- the interaction overlay yields fully in fullscreen: YouTube only reveals its
control bar while the iframe itself sees the mouse, so after pressing F the
native fullscreen button was unreachable
- remember the volume per account (a YT.Player is created per video and always
starts at 100), plus ArrowUp/ArrowDown volume keys that work in fullscreen
- Ctrl/Cmd+wheel falls through to the browser's zoom instead of the volume