Perek

Pretty solid, almost made it to round 40 on my first run.

I noticed some pretty heavy mouse input delay though, so I opened the game files with GDRE and found this in player.gd at line 180.
"camera.rotation.x = lerp_angle(camera.rotation.x, rotation_target.x, delta * 25)

rotation.y = lerp_angle(rotation.y, rotation_target.y, delta * 25)"

This is causing input delay, you should remove these lines and just set the player's rotation in the _input function

"rotation_target.y -= event.relative.x / mouse_sensitivity

rotation_target.x -= event.relative.y / mouse_sensitivity

rotation.y = rotation_target.y

camera.rotation.x = rotation_target.x"

(You could also just get rid of the "rotation_target" variable, unless you're relying on it elsewhere)

This is pretty fun.  I only played it for a few minutes so far but I love it.  

Gamepad support would be nice for when I can't find my mouse.  Of course, WASD / mouse is the best control for first person shooters anyway.

sick game11 an ability to  remap controlls would be cool