The art, audio and overall presentation is immaculate - I loved the gun seller lol. The environments are beautifully esoteric and the music compliments them. The controls are tight and allow for great satisfaction while manoeuvring around enemies, especially so paired with the level design.
The guns could've had more impact, and there needs to be some feedback for when you get hit. Past that, it would be nice if the weapon shop displayed the stats of each gun so that you could make a more informed decision, but it's not necessary.
Overall, really, really great job with this one man! I look forward to your future work!