One person, on, stands on one side of the room facing the wall, and everyone else lines up on the opposite wall and tries to sneak up. When the person on hears someone they turn around and if they see someone moving they say "X, theres no going back. they have to then run and touch the wall. If the are caught everyone except those that have reached the end already return to start. The aim is for everyone to reach the end in as few tries as possible.