I really like codes and ciphers and hidden messages.
When I was a kid my friends and I would exchange sheets of blank white paper with secret messages laboriously written out in lemon juice, invisible to casual scrutiny until you held the note over a lit candle. The heat of the flame would coax the words to appear in a satisfyingly aged-looking sepia hue accompanied by the acrid acidic smell of scorched citrus. How clever we felt. No-one could know our secrets!
These days the art of codes and ciphers - "cryptography" as it is more seriously known - is more or less the domain of the very very smart, involving complex and sophisticated concepts and lots of computer power. I have trouble understanding how to even implement something like PGP, let alone having the vaguest clue how it works.
I really like a lot of things about the modern world. Unlike Dennis Wilson, I think I was made for these times. But sometimes I long for the days of simple cleverness where a cool idea could be executed with ingredients from the kitchen cupboard.