Five Nights at Freddy's is essentially a very simple concept. All you can do is look around with the mouse, and click the light and door buttons on either side of you to turn them off and on. (Do not press ESC. Pressing ESC causes the game to immediately shut down and you'll have to replay from the start of whatever night you're on.) Mousing over the bottom of the screen raises your monitor menu, where you can click on room icons to switch the camera to display there. Your den of fear is helpfully marked at the bottom of the map, so your job is to cycle through the views and figure out where the things stalking you are, so you know when to close the doors, and when it's "safe" to open them. The light itself won't actually protect you when you turn it on, but it does help you see into the blind spots just outside your room where the closest cameras can't reach. If you see something in your doorway, you usually have a few seconds to slam the door shut before you're attacked, and you'll have to wait until it's safe to open the doors again. If your doors and lights suddenly fail to function, it may mean that you've got a visitor who's hiding and just waiting for you to look up from the screens...