Good challenge, took me a couple tries to defeat the first boss/ boss the first time... couldn't tell if it was the same boss or a different one.
Would benefit from checkpoints of some kind and a menu. Having to defeat all the small enemies then two boss enemies without a checkpoint is unfortunately quite annoying when the boss enemies take so long to defeat. A menu would also have been a nice feature.
Another feature that would have added to the game play would have been to have the turret fire at a limited speed/ have a weapon cool-down. Then again I do enjoy being an unstoppable, never reloading, flying mini-gun.
This game definitely has a consistent theme that's reflected in the art style of the models and environment, as well as the music and it all works with the genre of the game.
Overall it was pretty good.