Fiddling about a bit with structure. Moving GUI code further away from engine code. Thinking they should be basically independent modules, maybe to the point of having a translator module to convert from "business" logic domain objects to interface level model objects. Yeah, that's right, I'm just noodling around with these commits! It's extremely unlikely anyone will ever read this message again, and even more unlikely that it won't be me! Yep, yep...