Greasy Fork is available in English.
Moves the YouTube video to the top of the website and fill the window with the video player.
< 脚本 Resize YT To Window Size 的反馈
You can now press the w key to toggle the script, though it might be changing to another key now that YouTube is using it.
https://github.com/Zren/ResizeYoutubePlayerToWindowSize/issues/71
Love this script, been using it for years. Only addition I would love is a way to change back to non-theater mode without completely disabling the script. Currently you can't use the chat while watching a youtube live stream because the chat is stuck below the video.