Nice job on this game! The music works really well, and I enjoyed the variety of weapons available. The art could do with some work - for instance, try exporting your assets as PNGs so they render in front of the world, rather than as black squares. Some moving bullets and SFX would be good for the gun, as it took me a minute to realise it was actually shooting. The enemies moved a bit slowly, if at all, which was actually quite good at times, but try varying their speeds for a more exciting experience overall.
Good job!