Gameplay appears to take place in typical multiplayer maps revolving around abandoned towns and other locations. 4 players take control of the 4 main characters of the game, "The Survivors," who subsequently play through the level towards an apparent goal of rescue by helicopter.
Subsequent players can join the server and take control of the zombies. The first 4 to join can take control of the larger, more powerful zombies with unique abilities, then the next players to join, or when one of the larger zombies is waiting to respawn, players can take control of the regular zombies
There are 4 playable human characters in the game, each with a different and unique appearance to make it easier to identify which character you are looking at when you aren't close enough to recognise the face. Each player is randomly assigned a character when they join the server and, to prevent arguments, each character has the same abilities and may use the same weapons. Of the 4 characters shown so far, 2 have been given tentative names to identify them; Gun Girl and The Biker. It is possible the characters may be given proper names so as to further help with identification, mid-game.
Gun Girl, as her name suggests is a girl with an ammunition belt over her shoulders. The Biker is a large, heavy set man; a stereotypical view of a biker as seen in various media such as LucasArts' Full Throttle. The other two characters are what appears to be an elderly army veteran wearing a beret with medals on, and a nondescript, black man wearing casual clothes, jeans and a jacket.
The Infected are Left 4 Dead's name for what are basically zombies. The zombies in the game are based on the zombies from 28 Days Later, a film which the game takes a lot from design-wise. The zombies, as opposed to the slow, shuffling types associated with Night of the Living Dead or Half Life, are fast and can pounce, creating quite a formidable foe. They will however go down with a well-placed gunshot, meaning they can be dealt with easily on their own, but in great numbers are difficult to handle.
In addition, there are 4 mutated Infected who have their own special abilities and are more powerful than the regular Infected: The Boomer is a hugely obese zombie that can projectile vomit at The Survivors, blinding them. When it dies it literally blows up, creating a large amount of damage. The Hunter is an agile zombie who can climb walls and jump over rooftops, similar to Half Life 2's Fast Zombie. It can pin a Survivor down on the floor and slash at them with long claws, rendering the victim powerless unless The Hunter is killed by a team-mate or The Hunter retreats. The Smoker is a zombie with a hugely long, whip-like tongue that can drag Survivors away from their team-mates, similar to Half-Life 2's Barnacle, or Resident Evil's Licker. When in danger, it can leave a haze of black smoke, distorting the Survivors' vision. The Tank is a huge, muscular zombie capable of throwing large items such as cars or blocks of concrete. It has a huge number of hit-points.