Undead Labs has released a new behind-the-scenes video showcasing some in-game footage from their upcoming zombie MMO. Watch the video below. The massively multi-player game, codenamed “Class3,” will be an open world, survival game that mixes RPG and action video game elements. The MMO is being developed with the powerful CryENGINE 3 game engine and will be released for Xbox 360 on Xbox LIVE. The game is in production.