Claustrophobia

Another slow day at work... been slow all week now... so you decided to go home early. But as soon as you start to leave, the combine start to break in. Entering the bosses office, you arm yourself with a pistol, and try to kill every combine you can, but they were coming in overwhelming numbers. You chose to get the hell out of there ASAP, only to be injured during the process and to find yourself hiding in a sewer.

You wake up, wondering what just happened. As you get up from a blood stained mattress, you find more of your friends already dead. Grabbing a crowbar, you work your way through the sewer to find help.