Nicely made! My only issue is with it's brevity and not noticing shotgun guys took multiple hits to kill.
There's honestly not a lot to say about your game. You seem to have known exactly what you wanted to make, then made exactly that. It controls well. It was a good level of challenge (though maybe setting me to 3 health at the start of every fight would have been better than 5 health that caries between levels). The art was exactly what was needed to tell the enemies apart. The music fit the visuals, and overall, it was just really well executed.
It was a fun game. Thanks for making it!