I'm designing a game with similar mechanics to battleship and I'm trying to figure out how to do multiplayer. I want it to be pick up and play and games can survive app closings, for this reason I've decided to not use the multiplayer object and just store moves and game pairs on my server and pass them back and forth via AJAX. I can't figure out how to inform the other player has made a move though, the only thing I can think of is polling but that seems like it'd really hammer my server.