Released on the workshop in 2013, and having been worked on since 2010, Rayman1103s mutation mod is one of the most popular and widely known mods on the workshop to date; the mod has received dozens of awards and thousands of positive votes thanks to the quantity of mutations it includes.

But do these mutations live up to all the praise? Together with Witch83, we played through every mutation the mod has to offer, for the purpose of reviewing them. This guide will cover our thoughts on each mutation, giving you an overview as to what they have to offer and providing a final verdict on whether or not they're worth your time.

WARNING: We have reviewed these mutations based solely on our own experience with them. In some cases, a mutation might not have worked properly when we played it, or we just might not have enjoyed it; at the end of the day, these are just our own thoughts on the mutations and the scores given are not definitive.

Also, because there is very little documentation for most of these mutations, we can only go based off what we see for ourselves. There may be some missed aspects of certain mutations, though it shouldn't be anything major.

Finally, a number of mutations in the mod are very old, with some dating back to only a couple of years after the game released. Their age is a possible cause for the bugs that are present, as well as some of them being quite simple and boring; a mutation that isn't very interesting today could very well have been seen as revolutionary back when the game was new.

Each mutation (or group of mutations, for those that are very similar) will have its own chapter, set out as follows:

Chapter name: The name of the mutation being reviewed

Premise: A brief list of the major gameplay aspects of the mutation; what makes it different to vanilla L4D2?

Notes: A recount of our experience playing the mutation, as well as our thoughts on it.

Verdict: A final score out of 10 for the mutation, and (when it's needed) an explanation as to why the mutation has received that score.

Each mutation will receive a score out of 10. In general, a mutation will receive a higher score if it has the following traits:

• Builds upon L4D2s core gameplay by adding new mechanics or using existing ones in new ways
  
• Has a unique or original premise
  
• Has a clear theme that makes sense
  
• Runs properly with no bugs or other problems
  
• Is fun to play and keeps you wanting more
  
• Works with survivor bots and with other players
  
• Maintains a consistent and fair difficulty level

On the other hand, a mutation that scores poorly likely has some of the following traits:

• Is boring, tedious or unfair to play
  
• Puts more emphasis on the removal of content or mechanics, rather than adding new ones
  
• Is noticeably too easy or too difficult
  
• Is challenging for survivor bots to play through properly
  
• Lacks a central theme or idea, and feels more random than cohesive
  
• Contains bugs or other problems that disrupt the experience

In addition, a mutation may also receive a score of 0. A score of 0 is reserved for mutations that:

• Contain a number of major bugs or other problems that prevent the mutation from being played as intended (IE: mutations that simply do not function properly)
  
• Are so boring, repetitive or uninspired that there is no real reason to ever play it

As you read through the guide, you might notice several points that are consistently repeated amongst mutations with lower scores. Rather than repeating the explanation for these every time they're mentioned, here are some explanations for the most common ones.

Infinite ammo refers to the act of giving the survivors infinite reserve ammunition without the need to reload. When players are given this ability, it lets them continuously fire their weapons the entire game; there's no reason not to press or hold M1 at all times. It takes a lot of the thought out of the games combat, since you don't need to consider when to shoot and reload, you don't need to worry about shot placement or ammo management, and combat generally becomes quite monotonous. Overall, it is a negative aspect, and unless its inclusion is for a specific and obvious reason then any mutation with infinite ammo will score lower, even if it isn't specifically mentioned as a reason.

In some cases, item spawns may be removed in favour of having the players start with all the items they need. This isn't always a negative aspect; for example, if medkit spawns are removed, but the players are given a new mechanic that lets them regenerate health, then it's a fair and understandable change. However, for mutations that remove item spawns needlessly, it only serves to make the game more monotonous and boring. With no need to explore, you have nothing to do except walk straight to the end of the chapter. Mutations that remove item spawns will generally score lower, unless they have a good reason for doing so.

A few mutations feature low gravity as a mechanic. This lets both the survivors and infected jump much higher than normal, and stay airborne for long periods of time. Whilst low gravity isn't necessarily a negative aspect, and is often important for the theme of the mutation, it does make the mutation heavily map dependent. On open, outdoor maps, low gravity heavily favours the survivors. Most infected can't fight back effectively, and the game becomes much easier. On cramped indoor maps, the survivors ability to navigate properly is drastically reduced, which can be frustrating and slow down the pacing. The inclusion of low gravity won't always impact the score a mutation receives, but it is worth noting that it might have an impact on how fun the mutation is depending on which map you choose to play.

Special Infected spam refers to reducing the spawn timer of the special infected such that they spawn almost as quickly as they die. It can also optionally mean only spawning one particular type of infected. In either case, this is an issue due to how repetitive the gameplay becomes when players are forced to kill the same enemy type over and over again. It quickly devolves into a dull routine, with no downtime or opportunity to explore.

Premise
Low gravity is enabled. Survivors start with an M60 and Magnum. Medkits are replaced with pills, and temporary health does not decay. There are no common infected, but special infected respawn quickly.

Notes
Air raid was a fun, but somewhat repetitive and map dependent mutation. Since many maps have invisible walls blocking off the more open areas, it can be annoying being stopped midair constantly.

Verdict
7/10

Premise
Survivors start with M60s. Only Boomers and Leakers will spawn. Commons can also spawn, but only when a survivor is biled. Boomers move much faster, and medkits can be used faster. Survivors can only be incapped once. Special infected will target other biled specials.

Notes
The fast moving Boomers were funny, but its gameplay did suffer a bit. We were constantly stumbled, blinded and incapped, which meant a lot of blind firing and watching rather than playing.

Verdict
6/10

Premise
Every special infected splits into 2 when killed. No commons spawn.

Notes
This wasn't fun to play. The survivors have no downtime in which to heal or catch their breath thanks to the constant special infected spam.

Verdict
1/10, whilst the mechanic is original, it fails in the execution; this sort of spam isn't fun.

Premise
Low gravity is enabled. Survivors have infinite molotovs and no other weapons. There are no commons, but specials spawn constantly. There's no way to heal. and you die instantly when incapped.

Notes
Fire storm has several major problems, most notably that it feels hard to fight back against the infected. Chargers in particular take so long to kill with fire that if you get pinned, it really just feels like there's nothing that can be done to save you. Only having one weapon type available was also very repetitive, and the survivor bots struggled with the mode.

Verdict
0/10, constant spam, hard to play, repetitive and generally not fun or interesting

Premise
Survivors start with a magnum. The only infected are 8 Hunters who can't jump, but respawn quickly and run at the survivors.

Notes
Whilst there is some comedic value to the Hunters, the mutation ultimately isn't very good from a gameplay perspective. You die quickly due to the 10 damage per hit of the Hunters, and it's really just constant spam of a single enemy type, which is repetitive.

Verdict
3/10 funny but repetitive

Premise
Survivors must escort a gnome through the map. When the gnome is not being held, a 45 second timer ticks down. When the timer reaches 0, the survivors all die and the chapter must be restarted.

Notes
An interesting premise with a fun theme, Nuclear Gnomes only problem is the Gnome itself. Since players are encouraged to hold the Gnome at all times to prevent the timer from ticking down, it means that one player becomes a dedicated Gnome carrier the entire game. This experience is comparable to being AFK, since you can't fight back properly and you mostly just need to let your teammates play the game for you.

Verdict
4/10, whilst the mode is tense, it isn't fun for the person carrying the Gnome

Premise
Only common infected can spawn, and they only die to headshots. They also move slower and deal greatly increased damage. Each weapon spawn is single use. There are no medical items. Being incapped revives you and starts a 2 minute timer. When the timer expires, you die.

Notes
This mutation seems to be inspired by classic zombie films. Though the infected hit hard, they're generally easier to deal with due to their slower movement speed. The timer mechanic is interesting, since it gives you one final chance to reach the safe room, but it rarely came into play since the mutation isn't that challenging.

Verdict
5/10, very average in terms of enjoyment

Premise
Start with an M60 and Magnum, as well as infinite ammo. There are no item spawns and you die when incapped. Special infected spawn constantly.

Notes
Special Slayer takes most of the thought and strategy out of the game. With no item spawns, infinite ammo, and special infected spawning every few seconds, there's really nothing to do but hold M1 and walk to the safe room. The magnum also seems like an odd inclusion; you can't use it while incapped, and the M60 is much more effective in combat.

Verdict
2/10, constant spam and feels a bit braindead to play

Premise
Special infected have a small chance to spawn when common infected die. Survivors have infinite ammo, there are no item spawns, and they start with a Magnum and Random Laser sighted primary

Notes
It took us a little while to figure out what was actually happening here (we didn't realise the special infected spawns were tied to common infected deaths). The mechanic is unique, but it does mean that players are discouraged from killing common infected unless they have to. The lack of item spawns and being forced to use the gun you're given at the start of the chapter also doesn't do the mutation any favours.

Verdict
4/10, a lot of speedrunning, not a lot of zombie killing

Premise
Each special infected splits into 2 when it dies. No common infected spawn. Survivors have infinite ammo and get revived when incapped.

Notes
The concept is similar to double trouble. However, Split Decision doesn't work. After the initial few special infected spawns, they stop spawning entirely. This means the survivors have nothing to kill, and just have to walk to the saferoom in silence.

Verdict
0/10, non functional

Premise
Only Leakers, Tanks and Witches spawn. Survivors can only use melee weapons.

Notes
This mutation is very repetitive. Survivors are restricted to the simplest weapon type, and mostly only need to deal with one enemy type. To make matters worse, Leakers can't be killed with melee weapons. What this means is the survivors only option is to ignore them and speedrun to the saferoom.

Verdict
1/10, very repetitive and boring

Premise
Functions like Tank Run, except the survivors only have Magnums and a molotov, which can insta kill Tanks.

Notes
A greatly inferior version of Tank Run. The removal of most of the weapons only serves to make the mutation more monotonous, whilst the insta kill molotovs are just a get out of jail free card for when you mess up.

Verdict
1/10, a largely pointless mutation; stick to Tank Run

Premise
Functions like Tank Run. Survivors can only use melee weapons. They regenerate health and have no other items. Tanks die in one hit, but multiply when hit. Survivors can crawl when incapped.

Notes
Tank Brawl was funny to play the first time around. There's a certain novelty to hitting a group of Tanks with your melee and watching them all split into multiple other Tanks. However the difficulty was inconsistent due to some bugs related to their spawns, making the mode way too easy if they didn't spawn properly, or impossible if you got cornered.

Verdict
2/10, somewhat buggy and potentially unplayable at times

Premise
Functions like Tank Run. Tanks multiply, move faster than the survivors, and deal extra knockback. The survivors start with laser sighted weapons, have health regeneration, no movement speed penalty at low health, and can revive each other faster.

Notes
Tank Splitters had a very annoying bug that caused Tanks to occasionally spawn directly on top of the player, rather than up ahead out of sight or next to an existing Tank. This meant you would get punched instantly, and likely stunlocked immediately after. The idea of using a Tanks knockback to navigate the map is fun, but the potential to have your playthrough ended by an unlucky stunlock ruins it.

Verdict
2/10, the stunlocks aren't fun

Premise
Special infected spawn constantly. There are no commons. When a special infected dies, they spawn several uncommon infected. There is no friendly fire.

Notes
There isn't much to say about Uncommon Ambush; it's a simple but bland mode.

Verdict
4/10, not particularly fun or interesting

Premise
Witches spawn constantly and get startled from a distance. They move slower than the survivors and don't kill in one hit. The survivors start with a random laser sighted primary.

Notes
Witching Hour is rarely difficult or fun. Since the Witches are slow, you can easily just outpace them and run to the saferoom. It might be fun if you could find a shotgun to crown them with, but instead you start with a random primary weapon.

Verdict
0/10, very easy and very boring

Premise
Special infected spawn constantly. Survivors can only use melee weapons, and can revive and use medkits faster. There are no item spawns.

Notes
Another repetitive mode that follows the formula of "limited weapon options and special infected spam". All it is is just fighting specials with melee weapons.

Verdict
1/10, very repetitive

Premise
Survivors start with a random gun and a magnum, as well as infinite ammo. There are no item spawns. Spitters spawn constantly, and there are also Tanks. Spitters can sometimes instantly kill the player.

Notes
Another mode that boils down to special spam with restricted weapons, but this time there's a chance you get instantly killed. It's also possible to speedrun past all the Spitters to avoid being hit, but doing this just makes the mode a bit pointless.

Verdict
0/10, Acid Trip is as repetitive and bland as you'd expect

Premise
Special Infected have each others abilities.

Notes
This is a great idea for a mutation, but unfortunately the execution falls flat. The special infected spawn far too quickly and in great numbers; to avoid being overrun, you have to shoot everything immediately. This means you have no time to think about which special you're fighting or appreciate the fact that their abilities have been switched. If this played like a normal campaign, but with switched specials, it would probably be a lot more fun. There was also a bug where specials would occasionally get stuck in one spot and not attack.

Verdict
3/10, a great concept let down by poor execution and some occasional bugs

Premise
Survivors have infinite ammo, grenade launchers and magnums. There are no item spawns. Only Smokers and Boomers spawn, and they spawn constantly.

Notes
Infinite ammo is what ruins Blast Zone; the downside of the grenade launcher is its slow reload. You need to use your one shot wisely, since you're left vulnerable if you miss. With infinite ammo however, you can spam M1 and fire another grenade near instantly. The infected aren't a threat at all, making the mode repetitive and boring.

Verdict
0/10, completely ruined by a poorly thought out primary weapon

Premise
CEDA workers spawn instead of commons. Boomers spawn constantly, and cannot be killed by the survivors. Survivors have a silenced SMG, infinite ammo, and no item spawns. If you get biled, a Tank spawns. Survivors are revived when incapped.

Notes
Call Of Boomer really would've benefited from some form of explanation or documentation. The idea seems to be that you kill the CEDA workers and use the bile bombs to make them attack the Boomers. In practice, this isn't reliable enough to deal with the Boomers, leading to the survivors getting cornered and killed by Tanks.

Verdict
3/10, some original ideas are present here but it's unintuitive and confusing, and comes back to just being spammed with infected

Premise
Only common infected can spawn.

Notes
This mutation is redundant, as you can accomplish the same thing with a script, allowing you to combine it with other mutations.

Verdict
0/10, pointless and can be done with a script

Premise
Common infected only. Commons move slower and deal much more damage. Hordes spawn constantly. Survivors start with random weapons, and only grenades will spawn. There's no movement speed penalty for having low health, but survivors can only be incapacitated once.

Notes
Deadshot is surprisingly fun, though there are a few considerations that hold it back. The pacing can be quite slow, and it's easy to get bogged down in one area of the map for a long time, especially a choke point. Rushing is also the ideal strategy, since there's no downtime due to the constant infected spawns. Finally, it does get a bit repetitive at times, especially since you can't choose your weapon.

Verdict
7/10, a fun but flawed mutation

Premise
Low gravity is enabled. Survivors start with laser sighted T2 weapons, magnums and infinite ammo. Special infected spawn constantly, and you get revived when pinned.

Notes
The mutation itself isn't as fun as just exploring the map with low gravity. It's a highly map dependent mutation; picking an indoor map will make it much harder and you'll likely get pinned constantly.

Verdict
5/10, not particularly interesting, very map dependent

Premise
Survivors start with a magnum and infinite ammo. Tanks have less health, all other specials have 1 health. There are supposed to be no item spawns. Survivors can only get incapped once, but get revived when incapped.

Notes
Gun Of The Gods sounds cool, but ends up being a bit of a repetitive slog. Constant special infected spam, magnum spam, and since there's no way to heal it's very punishing if you get hurt; for some reason the movement speed penalty for low health wasn't removed. The survivor bots also somehow managed to find M16s, which wrecked the modes balance.

Verdict
3/10, repetitive and very punishing if you get hurt

Premise
Low gravity is enabled. Only Hunters spawn, and they spawn constantly. Survivors start with a magnum and only have one life.

Notes
As expected, this mode is very repetitive and not particularly interesting. The best strategy is to just rush straight to the saferoom. It is also incredibly map dependent, since it's much harder to avoid being pinned on a cramped indoor map than outside.

Verdict
1/10, repetitive and very map dependent.

Premise
Survivors can't deal damage to special infected. Instead, they must throw bile at them and let hordes of commons do the work.

Notes
Whilst the concept is unique, it is very poorly executed. The common infected take far too long to spawn and reach their target, by which point you're likely already close to being dead. If a special infected gets into the safe room, it can also be almost impossible to close the door.

Verdict
1/10, suffers in terms of playability.

Premise
Only items and specials that were added in L4D2 are present.

Notes
For some reason, adrenaline is not present in this mutation. This means that the only way to heal is to die and have a teammate revive you with a defibrillator, which can only heal you up to 50HP. You'll spend a lot of time moving slowly as it only takes a few hits to get below critical health.

Verdict
2/10, doesn't entirely follow its own premise, healing is very inconvenient.

Premise
A combination of Hard 8 and Hunting Party, with the survivors also starting with a Magnum.

Notes
Easily one of the most uninspired mutations in the addon. It's just a combination of 2 existing base game mutations.

Verdict
0/10, completely uninspired.

Premise
At the start of each chapter, certain variables are randomised, such as which special infected can spawn, if commons can only die to headshots, etc.

Notes
Random Mutation is somewhat ironic in a way. Once you've played through the majority of the mutations in the addon, you'll realise that most of them are actually very similar to the experience you get when playing Random Mutation; a particular special infected being spawned constantly, with some other seemingly unrelated variable being thrown in.

Verdict
1/10, its only redeeming factor is that you can play it instead of 90% of the other mutations and save yourself a lot of time.

Premise
Only common infected spawn, and there are constant hordes. Survivors have infinite ammo and start with a magnum. There is no friendly fire, commons deal expert damage, and each survivors killcount is tracked on screen.

Notes
The intent behind Swarm seems to be a kill contest of sorts, where you play a campaign with it and whoever gets the most kills is the winner. But if you wanted to do that, you could just play a regular campaign and wait for the end credits (or even the map transition scoreboard) to see who got the most kills.

Verdict
1/10, pointless, just use the in game kill tracker.

Premise
Functions like Tank Run. Survivors have infinite ammo and start with a magnum.

Notes
This mutation is just Tank Run.

Verdict
0/10, just play Tank Run.

Premise
All 8 survivors spawn in every campaign. Special infected spawn slightly faster, and Tanks have extra HP.

Notes
A surprisingly useful mutation; it's much more convenient and accessible than installing sourcemod to use an 8 survivor mod. The infected adjustments also help to offset the difficulty, even if it is still rather easy.

Verdict
9/10, a lot easier than using sourcemod.

Premise
Survivors start with a magnum, and sometimes have infinite reserve ammo. Witches spawn constantly, but are slow and don't kill in one hit.

Notes
Due to how slow the Witches are, this mode isn't much of a challenge. It's also unsurprisingly repetitive, and there was a bug where certain weapons didn't have infinite ammo.

Verdict
3/10, repetitive and easy.

Premise
Functions like the Witch Parade mutation, where every common infected is replaced with a Witch.

Notes
There isn't much to say about this. It's very similar to another existing mutation, which already wasn't particularly good.

Verdict
4/10, not very fun.

Premise
A set of 3 mutations (Dead End, The Last Of Us, Your Eternal Slumber) based around realism mode and not being able to respawn.

Notes
The modes are advertised as not letting players respawn at all (there's a chat notification when you start the game saying this) however dead players will still respawn between chapters. Dead End is pretty much just the ironman mutation. The Last Of Us features slow but damaging common infected, no specials and headshots only; it was very easy, not tense at all, and honestly felt a bit unfinished, like it was missing something. Your eternal slumber is like Dead End, but with constant special infected spam. None of the 1 Life 2 Live mutations are very good. It would've been more interesting to have a mutation where respawns were completely prevented.

Verdict
2/10, doesn't have much to offer.

Premise
Contains variants for every special infected. Only the selected special infected type will spawn.

Notes
Every variant just involves spamming one particular infected type. If you really, really want to kill one kind of infected over and over again, you might like these mutations. Otherwise, there's almost no reason to ever play them.

Verdict
0/10, just spam.

Premise
A L4D1 style version of Special Delivery.

Notes
This suffers from the same problems as every other mutation featuring special infected spam.

Verdict
0/10, the same sort of spam offered in every other mutation.

Premise
A group of 9 variants for each special infected and a random option. Survivors must beat each chapter in 6 minutes or die. They start with Magnums and a random laser sighted primary. Survivors can only be incapped once and there is no friendly fire. Special infected spawn constantly. There is no slowdown penalty for low health.

Notes
We tested this on the random variant and one of the special variants, and it was terrible to play. It once again suffers from the same problems as most other mutations; constant special spam, no opportunity or need to explore, no choice in which weapon you use, and being forced to rush to the end.

Verdict
0/10, symbolic of everything that's wrong with all of these mutations.

Premise
A group of 6 mutations based around survivors having infinite grenades. Survivors have one life and health regeneration, specials spawn constantly, and there are no other items.

Notes
Disinfected (bile bombs only): A buggy, boring and repetitive mode. Defending yourself with only bile bombs isn't fun. Sometimes the bile didn't work properly, and the specials wouldn't die. One of the survivor bots also managed to find a pipe bomb somehow.

Mutant Explosion (pipe bombs only): Whilst this was very easy and repetitive, there was some level of satisfaction in treating the pipe bombs like an infinite ammo but slow firing grenade launcher; it's cool to land a perfect throw and take out a special infected from a distance. Unlike in Disinfected, it's also reasonably possible to defend yourself.

Special Ignition (molotovs only): Completely pointless, very easy, you can just throw molotovs at your feet as you walk to the saferoom.

Three Throws (random grenade every few seconds): Suffers from exactly the same problems as the other modes, but you're sometimes stuck with a useless bile bomb instead of a pipe bomb or molotov you can use to actually defend yourself.

Bombing Run (the same as mutant explosion, but common infected spawn as well as specials): The common infected are a completely pointless addition and add nothing to the game mode. Since you're throwing pipe bombs constantly, they will never even get close to you and they just run off and die before they can do anything. The existence of this mutation is very strong evidence that none of the mutations in this addon were even playtested (there's much more evidence later on); if Bombing Run was playtested, it would be immediately obvious that the common infected do nothing to improve the mode.

Hot Zone (the same as Bombing Run but with molotovs): All the critiques of Bombing Run apply here. Common infected die as soon as they're lit on fire; so long as you're standing in the radius of a molotov (which you always will be) they can't hurt you.

Verdict
Every mutation except Mutant Explosion scores a 0/10, with Mutant Explosion getting a 3/10.

Premise
A group of 3 mutations based around the virus spreading between each survivor as they're injured.

Contagious: 1 incap only, if one survivor gets incapped then other survivors will start to have their permanent health turn into temporary health.

Infected: when you take damage, your health slowly drains until you die.

Virus Free: If you're infected and your health drops to 0 then you die instead of being incapped.

Notes
Contagious: There are better ways of executing a 'shared health pool' style mutation. You could give the survivors 500 health total, but make it so that whenever anybody takes damage, everyone else takes the same amount. That would be more interesting and tense than just temporary health.

Infected: This is a glorified version of the Bleedout mutation.

Virus Free: If you don't get incapped (which we didn't) then this is really just the same as campaign mode.

Verdict
0/10 across the board. All Gone Viral variants just aren't very good or interesting, and there's better alternatives available.

Premise
No weapon spawns. Progress through each weapon by killing special infected.

Notes
We assumed, wrongfully, that you would progress through the weapons by killing common infected. Because there's no indication as to when you're about to progress (which is what gun game modes usually have), we weren't gaining new weapons and we thought the mutation was broken. Once we figured out how it worked, it was still really bad. It's very difficult to kill the special infected with the low tier weapons you start with, especially when your teammate has a much better weapon; unless they intentionally let you kill the specials, you'll probably be stuck with only a pistol or smg the whole game.

Verdict
0/10, possibly wasn't even playtested, really needs some sort of HUD element.

Premise
Progress through each weapon by killing common infected. Only common infected spawn. They are slower but deal much more damage.

Notes
Gun Game Swarm has a major bug that renders it unplayable. If you get incapped, you lose every item you have. This means it is impossible for you to kill any infected or even shove, leaving you completely defenceless.

Verdict
0/10, non functional.

Premise
A group of 13 mutations that add Gun Game aspects to other mutations in the addon. Survivors have infinite ammo and start with a random laser sighted weapon or grenade. There is no friendly fire. Medkits will spawn, but no other items.

Notes
Apparently, your current weapon is supposed to switch every 10 seconds. When we played it, this did not happen. You were stuck using the one weapon the entire time.

Verdict
Every variant scores 0/10 because they don't work.

Premise
A group of 4 mutations, 2 of which are variants of other mutations in the addon. We reviewed Deadly Spawn and Undead Assault.

Deadly Spawn: Survivors are incapped when their temporary health drains to 0. Survivors start with a magnum and laser sighted M60, and have infinite ammo and no friendly fire. When a special infected dies, several commons will spawn at the location they died.

Undead Assault: Getting hit once infects you. Getting hit when infected kills you. Survivors start with an M60 and Magnum. Commons are a bit slower. A kill counter is on screen.

Notes
Deadly Spawn: The commons add nothing to this mode. All you have to do to deal with them is continue shooting for a fraction of a second after killing a special to clean up the spawned commons. It's really just a worse version of Gib Fest.

Undead Assault: the infection mechanic is pointless, since you'll never get hit just once. The kill counter is also unnecessary as you can just check the end of round scores.

Verdict
1/10 for Deadly Spawn, which is inferior to Gib Fest, and 2/10 for Undead Assault, which is simply not fun.

Premise
A group of 3 mutations based around regenerating health while killing infected.

Borrowed Time: Survivors health drains constantly. Get a small amount of health for killing a common infected, and a large amount for killing specials. There are no healing items and you can only be incapped once.

Healing Horde: Common infected only, which deal extra damage. Survivor health drains constantly and they have infinite ammo. Get a small amount of health when killing an infected. Survivors can only be incapped once.

Special Aid: Special infected spawn in large waves, and survivors are awarded health for killing them. Survivor health drains constantly.

Notes
Borrowed Time: A decent mode whose main weakpoint is its wildly fluctuating difficulty. When there are plenty of commons nearby, you can regenerate enough health to become almost invincible. During downtime, there's not enough to regenerate your health, leaving you at critical HP for long periods of time.

Healing Horde: Less fun than Borrowed Time due to there only being common infected and having infinite ammo.

Special Aid: Tanks are apparently supposed to grant health to the whole team, but they don't. This mutation is also quite frustrating as it feels like you need to let your low health teammates get kills instead of just playing the game.

Verdict
Borrowed Time is the best, scoring 5/10, whilst Healing Horde and Special Aid are considerably worse, only scoring 3/10 and 2/10 respectively.

Premise
A Last Man On Earth variant where only Hunters, Smokers and Tanks spawn.

Notes
Whilst it is atmospheric, it's not particularly engaging or interesting.

Verdict
3/10, nothing special.

Premise
A solo mutation with no survivor bots. Only common infected spawn.

Notes
As simple as it is, this mutation is quite relaxing and fun to play. You don't need to try particularly hard or worry about getting pinned, and you can just travel through the map at your own pace killing common infected however you like.

Verdict
8/10 a relaxing and enjoyable mutation.

Premise
A 2 player mutation with only special infected, though they aren't spammed. Defibs replace medkits.

Notes
A reasonably fun and challenging mutation that feels fair and demands strong teamwork. Only having defibrillators makes healing a bit annoying however. It would be better if each saferoom contained 2 medkits and 2 defibrillators.

Verdict
6/10, good fun with a friend.

Premise
A 2 player version of vanilla L4D2, with reduced special spawns.

Notes
Right 2 Live is well balanced and very fun, putting a strong emphasis on teamwork.

Verdict
8/10, a solid mutation in every way.

Premise
A 2 player mutation with only common infected.

Notes
Much of what applies to One Against Many also applies here, however Two Against Many has considerably less risk involved and it's hard to imagine ever dying.

Verdict
7/10, still fun and relaxing but there's no difficulty whatsoever.

Premise
A group of 8 mutations that exclusively spawn one type of uncommon infected, as well as Boomers and Tanks. Survivors only have magnums, infinite ammo, and there are no item spawns.

Notes
Regardless of which variant you pick, Uncommon isn't going to be fun. For certain variants however, it may well be unplayable. For instance, if only Mudmen or Jimmy Gibbs spawns, you'll spend the entire game blind from mud/oil and boomer vomit.

Verdict
2/10, boring and unplayable at times.

Premise
A group of 18 mutations, 17 of which are variants of other mutations in the addon. One survivor is chosen as the VIP, who only has a pistol. The other survivors have to escort the VIP without letting them die. If they die, the chapter restarts.

Notes
This mutation has a lot of bugs that prevent it from being played properly. Firstly, a survivor is supposed to be chosen as the VIP. Instead, another survivor is spawned and made into a VIP. The VIP is also supposed to only have a pistol, but they can pickup and use other weapons just fine. What this means is that you have 5 survivors on your team, making it very difficult to lose. Out of curiosity, we killed the VIP to see what would happen. You're supposed to be able to revive them with a defib, and doing so quickly enough lets you continue. However, it still restarted the chapter.

Verdict
0/10, doesn't work as intended.

Premise
Realism mode with headshots only, no specials, slow common infected that deal a lot of damage, and no HUD.

Notes
This just isn't a fun mode. You get incapped in one hit, with barely any time to be revived. Every weapon pickup can only be used once. Avoid this unless you're a masochist.

Verdict
1/10, simply not enjoyable.

Premise
Plays like Scavenge mode. A single Charger spawns, with tens of thousands of HP. Only boomers can spawn alongside it.

Notes
This mutation had a bug that also allowed Hunters to spawn. Outside of that, it was really awful, somehow being worse than vanilla scavenge mode. Getting pinned by the Charger basically means you're guaranteed to die. You're blinded constantly by Boomers, and the idea seems to be to let one person get pinned and then have everyone else actually play the game and grab cans.

Verdict
0/10, an awful mutation that's worse than vanilla scavenge.

Premise
Plays like survival mode, with infinite ammo magnums and grenade launchers.

Notes
There is no way this mode was playtested even once. It is so laughably easy that we were forced to quit so as to not override our legitimate survival times. The grenade launcher can be fired constantly with no need to reload. Commons can never get close enough to you to do anything. Tanks die in seconds, and all specials get dropped in one or two shots. If you put even a little bit of effort in, you'd easily break the one hour mark.

Verdict
0/10, the easiest, most boring way possible to play survival mode.

Premise
Plays like survival mode, but with only commons.

Notes
Yet another mode that wasn't playtested; sit near an ammo pile or weapon spawn, and you will never ever die or even take damage.

Verdict
0/10, no difficulty whatsoever, impossible to lose.

Premise
Combines survival mode and Gib Fest.

Notes
This is similarly easy to Hordes Survival, but at the very least there's a chance you'll get pinned.

Verdict
1/10, almost no challenge.

Premise
Plays like survival mode, but with only Tanks.

Notes
Tank Assault is an ok mutation, though Tank Run is a far superior mode in every way since you aren't just sitting in the one area and you have an actual goal outside of not dying.

Verdict
5/10, decent but Tank Run is better.

Premise
Versus mode but with the Big Daddy mechanics. One player spawns as a Charger with tens of thousands of health, the rest are Boomers.

Notes
Why would you ever play this over regular versus mode? All you can really do is let one person get pinned, then have the rest rush to the saferoom. By far the biggest problem however is that the Big Daddy can sit in the safe room and prevent the survivors from closing the door.

Verdict
0/10, worse than vanilla versus in every way.

Premise
Versus mode, but the survivors are restricted to only melee weapons.

Notes
This plays about as well as you'd expect; that is to say, pretty poorly. If the survivors stray more than a few feet away from each other, it's very easy for them to get pinned and take a lot of damage before they can be saved. Simply put, not being able to defend yourself properly isn't fun. The mutation is very heavily stacked against the survivors.

Verdict
1/10, severely unbalanced, not fun.

Premise
Only Tanks can spawn. Tanks have infinite health. Low gravity is enabled.

Notes
This mode plays a bit like Tank Run in a way. However, it very clearly wasn't playtested; if a Tank reaches the safe room before the survivors do, they can stay inside and since they can't be killed, it's now impossible for the survivors to win.

Verdict
0/10, potentially unplayable.

Premise
Versus mode with only Smokers.

Notes
An uninspired and incomplete mutation. Human players will spawn as Smokers, but the infected bots can spawn as any infected. With anything less than a full party of 8 human players, this is just versus mode with more Smokers than usual.

Verdict
0/10, doesn't function as intended.

Premise
Switches the L4D1 and L4D2 survivors in their respective campaigns.

Notes
This mutation works, and does nothing more or less than what the name suggests. If you want to play as Coach in No Mercy or Francis in The Parish, this is an easy way to do it. The only caveat is that all the dialogue triggers in the maps will no longer work, so you'll be playing with fairly silent survivors most of the time.

Verdict
5/10, niche, doesn't impact gameplay very much, but it works.

Premise
Note: Wave was one of the most broken, buggy and non functional mutations in the addon. We can only guess as to how it was meant to work, so the premise described below may or may not be correct.

Intended to function as a wave based survival mode, where survivors kill hordes of infected and have some down time to heal and regroup. Killing infected awards currency that can be used to purchase new weapons.

Notes
Not a single aspect of Wave was functional. Upon loading into the game, the survivors had 5 seconds to prepare before the first Wave started; when playing with high ping, you'd end up loading in once the wave had already begun. The first wave spawned in as expected, but then every additional wave spawned in rapid succession, with the wave tracker incrementing beyond it's limit (we managed to reach wave 293/10). Whitaker voicelines are supposed to play in between waves, telling the survivors to purchase weapons; however, because the waves happened so quickly, the voicelines played over the top of each other. Dozens were played at the same time, turning into a garbled mess that was impossible to understand and drowned out all other noise. Oftentimes, common and special infected didn't even spawn. The weapons that are supposed to be purchased are locked in an inaccessible area, meaning the survivors are stuck with only a pistol the whole time. The Tank has 10,000 HP, and for some reason its AI was incredibly broken; it would run at the survivors, only to turn around and head the other way.

Verdict
0/10, broken in every way.

Premise
A survivor vs survivor gamemode. Killing another survivor awards you with a new weapon. The first player to score a kill with every weapon is the winner.

Notes
A great concept that's well executed and functions properly. Whilst we tested this with 2 players and still had a great time, it would likely be a lot more fun with 4. Also, we would recommend playing on a map with lots of cover and alternate routes to flank the other survivors with; we played on the Dark Carnival finale, which meant sniping was very effective and shotguns and melees were a challenge to use properly.

Verdict
8/10, very fun and would be great with 4 players.

Premise
A survivor vs survivor gamemode where each survivor has a magnum that kills in 1 shot.

Notes
Whilst there is still some fun to be had, it's a considerably more repetitive and less interesting SVS mode than Gun Game. It also caused a game crash at one point.

Verdict
6/10, can be fun but is also a bit boring and repetitive.

Premise
A survivor vs survivor game mode, with the round ending when all but one player is dead. Survivors have health regen and their weapon cycles every few seconds.

Notes
This mutation was inconsistent and didn't function properly. The game crashed several times when the round ended. Sometimes the round also didn't end when there was one player left, and it would continue forever. The survivors also occasionally died immediately after spawning in.

Verdict
0/10, non functional and buggy.

Premise
Note: We have no idea what this mode is about. It caused us to spawn with no items, so all we could do was walk around the map in reference pose.

Notes
See above, the mode clearly isn't functional.

Verdict
0/10, non functional.

Premise
A survivor vs survivor game mode. The survivors have infinite molotovs which kill in one hit, and no other items.

Notes
For how simple it is, Pyro Rage PVP is surprisingly fun. As expected though, it does get repetitive since you only have one weapon to use.

Verdict
7/10, fun but repetitive.

Premise
Survivors start with a melee weapon and adrenaline. Adrenaline lasts longer and grants a stronger speed boost. Hordes are much larger and more specials can spawn. Survivors have no flashlights. Adrenaline is the only item that spawns.

Notes
This mutation has several questionable design choices and oversights, and some caveats that make it borderline unplayable. For one, laser sights will still spawn despite the survivors having no primaries. Having no flashlight just makes the mutation needlessly difficult on night time maps or even just when indoors. The hordes are also large enough to cause significant performance issues. Even with these problems fixed, at the end of the day all you're doing is killing lots of commons with a melee weapon, which isn't particularly fun.

Verdict
0/10, not fun and unplayable at times.

Premise
Constant waves of Boomer spawns, with no other specials

Notes
Very simple, and fine enough if what you're looking to do is just shoot a lot of common infected. You'll be spending a lot of time blinded and stunned however, which isn't particularly fun.

Verdict
4/10, all this really does is just remove most infected varieties

Premise
The survivors move very quickly while crouched.

Notes
This mutation is fairly pointless. It's main and only mechanic can be replicated using a script (it's only a single cvar change). If you treat this mode seriously, it's very easy to race to the end of the map in a matter of minutes, which removes most of the challenge. If you just want to mess around, the movement speed bonus is so fast that it becomes hard to navigate properly at times, which isn't fun.

Verdict
1/10, pointless, and either makes the game too easy or frustrating

Premise
Survivors have only shotguns, with no secondary slot. There are no incaps, and survivors get killed in 3 hits. Very few wandering common infected are present, but occasionally massive hordes will spawn.

Notes
Crowd Control is poorly balanced and occasionally unplayable. The hordes are big enough to cause performance issues. Medkits are also quite useless; since you die in 3 hits, you likely won't have a chance to use it.

Verdict
0/10, unplayable at times due to the significant framerate drops

Premise
The map is extremely dark. Medkits heal to 100 health. There are no outlines, but survivor name tags are still present.

Notes
Whilst an ultra-dark mode is fine in theory, Darkness Falls is poorly executed. The map is so dark that it becomes painful to look at, since you'll be straining your eyes to see anything. It would've been better to combine a weaker flashlight with some dense fog; this still reduces visibility, but still lets close up items be seen properly.

Verdict
2/10, poorly executed and painful

Premise
The map is extremely dark. Medkits heal to 100 health. There is no HUD, and realism mode is enabled.

Notes
A more immersive version of Darkness Falls that is somehow slightly less painful to look at. It's still not great, but at the very least it commits to the immersion.

Verdict
3/10, immersive but painful

Premise
Constant waves of Charger spawns. Chargers have low health and will charge very frequently.

Notes
Another idea that's good in theory but poorly executed. Stunlocks are a major problem; it sometimes takes ages for the survivors to recover after being charged, by which point they will have been charged again. Once one survivor dies, it's very easy for everybody else to die too.

Verdict
3/10, very frustrating at times

Premise
Constant waves of low health Jockeys.

Notes
Though it is funny, Jockeys! main problem is in the name. You're exclusively dealing with the most annoying enemy type.

Verdict
5/10, funny, but... it's just Jockeys

Premise
All weapons have greatly decreased reserve ammo. There are no ammo piles. Survivors start with an M16, Chainsaw, and secondary healing item.

Notes
Limited Resources is a fine mutation. It encourages you to switch weapons often to avoid running out of ammo, so it plays somewhat like gun game in that you'll be picking up every new weapon you find. For some reason, the M60 has loads of reserve ammo though. Ammo packs also felt like a missed opportunity. Something more could've been done with them instead of their usual upgrade bonus. Maybe turning them into a single use ammo pile? As it stands, the mutation is very simple, so some extra mechanics would've helped make it feel more unique.

Verdict
4/10, a simple mutation that's just ok.

Premise
Some of the games music is silenced.

Notes
Completely pointless; just mute your music volume in your game settings. It has the same effect, but doesn't require the use of mods.

Verdict
0/10, pointless

Premise
Survivors start with a Hunting Rifle and Pipe Bomb. They have no secondary slot. There are no healing items. Constant waves of Hunters and Smokers will spawn.

Notes
Snipe Fest feels somewhat unfinished, like it has the start of a decent mutation but it's missing something that really sells the theme. Having only ranged infected spawn (Smokers, Boomers and Spitters) but letting them use their abilities from really far away, and giving the survivors a choice of sniper style weapons could've turned the mutation into a real "Sniper vs Sniper" mode.

Verdict
2/10, in its current state it doesn't feel unique or finished.

Premise
Only Spitters can spawn.

Notes
Due to the AI that Spitters have, and the way their spit behaves, it's very easy to just run past them all and head straight to the saferoom. On the off chance that you do get incapped, it's a guaranteed death since the Spitters respawn fast enough to always have you covered in spit.

Verdict
1/10, inconsistent difficulty, very repetitive

Premise
A combination of realism and Headshot! The HUD is removed. There are no item spawns. Survivors only have one life, and infected deal extra damage.

Notes
Despite what the name might suggest, this mutation isn't hard; just unfair. The survivors have no means of healing. Any damage you take is permanent, so eventually you just won't be able to progress due to not having enough health. The removal of the HUD also serves zero purpose outside of inconveniencing the player. All the relevant information can be found by pressing tab. Combat also isn't fun in the slightest. You have nothing but a single pistol, and you can really only guess as to where your crosshair is to score headshots.

Verdict
0/10, unfair, likely not playable unless your entire team can consistently do no damage pacifist runs. Whilst this mutation was likely made as a joke, it's still not good in any way.

Premise
All weapons have much less reserve ammo. Only common infected and Tanks will spawn, and hordes are much larger. Common infected also move slower. Realism mode is enabled, and there is fog present.

Notes
The idea behind Chaos seems to be a slightly more realistic and atmospheric version of L4D2. However, it mostly ended up devolving into being forced to use melees, due to the smaller reserve ammo pool and larger hordes.

Verdict
3/10, you're almost forced to use melees.

Premise
Realism mode is enabled. There is no music, and fog is present. Common infected move faster.

Notes
Insanity is a decent mutation, and fighting against fast moving commons rushing out of the fog can be fun. Like a lot of other mutations however, it would probably be a bit more fun if it wasn't a realism variant.

Verdict
5/10, would be better if it wasn't realism.

Premise
Realism mode is enabled. Survivors have no flashlights, and the map is much darker.

Notes
It seems that in order to make the maps darker, the skyboxes were deleted. Either that, or this is some strange bug that's only present in this one specific mutation. Regardless, the skybox is extremely painful to look at, and completely ruins the mutation.

Verdict
0/10, ruined by the broken skyboxes.

Premise
Realism mode is enabled. Only common infected will spawn, but hordes are infinite.

Notes
Simple and fine enough, but realism doesn't really add anything to the experience, and it would be better if it wasn't enabled.

Verdict
6/10, would be better without realism.

Premise
Realism mode is enabled. The map is darker and there is no music.

Notes
Another attempt at a more realistic and atmospheric mutation. For some reason, the flashlight in this mode is extremely bright. All things considered however, it's still no better than ordinary realism.

Verdict
2/10, just a worse version of realism.

Premise
Realism mode is enabled. There is no HUD, and survivors can't vocalise. Only common infected will spawn.

Notes
Yet another realistic and atmospheric mutation. Ultra Realism was unique however in that something just felt 'off' about it. We couldn't really explain what it was, but neither of us wanted to keep playing.

Verdict
N/A, we never ended up finishing this mutation, so we can't accurately give it a score. It would likely be similar to the other realism variants.

Premise
Plays like Scavenge mode, but with a Big Daddy and several Spitters to assist him.

Notes
This suffers from all the problems that the other Big Daddy modes have, in that it just isn't fun to play against the Big Daddy. It is also bugged, and Hunters occasionally spawned on the infected team.

Verdict
1/10, not fun or engaging.

Premise
A combination of survival mode and Last Man On Earth. 1 player must survive against groups of special infected and Tanks, getting revived when incapped.

Notes
A very fun take on the otherwise boring survival gamemode. There's plenty of available medical supplies, so with a bit of planning it isn't challenging to get a decent time. The mode as a whole felt very balanced and fair, and is definitely one of the better mutations in the mod.

Verdict
9/10, very fun and balanced.

Premise
Only healing items are present. The player is hunted by an invincible Charger.

Notes
Nemesis was a fun and tense way of playing the game, requiring you to think and act quickly to avoid getting taken out by the Charger. Some Tanks and Witches occasionally spawned, though it's unclear if this was intentional or a bug.

Verdict
7/10, fun and tense.

Premise
Note: We don't know for sure what the intent behind this mutation is. When the game starts, there's a bunch of weapons on the ground at your feet. Only special infected will spawn, but no Smokers. Our best guess is that you're meant to be able to hold every weapon at once, but it just doesn't work for whatever reason.

Notes
See above, we're not sure what this mutation is about.

Verdict
0/10, if it's broken in the way we think it is, it deserves this score. If it's functional then it's just specials only with no smokers and extra starting guns, which is pointless.

Premise
Very thick black fog is present. Only Hunters will spawn.

Notes
Pitch black is a true horror experience. The Hunters will move around just outside your view, leaving you always on edge, and having one jump out at you is a bit like a mini jumpscare.

Verdict
9/10, a great horror themed mode.

Premise
A realism variant of One Against Many, with no HUD.

Notes
Though it's still a perfectly fine mutation, it lacks the relaxation element of One Against Many, due to the realism mechanics.

Verdict
6/10, fine but not as relaxing as the non-realism version.

Premise
Last Man On Earth with increased HP specials and an infinite ammo grenade launcher.

Notes
We only had a single word written down to describe this mutation; Lame. As you'd expect, having an infinite ammo grenade launcher tends to take a lot of the fun and challenge out of a mutation.

Verdict
3/10, lame.

Premise
Only Magnums and Pump shotguns are present, with half as much ammo. Special infected spawn rates are slightly lower.

Notes
Horror 4 Two really just feels unfinished. Like it had the start of a horror movie theme going, and ended up being abandoned before the main mechanics were implemented. With less pump shotgun ammo, it's pretty much just 2 players with Magnums.

Verdict
2/10, feels unfinished, basically magnums only.

Premise
The same premise as Horror 4 Two, except other weapons can spawn and they have even less ammo.

Notes
As expected, this suffers from the exact same problems. It feels unfinished and you're forced to use a magnum.

Verdict
2/10, unfinished magnum spam.

Premise
2 Chargers will follow the players, charging constantly and incapacitating a survivor when pinned. Survivors only have 1 life, and they start with no items.

Notes
At first, Karma Bros seemed a bit frustrating, as it was easy for both players to get pinned at once. However, we eventually figured out a strategy that involved trapping one of the Chargers in the safe room and having one player watch it to prevent it from despawning. The other player could then run to the other safe room whilst only needing to deal with one Charger, and the first player could follow them afterwards. Whilst this likely wasn't the intended way to play, it was pretty fun. A major consideration is that this mutation is very map dependent. You need room to move and dodge the Chargers, otherwise it's too easy to get pinned.

Verdict
7/10, fun but very map dependent.

Premise
Survivors start with a Pump Shotgun, pills, medkit and molotov. Realism mode is enabled, and survivors take greater than expert level damage. Commons move a bit slower, and less of them will spawn. There are no item spawns. Medkits heal to full health.

Notes
Travelling light doesn't feel finished. There's no real theme to it; the name suggests something to do with not being able to hold as many items, but you start with a full inventory. It's pretty much just a downgrade to realism mode.

Verdict
1/10, much worse than regular realism.

Premise
Survival mode with only molotovs. Survivors die instead of being incapped.

Notes
A completely pointless and braindead mutation. Commons are useless. Most specials are useless. Tanks are dealt with solely by running away to stall out their burn timer. All you can do is camp somewhere and spam molotovs.

Verdict
0/10, pointless.

Premise
Survival mode but only Jimmy Gibbs can spawn.

Notes
Many players have likely never even fought Jimmy Gibbs, let alone an entire army of him. He has almost as much health as a Tank, but can be killed in a single hit by melee weapons, therefore turning this into a melee only survival mutation where every infected blinds you on hit.

Verdict
0/10, not fun.

Premise
Versus mode with a Big Daddy present.

Notes
See every previous Big Daddy mode.

Verdict
1/10, see every previous Big Daddy mode.

Premise
Versus mode with only Tanks and common infected. Survivor health drains over time and there are no medkits.

Notes
Tanks are spawned directly on top of a survivor, meaning you're likely to get hit instantly and probably incapped right afterwards. Your only option is to rush to the end and hope the Tanks spawn on your teammates instead.

Verdict
1/10, speedrunning is the only option.

Premise
Versus mode with only molotovs. Survivors die instead of being incapped.

Notes
Flame War is about as boring and repetitive as it gets. Survivors can only spam molotovs, infected can only hope they spawn as a Charger or Tank.

Verdict
2/10, very repetitive and boring.

Premise
No weapons are present.

Notes
About as fun as not being able to play the game can be.

Verdict
1/10, not fun at all.

Premise
Versus mode with 2 players on each team. No common infected will spawn. Survivors are revived when incapped. Specials deal increased damage, but extra medkits will spawn.

Notes
Whilst the idea of 2v2 versus is good, it's very poorly executed. Due to the increased number of medkits, the only reliable way to kill the survivors is to sync up with your teammate as 2 pinning specials to get them both at the same time, then do this multiple times before they can find another medkit and heal up. However, this isn't possible if one of you spawns as a Spitter, making them effectively useless. The survivor bots also seem much worse on this mode than normal.

Verdict
2/10, a good idea that's poorly executed. It would be better with less medkits and no extra special damage, letting the infected chip away at the survivors over the course of the chapter.

Premise
Survivors have infinite ammo grenade launchers and no other weapons. Only pills can spawn. Only Tanks and commons can spawn. Commons deal expert level damage. Survivors take extra damage from their own grenade launchers.

Notes
Not a single aspect of this mutation was well thought out. Taking extra self damage means the grenade launcher is useless at close range; if you get swarmed by commons, you'll either die due to their massive damage or die trying to save yourself. Tanks will also spawn directly on top of the survivors, and they can't be dealt with using the grenade launchers due to the self damage. Common infected are also bugged and don't always deal the right amount of damage.

Verdict
0/10, very poorly thought out.

Note: Despite having a dedicated menu icon on the main screen, there exists almost zero documentation or mention of Zombie Sports League anywhere on the internet. All information below relating to the intent behind it is just our best guess based on what we saw.

Zombie Sports League refers to a collection of competitive mutations themed around a weekly sports game schedule. The idea seems to be that you would organise to compete with several other players, and play a new mutation every morning and night, eventually determining a winner at the end based on who has scored the most points.

In general, all Zombie Sports League mutations will contain these gameplay changes:
- Survivors score points for completing certain objectives depending on the mutation, such as reaching the saferoom first or killing the infected
- Scoreboards are used to encourage players to compete against one another
- Special infected are covered in brightly coloured paint
- Survivors and sometimes other infected will have coloured outlines
- Item spawns are disabled or limited, and survivor loadouts are predetermined
- Survivors have infinite ammo

Other mutation specific changes will be listed for each mutation.

Furthermore, most of the Zombie Sports League mutations are extremely buggy, to the point of being non functional. This, combined with some other issues that will be covered later, makes them impossible to use in any real competitive format, and therefore basically completely pointless as a whole.

Premise
Survivors score points for killing the infected. Survivors take no damage from pins or friendly fire, and are freed from pins after a few seconds. Survivors start with laser sighted silenced SMGs.

Notes
Being our first experience with ZSL, we weren't sure how it was meant to be played or what the intent was behind it. The end result was that we found the experience comparable to a modded Chinese server due to the massive number of seemingly random changes, and we didn't enjoy it at all. Whilst we rated it 0/10 at the time, in retrospect the mutation was likely functional, which would save it from a 0/10 score. Since we can't accurately rate it, it will be given an N/A.

Verdict
N/A, see above.

Premise
Survivors score points for reaching the saferoom before their teammates. There are no weapons, and the survivors only have pistols. Survivors are freed from pins after a few seconds and take no damage from them.

Notes
A mutation that is intended for nobody. It's set out as if it were a competitive event, but it's impossible to compete with other players due to how the maps are designed. For example, if you're playing on No Mercy chapter 4, you can't ride the elevator until all players are in it. Therefore, anything that happens before that point is entirely irrelevant, and the actual "race to the saferoom" part is just the last little bit on the roof. You also can't grief other players to slow them down. If you wanted to compete to see who can beat the campaign the fastest, just play it in singleplayer and compare times with the other players. There's also no victory screen at the end to show who won, the game just ends and takes you back to the lobby.

Verdict
0/10, nobody will enjoy this.

Premise
Constant Spitter spawns, and survivors start with infinite ammo magnums.

Notes
We couldn't leave the finale, meaning the game never ended and there was no winner.

Verdict
0/10, non functional.

Premise
Functions like Tank Run. Survivors start with a random laser sighted T2 weapon, molotov and adrenaline. Survivors have infinite ammo and score a point for reaching the saferoom. Survivors die instead of being incapped.

Notes
At the very least, this mutation was functional. There were no major bugs that prevented it from being played. However, it's significantly worse than normal Tank run due to the removed item spawns. Not a fan of the weapon you got given at the start? Too bad, you're stuck with it. If you want to compete with your friends in Tank Run, just play Tank Run and say whoever dies the least is the winner.

Verdict
2/10, functional but still largely pointless and much worse than normal Tank Run.

Premise
Only Riot cops spawn. There are no item spawns. Survivors start with a Spas Shotgun and Baseball Bat. Survivors can be incapped once, and are revived with full health.

Notes
During the finale, a bonus point is supposed to be given out. However, this did not happen, and a winner was never determined. Also, it's just Riot cop spam, it doesn't get much less engaging than that.

Verdict
0/10, non functional, Riot cop spam.

Premise
Witching hour mutation but with a scoring system for reaching the saferoom. There are no item spawns. Survivors only have 1 pistol.

Notes
Much like every other ZSL mutation, the scoring system here probably didn't work. We couldn't confirm this because the game was ruined by another game breaking bug. The survivors are meant to start with a pistol, but we started chapter 2 with nothing.

Verdict
0/10, non functional.

Premise
Chargers and Hunters constantly spawn. Survivors start with a random laser sighted T1 weapon. There are no other item spawns. Survivors get revived when incapped.

Notes
This mutation conceptually doesn't work. You're supposed to be competing against the other players, but you also have to save each other from getting pinned so you can progress.

Verdict
0/10, conceptually flawed.

Premise
Survivors start with a random laser sighted T1 weapon. There are no other items. Only Jockeys and Tanks spawn.

Notes
Easily one of the worst, most broken mutations in the entire addon, being so bad that it can't even follow it's own premise. The Jockeys stopped spawning a minute after the leaving the saferoom. When they did spawn, they wouldn't jump or pin players properly. If you did get pinned, you'd be freed after a few seconds, not that this mattered since we only got pinned once. Tanks would start spawning, but they only dealt 2 damage per hit. The scoring system (the entire point of the mutation and ZSL as a whole) didn't work during the finale. The saferoom had a mechanic that was supposed to burn you to death if you stayed in it. However, there was a very easy way to negate this and stay there indefinitely, guaranteeing a 'win'.

How was that done? Going idle. If you go idle in Jockey Trouble, then resume playing, you'll regain all your health and your inventory will be returned to it's default state with any starting items you're missing. If you go idle every 5 seconds or so, you become invincible, and you can never lose.

Verdict
0/10, the worst of an awful bunch.

Premise
There are no items, and survivors die instead of being incapped. Survivors must escort a gnome to the saferoom to score a point, with each survivor having 1 gnome to escort. Hunters, Spitters and Boomers will spawn, with Commons spawning from Boomer vomit. Survivors have a pistol, but it deals no damage, so infected can only be killed by shoving.

Notes
This wasn't playtested. You can't finish the chapter unless all gnomes are in the saferoom. Unless everybody makes it (which won't happen since medical items are removed and survivors don't have weapons), this mutation doesn't work. Also, the gnome can't even be thrown, only dropped.

Verdict
0/10, playtesting is important.

Premise
Survivors have infinite ammo and start with a laser sighted M60 and molotov. Only commons will spawn, and there are fewer than normal. Survivors can get hit 3 times, after which they die. No other items will spawn.

Notes
2 very strange parts of this mod were related to the common infected. For one, hardly any spawned. This meant a lot of the time playing this mutation was just walking in silence and barely shooting anything. There was also a bug where common infected would randomly die when a survivor got near them. We couldn't work out why this would be happening, but it meant even less zombies to kill.

Verdict
0/10, not hard, not interesting, likely not properly functional.

Premise
Survivors start with a random laser sighted T1 weapon. There are no other items. Survivors will be revived when incapped. Special infected respawn faster.

Notes
At the very least, Special Edition does offer some level of difficulty. There's plenty of Special Infected, and with only T1 weapons they aren't as easy to get rid of. Still, the mutation is very boring and repetitive largely due to having no choice in which weapon you use, and the main threat just being special spam.

Verdict
1/10, very boring and repetitive but it is at least somewhat challenging.

Premise
Plays like Tank Run, with infinite health Tanks. Survivors score points for reaching the saferoom. Tanks move faster than the survivors. No items are available. Low gravity is enabled.

Notes
Though it's fun to evade and juke Tanks with low gravity, the mutation ultimately suffers due to it being highly map dependent and very easy to get stunlocked.

Verdict
3/10, moderately fun but highly map dependent, and stunlocks are frustrating.

Premise
Survivors have infinite molotovs and an infinite ammo pistol. No other items are available. Only Smokers will spawn, and they spawn in greater numbers and more often than usual. Survivors get revived when incapped and can be incapped 3 times before dying. Survivors score a point for reaching the saferoom.

Notes
A buggy and poorly thought out mutation. Despite the title indicating you're meant to use molotovs against the Smokers, the infinite ammo pistol is much more reliable and effective; that is, until you're incapped, after which you lose the pistol and you can never get it back. The saferoom door would also occasionally be locked shut, preventing survivors from reaching the end. Finally, due to the number of Smokers being killed, you'll spend a lot of time blinded by their smoke, making it unnecessarily hard to navigate the map.

Verdict
0/10, too many bugs and problems.

Premise
Survivors start with a baseball bat. Only Leakers will spawn. Leakers are faster than normal, and survivors are slightly faster than normal. Survivors die instantly instead of being incapped. There are no other items.

Notes
Leakers are unique amongst the special infected, as the only way to kill them is to make them trigger their own explosion. They are immune to gunfire and other weapons, meaning the baseball bat you start with is completely worthless. This mutation came down to either sprinting past the Leakers before they could explode, which was in no way difficult and was very boring, or getting cornered by multiple Leakers and dying instantly, which felt unfair and meant watching other people play the game for a while. The finale was also bugged and didn't give points properly.

Verdict
0/10, Leakers don't work well in situations like this, and they aren't fun to play against.

Premise
Plays like survival mode, with only riot cops and Tanks. Survivors start with a random T2 shotgun and adrenaline, and have infinite ammo. The survivors health drains over time, and you score points for outlasting your teammates.

Notes
This mutation is supposed to last for 4 rounds, giving survivors points after each round based on how long they survive and then deciding a winner at the end. However, it doesn't do that, and just continues infinitely.

Verdict
0/10, doesn't work properly, and it's just riot spam.

Before we give our final score for the Mutation Mod as a whole, here are some important things to consider

- The quantity of mutations in the mod is vastly inflated due to the number of minor variants some mutations have. For example. the mutation "Uncommon" has the premise of spawning a single type of uncommon infected. However, it has 8 separate variants for each infected. This makes it seem like the mod contains many different mutations, when in reality the same mutation is reused dozens of times with minor variations.

- Many mutations in the mod don't work, either due to a variety of bugs or conceptual design flaws that make them unplayable. Despite being impossible to play, they still contribute to the total mutation count.

- Many mutations are faced with glaring balance and design issues, a lot of which are so obvious it suggests they were never playtested.

- Zombie Sports League as a whole is a complete dud. It doesn't even work as a functional group of mutations, let alone as a serious competitive mode.

- Better alternatives to a lot of mutations in this mod exist on the workshop or in the base game. There's half a dozen variants of Tank Run in the mod, but they're all worse than vanilla Tank Run.

- Of the mutations that DO work and are playable, many of them are extremely formulaic. Their design can be boiled down to:

1) Pick a certain type of infected, and spam it constantly the whole time.
2) Restrict the survivors to a specific weapon or set of items.
3) Optionally include some other minor mechanic or gameplay difference.

We spotted this design pattern many times as we played. "Blast Zone" spams Smokers and Boomers, restricts the survivors to a grenade launcher, and adds infinite ammo. "Air Raid" spams all special types, restricts the survivors to an M60, and adds low gravity. "Infestation" spams Hunters, restricts the survivors to a magnum, and removes the Hunters ability. It's boring, repetitive and predictable. Very few working mutations in the mod offer actual unique mechanics that build upon L4D2s base gameplay. Unless you really like killing one specific enemy type with one specific weapon, you simply won't enjoy the vast majority of the mutations featured in this mod, because that's what the vast majority of them are.




With all of that taken into consideration, here's what the mod does right:

- Despite being non functional, there are a number of unique mechanics and ideas present in the mod. Things like the infected splitting in 2 when they die, or the SvS modes. When they work, they can be very fun, and it's interesting to see L4D2s core mechanics used in a new way.

- The number of variants can be helpful for some players. On the off chance you're looking for a very specific sort of experience, you can likely find it in this mod. The sheer number of mutations it features means that at least one of them is bound to come close to what you want.

- It's a valuable source of information for those looking to make their own mutations. There's plenty to take inspiration from, and the mutations serve as a great template to make new mutations based around the mechanics or ideas they feature.

- It offers an easy and convenient means of adding a lot of content to the game. If you enjoy playing mutations with friends, Raymans mutation mod can give you plenty of hours worth of gameplay without the need to find and subscribe to dozens of individual mutations.



All in all, Raymans mutation mod contains a moderate number of decent/pretty fun mutations organised into a single convenient package, with a very large number of broken/boring mutations thrown in. Whilst there is some entertainment to be had, it would be advisable in a lot of cases to look for better alternatives on the workshop or even in the vanilla game.