This project began life in 2017 when the author had just begun experimentation with GPIO pins on a Raspberry Pi 3. At that point in time a greatly appreciated Christmas present was an “Explorer Hat” module which provided the aspirant programmer with 5 volt tolerant input and output channels (analogue and digital) , capacitive touch pads, built in light emitting diodes (henceforth referred to as LEDs) and a breadboard on which to build proto-type i/o systems. The module is apparently no longer stocked (not by Adafruit anyway) but was certainly a useful “training ground” for programs which have digital inputs and outputs from/to the real world.