This is not a game, more of just a gadget to mess around with if you are interested in this sort of thing.
You have a grid of pixels, where each pixel can be empty, a wire, a signal head or a signal tail. After each "second" of time passing, signal heads become signal tails, signal tails become wires and a wire can become a signal head if one or two of the adjacent pixels are signal heads.
WireWorld is Turing complete, meaning that it is possible to create many logic gates, and even large computers (but not in this version, the grid is too small).
Original concept by Brian Silverman.
This site provides many patterns that you can create within WireWorld, and will get you started making your own devices:
Replace "*" with ".", obviously.