Neowin.net

On April 21, Valve will be releasing the first downloadable content for the highly successful first-person shooter Left 4 Dead. It will available for both the Xbox 360 and PC, free of charge. The downloadable content titled the "Survival Pack" will make the remaining two more campaigns playable in Versus Mode as well as adding another gameplay mode, Survival.

On the official Left 4 Dead blog, Valve's Kerry Davis and Scott Dalton explain the rules to the new gameplay mode. "Survival Mode pits your team against never ending waves of infected. Sounds simple. Just trap the survivors in a small part of a map, unleash the hordes, and record the longest time. Survival Mode, which will be released next week, is actually a bit more than that."

They continue to say that with the "extreme pace" of the gameplay mode, "the number of zombies killed in a single round often outnumbers an entire campaign."

Survival Mode will be very different from Versus Mode for a number of different reasons. "The Hospital Elevator, for example, might seem like an easy Crescendo Event to conquer. Hit the elevator button and holdout until the doors open for a quick escape. In Survival Mode, however, the area begins locked down. Areas open as the hordes come in, breaking down the doors to reach the survivors. In each room there are additional caches of vital pills, pipes, and Molotovs. By moving from location to location, using up the plentiful supplies as needed, a team can maximize their time in a game where the elevator never arrives to offer escape. In other maps, items may be less plentiful and require careful planning on their usage. Managing one's inventory and resources works hand-in-hand with teamwork in Survival Mode."

The following chart shows just how chaotic Survival Mode will be. When games last beyond the expected ten minutes, new tanks will spawn every 45 seconds, spawning every 10 seconds when the game lasts fifteen minutes.