Hell yeah rhythm game representation! It's the genre I play most often. This is more or less osu! with FPS style 3D aim. I like that clicking on the circles produces hitsounds that fit with the song. It always feels more immersive. The moving circles was also creative, requiring you to have even sharper reflexes.
I think my only criticism is that I don't really know whether I hit it at the "right" time - you did mention this in another comment that there is no "scoring", but even so, I couldn't find the "rhythm" aspect to it. I tried to hit to the beat of the background music, I can't really tell if I'm on beat because the music is designed so that no matter when you hit it, it'll never sound "off" (at least not in my experience). That's honestly cool and fits the zen mode, but I'm used to having judgements made very clear in the game. Even just the circle looking different when it's supposed to be hit would be useful.
Still, really cozy, and more relaxing compared to the more adrenaline based rhythm games out there. Very creative take on the theme! I also really liked the music - whatever effect you put over the vocals to make it sound slightly robotic, it was pretty cool.