You play as generic Umbrella goofs fitted with Zombie Jammers—backpacks capable of keeping zombies from attacking you—duking it out in 3-v.-3, PVP matches. Movement is much quicker than the proper Mercenaries modes/games, and you are given a bunch more options for moving and interacting with the environment.
It has a really cool door opening mechanic D:
It has a really fun online logo designer, and other customisation is pretty nice too.
Rounds are quick.
So it moving while crawling.