I very seldom buy "pay-what-you-want". I prefer when games are either free or has a fixed price tag. But okay, I forced myself to download Gemstone Shooter, yeah, without paying.
There's a lot to like here - the simple graphic has style, and I dig the flying eyeballs. Reminds me of Residents Freakshow. The finger guns are a great!
The big negative is that the game is won in a couple of seconds, thus newer allowing you to get into the flow. The GUI right in front of my eyes are distracting and it is hard to tell the gems apart with that monster in the background. It would also be nice with some background music.
It has a good foundation, and I think the casual match-3 gameplay could work well in VR. Please give it some more work!