Last week Valve revealed a few small details on the first DLC pack for Left 4 Dead. It's going to bring Versus mode support to the two retail campaigns that currently don't have it, and also add a new game mode called "Survival". We've now learned what this Survival mode actually is.

According to Game Trailers TV, Survival mode will have up to four players trying to survive for as long as they can against waves of zombies. Doesn't sound entirely unlike Horde mode for Gears of War 2 or Nazi zombie mode for Call of Duty: World At War, though you'll trying to "set records for the longest time." Maybe Valve will create some sort of online leaderboard for this?

The Survival Pack is said to come with twelve maps for this Survival mode. It's possibly they're just slices of the existing campaigns but they could be original creations, too. Ultimately the players are probably just going to be in one entrenched position fending off zombies so these figure to be fairly small maps.