The easiest option would be to join in. Video games can be pretty entertaining and its always nice to get one over on him and use it against him for months to come.
You could promise him some sexy time..
Cats love to claw things. Have a cat? Introduce it to the offender's head.
Don't let him have all the fun! Whilst he is in trance mode, you could play the stacking game. Although if he is playing an intense game, stacking might not be so easy on someone who likes to shout down to 9 year old "campers".
Another fun task to do whilst he is in a trance, is to send him off on a raft or other mode of transportation. Chances are, he wont notice.
There is a chance, JUST A CHANCE, that it might work and you might actually be able to pull him away! Good for you. Enjoy the moment.
I did say moment, didn't I??
There seems to be only one thing for it.............................