Try going to the options and changing the resolution? It might be detecting the wrong one automatically for some reason? If that is the case, please answer back what resolution it was detecting and what is the appropriate one you usually use.
Does the same happen if you try to play on the browser over on itch?
I will look into that, but kind of stretched thin at the moment, so that will be a long term goal.
As always, I am sorry if the overall experience is still rough. I can only do so much at one time while handling a day job, and I get keep new content coming which makes it all the more complicated, sorry!