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You can fullscreen the game with alt+enter (that is to say, after you open the game window, hold the alt key, and hit the enter key while holding alt)

This is the key prompt for fullscreen on a lot of games (most rpgmaker games, most visual novels, etc etc) so it's always worth checking if it works when you're dealing with games that don't have a settings section where you can change between windowed/fullscreen with a toggle!!
I think a lot of game makers are so used to just knowing the shortcut prompts for these things, that they don't bother putting controls for them in the settings because they assume it isn't necessary;;;;

Editing to add: alt+enter also works to undo fullscreen and go back to windowed mode.

I am so used to toggling fullscreen with alt+enter, that I sometimes do it out of habit when trying to exit fullscreen on a youtube video 😂