I like it, the bullets on occasion seem to slow down for no apparent reason, which is somewhat interesting. I'd suggesting adding a bit more in terms of effects when you die, perhaps an explosion or something. Maybe a message based upon the score they received?
Graphics wise, I'm enjoying the simplicity, although I would recommend a little bit more detail in terms of the cannon, or maybe fill it in, so it's not a box/circle.
The music was good, not too irritating, though it could get boring if one plays long enough, so maybe have a track of songs.
My last suggestion is something to the effect of acheivements, or medals, not only will that help game fit in with v3 more easily, but for some people it will make them want to keep playing even after they've gotten bored.
Overall I really enjoyed it, and I think once you get it finished up and give it some polish, it'll be a great game and a lot of fun.