I like the designs and the backgrounds, remind me quite a lot of Space Funeral.
A few issues: I think just a little bit more of an enemy variety per stage would be good.Also,4 of the 5 the Bosses simply slowly fly towards the bottom of the screen, which means that for the most part you can kill them very easily while just running away from them. First time playing, I didn't even get to see more than a split second of the second boss before killing it offscreen. And that's a shame since the 2nd Boss is probably my favourite, design and animation wise.
Also some stage hazards you can't destroy but have to pass through, say when a gate opens or to avoid being hit by a fan blade, or avoiding something like a giant worm going back and forth on the screen (as an example of something that I think would fit XD thematically) would make the levels a lot more interesting and give them some individuality.
I did enjoy this overall, just a tiny bit more would make it stand out even more : D The ending screen is pretty damn funny too.