OMG the security codes of those games.
But do you remember the security codes for Manic Miner and Jet Set Willy ?
It was a card with a grid of different colour patterns.
So when the game finally (took ages didn't they ?) loaded, it asked you a code of say A3 for example and then you had to type in the right sequence of colours.
What was good with the long loading times, (especially the 128 K ones) was that while you were waiting for it to load you could read all the instructions.
Probably apart from Carrier Command, OMG the instructions for that were huge. It was a book. No wonder it came in a big box. Lol