I really enjoyed my time with this game, it has a ton of potential.
I only tried a few songs and they ranged from being quite slow and easy to being downright impossible on Easy mode for one of them (the chorus just became an array of flashing light.... and the spinning haha).
No real bugs that I could see, though the features were a little lacking but it is an Alpha though so that's fair.
I'd love to see a custom map creator so users can make their own "levels" for songs as the current automatic generation is a little rough on some songs and it can take away from the satisfaction of having the "bullets" hit on the beat like I assume was the intended effect. Maybe a website like OSU's beatmap site, where users can upload songs and maps?
My other suggestion, and this is purely subjective, is to make the movement in steps rather than free moving. Instead of circling around the hexagon, the player would move one "step" at a time to the side next to them. I personally think that this could be a little less frustrating but it would also make it easier for the player and would be more precise. It's simply a question of the kind of game you want this to be, challenging or relaxing/casual.
Either way, I had fun and I'm eagerly waiting to see where this game goes!