This is actually really enjoyable to play. Only having one shot requires you get into a good, satisfying rhythm, or risk being defenseless for a bit. I think this is a perfect game to play when you have a few minutes between things because the only real threat to you is your own concentration. I'd definitely download it on my phone.
Also, I really liked the colors, the bubbles that serve as both targets and shot refreshers, and the big enemies that charge you - the first one gave me a shock.
P.S. my high score was 55490