Left 4 Dead series

Brief

The Left 4 Dead series puts players in the roles of 4 characters trying to get to safety in a world where the majority of all people have been infected with a disease making them homicidal maniacs. Although similar to zombie movies as Dawn of the Dead or even more so infected movies such as 28 days later, it adds the concept of some infected being mutated to get various abilities. These mutants are simply referred to as special infected. Overall, the gameplay is similar to most first-person shooters but with heavy emphasis on co-operation and getting from one safe house to another. The series currently consists of Left 4 Dead (L4D) and Left 4 Dead 2 (L4D2).

See wikipedia entries and the Left 4 Dead wiki for more detailed description of the games. List of player statistics regarding Steam Achievements are available from the Steam Community site.

Main Gameplay Design Patterns

Aim & Shoot, Cooperation, Group Belonging, Helplessness, Survive, Tension

Platforms

PC, 360

Gameplay

Cooperation is a fundamental gameplay mechanism in this Real-Time First Person View series. For most types of game modes, players belong to a Team that share the Mutual Goal to Survive attacks by the infected while Traversing the Levels of the game. Given that players have Limited Resources and that the infected Enemies continuously spawn the Traverse goal has aspects of being a Race. Players can affect the number of Enemies encountered and Resources found through selecting the preferred level of the four Difficulty Levels (easy, normal, advanced, expert). The exceptions to the Traverse goal are the Survival Mode which replaces it with a Time Limit goal and the Versus Mode when players having the role of special infected have the Preventing Goal of hindering those playing uninfected humans. The game Levels are arranged into groups that define several different Campaigns, giving the games Predetermined Story Structures (in L4D2 these Campaigns are also diegetically linked). One of the Campaigns in L4D2, Hard Rain, is uses Deliver as a deigetic theme but does not affect gameplay other than that the Levels are Backtracking Levels. All game modes except Survival Mode follow the campaign structures of the Levels although the Versus Mode runs each game level twice before proceeding to the next Level so that both Teams can play both as humans and as special infected. Completing a campaign gives one of the Achievements in the games and there are additional Handicap Achievements for completing the Campaigns at the most difficult level (and one additional one for completing it in Realism Mode for L4D2).

Player Roles and Enemies

The players take the role of one of four Avatars which are diegetically different but have the same abilities within the game. The game always starts with all four Avatars in the game as a Party, using Substitutional Algorithmic Agents when not enough humans are playing. Through making it possible for people to temporarily give over control of their Avatars to Algorithmic Agents, the series shows that one can provide individual Interruptibility in Multiplayer Real-Time Games, although of course the overall gameplay continues. This, and the fact that players can log-in and take over Avatars that were controlled by Algorithmic Agents initially provides the games with Drop-In/Drop-Out possibilities and makes them support Asynchronous Gameplay. The Character aspect of the game is nearly non-present, limited to health and equipment stats (described below). Besides choosing their Handles, players have some Creative Control over the Game World through the possibility to spray tags.

The games have Dedicated Game Facilitators in the form of AI Directors and Music Directors. The former measures how much problem the Avatars are having as an indirect indication of the players' Tension level to be able to vary intense gameplay periods with calmer ones and vary what special infected are encountered. The Music Directors are individual for each player and personalizes the music according to the health and context of player's Avatar.

The infected that passively wait for the characters, or come charging in hordes, are the basic Units and Enemies in the game. These are mixed in with the rarer special infected (Hunters, Smokers, Boomers, Tanks, and Witches; L4D2 adds Jockeys, Chargers and Spitters) that function somewhat like Boss Monsters in that they are tougher opponents with special abilities but they are not only present at the end of levels or Campaigns. L4D2 adds uncommon infected, one for each campaign with a minor unique ability such as being protected from fire (medical professionals in hazmat suits) or gunfire from the front (police in riot gear). The uncommon and special infected all have Achievements coupled to them, typically either killing a number of them in a certain context or performing a specific type of attack or defense against them. All infected can be killed by attacks from the players with various difficulty depending on the type ranging from Boomers and normal infected as the easiest to Witches and Tanks and the most difficult. However, the abilities of Boomers and Witches make it disadvantageous to attack them in certain contexts and can give direct Penalties to those that do so. Boomers explode when shot and cover nearby Avatars in their infected-attracting bile (which is equal to being hit by its attack) giving players a Continuous Goal of keeping a distant to them. Witches are powerful opponents but do not attack until disturbed and if possible the most efficient way to complete Levels are to avoid them if possible.

Like many First-Person Shooters each Avatar has hit points that is reduced as they take Damage. Beginning with 100 in health, the Avatars start having Decreased Abilities in the form of lower movement speed as they go below 40 in health and get progressively slower the more they are hurt. When health reaches zero one becomes incapacitated. In this penalized condition it is only possible to look in different directions and shoot with pistols while awaiting Rescue from the other players; if all players are incapacitated the game level has to be restarted. Avatars can be incapacitated in others ways, either by falling of ledges or by being the victim of the attacks of the Hunter, Smoker, and Witch special infected (and Charger in L4D2), and in these cases also need other players to save them. Those incapacitated have Time Limits in which they must be saved or they will die. These negative Progress Indicators are presented as decreasing meters (fatigue for those hanging from ledges and 300 incapacitated health otherwise) that provide both Anticipation and Tension. Players that have been incapacitated three times in a row without being healed with medical equipment dies automatically, making the ability to become incapacitated a Limited Resource of sorts. Dead players respawn during Levels in rescue closets (except when playing in the Realism Mode) and always at the beginning of levels. This means reinforces the Mutual Goal of completing the level since only one players needs to succeed for all players to continue with the next Level.

The primary actions possible by the Avatars is, like in most First-Person Shooters, Maneuvering and Aim & Shoot. In addition, one can reload weapons, push away infected, pick up items, jump, and crouch. Other actions in the games are both Extended and Interruptible Actions, specifically those that help the other players. Helping other players when they are lying down or hanging from heights takes time, as does healing them, and these actions can be interrupted by attacks (and is best done with yet other players having the Supporting Goals of protecting them). Besides providing Time Pressure these actions can also be seen as a form of Delayed Reciprocity since there is typically an unstated understanding that the helped players while in the future be helpees. Healing oneself with first-aid kits is also an Extended and Interruptible Actions in the game, but since this also is best done when guarded by other players it also encourages Cooperation.

Game World

The game Levels are rather linear in structure, making the Traverse goal rather easy from a navigational point of view although L4D2 introduces some variety by randomizing between several different routes to provide changes in the level. This is further eased by the Avatars providing the players with directions as part of the discussions between themselves and that Diegetically Outstanding Features such as lights or painted arrows form a Trace for the players to follow. Even so the game requires some Game World Exploration since they need to find Pick-Ups in the form of weapons, ammunition and medical equipment and these do typically require some detours. Initially the Avatars only have a few types of weapons to use, limiting the efficiency of their Aim & Shoot actions especially since ammunition is Limited Resources for all weapons except pistols (the chain saw in L4D2 also has limited fuel). In L4D2 one starts with only melee weapons, probably to provide Smooth Learning Curves since they do not exist in L4D. Various firearms can be found later in the game as well as ammunition piles that vary in attack strength, fire rate, magazine size, and accuracy. The last of these can be affected by moving or by recently having moved as well as by crouching, making weapons have Variable Accuracy. Grenades are either Pipe bombs that attract infected before exploding (creating Anticipation), molotov cocktail that causes fires, and, for L4D2 Bile bombs that both attract infected and cause them to attack those directly hit by them. Since all grenades can affect the Avatars negatively, they all have associated Risk/Reward components. Through the possibility of choosing different weapons, players have the option of selecting Functional Roles and certain Team Combos can be achieved, e.g. covering one team mates while that he or she is healing a third team mates (besides Kiting enemies than can be done regardless of weapons chosen).

All the medical equipment are single use Limited Resources. First-aid kits allow Avatars to heal themselves or others back to near full health while Pain Pills (and Adrenaline Shots from L4D2) give temporary health benefits (performance benefits for the adrenaline shots). L4D2 adds the possibility of other players reviving dead Avatars if they have defibrillators but people that have fallen out ledge are dead until the start of the next level. L4D2 adds tangible Shared Rewards through cases with laser sights or special ammunition (explosive or incendiary) that can be handed out to all players. Weapons and medical equipment are separated into different groups (primary weapons, secondary weapons, grenades, primary healing slot, secondary healing slot) which functions as Tools with Equipment Slots for each group since picking one up drops what is currently carried in that category. Some of these (pills and adrenaline shots) are Transferable Items since they can be given to others, and the others can indirectly be these since one player can pick up something just to drop what is being held so that someone else can pick up that dropped item. Although there rarely is any reason not to pick up all possible items, the Hard Rain campaign turns picking things up into a Risk/Reward situation since the item taken early in the campaign might have been more useful later when returning through the same area.

The games contains some additional Pick-Ups besides weapons, ammunition and medical equipment. Gas cans, propane tanks (and for L4D2 fireworks) function somewhat like grenades in that they can be pick up and thrown, but must be shot to explode or start burning. The gas cans are used in the finale of the Dead Center campaign of L4D2 as Delivery items and players can in this case fail the goal if they are set on fire. A six pack of Cola is a unique Delivery item in the Dead Center campaign of L4D2 while the Gnome Chompski is an item in the Dark Carnival campaign of the same game which gives an Handicap Achievement if carrying to the end of the campaign. Carrying any of these Pick-Ups do however make it impossible to use other weapons leading to Risk/Reward situation, and in the case of the Gnome Chompski making the gameplay more difficult.

Besides Traces players can encounter Traps, Alarms, Switches, Safe Havens, and Location-Fixed Abilities in the Levels. The Traps are in the form of cars with still-functioning Alarms that attract horde of infected if disturbed, although the Witch and Boomer Boss Monsters can be seen as a type of Trap as well. Various types of machinery (e.g. generators and lifts) function as Switches that need to be activated to allow progress but these also alert hordes of infected and thereby also act as Alarms. These Switches tends to be Ultra-Powerful Events in that they cannot be interrupted when started. In L4D the Alarms stop eventually while L4D2 introduces some Levels where Alarms can continue until the players are progressed until a certain point (e.g. the safe room) or have be deactivated. The safe rooms that represent the begin and end of many Levels also double as Safe Havens where Avatars can safely restock and shoot out at infected as long as the doors are closed. The exception to this is that Tanks can break down the doors. Mounted miniguns and machine guns are located on some Levels and are examples of diegetic elements that provide Location-Fixed Abilities.

Cooperation and Group Belonging

Many of the design choices described above gear the overall gameplay towards encouraging Cooperation in the player Team. The number of infected make it difficult to handle alone and typically they attack from many directions at once making solo exploration difficult. These Simultaneous Challenges triggering Cooperation in order to survive, resulting in Alliances with the Continuous and Supporting Goals. As noted earlier regarding being incapacitated, players can easily find themselves in dangerous situations they cannot get out of on their own, i.e. experiencing Helplessness. The attacks by Hunters, Smokers and Witches (and Chargers in L4D2) are examples of this, as are hanging from ledges, but other special infected promote players to collaborate in other ways. The Tank is most efficiently fought by several players at once, victims of the Boomers' bile attack can with efficiency be defended by other players, and those ridden by Jockeys need to be freed by other players. Even players whose Avatars have been incapacitated can support other players since they can still shoot with pistols. All these types of actions make the players often interact with each other are thereby share Common Experiences in the game. Coordination between players are supported through several Communication Channels: global and team text messages, voice chat systems, and an easily accessible Game-Defined Vocabulary which make communication independent of typing skills and languages.

The possibility to select different weapons allows Cooperation through finding Functional Roles that improved the group's abilities in different situations, e.g. sniping lone infected at long distances or meeting charging hordes in close-quarters battles. Although this Cooperation creates Team Combos through the group being able to handle various situations more efficiently, it makes the individual players more vulnerable to certain situations and requires Coordination. While successfully performing this can result in the aesthetic patterns Team Strategy Identification, Mutual FUBAR Enjoyment, and Team Accomplishments, it is harder to predict if failure will lead to Spectacular Failure Enjoyment.

Coordination is typically more difficult when one is not co-present. The Left 4 Dead Series partly addresses this through making players want to stick together (due to Helplessness). However, the dark and often confusing environments make it easy to lose each other even when players try to stick together. The games use the mechanical pattern Geospatial Game Widgets to further the Coordination, outlining the silhouette of the other players through walls (except in the Realism Mode). Even so, the Left 4 Dead Series also supports has many types of Diegetically Outstanding Features in the levels that can act as reference points. Through making the players aware of the other players’ actions most of the time (including the characters comment what is happened) and making them moving in a group throughout the levels, the games promote the dynamic pattern Virtual Co-Presences between the players. This in turn means that players are likely to have Mutual Experiences from a game since they have observed most of the others’ actions and know that the others’ have observed their own actions.

However, the Cooperation is not forced on the players since they do not have to help each other or fulfill the implied Delayed Reciprocity. Besides making players have Uncommitted Alliances in this way, the series allow Betrayal in that players can opt to run to the Safe Havens of safe rooms or the escape vehicles while leaving the other players to their fate. Completing Levels alone only penalizes the other players through loss of equipment but Betrayal at the end of Campaigns are more severe since only players alive get the Achievements associated with it. Countering this are the Community Functionality of the Steam platform which the games uses that allows players to invite each other to games and have text and voice chats. Further, the Game Lobbies in the games helps players synchronize their play sessions by setting up games that only their friends can join initially. In-game support for Voting can can be used to moderated gameplay with strangers , including kicking other players, but can also be used to set Challenging Gameplay through Player Decided Rule Setup. These features combined with the design choices regarding Cooperation and Common Experiences promote players to have Identification with the group as well as the individual Avatars as thus have feelings of Group Belonging and Team Accomplishments among the players when Mutual Goals are reached, or at least seen to be striven towards together. However, when the group fails it is easy that one or more members become Scapegoats for the group failure.

Challenging Gameplay in the game is primarily controlled through Difficulty Levels, which in L4D2 can be modified by playing in the Realism Mode. Besides offering these difficult settings, the games rely heavily on Achievements to provide Replayability of the levels and campaigns. Some of the Achievements are simply gained by completing the campaigns, others one can gain more or else through Grinding (i.e. they are Grind Achievements) since they are based upon achieving an event a certain number of times (e.g. killing zombies with machine guns or honking the noses of infected clowns), and others through actions that require Timing or Gameplay Mastery (e.g. throwing Molotov cocktails on a special type of zombie or killing Witches in a single shot), and yet others which make gameplay more difficult for the other players. The last category consists both of voluntarily limiting oneself to using less effective weapons and of goals such as carrying garden gnomes extensive distances (in L4D2. Although some of the Achievements can be seen as Optional Goals, these and the goals of completing levels and campaigns might effectively become Incompatible Goals.

Game Modes

Campaign Mode

This is the default mode as described in the previous sections.

Single-Player Mode

This mode is simply the Campaign Mode run locally on the same computer as one player and having all three Avatars be controlled by the AI. In the Xbox 360 version other players can join in locally through a Split-Screen View.

Realism Mode

Added in L4D2, this mode removes all the glowing outlines (i.e. the Geospatial Game Widgets) around the PCs, weapons, and health equipment. The ammo dumps are an exception to this. By doing so the game makes Game World Exploration to find items (i.e. fulfill Gain Ownership goals) more difficult, Rescue goals more challenging, and increases the risk of friendly fire (i.e. makes Cooperation more difficult). All these make this mode provide more Challenging Gameplay.

Versus Mode

The Versus mode pits players against players in Teams with some playing humans and others playing special infected (except for Witches). The infected team have the goal to Overcome the other team as they are trying to Traverse a game Level, making it both a Continuous and Preventing Goal. The Overcome goal strengthens the Race aspect of the other team's Traverse goal since the quicker one completes the level the few attacks the other team have time to launch.

Having the special infected be the Avatars for one team introduces Asymmetric Abilities on both team and player level. All special infected can see the outlines of both each other and the non-infected Geospatial Game Widgets giving them tactical advantage in positioning themselves. Having the same characteristics as when they are used as computer-controlled Enemies, the special infected die quickly and often compared to the non-infected. To compensate for this, their players can Spawn in any non-restricted area not currently seen by the other team (just like the AI-controlled versions can). The special infected also have Asymmetric Abilities among themselves as well, primarily how they attack but also regarding their movement and health characteristics. Since many of them have Cooldown periods and effectively functions as Team Combos with other attacks (e.g. spitting goo on the ground that damages survivors in it on a survivor currently incapacitated by another special infected), the players controlling these are encouraged to Collaborate in Coordination of attacks.

The Versus mode is playing in rounds where each team gets to play both sides in a Role Reversal pattern that provides a level of Team Balance by removing the influence of the Asymmetric Abilities between the teams. The non-infected team gets a Score based upon how far they Traversed the Level with a bonus for making it to the end, and the team with the highest score winning (L4D2 also awards the infected team with points for incapacitating players in the other team). Damaged dealt is a Tiebreaker. Check Points per se are not used in the Versus Mode, but the infected team is informed when the survivors have completed 25%, 50%, and 75% of the Level.

Scavenge Mode

The scrounge mode is basically a Time Limited version of the Versus Mode where the non-infected team as the Deliver goal of finding up to 16 gas tanks and refueling a vehicle instead of Traversing a level. The Score is simply the number of gas tanks delivered.

Survival Mode

Added in an update of L4D but present from the release of L4D2, this mode gives the gamers a Survive goal where specific medals are achieved by being alive beyond specific Time Limits (4, 7, and 10 minutes for bronze, silver, and gold medals respectively).

Other Noteworthy Aspects

Developer

Valve Corporation (Windows version)

Certain Affinity (Xbox 360 version)

Publisher

Valve Corporation

Acknowledgments

Jonas Linderoth