Hmmm, I can't do that. I think you should make this in the game upload screen settings that game should have fullscreen.
Viewing post in Kookie Karma jam comments
Ok, so it seems that Itch has a problem with the camera dimensions, on some devices it is smaller and on some others it is larger. I've set the dimensions to a large number that on mine device sets the camera on a dimensions larger than the actual game screen (this will result in things that should have been cut off to appear) but on another computer I have sets the actual resolution of the game. Hope it helps, if it persists try to download it instead, as it doesn't have this problem.
(The game cannot be fullscreen for the same reason, the camera would get bigger but the actual game would remain the same resolution)