Auto fullscreen: the player fills the browser window on each new video. Theater mode is engaged for you and restored on exit.
Player button: a Zen button next to YouTube's fullscreen button.
Controls hidden until clicked: while playing, player chrome stays out of the way; a click shows it for a few seconds. Paused, ended, and ad playback keep controls visible.
No settings page, no storage, no network, no tracking. Shift+F toggles, Esc exits.
