Fixed in the latest update! There were some weird windowed / fullscreen logic to work through, but the latest version accepts Alt+Enter and F11.
There is some small weirdness to note - the game starts off in windowed mode, but if your monitor resolution is 1920 x 1080, then the game will look like it's in full screen mode. It's really windowed, but the title bar is drawn outside the monitor. Working through the weirdness this week.
Thanks for the feedback - that's how the game gets better!