Music is fun and interesting for the levels sets a fun tone for each being different.
Guns, what I felt was that things weren't really well balanced in this aspect, or in the sense of aim. It's bad on almost all of them i've gotten to thus far(being the rocket launcher).
There is no aim boost skill which is a bit of a downer, can't have them group better or take off some of the recoil arcing.
That being said that'd be fine IF there was a damage skill then, since you're then able to make up for lack of aim with better damage per shot.
Bosses are simple and fun, little bit of learning what they do if you don't power level but that is enjoyable.
The last level is alright the boss manages to kill you even if you can kill him at times which is kind of an issue.
The only other thing i can really think of is it doesn't really follow much of a story, while it's a decent game over all a small bit of background why this dude is after these people with a boss that fits an end to it would make it better so over all 3.5/5
Has some work to be done with, but over all still solid, look forward to a second one if it ever comes out.