Thank you!!! I had never encountered this bug before. This had never happened to me, and I knew about the bug where the game becomes a tiny rectangle if you put it in fullscreen mode through itch.io, but I had never seen the black vignette appear like that. (That's actually why I removed the fullscreen option.)
I honestly have no idea why it happened, since the game's window size is the same as the size I set on itch.io (640x360).
But if you'd like to test it, you can download the Windows ZIP file. The game should start in fullscreen mode, and if you want to exit fullscreen, you can just press Alt + Enter.
But since I've never encountered this bug before, I'm not sure if this will actually fix the problem.
