Some time passed since Immersive mode has been introduced to android (https://developer.android.com/training/system-ui/immersive.html).
However it is still hard to find android game that uses that mode.
Main advantage of that mode is that it hides virtual buttons so user won’t tap it accidentally when engrossed by the game.
Main disadvantage is that it hides virtual buttons (what a coincidence ;)) so novice user might have hard time finding how to exit the game.
I wonder if somebody had some experience with this mode and can share whether it caused user complaints.