This site is a learning tool for front-end web developers. Its goal is to make learning a library more efficient.
I believe code sandboxes are the most important learning resource for a code library. The established method for learning about the world, science, it built on upon an approach of doing & feedback. My experience as a teacher leads me to believe this is the most effective learning approach. Documentation can tell the user how something works but a sandbox allows the user to prove it to them self. This also has the benefit of removing a level of trust between the author and user. The user can create the mental model of how the library works by doing. They can then test their model and make adjustments, solidifying understanding. This approach can also been viewed as 'play'.
To minimise cognitive load, each sandbox contains: