Ok, I've added that in case you need it, but what I don't like about this option is that then F won't work to exit fullscreen. I use Firefox myself and F works fine. Sometimes you have to click on the game first to put it in focus, and changing from fullscreen to windowed makes it lose focus so you have to click on the game again, but it should be obvious enough, because if it's not in focus you can't move the player either. Maybe some extension or some keyboard layout or configuration difference? I can't see why would this cause any trouble.