There are three different weapons: the Chainsaw, Pistol, and the Sniper Rigle. Press the keys 1, 2,3 to change from one weapon to another. Use the Chainsaw for Tubbies wich show up in a very close distance, the Pistol to shoot all Tubbies in a medium distance and the Rifle for all Tubbies in the distance. The aiming crow shows you the available area for every weapon you choose. If you抮e out of it, just press Space to reload your weapon. The Chainsaw does not need any ammo.