I have used a closed-source framework pretty heavily for a few years, and when I need to really understand how to use some part of the API, I will go home and r

I have used a closed-source framework pretty heavily for a few years, and when I need to really understand how to use some part of the API, I will go home and recreate the observed behavior from scratch. While it's sort of inefficient (why continue using a framework when I have many core pieces sitting around at home?), I think it's fun to approach the problem this way and I've learned plenty that applies to other problems.