Need to correct something, it's not true full screen, full screen within the browser window, so changing the 10%, 100%, or 250% zoom on the browser has a no effect.
Ah yes, that’s correct. Unfortunately that’s an issue between gamemaker and itch.io which I could not solve yet. If I don’t post it as Fullscreen on itch, something in the js runtime code of gamemaker prevents it from starting at all. No solution on that (yet)