Sorry, fullscreen is not currently supported. We're working on it, but it messes up quite a few things;;;
I'm not sure what your screen resolution is, but the window of the game should be 1068x600. My desktop screen resolution is 1920x1080, so it takes up most of my screen. I know it's not ideal, but if you lower the resolution of your screen it should "get bigger". I hope this helps.
I will try looking into a temporary solution for now to avoid ^ if it's that distasteful.