This is still what I tell people in interviews was my most difficult technical challenge. I had nothing but an old 386 and the K&R book -- no Stack Overflow back in those days, and I didn't know any programmers well enough to ask them for help. It was the first time in my life I ever truly grinded on a task. It happened just suddenly, and it was glorious, and I've been chasing that feeling ever since. "Hey, kid, you wanna fly?"