Coding & Programming.
A computer hacker is any skilled computer expert who uses their technical knowledge to overcome a problem. — Wikipedia
By that defintion what perhaps I could be described as a “hacker.” Maybe more “competent” than “skilled”… and I don’t pretend to any expertise. To paraphrase, or perhaps outright mangle, Toad, I enjoy “simply messing about with computers.” This usually takes the form of building websites, messing around with Python and most recently building ebooks.
The fun is breaking things down into their constituent parts and putting them back together in new and innovative ways. I’ve been doing this since the days of ProDOS on an old Apple IIc and have been managing to break and rebuild various bits of code ever since.