At each step in the WireWorld cellular automaton, background cells go to background, electron heads go to electron tails, electron tails go to wire, and wire goes to either wire or head, the latter when the wire cell touches 1 or 2 electron head cells. Electrical circuits can be modeled with WireWorld.
This Demonstration tests square 25-bit templates by running eight initial conditions for three fixed pins at the left, top and right of the template. The signs of results at the bottom pin are interpreted as digits of a rule number. The interpretation can append a zero to obtain an elementary 8-bit rule, as there are no WireWorld templates which generate output from zero inputs.
Change the template by choosing its number, or modify it by clicking pixels in the larger plot. Adopt the modified template to obtain its number and run it with the eight configurations of the three pins to see its evolution. Reset clears the result counter and refreshes the initializations.
CellularAutomaton runs a pure function which implements WireWorld rules: Every head pixel becomes a tail pixel and every tail pixel becomes a wire pixel. The free pixels do not change, but wire pixels become head pixels if one or two of their neighbors are heads.