The game has 3 difficulty modes, 10 levels each.
You can buy first aid kits and weapons.
In the settings, you can turn on / off general sounds, change the sensitivity of the mouse.
Instructions:
Move- Arrows or WASD.
Jump - space bar.
Shoot - left mouse button.
Aim - right mouse button.
Pause - Tab / P.
Run - Shift + WASD.
Medical kit - F.