The Combine continue to research human responses and reactions to various stimuli. They have created a system where humans believe they are in dangerous situations. The humans play out these situations by trying to reach the next Transition Room, using weapons and physics to survive. This research will help train the Combine soldiers to fight more effectively against the rebels. Whilst you hate the idea of helping the Combine you have been told that your family will receive extra rations; water, rice and cake for example. Of course this may be a lie but you do not really have much choice as refusal to participate will result in your immediate death.