This is a top secret mission. There are these nasty critters out there, created from a science experiment gone wrong, that turn into whatever they eat and they are devouring anything and everything in their path. You can understand why they must all be destroyed. You are being called in to kill all of these awful things no matter what it takes and you cannot tell a soul. You will not have to worry about moving, you automatically move the way you need to. All you need to do is aim and shoot. In order for you to collect your ammo or health packs you have to shoot them.