The Logic

Take two identical switches. Put them one after the other and both must be on before a signal passes. Put them on separate paths and either one can let the signal through.

The switches did not become smarter. Their connection changed the rule the circuit follows.

Arrangements like that are called logic gates, and there are only a handful of them. Each one is simple enough that you can check it exhaustively, try every possible input, write down every output, and be finished in a minute. There is nothing left over to wonder about.

The interesting part is what happens when you stop treating them as separate. Feed one gate's answer into the next as its question, and small certainties start stacking into larger ones. Comparing two patterns, adding two numbers: these turn out to be nothing more than a few of those tiny decisions arranged so their answers fall in the right order.

Remembering is the one that feels like it should need something else. A signal passes and is gone, so how does anything stay? The answer is almost a trick, and it costs no new parts at all.

None of this is intelligence, and none of it is software yet. It is the floor underneath both: parts too simple to be interesting on their own, doing something worth noticing only because of how they are joined.