I was a younger teenager, dreaming about making money and being rich doing software. Despite some 'hello world' apps, I always wanted to build an OS.
I kind of did it, in BASIC, calling it OSB (Operating System Basic). Now I know it is impossible, a high-level language cannot do this, but it was a dream, and you don't fight back against a 12-years-old dream ;)
I pushed to GitHub some time ago. The code is a mess and a shame, but I am proud of everything I learned on the way.