Project Euler
I guess I'm becoming an old fart. I used to like programming puzzles, challenges, things like this. But as time marches on, I realize that the real-world problems I have to solve are already so challenging and require enough critical thinking, that I'm best served just focusing on them. Between family life, doing real-world challenges for income, downtime to breathe, diverse hobbies for the spiritual good of my person, I just don't see how to fit in Euler problems and other similar endeavors. Perhaps if I was a teenager again, I'd be jumping into them with much enjoyment.