Can you try change your layer background color to red or blue? This is to see that the preview does indeed draw the game correctly.
Also, I have a feeling that you might be using Letterbox Scale. See
https://www.scirra.com/tutorials/73/sup ... reen-sizes for more info. Because right now, your layer backgroundcolor is black which is the same as Letterbox Scale's filling color.
[quote:2h4ltsma]Letterbox scale mode simply scales the game to fit the window. If the aspect ratio does not match, black bars appear down the sides of the window.
Is this indeed the case?
The letterbox scale is definitely what's causing it, having tried it with a few different colour backgrounds. The problem is that the letterbox scale is essential to make the game properly full-screen, all the other ones don't really work as well. So I guess it's a trade off huh?