This was really fun to play!
The polish of the game was pretty astounding, but what I really loved was the "physics" of how everything feels, the recoil of the gun allowing me to get to higher places, the momentum boost from the swing of the sword, that was what really made the game feel good to me (other than the really cool sound effects haha, loved those too)
The music also did give the right "vibe" to the whole space thing too, so that set the atmosphere well right from the start.
Have to agree with Rusty Bailey though, the sword was way too fun with its speed boosts, so the gun really became irrelevant after getting the sword (even though it was a really nice starter weapon).
Overall a really great game! Kind of learnt a couple of things in game development while playing this too!