I think it’s probaly an artifact related to either your video driver ─ in which case we’ll need more information; see the quoted post below ─ or possibly due to scaling. Or maybe both.
That said, consumer-grade hardware has no protection against things like atmospheric interference or cosmic rays. It might have been caused by that, and then shutting everything down, waiting for about 10 minutes and booting back up remedies the situation.
Yep, for security reasons, we’ve disabled that for new registrations until they’ve baked enough cookies.
─ or possibly due to scaling. Or maybe both. 
