You are the only human left on the planet, and to keep your job as traffic controller, you have to keep traffic flowing without letting drivers get stressed out! Look at each car for its stress meter. When a stress meter fills up, you get a warning. After three warnings, the game ends. To change the traffic lights, just click on one to change it to the opposite of what it currently is. You have a limited amount of green lights you can use each level, so use them wisely. You don't want to leave any drivers stranded or they will definitely get stressed!