Impossible Guide

Key Elements
The 4 key elements you'll require to tackle impossible are as follows:


 * Luck
 * Initiative
 * Optimised development
 * Tricks, many of which are bordering on exploits

The impossible difficulty is quite close to it's name when tackling it "from scratch" AKA without a pre-trained team. Unless you're experienced and are looking for quite a tough and not quite pleasing challenge I'd recommend doing your first mission on a lower difficulty to train the said team. If you still want to do it from scratch, I'd recommend the smallest map possible - without the starting momentum provided by a trained team it's going to be pretty much impossible to catch up to the zed escalation of the larger maps. In other words you will almost assuredly LOSE the late game, and your only chance of winning is to win before it gets to the late game.

Rebuild in general can be described as a one on one race of escalation with you VS the zed. And zed will not slow down so you can't afford to either.

Initiative
Never ever let your fort buckle up and go on defensive. While this lame move may not kill you on lower difficulties it most assuredly WILL kill you on impossible. Slowly. Painfully. Inevitably.

Even if your fort is large enough for all your needs and you already have more land than you know what to do with KEEP EXPANDING. Zed threat can only be contained by reclaiming pretty much the whole map.

And land is not the only reason why you want to keep the pressure on. Your soldiers train by killing zed, killing zed reduces the danger of zed attacks, but most importantly...

Best defence is good offence. Literally, in this case.

When a horde of zed pops under your fort don't just sit like an idiot across the fence from it. ATTACK IT instead. On top of carrying the other benefits of aggression mentioned above this also comes with a few defensive benefits.

First is concentrated defence. If a horde can attack multiple tiles defending from it would require covering them all, while counter-attacking doesn't. A horde that attacks while it's being killed is treated as a horde that attacked the team that was killing it.

Second is chain-able defence. Sitting across a horde waiting for it to initiate an encounter does NOTHING for you. You'd think your soldiers would use that time to prepare, but no - it's exactly the same math regardless of how much time you've wasted waiting for the zed to make the first move. The next logical step that comes to mind is only being there at the time of the attack. And the next logical step after that is that one mobile defence squad could cover ALL the attacks from ALL the hordes as long as it's moved to the right place at the right time. Except... The one thing that DOES happen while you sit across the horde is that it's attack gets delayed. Meaning that you can NOT predict the right time and place while your defensive effort interferes with the timing. And this is why offence really IS the best defence. Attacking a horde does NOT cause this delay, meaning that if you move your counter-attacking squad from one horde to the next in the same order they appeared in you will be able to defend the entire fort with one mobile force.

See, we haven't even gone to the section dedicated to tricks bordering on exploits, and we've already resorted to some.

Optimised development
This is the most sane, logical and exploit-free (relatively?) part of our survival effort.

The key here is being able to understand the difference between what you want and what you need as well as the importance of doing the later not the former.

Followed by being able to determine what is it exactly that you need in order to win.

Followed by being able to go about acquiring that in the most efficient manner.

What you need is to be able to develop your fort as quickly as possible.

And for that, first and foremost, you'll need to balance the speed of various processes and get rid of bottlenecks. (this is what most of this seciton is about)

"OI! There's a power plant in the vicinity of a faction fort, I need to direct my expansion efforts that way and snatch it ASAP!"

No you don't. Weren't you paying attention just now? What you NEED is more people, more room for more people and more food for more people, so that you could grow stronger and grow faster.

I get the desire to chase after gimmicks, we all have it to some extent, but gimmicks don't win games. If you want to chase them badly enough - lower the difficulty and do it there till you're content.

Now that we've dealt with the distracting urges of chasing after shining precious power plants let's get back to business. Where were we? Ah, bottlenecks.

1. Expansion threads
Expansion in rebuild looks deceptively simple, while in reality it runs on several simultaneous processes which would need to be properly balanced for best results.

1.1 Workforce expansion
This is your first expanding priority, and the main (if not the only) bottleneck of a well balanced fort expansion.

This consists of everything that directly relates to your fort's potential of accomplishing work. (As such pretty much everything loops back to it. This is the non-capitalistic version of "you need money to make money".)

Which is the total sum of all skill levels of all active characters, which in turn depends on:

1.1.1 The number of characters.
This is THE bottleneck of the game for most of the time. This is fuelled and/or held back by:

1.1.1.1 Amount of available recruits.
Scout more, research signposts and searchlights, research better scouting to scout even more.

1.1.1.2 Leader workload.
Train leaders in schools. PRE-EMPTIVELY. From the get go, ASAP.

This is, quite possibly, the most important job for your main character to focus on in the earliest stages of his development, as the other leaders do not contribute much of anything in the early game when they are not actively head-hunting. Furthermore, it's easiest for your MC to combine leadership with defence meaning that you can grab some people from some riskier places.

DO get a second leader relatively early on though. You'll want one that can "negotiate" (talking about the trading perk here, obviously), and MC can't.

1.1.1.3 Amount of available housing.
This is almost 100% fuelled or held back by your builder workload. If you can't reclaim any housing in the vicinity build your own. If you don't have the materials, demolish a building. In fact, demolishing a building and building a different one in its place will not cost you (in total) any materials.

Nonetheless, this IS partially fuelled or held back by your stock of materials, as the methods you are forced to resort to without materials delay your overall expansion progress. To that end watch your materials and if those are declining, involve more scavengers and leaders (Don't stare at me like that with those questioning eyes of yours. Unless you are using your soldiers or engineers to trade or something... but in that case I reserve the right to stare back).

1.1.1.4 Amount of available food.
More or less "housing+". All the ways that you'd resort to to get more housing can and should be used to get more food as well.

Food is hell of a lot more flexible though. Also the degree of involvement of scavengers is somewhat bigger here.

DON'T overload them though. More on this later.

1.1.2 The training of characters.
Not much you can feed this with. This is a mostly natural thread and if this is your current bottleneck then things are either really good or really bad. I trust in you having enough common sense to make out the difference without me explaining it. But if it IS the bad scenario then try falling back on schools. Either this will help you or nothing will. And while we're at it - an ounce of prevention is worth more than a crapton of cure. THIS is why you recruit more people ASAP. Your recruits need time to mature, before they do they aren't contributing (much) to the work output and while they aren't contributing to it they aren't helping you to get more recruits. In other words don't plan for concentrated "recruitment spurs" in the future, get what you can now so that they can help you get to the rest faster. The only thing that should delay your recruitment effort is the risk of losing people (including potential recruits) as a result of haste.

I should probably drop a few words about RE-training here. It's closer to the expansion balancing side of this part of the guide, but it's a tool, and as any other tool in your expansion arsenal it deserves mention here. A short one though. Basically, you're going to need schools to feed that. It's not among the most pressing needs mind you, but if you ever find yourself in a situation where you can spare some workload after hitting bottlenecks in all of the more urgent directions and in that same situation you find yourself lacking schools, well, don't stand there twiddling yer thumbs, build/grab a few. Like I said, not the biggest of mentions, but there it is. The point was - it's better to make a school available in case you need to re-train some people BEFORE it comes to down to you needing to retrain some people. (only marginally so if your MC is a real estate developer)

1.1.3 The equipment of characters.
Take "housing+" (aka food) subtract the original housing, and this will more or less be what you get.

Trade and scavenge, trade and scavenge. ...is what this is fed by.

What this feeds in turn is your total workload. So basically almost everything. In a way this even feeds character training, because you can make newbies more usable with good equipment.

1.2 Land expansion.
Fuelled by your "military", fuelled by your builders, fuelled by your materials. All of which should not cause any questions by now.

Fuels your housing and farming, your crafting, your training, your healing, even those shiny precious power plant acquisition efforts of yours are fuelled by this. Actually it's hard to find an aspect that ISN'T to some extent fuelled by this. However to all that there's a limit. There WILL come a point where you don't need more farms, houses, labs, schools, power plants (NO! MY POWER PLANTS! MORE POWER PLANTS FOR THE POWEPL..) or whatever the hell else you'd want on your land.

Does this mean that you should at some point stop expanding? Hell NO! (although it DOES mean that there are times when fuelling your land expansion is LESS important that fuelling your other expansion threads) You should NEVER (permanently) stop expanding land because land expansion is what fuels your victory. Whether it's building your HQ and GTHO-ing ASAP, or complete lock-down of the city with the goal of sitting on your virtual ass and waiting for the new hero (read, a character with a scrapper perk) that you can take with you to Valhalla (read, next map) to emerge from the untrained masses, you're going to need to expand land to get there. And you want to get there ASAP, so you want to expand land ASAP. Which basically means that it's only ok to slow down on land expansion when you are redirecting your efforts to something that will later loop back around and accelerate your land expansion to even greater heights. But you probably know that much already.

1.3 Resource expansion.
The part labelled 1.1.3 kinda belongs here as well. So do your food, you materials, your medicine and... well, it's long but thankfully obvious list so I'm not going to list the whole thing.

This fuels and is fuelled by a crapton of things, but since this is the end (yay! finally) of the long list most of the links here have already been explored. I should bring attention to a few of them though.

1.3.1 Stock
This is the first issue you'll need to watch out for. It's somewhat closer to the balance side of things, but nonetheless, watch your resource stock. You want to deal with bottlenecks pre-emptively and this is how (or at least this is how for the ones that relate to storable resources). If any of your resources are in decline slow down that gimmick hunt of yours and go do something abut the incoming shortage BEFORE it gets the chance to happen. Needless to say you should also watch for build-up of any excess resources and redirect some efforts where possible. But that's the balance side of things.

1.3.2 Trade
Fuelled by farms, leaders and warehouses. Also by some food-related research.

In turn fuels potentially more than half of your wealth accumulation.

Considering how much workload the trade requires compared to how much income it brings and how limited the opportunities are, there's almost no place left for redirection of any kind here. Only do something else over trade if it's for the sake of resolving a serious bottleneck issue. The kind that you should normally aim and do your best to NOT experience in the first place.

1.3.3 Abundance

This is what 1.3.2 can, and eventually WILL do to your 1.3.1. At that point it's time to start treating some of your resources differently.

On top of getting virtually permanently rid of some of the bottleneck sources (such as lack of food or materials) abundance opens several secondary (yet still equally important to master) avenues of expansion fuelling.

A lot of it is a matter balance, of taking some people of the (now) less useful jobs and redirecting them towards the (now, relatively) more useful jobs, but there are also tricks here that are directly about the use of those extra resources of yours. Mostly it's advanced crafting in workshops (of which zombie killing traps deserve THE medal of the day), but also it's less scrupulous use of materials. See the tricks section for details.

2. Expansion Balance
You could say that the above were the bones which hold your optimised development, and this will be the muscles that make it move.

I listed all of the above because we need that knowledge to be able to identify WHAT is being the bottleneck and is slowing us down.

Now we talk about HOW to deal with that bottleneck once we have identified it. And more importantly how to pre-emptively avoid it becoming a bottleneck in the first place.

Like I've explained above our first priority is work output, and the manpower it comes from. So basically recruitment and maintenance.

If you can recruit and maintain, recruit.

If you can't maintain, fix that asap and recruit.

If you can divert manpower from elsewhere to accelerate the above processes, don't just stand there, DO IT! We need those recruits yesterday!

If you can maintain but can't recruit, scout more!

That last part is a recurring theme and is also a buffer of sorts. If any of the 5 aspects (fighting, scavenging, building, engineering, leading) has more workload available that it can put to use than the first thing to do is to shift it to scouting. If that problem is notable and persistent, then send some of those slackers back to school.

That said, this is a solution that should not last long. Scouting is the first kind of work that you should run out of, because it is one of the main bottlenecks of your recruitment process, which itself is essentially the bottleneck of almost everything else.

Most of the games problems can be solved by throwing more workers at it, and many simply can't be solved in any other way.

The trick however, is to throw 'em to the right places at the right times.

The key aspect here is defined simply as "think ahead". For example, it's not ok to sit at exactly 14/14 housing just because at the moment you scouts still haven't found anyone for you to recruit. If your builders are done bringing up your food income to the acceptable level have them build up a buffer of houses instead of wasting their time reclaiming parking lots and such.

Close second to that is of cause balance. In the same way that it's not ok to not have a few houses ready for when you might need them, it's also not ok to not have a few parking lots ready for when you need to build something. Don't divert your efforts towards fixing one bottleneck just to create another.

And you can't really talk about effort balance without talking about effort outlets. Half of the balance is all about what you can't have too little of, to avoid bottlenecks. The other half is about where to divert the effort once the rest of aspects of your effort distribution are in harmony. And that would be the outlets.

What makes rebuilt so complex is that it doesn't have many obvious outlets. In a way most fields of work share a common "outlet" of sorts in retraining. "don't have enough work for your builders? re train some of them into soldiers". But when even that part is balanced where do you direct your effort then?

The answer to that question, and more or less the final outlet of the whole rebuild would be the Land Expansion (since it's more or less your winning condition).

Outlet, is essentially the last item on your list of priorities. Make no mistake though, land expansion is an item that appears on it more than once. It's at the bottom as an outlet, and it's close to the start as one of the pre-requisites of your recruitment efforts.

Basically most elements are "multi-present" that way.

And there really isn't any "one size fits all" solution that I could give you here. You really need to get the feel for the game and then be adaptive and adjust your decisions based on your specific game's unique developments.

What I CAN give you is the awareness of methods. There's often more than one way to skin a zombie (no rotten faction members were harmed in the process of making this guide).

Characters
I'll start with the differences between MC and the rest of the characters.

MC can't be killed. EVER. Injured? Yes. Killed? No. Use this to your advantage when it comes the time to risk someone's well-being and you get to chose whose.

MC comes with his own unique set of perks, and without access to most of the common ones.

MC doesn't need to spend time in school to switch from training one skill to another. I repeat, TRAINING, not using. The game is deceptively un-obvious about it, but a lvl 10 builder that switched to training his defence skill does NOT stop being able to use his lvl 10 builder skill. He's going to be a pain in the ass to find though, as he will, without closer inspection, look like a lvl 1 soldier. With most characters you probably shouldn't bother with giving them a second profession, while some defence for emergencies would probably come in handy, especially on scavengers, most of re-training worth bothering with is best done on low level characters. Lvl 10 builder's time is best spent building.

4-6 notable exceptions to the above would be MC and his band of vagabonds to be taken to the next map. Obviously the time to train them is right before leaving for the next map. 4-6 versatile characters are generally more than enough to avoid any real need to multi-class any of the "locals".

MC Perks
Outside of campaign Doctor, or Police Officer.

In campaign, Doctor.

We're talking impossible here, you WILL get strained military and injured survivors. Once that fact is established only one perk can compare to doctor and that's Police Officer. And that's conditionally btw.

What do you think happens to a strained military when one of them gets injured? It gets more strained. And so more people get injured. It's a spiral you want to jump off ASAP (the longer it takes the worse your chances to outlive it get). And the Doctor is here to help you do exactly that.

Police officer is conditionally comparable and is even for a short while notably better, due to how much the added defence matters while you're going through your first map without pre-trained characters. but once that stage is behind you it's Doctor all the way.

In campaign, AFAIK you simply can not pick that perk as a result of an event, not to mention that campaign is a series of maps.

Speaking of event perks:

Wentachee - take Rock Star or Police Officer. If you have P2W edition it's probably Rock Star. Wentachee isn't your first map which makes police officer a lot less useful, and Rock Star ... well... rocks.

Mosses lake - Politician. Nothing else here matters.

Spokane - Take R.E.D. or Hobo. If you have P2W edition definitely take R.E.D., it's what gives P2W edition it's name. Or at least it's what contributes the most towards it.

Nelson - Construction worker or programmer. CW is still a good option even with P2W edition.

Kelowna - ummmm.... gang member? If you can have R.E.D. you should have taken it back in Spokane. Of the other two sorry excuses for an option gang member is slightly less worthless.

Chilliwack - shhh go away let me sleep through this... ok... ok... so if you're not on P2W edition you shouldn't even get a choice at that point. If you are than you get not much of a choice instead. This late in the game none of them are going to do you much good. Unless your plan is to gather perks on an easier difficulty and then to re-play the whole thing on impossible but with a pocket full of perks. In which case take college student, since you can't get it elsewhere and all that.

Oh, and speaking of re-playing you can re-select maps that you have previously finished (just not the same one twice in a row) to grab more perks from there. If you fancy being selective about doing that then the obvious targets would be Nelson and Spokane. In that order of importance.

Normie Perks
Tier 3:

Scrapper. Because nothing beats having lvl 25+ defence.

"And nothing else matters", that is if you have enough scrapers then this is the only kind of T3 perk you want.

If you're out of scrappers and aren't in a position to get more, then look for a MacGyver. If that Mac Gyver happens to have a good T3 perk, good for you. But most likely (s)he will not.

Tier 2:

MacGyver. Because some times there just aren't enough scrappers around. It's also a solid T2 perk to take alongside with scrapper.

Resourceful. For your scrappers.

Fighter. For your scrappers/MacGyvers, if we're beggars and not choosers.

Tier 1:

Bookworm. For your MacGyvers. Also nice to have when researching. So a scrapper with one is also a solid candidate.

First Aid. For it's intended use.

Negotiator. Because this is THE best way to rack-up reputation with factions. If you got it on one of your elite vagabonds, rejoice. Otherwise, writhe in agony of having to raise a new dedicated negotiator on every damn map.

Hoarder. Maaaaybe. For that OCD scavenger that lives in each of us. Thing is, since you'll be hunting scrappers this more or less is GUARANTEED to find its way into your set-up. But if that wasn't the case, then that'd be one of the perks to watch for, albeit as the last order of business.

(Note: the author here seems to have forgotten fearless reclaim, arguably the most powerful perk a survivor can get. With this perk builders can reclaim a building with zombies on it. Also, to get the "powerful" perks, in short, choose the first option the first two times you talk with them and try to eliminate less powerful options by equipment that grants perks.)

Nope, I didn't. What I DID forget is to mentioned that this was mostly about what perks to look for when taking people with you onto the next map, ergo anything that's incompatible with the scrapper perk might as well not exist. Superhero was mentioned because I was not entirely sure if it's a tier 2 or tier 3 perk (still aren't 100% sure btw, but nowadays I think it's T3 so I removed that).

I edited the perk part of the guide to make this clearer, but I left the "fearless reclaim" comment alone and added this here response to it, because if I just remove and ignore it some is bound to re-add this same heresy eventually.

Let me remind you that this is specifically an impossible guide. Fearless reclaim is actually more efficient than scrapper on the lower difficulty levels because you have zero need for such a high defense stat on difficulty 2 and 1, and barely any need for it on difficulty 3 (unless you just LET things get bad). On 4 and 5 however high defense is hell of a lot more valuable while fearless reclaim actually drops in value due to now needing extra people for the protection of the builder. It's still good enough to rival a tier 2 perk but that doesn't MAKE it a tier 2 perk. It's still a T3 perk which is NOT a cost it deserves any more.

And now that I've explained that the above was mostly focusing on persistent team let's talk a little bit about the rest of perk taking.

More often than not you want to stick to the "get me a rare one" strategy. Even if you don't end up taking this character with you to the next map, having a rare perk around is generally worth it. It's not worth it ALL the time and we'll discuss the exceptions in a bit, but generally it IS.

The strategy itself focuses on eliminating the perks from the perk lists.

There are 3 ways to do this.

1 - Get a free perk.

Mostly you get them through events. Some survivors will join with free perks already. Most noteworthy example are the ludites as they have a free green thumb perk and that helps a lot with getting a scrapper.

2 - Get a temp perk.

Look for items that grant perks. If you still don't have a satisfactory roster consider even taking these to the next map so that you can have an easier time building up your persistent roster there.

3 - Exploit storyline perks.

More on this is a sec.

To the best of my knowledge the perk selection functions as follows:

First it will fill your list with "storyline" perks. Refer to the backstory page if you don't know what those are.

Then it will fill the rest of list with class-based perks of an appropriate tier.

If any perk is already taken or if character has an incompatible perk taken then the perk will be skipped.

What a "tier" of a perk refers to is when it can appear.

First time a character takes a perk (I repeat TAKES, it doesn't matter how many free or temporary ones you have for this purpose, or what you skill level is, only how many times this character have taken perks already matters) it'll be up to one storyline perk and the rest filled with tier one class perks.

Second time it's up to two storyline perks and the rest filled with tier one and two perks.

And the third and last time up to 3 storyline perks and the rest tier one two or three perks.

So, like I said, the essence of "give me a rare one" strat is in eliminating as many perks from the list as possible.

Eliminating perks by items on your first take is practically pointless. It's quite likely you'll just NOT get a replacement option at all.

If you're hunting for rare perks ALWAYS take the storyline one as your first. Unless of cause it's a perk you consider to be a negative one. If it's negative, or maybe even if it's just useless switch to a different strategy and just try to make this character a productive member of society. There's one more exception to that "always" which we'll get to in a sec.

Second take is risky. You still cannot take a tier 3 perk, only tier 2, and not taking a storyline perk will make it that much harder to take the T3 one on you last take, but taking a T2 perk now is your only option for combining T3 with T2.

Third take is easy - what you get is what you get. There's no more takes after this one so just take your best option.

The other part of exploiting the storyline perk is to use them to eliminate the class perks from the list.

You can't have duplicates on the list. Use the backstory page to look up what storyline perks this character will get.

If one of the later perks is a T1 class perk you can eliminate that storyline perk pre-emptively. This is particularly useful if your first one is undesirable (or is eliminateable by an item) or if you're trying to catch both a T2 perk and a T3 perk on the same character.

Also, obviously, you will have better chances of finding rare class perks if your characters storyline perks match his currently active class. Both the ones already taken and the ones still being presented will shorten the list of possible class perks and as such may help a rare one to appear.

P.S. for this section - should be obvious, but if you see a perk you can eliminate you can just cancel out of perk selection and either equip an appropriate item (in case of item-eliminated perks) or wait for your character to become devout (in case of religion perk) though the later is only a good idea if your devotion acquisition rates are high (priest MC, several preachers, many other characters are already devout).

Now for the specifics:

Scrappers. Enough said already. This is both the best T3 perk to have and the easiest one to get.

MacGyver. Second strongest and second-easiest to get. (Doctor bags can eliminate first aid, and most of T1 engineering perks are actually good ones.) also it's merely T2. There may be better perks to have on a scrapper, but for any other purpose this is the second-best perk.

Commander. You need a total of 20 fighters for one commander to catch up (in total defense added) to a scrapper and that's BEFORE equipment comes into play. Still, a solid T3 for a character who's storyline includes fighter perks.

Fighter. Solid T2.

Resourceful. Scavenger T2. If you manage to put this on a scrapper it's better than a fighter. Also solid t2 for a scavenger except you don't really need many skilled scavengers for the actual scavenging. Usually, one member of your dream team should be covering most of your scavenging workload.

Handyman. Solid builder T2. If you already have a tools expert and your mc isn't a R.E.D. Actually weaker than tools expert if you have the best tools available.

Genius. Engineer T2. Another T2 that is weaker than it's T1. It's a solid choice when you need an actual engineer. Occasionally this coincides with MacGyver giving it a bit of a boost. They are BOTH T2 though.

Fearless reclaim. Don't forget to train your fearless reclaimer in defence as well. The perk itself is not too bad, but the hoops you have to jump through to get it make it almost not worth getting. ESPECIALLY if your mc is a R.E.D. That said, if you spotted a character with builder-focused storyline, go for it. This would have been rated higher if it was T2 (and maybe not on a builder list). Could have tied for the second place even... oh well...

Superhero. Lets see... same +5 in total as a MacGyver, but they are spread all over the place, and THAT is a T3 perk? Yeah, no thanks, even some T1 perks give you a better deal. Basicaly if you went for T3 and this is the best you've got than this is NOT a case of good luck - you'd (probably) have been better off with a good selection of T1 perks.

Peacekeeper. If all goes well you will not need this. Still, as far as leadership perks go this is one of the better ones. Still not exactly a shining example of T2 perk.

Defenses expert. Garbage perk. Hell of a lot less useful than how it looks to a newbie. This is because, like I explained already, you should be attacking, not defending. That said, sometimes you will have to defend (from factions that is) but +0.5 defence per builder with a T3 perk is not even funny. Well at least it's better than some other builder perks (like redecorator or artist).

Perks to look for outside of the rare perk hunt:

Negotiator. Must have one of these.

Bookworm. For your scientists.

First Aid. For your fighters. It's an engineer perk though. But obviously engineer has no place fighting.

Preacher. We want this to help with the rare perk hunt, to eliminate devout from the list.

Tools expert. Solid building aid when your mc is not a R.E.D.

Crafter. For your crafters. DUH.

Hoarder/green thumb/good cook. This is only at the bottom of the list because you will find yourself with a lot of them anyway.

Perks of at least some use:

Class: Born leader, fighter class perks

Story: Animal lover, driver, immune, loner (but not for fighters on impossible), team player, ninja.

These are "ok" picks for your locals if none of the perks from previous lists are available. They don't shine but they also don't "suck".

Perks of minor use:

Sceptic (for engineers), devout (for less important survivors, because it can spread and help other survivors in rare perks hunt), ex-faction (very minor), musician, easy going, friendly, fast recovery, camper, half-rations, no rations, loner (for fighters on impossible), tough (very minor).

These are almost a waste of a perk pick, but they are less of a waste then the following list and probably should be taken over those.

Perks to avoid.

Practically useless class perks:

Artist (imho), redecorator (imho), hunter.

Practically useless story perks:

Scholar, coward, eccentric, pacifist.

Negative story perks:

Stinky (it's a def+ perk, yet soldiers can't afford to be dedicated loners on impossible and this makes working with others a hazard), coward (for leaders), pacifist (for soldiers), intense focus, light sleeper.

Negative (imho) class perk:

Redecorator.

Yup. Almost all the time it's just useless. Rarely it's harmful (wrecks event-related buildings). And even more rarely it's useful (turn an actually useless building into a building you actually have a use for at the time). Fun fact - it can actually turn rubble into buildings. But even that doesn't make it worth taking. It's more annoying than negative though.

Non-pickable negative perks:

Addict, cultist.

The perks page lists these as a trade-off perks. Technically they are trade-off, since they DO have benefits. But in total these are purely negative.

AND, (because, evidently, nothing is obvious enough for someone not to think it's not obvious enough...) everything listed as negative perk on perks page is purely negative.

You'd think that'd be obvious enough, but NO... even though these perks don't have ANY benefit, and even though you can't even PICK them (because these perks are never offered as a perk pick in the first place) someone had a bright idea to add one of them here. Making me update this section yet again.

They aren't a huge deal though. Even clumsy, the worst of the purely negative ones, can be worked with.

Fighting.
You DID read the "Initiative" part, right?

So aside from that and some common sense here's a few more things for you to know. (common sense compatibility NOT guaranteed)

If you have pre-leveled characters you can often get away with fighting without scouting first. DON'T Count on it to last, but while it lasts, use it.

If you don't have pre-leveled characters... get on with that scouting. Also get ready to feel the pain. You WILL, at times, have to deal with yellow mission danger levels. This is why we're a doctor. Just don't go orange. And orange a day keeps doctors away, but only because they can't help you once you're dead.

Mission handling in rebuild is wonky. This is most noticeable for zed killing missions. You can use it to your advantage, but this WILL feel like an exploit. Console yourself with knowledge that the game will NOT hesitate when using it to your disadvantage.

The wonkyness itself comes from retaining the difficulty and progression of unfinished missions.

Example - a horde of zombies appears on a tile, you attack that tile, zombies attack you, the horde dies, only one zombie is left. What do we get left with? A mission to kill ONE measly zombie with a difficulty rating still at the level it was at when it was the whole horde out there.

So either we get stuck with a whole army chasing after one zombie or we have to go chill elsewhere while the game is trying to get over what happened there (read: while the mission is resetting).

Example 2 - we have more fighters around then builders, we're about to finish clearing a tile we want to reclaim next, but if we do so now then it will soon re-populate with zed creating anew mission (albeit an easy one) to clear it riiiiiight around the time we can finally spare the manpower to reclaim it. So what do we do? We almost finish the mission but instead of actually finishing it go do something else while we wait for our builder to get free. Once he's about to get free we go back and finish it off. And presto - our wanted tile is ready for the taking right when we're ready to take it.

I'll leave most of the rest to your creativity, but let me just point out that zed killing mission progress does NOT reset when a horde appears there.

Strategically speaking fighting can be separated into 3 parts.

Defence. Or rather counter-offensive which you should already know from the initiative segment. Until your materials get to the point of abundance this is has survival-level priority. Once they do however... Some attacks are not all that worth defending against. I mean if you can defend, by all means do it, but if that is somehow a problem, let the zed take ze tile. What you get left with is a newly lost tile which is not difficult to re-take. It takes less work from your fighters, more work from your builders and you have to pay the materials cost for reclaiming it a second time, BUT it is nonetheless a viable alternative to having your people injured or even killed trying to protect a bloody building.

Expansive offence. Clearing tiles to take tiles. With intent of acquiring crucial buildings (most of the time crucial buildings means farms and apartments, although having one lab is crucial as well), or space for those buildings. This is a key element of your expansion and a big part of your overall development balance. Shouldn't stop till after the point of abundance of fort size. Unless you messed up your effort distribution and your land exploitation can't keep up with your land acquisition.

Excessive expansion. Clearing more tiles then you know what to do with. You CAN afford to slow down this or even stop this temporarily after the point of abundance of fort size if something pressing came up, just not for long. Zed never stop escalating, and these delays WILL cost you.

Scavenging.
Surprisingly little can be said about this.

If you have a pre-trained team try to use that to your advantage. Give your scavenger a ninja sword and send him to snatch all those goodies from under the "competition's" walls.

Same as with fighting you can use pre-leveled characters to save some time on scouting.

If you don't have 'em... well you guessed it, more pain coming your way. Those wimpy normal scavengers of yours can't even take the heat of un-cleared tiles. Meaning that you'll have to resort to scavenging on re-claimed territory for the most part. Which means that your scavenging effort is now also bottlenecked by your land expansion. Which severely cuts down strategic flexibility of your overall development. Yeah, back in the days when taking those pre-leveled monsters everywhere with you wasn't an option Impossible was VEEEEEEEEERY close to it's name even with every single possible exploit (many of which will be left unmentioned in this guide) stacked against it.

One important but kinda un-obvious part is how farming missions are NOT good for you.

Yep, meant it. Even with farms natural output reduced by difficulty you should sill be getting most of your food through the number of farms not through the number of farmers.

Don't waste your manpower. Ether send those idling scavengers to scout, or convert them to some other more understaffed profession. One of the first that comes to mind would obviously be builders. So that you can devote a bit more effort to exploitation of your land including (but not limited to) building more farms. Or soldiers when it's the amount of land that's lacking not it's exploitation. Regardless of what it is, almost anything is better than sitting on yer pitchforks and watching grass grow. Only keep as many scavengers idling around as you feel would be required should the scavenging business "pick up pace again".

Worst case scenario - dual-train a few of them for defense and send them to scavenge where zed still dwell.

Engineering.
Did I mention the importance of having one lab yet? Don't look at me like that.

Surprisingly little can be said about this as well.

Construction and people management are crucial.

Scouting upgrade is pretty good if you can get to it early enough AND you have ninjas/vehicles to use with it.

Just to be clear, scouts themselves DON'T need to be ninjas, or have vehicles. It's the guys that are going to recruit and scavenge afterwards that are going to need that. Oh and kill to. IF you don't have a pre-trained team.

Signposts and searchlights are a nice addition to your recruitment drive.

Farming branch is a nice fuel for your trade. (and thus greatly accelerates the arrival of resource abundance)

And zombie traps let you make good use of said abundance.

And so do medkits (to a lesser extent).

Building.
Heck of a lot CAN be said about this. But I'll try to keep it short by sticking to the more important bits.

You can use excessive building workforce to alleviate pressure on your materials.

Surprisingly I'm NOT speaking about chopping wood. Once you're not quite so all around hard-pressed for manpower, put one, and later two builders on demolition duty.

First priority - demolish the useless buildings. Parking lots, office buildings, clothing stores, the works. Mind the following exceptions:

Fire departments. Contrary to what it says on the tin they do not let you fire entire departments. Nor are they departments that fire you. Instead you use those to put out fires. And just in case we're not clear here, that last sentence was NOT a joke.

Water treatment Plant, Power Plant. I'm listing them here because nothing is obvious enough for some smart-ass not to decide that it is not obvious enough.

Warehouses. Should be obvious if you're reading what you're demolishing, but if you're into burning your letters BEFORE reading them, here's the old news for you - these nice little things expand your food storage capacity. 50 Points per warehouse. Which, in turn, helps you with trading, especially on larger maps.

Xor Gas Station. When Last judgement faction is on the map.

8-11-mart. For the ice cream event.

Parks. Just in case. On the maps where you do NOT border any forest border tiles (yet?).

Also I'm not 100% sure about radio towers and those car-cinema things. I vaguely remember reading about them having some effect after you have a working power plant, but I can't quite confirm that. They DO tend to be relatively rare though, which, I guess, can be interpreted as a hint to their significance. Never felt particularly short on useless buildings even when sparing those though, so what's the harm, right?

Anyway, once you got your hammer time on with all of those OTHER useless buildings, you end up with a sizeable pool of materials and empty space.

Materials you can use on more reclamation. Empty space you can use to build stuff. And all it takes is "your money back" or rather "their" money back. I should probably start at the top with that.

First advantage we achieve with that is that we get a sort of a "credit line" of materials. We're going to have to "pay" those back later if we want anything build, but that repayment comes at no added cost. And obviously our need for materials early on is bigger than later down the line, so that alone is a good deal. Furthermore you don't really have to give all of it back. It's quite easy to end up with more space then your space exploitation can make good use of. And while normally you'd end up with excess space only later in the game, this demolishing line of credits lets you tap into it earlier, when you're more hard-pressed for resources. On top of it razing a building and then putting a different one up from scratch nets you with a total of 0. No materials lost, no materials gained. Wherein converting one building directly into another would cost you 2 materials. The later saves you workload though and thus should be the preferred method once your materials reach the point of abundance.

But wait, it gets better. (or worse, depending on how you look at exploits). If your MC is a construction worker demolishing a building before building a new one from scratch leaves you with parts to spare. Not funny enough yet? Well how about demolishing that building a second time and ending up with even MORE spare parts. Who knew that simple matter such as bricks and boards is capable of multiplying through division? This is mostly just here for laughs though. Just the usual legit -50% to material costs is generally more than enough to completely legitimately solve nearly all of your materials related issues. Yeah, it doesn't have to be an exploit to be op.

Second priority - demolish large buildings. Somewhat opposite to the above this should mostly be done if you're coming up short on space, but not quite short on housing/food yet. This is because large buildings are NOT space-efficient. The ones that take 2 times the space give 1.5 times the benefit. The ones that take 4 times the space give only 2 times the benefit.

So should you find yourself with free builders, need for space on the horison and nothing new to reclaim in the vicinity, this is what you should attempt as a stopgap measure. For a more serious cases of the same you'd need a more lasting and permanent solution though. Namely - converting some builders into fighters. But if it's not TOO bad (and only temporary), you should stick to this instead.

Watch out for their strategic importance though. A large building bordering a not quite friendly faction can make defending from them easier. If it's only bordering zedlands though, don't bother. Defence against zed is NOT a happening thing on impossible difficulty.

Leading.

Don't think I WANT to say anything about this. Oh well, here goes...

If you don't have pre-trained people with you, get a high level leader ASAP. First time you see a radio in trade buy it (Unless your leader is already at 8). Sell something if you have to (long as that something isn't crucial).

Consider making you MC that high level leader.

You'll want one that can take the heat, and normies can't take the heat without going through the whole dual class school regiment. You could just send them out with "armed" escorts though.

Another added bonus to making it MC is that you don't end up with a person that has nothing to do (but scout) half the time.

Regardless of HOW you do it, it's of key importance that you DO it and do it ASAP. I'm not even going to bother listing all the reasons for it here, if you're not familiar with those yet you're not ready to play impossible yet either.

Second order of business get your leader a ninja sword, or a vehicle. You want to be able to grab those yummy survivors half the map across.

This is more or less the same as with scavenging except this time it is more important and less demanding.

Did I mention negotiators yet? Blink-blink. Go get one. Unlike the above case though you don't need vehicles or ninja bodyguards for those.

Doesn't have to be the same guy as your high level leader either, but in this case you'd want to send them out to trade as a pair.

That diplomatic mission will have 2 somewhat competing goals - building up relationships with factions and milking their trade assortment for all it's worth.

The first is best done buy showing up to trade giving them 1 apple, and then when the trade ends saying "nah, they can keep it". That's 5 respect points per visit. 10 if your MC is a Rock Star.

Visits CAN give you more if you're lucky, or they can give you nothing if you're not. This one-apple bribery however is stable. But mostly it's recommended for when your own stock is dry and you can't really milk that faction for what it's worth.

The second is best done by showing up at their doorstep with warehouse choke-full of apples. Apples aren't going to stockpile themselves infinitely. So go and take their materials in exchange fr your apples. Then their fuel and useful equipment. Then, apples permitting, everything else, including useless equipment. BUT make sure to leave them one of either fuel, materials or nothing. In that order of priority. When the trade ends the negotiator perk will trigger (it ALWAYS does if the conditions are met) and you can get more fuel or more materials for free. If they had neither fuel nor materials for sale and aren't at 100 respect points yet, don't bother taking their food. Pick "nah, they can keep it" instead for extra respect.