The tests become more and more dangerous farther into the game. In some rooms, there is poison on the floor. In others, there are balls of electricity called High Energy Pellets which will kill Chell if she touches them. During these tests, GLaDOS becomes more and more sarcastic, giving Chell useless advice, such as "The floor here will kill you. Try to avoid it." At one point, GLaDOS tells Chell a chamber is broken and she must go through a chamber full of sentry guns, called Turrets, instead. If a Turret sees Chell, it will shoot at her until she dies. In this chamber is a hidden room. In the hidden room are drawings and writing on the walls left by an unknown person. The writing says things like "the cake is a lie" and "she's always watching" with a picture of a camera. There are more rooms like this in later chambers.