Honestly? And I'm basing this on the screenshots above - nobody is going to buy that. It's graphically awful - what's happened to the background image in pic 1 (its square and stops abruptly)? Why is it blurred to buggery in pic 3? why does the ship in pic 3 have a black box around it? And what's with the comet things in pic 4 being square at one corner? There is far too much black (aka: I can't be arsed to draw anything there), and the less said about the info panel down the side, the better. Even without all that in mind, I can't see many people buying a bad galaxians clone these days.
Not saying give up (though, that may not be a bad idea as far as this game is concerned), but people are not stupid and they won't buy crap - not even for $1-$2. Learn about particle systems and implement them. Give it a decent UI and tidy everything up. Hire an artist (for the love of God, hire an artist). Give the player a reason to be playing it - make it interesting. Add some variety. Based on what I've seen I wouldn't download this for free.