I think this was a cool idea. The issues i had - with the bullet absorption mechanic, having bullets destroy each other is a problem, you have to wait to get bullets, then your bullets might just bounce off enemy bullets, and you cant get more bullets till you use the ones you have, so you're always fighting a losing game.
Also the aliens like to randomly shoot offscreen for a while which meant no ability to absorb bullets so you'd sit around waiting for them to shoot onscreen again and hope you were near enough to wherever they chose to shoot.