The streets are not safe anymore because the undead have come out of their graves to cause havoc all around. You will be challenged to the extreme as you try to survive for 40 days. Go around destroying waves of walkers and do very well to defend your farm. The areas will have some weapons and survivors that will give your chance for survival just the right boost. Use the mouse to aim and shoot, r to reload, f to change fire mode and 1,2 to change weapons. Head shots are the most effective shots and that is exactly what you should look to do.