Back in the mid 80s, I'd killed several joysticks playing Daley Thompson's Decathlon on my Amstrad CPC (which was more-or-less a standard Atari pinout apart from 2 select lines and 2 fire buttons). By chance, my parents had a push-button phone that was being scrapped because it wasn't very good for some reason that I've forgotten. I reverse-engineered the PCB and figured out that 2,4,6,8 and # would all be individually detectable if I cut a couple of traces on the PCB and I soldered and old joystick cable to the where the original edge connector on the keypad board used to be. That was aged around 10. I suspect I still have it somewhere, nearly 40 years later, as I was still using it with my Amiga when I packed that away when I went to university.