I play computer games
I engagine in multiplayer gaming
Playing social games on Facebook totally counts as "multiplayer with friends" (if you interact) or "single player" (if the only interaction is trying to beat each other's high scores).
"On the sofa" means a console, a TV, and two or more people playing a game at the same time. Not two of you sitting on the sofa with laptops. That would be "on a local network".