Playing video games can be a fun way to unwind or spend time with friends.In schools, teachers use games like Minecraft to encourage teamwork and critical thinking. (77)But for some players,gaming has become an unhealthy habit.Late at night,they are glued to a screen. Schoolwork suffers. The video-game world seems a friendlier place than the real one. Mental health experts have taken notice.In June,the World Health Organization(WHO)added gaming disorder to its list of diseases and health conditions. A person may have the disorder if gaming has damaged his or her relationships with family and friends,and if it has affected his or her daily activities. Not all experts agree that excessive gaming should be called a disorder.They say people hooked on video games may be suffering from other mental health problems that should be treated first. Others think WHO made the right call.Psychiatrist（精神科医生）Clifford Sussman treats gaming addiction（上瘾）.（78）He says kids often have feelings of anxiety and loneliness. They get angry when a parent asks them to stop playing video games. What makes video games addictive?Playing excites the brain's reward center. After a while,the brain becomes numb（麻木的）to pleasure.You feel bored without a controller in your hand. So you play even more. One key to healthy gaming is to track how long you play. Sussman recommends taking at least an hour-long break after every hour of play. That gives the brain time to recover. Young gamers who think they might have a problem should seek help from an adult. Sussman suggests you first answer a simple question:"Are you in control,or is the game in control？”