I hated it, it was super frustrating and the screen was too small and I had to sit super close to the monitor to even see what was going on. I also played it longer than I've played any other game tonight, I literally could not stop.
Ok but seriously its a hell of a lot of fun. All I can say is some indication that I'm doing damage would be nice, especially on that boss. Maybe a small explosion after a certain number of shots, some shaking or something. The soundtrack was good and fitting, as well. Not giving it 5 in audio though, just because of how much there was to gain by adding some shoot noises or hit noises.