Bugs are difficult to hit because they don't always line up with your gun, and there's no way to hit them unless they're directly in your line of fire. I wish there were either more aiming options or more suicidal enemy AI.
Also think going with lives was a big mistake. I get that it's retro, but lives were always a frustrating artificial lengthening mechanism. It discouraged me from continuing when I got a game over and lost all my progress.
Love the music and visuals, though. Hope my feedback was helpful!