I felt like this section is justified since some people find it too difficult or impossible to clear. Given that this is a skill-based map, you can certainly clear the entire campaign with 0 restarts if you understand the map and are skilled enough yourself.

If you feel that this campaign is impossible or think that I'm insane (I do occasionally feel sadistic designing this at times XD) or think this campaign is unfairly difficult, do read. I hope I can provide you my perspective on why I design them the way they are.

Complex Course is basically a Skills Based Challenge Campaign like QE. If you have played QE, you'll have a rough idea on what to expect for this campaign. My general philosophy in designing levels in games are always bounded by one rule: Fair difficulty. It has to be fair. However, certain design choices by Valve made it hard for it to be Fair and that is understandable due to the direction L4D2 is going for.

So now with all that said, I shall be diving down into the strategies of clearing this campaign. Half the fun is figuring them out yourself, so if you don't want to be spoiled, close this page now!

As usual, do note that Complex Course is not your standard campaign. As it will test your teamwork to its limits unlike your typical campaign that focuses on Exploration! Especially on Expert Difficulty. If you can clear this on Expert, congrats, you're a pro at this game. :D

Nothing much. Just a standard exploration map.

A simple stage that showcases turrets and lasers which will be prevalent across the entire campaign. Later a simple holdout area that tests your teamwork! If you're on Single Player, this part can be cleared relatively easy by holding out at the door area to avoid Boomer.

However on Expert Difficulty, you and your teammates have to holdout at different spots as Infected comes from all sides and you need someone to cover from all sides. If you're good at looking over your teammate's shoulders, this part will be so easy that it will feel like a chore. The Boomer drop and the open hole at the top at the dead end area is to prevent you from using that area as it is very easy for all 4 to holdout at that exact location and kill.

Design goal? Place faith in your friend to cover you like how you'll cover your friend! If you only lookout for yourself - especially on Expert - you will fail here.

A rather tedious stage. This will involve you running up and down collecting items necessary to complete the stage. Think of it like a 'breakout' house of sorts? It will also involve a section where you'll be introduced to the application of Turrets and Lasers in a tight area where you have to time yourself to move across without taking damage. It will be important in later stages.

The finale of this stage will feature a holdout against a horde + tank in a small tight space.

How to Clear:
You have to use Bile when the Tank spawns. If you're on Normal, one bile is enough.

If you're on Expert:
You will likely need to use more than 1. Be sure to horde some beforehand.
The small space also hinders use of Molotov, though possible if you have good teamwork.

You will need to kite around the pillars while throwing bile whenever necessary to distract the horde. The presence of increased Smoker spawns will serve to disrupt your ability to effectively kite. Be on a lookout!

This map is basically the hardest if you suck at gauntlets. Even harder if this is your first blind attempt and you are not sure what to expect.

Gauntlet 1:
The first gauntlet is basically a test of Special Infected reflex. With high platforms, you are extremely vulnerable to Smokers, Chargers and Jockeys.

When you approach the ladder, you're supposed to throw the Molotov provided earlier below to clear the infected OR use a bile you saved up before hand to distract the infected.
Then later descend quickly to switch off the alarm.

While you're MEANT to use a Molotov as it forces you to wait and lookout for Special Infected, it's okay to use a bile if you have them stocked up from the previous map. I mean why not right since it's much better than throwing a molotov. XD

Gauntlet 2:
This is the ultimate Gauntlet challenge of this map. The Tank's HP is fixed with this exact purpose at 6000 HP. Your goal is to trigger alarms and cause a horde to spawn behind you. You are supposed to form teams of 2. One will cover the zombies who spawn from the back and one to push forward with the cars.

Right before the Tank area, be sure for the team covering the back to retreat so the team who trigger the Tank can set it on fire and attack it in peace without worrying about zombies. You can use Bile for a bit of relief. You can find a Molotov and a Bile Jar in this part.

Another alternative is to let it die from idle fire. This tactic will require all of you to retreat back while handling the zombies. Do note the pockets of holes the tank can use to 'bypass' the passage.

Turret Tower:
I think this is quite obvious, use the walls around to take cover from turrets. Don't you feel like a secret agent? Dodging turrets and lasers.

Gauntlet 3:
Running against a gauntlet of zombies in EXTREMELY tight space with slightly lower than usual special infected timer. With a maze to boot. In my later updates, this maze will now be dynamic to better suit my original design intention. Your goal is to figure out the path while taking out hordes of zombies coming against you. - Spitters and Chargers are extremely dangerous here.

Holdout Area:
I initially added this area as a for fun zombie killing arena. It is not meant to be a specific challenge, rather it serves as a break. It has 2 machine guns to help you confuse the Tank,a nice area to fallback on as well as plenty of props to impede on infected's movement. Though I admit given the long haul of this map, this can feel kind of redundant.


- Gauntlet 1 -
The very first gauntlet is just an 'extra' to illustrate the fact that you're in a prison and trying to escape. The first gauntlet is very easy to clear if you know the way because if you run fast enough, you can actually reach the Switch to turn off the alarm FASTER than the zombie spawn.

If you lag behind, you will easily be drowned out by the common infected and die. Though it would be pretty interesting if 'Speed' is actually a skill in L4D2 don't you think? Oh wait, Bunny hop is a thing.

- Tower Map -
The design of this map is specifically meant to amplify the dangers of certain special infected. Such as Smokers and Chargers which will be much more obvious in a later Scavenge event that I will elaborate more on.

- NPC Live Firing -
Not present in the current version, but the new version will include more of them as they have been heavily underutilized. The goal of these is to pre-emptively take them out before they can deal damage to you. As usual, it is possible to take them all out with a sniper rifle taking minimal or no damage at all.

- Boss Hunters -
Boss Hunters basically tests your ability to deadstop a Hunter when it pounces. Because Boss Hunters have very high HP that make them hard to kill with guns, you will need to melee them for instant kill. Which means you're forced to lure them close to you, then proceed to deadstop them and slash them to death.

Given that a total of 3 Hunters will spawn, you will need to stay close to each other so in the event of being pounced, you can easily take them out with a melee weapon. In Expert, before you can kill the Hunter, the Hunter would have already killed your teammate if you rely on gunfire alone.

- Backtracking for Newspapers - AKA - An Elaborate Trick
While understandably tedious, it is meant to trigger AI Director's distaste for backtracking. Forcing it to summon a horde as well as a few 'Dominator Class' special infected behind you meant not only to trap those who are lone rangers trying to find a key by themselves given the random nature of the key spawn but also... (Read below)

It is also why sometimes a horde will spawn right when you spawn the tank. It isn't because I called it, but rather the distance of the common infected that the director spawns. If you don't take them out when they are trying to run up and reach you, there will be hell to pay when you spawn a tank and realize that the zombie horde has caught up to you.

Basically: If you have to go all the way down to find a key, you can dispose of the 'AI Hurry Horde' causing you not having to worry with fighting a tank and a horde.

If otherwise, you will THINK the scene is finally clear and happily spawn a Tank with a small horde chasing behind you.

Tl;dr: A psychological trick never before implemented in L4D2 :D Of course the effectiveness is dependant on how the AI Director reacts since even the 'Hurry Horde' itself is quite random and up to the AI's discretion. As usual with all psychological tricks, the magic is gone once you've figured it out.

- Scavenge Event -
The extremely small aisle while having to deal with dangerous special infected, an incoming horde and fill a scavenge. IS THE AUTHOR CRAZY!???

Nope. There is actually a very simple way, though still not easy, way of clearing. This will highly depend on your team's individual skill though.

Given that the Special Infected spawn from above and the horde spawn from below, you can assign one team member to stop gap the ladder area. This will prevent all common infected from reaching your other teammates.

The remaining 3 teammates job is basically to lookout for each other. 2 of them will run around taking gascans while one will look out for special infected like Smokers and Chargers.

That's where Spitters come in, while not lethal, their Area of Denial spit attack can deny your teammate of staying at the ladder area. Allowing common infected to flow in. Jockeys as well can accomplish this. Thus, this area again, is a test of special infected reflex, this time with more teamwork involved!

The Spitter limit for this area is raised. It is meant to catch you off guard while you concentrate on more dangerous SI such as Chargers, Smokers and Jockeys.

Arguably one of the hardest part in the entire campaign together with Map 3's Gauntlet event with a Tank.

- Gauntlet Finale -
This gauntlet is not meant to be hard. However it is meant to psychologically screw with your frustration and eagerness to finish this map. Proceed slowly with your teammates, you will clear this area with ease.

This is basically a Boss Map where you fight against the Mastermind of Complex Course. There are no 'specific' challenge per say, but teamwork and communication is definitely needed to be able to beat it on difficulties higher than normal.

This last map is designed to again, psychologically screw with your brain. This map is carefully designed with the intention to provide you with an 'illusion of security'. Of course anyone with a careful eye can tell that none of these areas are safe. The 'best place' to holdout with all the supplies either have turrets trained on them or are places where zombies will come out from.

So this means you'll have to settle for something less than ideal. It's a bit of a psychological thing that I try to invoke here where people will tend to settle for somewhere ideal only to find out it's not quite ideal. Of course this only works on first try, once you've figured out where you can holdout, the magic is gone :(

Of course Boss Hunters can appear here. The same tactic applies.

The final sprint to the end portion is just me paying a bit of homage to the original questionable ethics series.

Again, another part that you probably don't care, but I'll like to say a HUGE THANKS to all those who provided feedback for me in the early release of the campaign. If it weren't for you, all the bugs wouldn't have been fixed. Not to mention those who provided suggestions for me to improve my map as well. For those who did a playthrough for the early version of this campaign, especially on Expert Realism, I'll like to say congratulations! You've beaten a campaign where numerous bugs exist and the version where SI Infected Spawn timers are virtually non-existant in gauntlet hordes. I tip my hat for you.

I also understand that all said and done this campaign is not without its own set of design flaws. There are definitely things that I would rather do differently. Such as adding more explorable areas to give you a breather instead of a test after another test, splitting the Gauntlet map into 2 section with its own set of explorable areas and etc to make it more fun and less tedious while remain challenging like QE.

If you didn't realise, it is the first campaign that I tried my hand at in Source Engine. So yeah. Partly I'm inexperienced in Map making, but I'm also quite strapped for time so I hope you understand. If I had another chance at making another campaign, I will certainly make a much better one compared to this. Provided L4D2 doesn't die from a heat death by then :p

If you read the entire chunk of text, thanks. If you didn't and want a Tl;dr, here's one.

Don't play this campaign if you already have a hard time completing the standard Valve campaigns.