So, first of all - auto-fullscreen is such an annoying feature, especially in a demo...
As for the engine, it works quite well, I think... If you have the button layout at hand (I tried to figure it out without looking at your list, and it just doesn't work - might think about including it in the editor), it's quite intuitive from there. What's missing is a regular text editing feature, as every time you click a text field, the whole thing empties itself, which isn't too regular and therefore hard to use.
Other than that, it happened a few times that upon exiting the editing window, the map screen didn't allow me to do anythign anymore but moving the mouse cursor... might wanna check for that.
But yeah, like I said: I think it's coming along well, and although it looks like a v0.8 or so, I like what you did there ^^