I dont even know why or how this is a thing. But it makes the game impossible to play in full-screen.
What browser are you using?
Firefox, if I switch to chrome the problem stops. I really just don't like using chrome.
It's because of page zoom, click the 3 dots and zoom out, that should fix it.
Just to add, if your page is zoomed in through firefox, you can see the zoom % level in the address bar at the top of the screen. See image
