Hey the itch page is kinda fighting against your u/x here. Without the game fullscreened, my mouse isn't captured by the screen, so in trying to look right my mouse slides off the screen and I'm no longer in the game: on fullscreen this problem doesn't exist, but the escape button bound to pausing and bringing up the menu now just unfulscreens me. I'm new to designing games to run in the browser here, but I noticed that some devs used 'TAB' rather than 'Esc' for their pause menu, which gets around some of the problem.