At Hack Nashville 6 we made a HTML5/javascript multiplayer game. Each player gets a planet on the screen, and you bounce around trying to absorb the other players and gain mass. It’s a pretty simple game, but to make it interesting we made mobile apps as controllers, so you can move your planet by tilting your phone. We used the NodeJS/Socket.io stack as well as Phonegap for mobile support. Check it out at http://gravity.mitchgordon.me.