It often seems the advent of the computer has complicated what were once simple things, but one counter-example is pinball machines. The fancy electromechanical pinball machines of the 1930s through the mid-1970s had complex stateful scoring rules, multi-player scoring, award of free balls and games, and all of this was accomplished by relays, solenoids, motors, cams, and switches. The “ladder logic” used to describe this is intimidating even to a programmer accustomed to tricky code. Looking inside the machine makes one wonder how they ever mass-produced these devices, with dozens of relays and hand-wired and soldered interconnections. Most of the relays and solenoids operate on 24 volts AC, and make impressive fat sparks when making and breaking circuits, so it’s a wonder they lasted so long in service without difficult to diagnose and repair breakdowns.