Documentation on how to use mobile GUI

[Alestrix]

When I play a song via the web page on a smartphone I only see a floating icon that I can move around. There's no way to switch this into a regular player screen. The only thing I can do is close the icon which stops playback.

In trying to solve the problem I searched for a documentation regarding usage of the Navidrome web page and realized such documentation doesn't seem to exist.