The game is played over Google Maps, launching virtual snowballs at unsuspecting players in order to rank up, earn points and even win prizes from retailers you hit. You can also add buddies, connect via Facebook and receive special powerups.
Utilising Flash with AIR 3 and native extensions, we were able to build a game for iOS, Android and also PC. The game uses native extensions for deeper platform integration, such as the compass sensor or push notifications, as well as GPS to pin-point your location.
Head on over to the site to download the game and get throwing some snowballs!
Update: See comments for iOS compass extension source.