Sorry to hear that, I have no idea what might be the cause of that to be honest. I haven't heard of anyone else who has that particular issue. I should admit that I'm no Mac expert since I'm not a Mac user myself. (If the same thing would have happened on Windows I would have presumed that it is a graphics driver issue). If you ask for a refund here on Itch I'm sure they will be able to arrange that for you.