[G] Left 2 Die Guide & Brutal Strategy

Left 2 Die is a free Blizzard mod in which you and an ally defend your base from Zerg attacks by night and build your base and reinforce your army by day. It's a lot like the campaign mission Outbreak, only harder, longer, more fleshed out and co-op. This guide is targeted towards players attempting Brutal, but a lot of the information is relevant on the lower difficulties as well. However, I will assume you have a basic idea of how the game works.

If you're unfamiliar with Left 2 Die, have a look at Blizzard's page on the subject, or just try it out with a friend. For a free mod it's fun and quite extensive.

- Stay alive until Siege Tanks. This pretty much sums up the whole Hard/Brutal strategy in one sentence. The early game is the hardest part, as you are limited to bunkers and whatever units you can squeeze out to defend with. Once you get them, Siege Tanks provide excellect ground defence when paired with Planetary Fortresses and repairing SCVs, Missile Turrets and Marines will take care of the rest.

Note: good strategy on Hard is to let your Biomass stack up then buy Tanks ASAP when resource trading is enabled and you can pool your resources - on Brutal resource trading takes 20 minutes to become active, so this strategy does not work. As such you will spend some Biomass on other units before getting Tanks, despite their importance.

- Kill as much as you can during the day. The more you kill, the more biomass you earn, the faster you are able to unlock your desired tech and the closer you are to completing the game. So when budgeting remember to think about your day army as well as your night-time defenses.

- Don't waste resources. This goes for minerals/gas as well as biomass. You will be mining on that one base for the whole game, so you need to pace yourself and buy only what you need, when you need it. Otherwise you'll end up behind and in trouble.

- Repair, repair, repair. This is extremely important for survival. Plant a half-dozen SCVs behind every PF you create. Stick a few around all your Missle Turrets and Tanks, Build more than you need so you can fully saturate your base and still be able to repair all your stuff. Replace any lost ones ASAP!

- Upgrades are important. Not just the +Attack/Armor upgrades, but the building armor and range upgrades as well as the unit-specific ungrades available from tech labs, some of which are equivalent to the ones bought with credits in Singleplayer. I will go into detail about which upgrades to buy and when in the guide.

Medic - Very useful during the daytime. Lets your Marines stim and not die to infested bunkers, also keeps them healthy at night when fighting Spotters.

Firebat - Quite useless. They will die extremely quickly to anything other than a standard Infested Terran, and their range is short (I believe they are actually outranged by Infested Marines but I'm not 100% sure).

Reaper - We never actually tried these. I suppose you could try to use them as your daytime army, killing building very quickly and avoiding Bunkers, but I imagine they'd be far too expensive to mass produce and still have enough money for Turrets/PFs/Tanks. No to mention their exorbitant Biomass cost.

Hellion - We got these on the attempt that we completed Brutal. I'm not 100% convinced of their effectiveness, though they did fit in nicely either side of a PF on hold position, roasting Infested Terrans. They are not much of a Biomass investment, though I would not bother training any once you get the tech - the mercenary units you get when you buy it are enough.

Goliath - We didn't try these either so I don't know how much they cost or what upgrades are available. Perhaps they could be used as air defense at night, but Marines combined with Missile Turrest do the trick well enough and don't require you to spend extra Biomass.

Siege Tank - The most important unit to unlock for obvious reasons. Very expensive but worth it. I will go into more detail about their use in the guide.

Omnisteel Bunker- You will only be using bunkers for the first night or so, so this upgrade is not as useful as it might seem. Something to spend spare Biomass on in the later stages if you feel like it.

Perdition Turret - Like Firebats and Hellions this is good at roasting the light Infested units, but it has its own drawbacks. It does not fit nicely besides a PF and if place out in the open will quickly get overrun. Not terrible, but once again there are better options.

Fire Suppression System - This is quite useful for isolated Turrets that your SCVs can't get to if something's blocking the way. Something to buy once you've got the other stuff.

Tech Reactor - We got this at the same time as Tanks, since we had the Biomass. Saves some cash and base area (which is actually an issue later on) that you'd use on extra factories.

Day 1
First things first: start SCV production, make a Marine and put a Reactor on your Factory. Salvage your low ground bunker and put two new ones side by side in its place. Build a bunker on the high ground (the Southwest side rather than the Northeast). Swap your Reactor onto your Barracks when it's done.

Pump Marines out of the reactored Barracks and fill the bunkers. Send your Vulture to plant mines if you like, then put him on the high ground with your Bunker. Keep making SCVs and Marines. You'll probably want to put a couple of SCVs on gas, but don't mine so much that you can't afford all the stuff you need at the start.

Night 1
The attacks start out pretty light, though you will get Hunterlings at some point. It seems to be random how many you get on either side and from what direction, but hopefully you should have enough marines to fend them off.

Remember to put your Marines in front of your high ground Bunker to start with, then spread them around once the space is full. Do NOT put them on the second high ground ledge yet, or Hunterlings with jump up there and eat them. Keep making Marines and SCVs, repair any structure that gets low.

Once you can afford it, make another Reactor on your Factory and a second Barracks. Once the night ends you should have two rax with reactors up and running. Towards the end of the night there will be a final round of Hunterlings, these can appear in your mineral line so be ready to deal with that.

Day 2
Empty all your Bunkers and salvage them, gather all your Marines and venture forth. Keep pumping Marines out of your two Barracks and rally them to your group. Be careful around Infested Bunkers as they can take out a few marines before you kill them. Kill as much as you can, then get back. We usually turned around at about 30s before nightfall just to be safe, but as long as you are not right next to a building when the night comes you should be able to get back without losses.

Meanwhile, use your bunker profits to make a PF at your choke and 5 Missile Turrets, 3 on the large high ground platform and 2 on the small one. Research the Hi-Sec Auto Tracking from the Engineering Bay (yes, really). When you can afford it, make 2 or 3 Turrets behind your mineral line as well.

Night 2
This is where it gets interesting. First priority: build two PFs at the Northeast barricade and plug any holes in the wall with Bunkers (notice you can't build Depots). Keep building Marines here for as long as you feel you need to. Make a Tech Lab on your Factory and swap it to a Barracks for Medics and Stim. Do this early so that Stim is done by the time day comes (we failed to do this but it still turned out ok).

The Missile Turrets are for Spotters, reason we get so many and the range upgrade is so that when one Turret is disabled the others can fire on the Spotter even if it's at max range from the one it's targeting. You should also plit your Marine forces up half and half on each high ground platform. Spotters will also try to bypass your defences and hit your mineral line, that's what the Turret there are for.

You should get Medics before the end of the night, and Hellions too if you feel like it. Also start the Medic Tech Lab upgrade, +1 for your Marines and Building Armor.

Day 3
Now you can really start killing a lot of structures and reaping the Biomass reward. Don't spend too much cash on Marines but get enough to kill stuff efficiently and Medics to support them. Towards the end of the day you should be able to get Tanks, and you ally should get the Tech Reactor. Put down a second Factory and an Armory in preparation for this, and start churning out Tanks ASAP. Be sure to get both their Tech Lab upgrades.

Night 3 and beyond
With a good amount of Tanks you should be able to hold off almost anything the computer can throw at you. You will have to build PFs at the Southeast barricade before the Infested break through and Missile Turrets on the ledges overlooking it, same at the Northwest. Place Tanks on the high ground wherever there isn't a Turrent. Repair constantly and be vigilant about Hunterlings in your mineral line (you may want to make a PF out of your main CC to help with this since you can't get an Orbital, however when we tried it we found that Hunterlings would still get a fair few kills before they got taken down, so it may not be worth it). Send your Marine ball around whenever there's a weak spot or your ally needs help.

At this point the computer will send the Stank to attack you. Since you have PFs at every spot where it can attack, you it's just a case of pulling your SCVs to repair, Stimming your Marines and focusing your Tanks on it until it dies. You'll be probably get a sweet achievement for it too!

Nydus worms can just be ignored. Sending your marines out to kill it is suicide on Brutal and your Tanks can mop up anything that comes close, so there's really no point.

Once you survive the night, just go kill some more stuff. Get whatever Biomass upgrades you like, max out your unit upgrades, don't do anything dumb and you should be able to complete it easily.

Here's a replay of a friend and I doing it on Brutal. Hopefully it's easier to understand when you see it in action. We won on the 7th day, though we would have done it earlier if we'd paid more attention during the day. Note that this is just our way of doing it, I'm sure there are other ways that work just fine if you want to experiment. This was the first time we managed to get Siege Tanks before dying on Brutal, so that should tell your how important they are.