Imagine having a big Meccano set with thousands of moving parts which you control using a computer.
I have played with Meccano toys. They are fun. They have been around for more than a century. I am pleased to live, now, in the homeland of Meccano toys.
When I was doing PLC programming, my Meccano was an industrial plant featuring more than two thousands devices to control such as balances, pumps, valves, mixers, coolers and more.
Ten times per second my software had to compute opening or closing orders to send to those devices.
Sure, it’s no game. You make a mistake and maybe you hurt someone. Or you stop production or make a lot of product go to waste.
You can’t test this sort of software. You can only test it in production and have less than 15 minutes to fix any error, otherwise production stops.
This is extreme programming!