, let us begin by considering how Andrew Ilachinski, in his review of the literature, narrows down CA applications to four main areas, which will be referred to in the rest of this entry (Ilachinski 2001: 7): 