Controls:

A,W,S,D & KB arrow keys - Move around
Alt - Strafe (and A,D)
Mouse 1 / LMB - Punch / fire
Mouse 2 / RMB - Aim / equip weapon in inventory / use item
Mouse 3 / MMB - Drop item
Q,I - Open inventory (LMB to select to sort)
R - Reload
C - Crouch
Space - Jump
Keypad 0 / '.' - Enable / disable the compass
H - Hide the helmet overlay (G to show the helmet overlay)
Esc - Menu
F3 / F4 - Reveal level code (when indicated)
The save & load function may not be working just yet. Luckily, at the start of each level you start near a collection of firearms to use, as well as a level code.