This is an easy one for those familiar with integrated circuits, but it's been bugging me. Say you build a circuit out of NAND gates, which have two inputs and one output. Doesn't this mean that the circuit as a whole has multiple inputs (or do some of the outputs loop back to the inputs so the circuit as a whole has only one input)? If so, how does feeding a single current (from the wall) into the circuit do anything for the multiple inputs: they'd all get the same input current and this restricts what the gates can do (for example you can't have input A getting zero current and input B getting nonzero current)? So how do you get the inputs to be different?