[forinti]

When I was about that age I spent a whole afternoon playing Sim City. When I realised how many hours I had lost, I just uninstalled it and never looked back.

You should definitely talk to a psychologist if you can't convince him yourself.

The Epicureans taught that pleasure should be sustainable. He won't be able to sustain his gaming if he keeps neglecting his education. So this argument might reach him. Good luck.