These pages had gotten wet, so are extra crinkly! By the way, sorry for the weird movement of the image, it happens when I use YouTube capture so I don't use that anymore. My more recent videos should be better quality than some of the earlier ones.
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app