I wish the first level started out simpler as I think it may be overwhelming for most players. For me it feels little bit overscoped, stuffed into one thing and like it should have started with one weapon and one enemy to see if the mechanic could work or not then progress through in simple levels.
That said, I really liked this game a lot, there's a lot you got done and it shows. The controls feel smooth and the overall mechanics like shooting, being hit, weapon switching, etc. worked well. Nice job!