Your mission in this awesome 3D game is to get rid of the alien scum. Eradicate the alien infestation and complete the mission objective and make sure to blast every last one of them into a green pile of muck. Use the ARROW KEYS or the "W", "A", "S", "D" KEYS to move around. Use YOUR MOUSE to aim and fire. The green dot to determines the perfect moment to fire. Try to aim for the head. Press "R" KEY to reload. Press SPACEBAR to open a door. Press 1,2,3 to select weapons. Press "C" KEY to go to the upgrade screen when you have leveled up. and hit "M" KEY to use a medikit. Good luck!