This was... interesting. I couldn't get the camera to turn, is there something I have to do besides moving the mouse?
The aliens were fairly easy to kill, the way the raycasting works meant I could do it from far away. I didn't have a problem with reloading, I just always had bullets. Not sure what the grey were... I guess they started the wave, but I had to jump around them for a bit before they'd disappear.
It's very ambient and spooky!