Interesting and fun game, and seemed really big, though there were a few problems I ran into. The enemy's fire-rate seems way too high, and I was half-dead within the first 10 seconds of the first area. Meanwhile, my attacks did almost nothing in comparison and most of the enemies were bullet-sponges.
There should be a way to get back your previous gun, rather it vanishing upon picking up a new one. There should also be a way to drop the gun you have if you want to. I ended up getting stuck because after I picked up the new one, it stopped working even though there was ammo left, so I couldn't attack anything anymore.