This 16-year old student built a browser... in C++... writing hundreds of thousands of lines of code... This would be hard enough work today, but this was in 2003 (!!) He's had a very successful career since, and he works on browsers today, as well. You probably use his work:

I'm talking about @addyosmani of course. Just incredible stuff, even back in high school:

@eterevsky @addyosmani I agree with you btw that creating a fully functional browser is more difficult every passing year!