A good game. With some polish and some clarification, it would be great.
What spoiled it for me was that it's unclear as to which order the pirates shoot in. When you spawn 4 or 5 at once, you get shot before you've hit 3.
It makes a good snacky game otherwise. However, I can see this working on a larger scale. I'd love to play this in the arcade. Just add some more ships, a story mode and some more inventive bosses.