An example of complex system that laypersons might ponder themselves occasionally is car traffic. Alas, the main obstacle is this: you actually want to teach h

An example of complex system that laypersons might ponder themselves occasionally is car traffic. Alas, the main obstacle is this: you actually want to teach how simple rules create a system (complex or not, doesn't matter, but a system). Well, a non-programmer has a difficulty mentally "running the instructions step by step" correctly as a CPU would do. You can give them some really simple mechanistic orders and watch them miserably fail after a few iterations; they usually anthropomorphize the entities, assigning to them intentions or emotions which by definition cannot be present. Since they cannot approach from the side of simplicity, any complex system becomes impenetrable and they apply general heuristics to deal with that, which you would like to prevent. No idea how to help you.