The problem is playing any game has negative effects on people. You can play Angry Birds all day and you will still end up being more easily agitated, having a shorter attention span, and being more likely to be depressed just because how video games work. Achieving goals in video games basically rapes your brain with dopamine and after you stop you get a kind of withdrawal like effect that causes the previously mentioned side effects. I did a paper my senior year on video game addiction but I forgot most of it I got an A on it and it was like 14 pages long since the topic interested me.