A small light-and-touch toy for iPhone and iPad, made by Krandesi.
Saving a picture puts a copy into your photo library, so iOS asks once whether that's okay. It only adds; nothing in your library is read. If you said no and changed your mind, open the Settings app, find Obrelyn, and allow Photos to add images.
Pick 1, 3 or 5 minutes in the app and follow the points as they swell and draw in. You can leave at any time; the shapes keep drifting either way.
Yes. Both have their own switch in the app's settings. Your phone's silent switch also mutes the sound.