This game is great! I feel that it really embraces the purpose of the theme. It's really tough, but really fun. My only complaint is that maybe the game should start off a bit easier before the difficulty ramps up. The interest curve would be a lot better if the game had a wave based system. There's a lot of depth to this game wrapped up in a two button control scheme. I was gonna complain about not having a way to go down fast until I realized I could spin all the way around and shoot up. This game is incredibly elegant it its simplicity. Amazing work!
Side note: I noticed the vertical aspect ratio. Are you planning a mobile version? Because that would be sick! This would be the perfect thing to pull out on the bus. I'd love to play a mobile version of this expanded with waves and unlockable guns/characters.