Ca2d -- Defines abstract protocol for cellular automata.
Inherits from DblBuffer2d, defines abstract protocol for cellular automata.
Use this to set up your CA to a default initial state. Unimplemented in Ca2d; subclass this to set up initial state of lattice.
Record the number of states the CA understands.
One iteration of the CA rule. Unimplemented in Ca2d; subclass this to implement your CA rule.