As the game says – you are mountain, you are god. However, that's pretty much all it says. MOUNTAIN is a procedurally generated ambient game where you interact with a floating mountain hanging in space. While observing, you'll find objects which can be collected and organized, but I'm not sure why.
The weather on this craggy chunk of rock changes throughout the day and that affects what grows on the slopes. There are no instructions in MOUNTAIN, but apparently there is a finite amount of gameplay, and there's an ending of some sort.
It's hard to know if MOUNTAIN is an interesting departure for gaming on a mobile device, or just a weird thing that you'll lose interest in. Either way, it's going to cost you a buck to find out.