This was a lot of fun, loved the oldschool style, and there was even a boss fight. It would have been nice if there was some kind of hit stagger or other effect to indicate that a shot was hitting, sometimes I thought my shots were being blocked by level geometry when the line of sight was actually clear, leading to a game of peeking around corners and shooting at hands by the end.
With some tweaks to the AI and some more weapons/levels this could be an awesome full game. Also, a plea to all FPS developers, please add an option to invert the camera. Some of us played Starfox 64 as kids and had our brains permanently ruined for 3d camera controls.