Ah, thanks for typing all of that all over again! Your kind works are very encouraging to me, I'm glad you enjoyed playing! There is actually a way to toggle fullscreen, you can press ESC at any time to bring the Options menu, where you can toggle things like fullscreen and instant/smooth movement. I realize it's not obvious enough beside a tiny text in the corner of the title screen (which might even have been unreadable on a 4K screen). I'll add thart information on the game page.
Thanks for playing!