I like it. It's basically Space Invaders, the aliens look the part and it plays like it.
What I feel is missing though are sound effects. If you cannot fit both in, see if you can include the choice between music or sound fx.
It sort of has a handheld led gaming look about it. I have one called Astro Invader which is basically Galaxions. That has a scrolling starfield too. It was top end stuff for its day.
Personally the music for me doesn't suit the style and genre of the game, so sound effects would be great, with a good woooo alien ship noise, shot and kill effects.
As for any empty space as someone on Lemon64 mentioned, I say keep it minimalistic simple, keep that handheld vintage feel.
Good game.