For most 15 year olds it would not be an extremely easy task. What's impressive is that someone has gone down such a specialised skill-development route by that age. So both the OP, and you, are impressive.
I still remember building my first VB Application (A browser), the moving on to HTML, PHP, then teaching a Python Class at my old school and now I'm proficient in Node.JS and know how to use most of the HTML5 API, so I guess it does take time to evolve your skills.