This folder contains the actual engine source code.

As long as you are working on something new, please put it into the "Experimental" folder instead. This allows other people to have a look at it, without polluting the source tree. Once people agree that an experimental project is good and should be included into the core engine, it can be easily moved over. That does not mean that it must be finished.

The Experimental folder gives you a playground to test and show off whatever you like. The Engine folder contains the code that is "mostly stable" and will definitely be maintained and thus can reliably used by others.