Arm yourself with a vast array of weapons, equipment, and abilities to fight off the alien forces and save the human race. Or become the enemy and fight for it's destruction.
Movement - WASD/Arrow Keys (or Space to jump). Aiming/Shooting - Mouse. Next/Previous Weapon - Q/E or Shift/Enter. Select specific weapon - Number keys. Use Ability - F/Ctrl. Pause - Esc/P