The Editor needs to do all kinds of complex window management, and other stuff, and also uses all sorts of 3rd party middleware (like Enlighten, for global illu

The Editor needs to do all kinds of complex window management, and other stuff, and also uses all sorts of 3rd party middleware (like Enlighten, for global illumination) that wouldn't work as being part of the runtime itself. The editor is, however, largely written in Unity (uses the same APIs, etc, in addition to a bunch of private ones).