Left 4 Dead is a FPS cooperative zombie survival game, which has the players, work together to navigate a zombie world where you must reach safe rooms in order to reach rescue. The game includes four campaign, each set in different locations. Each campaign has 5 chapters and each chapter ends once the team makes it to the safe room. The final chapter includes the team having to reach a rescue zone where they can call for help, and then wait for a rescue vehicle to save you. In the meantime you must defend yourself against the hordes of zombies and special infected. There are two game types that involve players moving through a full campaign: 1- 4 player campaign (survivors only) and 2 – 8 player versus (survivors vs infected). I versus mode, half the players will play as survivors while the other half play as the special infected zombies. Each teams objective is to score more points. Survivors scored by making it to the safe room without dying. Bonuses are awarded for health. Zombies score by attacking, killing, and preventing survivors from making it to the safe room.
Excluding DLC, the game only has these four campaigns to play: No Mercy, Dead Air, Death Toll, and Blood Harvest. In my own gameplay, one of the things I noticed about most of the chapters in each campaign was how the they were often designed to force the player to eventually move either up or down as they make their way to the safe room. For the sake of this analysis, I have defined up and down as sort of a current state, meaning once the player enters the state up or down, it will remain in that state until they switch to the opposite state. Moving up and down will only qualify for specific instances such as staircases, ladders, ramps, or areas where the player must fall or drop down. I did not include inclined or declined terrain as up or down, mostly because I am looking at how the designers have used man made platforms.
No Mercy’s pattern:
Chapter 1: Down
Chapter 2: Down, Up, Down
Chapter 3: Up, Down, Up
Chapter 4: Up
Finale: Up, Down
Dead Air’s pattern:
Chapter 1: Down, Up, Down
Chapter 2: Down, Up, Down
Chapter 3: Up
Chapter 4: Down, Up, Down, Up
Finale: Down
Death Toll’s pattern:
Chapter 1: Down, Up, Down, Up
Chapter 2: Down, Up
Chapter 3: Up, Down
Chapter 4: Down, Up, Down, Up, Down, Up, Down
Finale: None
Blood Harvest’s pattern:
Chapter 1: None
Chapter 2: Down, Up
Chapter 3: Down, Up
Chapter 4: Down, Up
Finale: Up, Down
The first thing noted here was that no particular patterns seem to be occurring. Each campaign has its own variance and isn’t repeated in the other campaigns. There does not seem to be a pattern regarding chapter number either. We can see that Blood Harvest has no force up or down in its first chapter, while Death Toll has the state change four times in its first chapter. Death Toll has the players changing state 7 times in chapter 4, while No Mercy stays at Up. Repeats do occur between the first two chapters of Dead Air, and the middle three chapters of Blood Harvest. From a design perspective, I think making the player move up and down is a way to keep the player interested and add to a level of discovery. Figure out where exactly you need to go the first time you play may seem a little overwhelming. Having areas such as stairs, ladders, ramps, and drop downs help to lead the player in the right direction. These areas can also be advantageous to the player for escaping zombies or for funneling them into your gunfire. Stairs can be useful for taking a moment and waiting for the horde to pass. Climbing ladders and falling down holes are good for quick escape. I’m not sure there is any particular difficultly curve in relation to how often the player must move up or down within a chapter. There are certain aspects that I think come into play here though.
Having looked at each campaign level and defined the up and down moments of them, now we can begin to assess if there are any relationships with these fluctuations of up and down states with the games dramatic beats provided by the AI director. Having looked into how exactly the game designers went about handling the AI in Left 4 Dead, it seems like there is no direct correlation between the players movement of up and down and the spawning of enemy AI. This is mostly because the AI director spawns enemies based on the survivors’ location and their intensity level (how much damage they’ve taken). The AI director has three phases: The Buildup, Peak, and Relax. The Buildup occurs when players leave the safe room and zombies will regularly spawn. There does not seem to be specific areas where common infected or special infected will spawn, just that it is relative to the position of the survivors (it must be within an certain radius depending of character position). Zombies won’t spawn if they are too far away from survivors. The Peak occurs when max intensity is reached and zombies will stop spawning at this point. At the Relax phase, zombies will completely cease to spawn, and players can regroup for a short time. The goal here was to maximize replayability, and having enemies spawn in the same locations turns it into a game of memorization and diminishes suspense, which is not what the designers wanted. Boss infected, tanks and witches, always spawn on the main path, but this does not relate to a change in the up or down state.
So there may not be a direct correlation between the up and down state and enemy spawning, but what can be learned here? I think the function for the up and down state, besides offering a level of discovery for the players, is meant to provide moments that enable the zombies to maximize their attacks and as a result increasing danger for the survivors. This becomes even more apparent in the versus game mode, where players can play as infected in addition to the survivors. These high danger hot spots teach the survivors players to be wary and on the look out at for oncoming attacks, while teaching the infected players to take advantage of a moment where players must move up or down.
If we look at the Death Toll campaign, we can see how this may occur. In the first chapter, the state changes from down, up, down, up. During the first change from down to up, I’ve found that this specific area has becomes a prime opportunity to strike when playing as infected. This was always an area where chaos breaks loose in my own personal gameplay. Here, the survivors will climb up two ladders. When playing as infected hunter, the player can climb a nearby mountainside, and then pounce down onto survivors as they are climbing the ladder. If a player can successfully pull off a pounce, they will also learn that the amount of damage inflicted is higher than if you had pounced just from ground level. This area can be beneficial for smokers as well. One of the goals of a smoker is to separate a survivor from the rest of the group. If a smoker hangs back behind the survivors, this area with the ladder is the perfect setup for a smoker attack. If they successfully pull a survivor, they will also learn that the attack will inflict more damage if the survivor was pull off a high ledge, and then lands on the ground while being pulled. This particular area where the state changes from down to up really enforces this sense of a potential dramatic onslaught. Survivors having to climb ladders creates a moment where they become defenseless, as you can’t shoot or melee while you’re climbing. It offers the infected the perfect opportunity to strike.
This brings us back to the designers designing for cooperative play. Creating areas where the up and down state changes provides players with dramatic beats in the sense that survivors must be ready for an possible attack while infected must be ready to strike. Cooperative play here is really being encouraged in this way. If the survivors want to successfully make it past the state changing from down to up in this area, they must watch out for one another. Once the first person makes it up the ladder, they will quickly learn that they need to stay nearby and cover teammates as they make their way up the ladder as well. On the infected side, they will learn that this area where the state changes is when a coordinated attack would be most effective. Even if a player cannot successfully manage a high pounce from the mountain, this area is still the best place to strike because it’s when you can most easily separate the survivors into opposite states. If a hunter manages to pounce the first player who makes it to the top of ladder, another player may have to climb the ladder to save them. Meanwhile the other two survivors may still be at the bottom of the ladder. Trapping players in different states can prove to be fatal. If a smoker now pulls one of the survivors at the bottom of the ladder, half the team will remain separated. Throw in a boomer attack now, and the infected team has really created a powerful coordinated attack. The longer a team is separated, the less likely they are to survive. So ultimately I think that the changes in the up and down state serve as opportunity for dramatic attack moments, especially in versus mode, while also teaching the players to really coordinate and cooperate for maximum success.