XCOM 2 Analysis: Map Overview

One of the more broadly relevant improvements in XCOM 2 is that of its approach to map design.

First is the point that XCOM 2's map design is built with more of an understanding of not only what can be done, but what actually behaves well. The engine, in Enemy Unknown/Within, was capable of producing smoothly sloping terrain, and could animate units moving along it just fine, but slopes were, in practice, unbearably terrible to make heavy use of because the engine couldn't do things like have units use Cover if their tile was part of a slope. As EU/EW's maps were quite fond of heavy slope usage, this led to a lot of jank, where sections of the map were basically traps, because they looked like they should be good Cover but were actually no Cover. It also noticeably hurt the value of Alloy SHIVs functioning as mobile Cover, as it was easy to drop an Alloy SHIV into a spot, then move a soldier adjacent, and whoops one or the other is on a slope and so the mobile Cover behavior broke!

XCOM 2 is much more careful about slope usage. They still see use, but they're a rarity, and their placement is a lot more considered -it wasn't just that slopes broke Cover behavior in EU/EW, it was that map designs were bad about being designed so it was a natural error to run into. The observatory map has an excellent example, where a ramp goes up around a secondary building, and specifically the ramp starts right from the building's corner; this is the exact spot one would want to position a soldier to peek around the corner from good Cover, and if you try that the soldier will not be in Cover at all and also won't engage in step-out behavior, potentially preventing you from firing on a target you were expecting to be able to fire on from there. XCOM 2's slopes, when they show up at all, are almost always designed so you have no real reason to think of stopping anywhere on the slope. (Or more accurately that it takes edge cases for such to crop up, instead of it being a constant problem)

Height is another great example. EU/EW has several outdoors maps for smaller UFOs that have significant visual variability in height, but where the primary mechanical impact is to make it harder for SHIVs to move about in Enemy Unknown; on some of these maps, it's impossible to trigger the height advantage Aim bonus without flight or climbing atop the UFO itself. (Which isn't something you're really intended to do; no Cover up there, for one) XCOM 2 's map design embraces artificiality in pursuit of clearer gameplay: height deviations in XCOM 2 occur almost exclusively in 'height advantage steps' -that if a unit is standing above another unit, it almost certainly has enough height to trigger the Aim bonus. The primary exception is intuitive enough; shallow water, such as rivers, will be slightly lower in elevation than surrounding terrain, so slight an elevation difference it doesn't feel like it should trigger a height advantage mechanic, among other examples of slight height differences that are understandable to use.

More generally, XCOM 2 is a lot more clear on the map design implications of its mechanics/engine/number tuning. EU/EW maps suffered frequently from Cover placement not being spaced appropriately to actual unit mobility and action point economy; with the way both games are constructed, ideally any given piece of Cover has at least one other piece of Cover close enough that a unit with 12 Mobility can move to it without needing to Dash, preferably at least one example of such in every direction. EU/EW maps were... unreliable about holding to this metric, with it being common for maps to have isolated 'islands' of Cover that were never going to see real use because of how inconvenient they were to reach at all, and more problematically it was common for visually dense environments to nonetheless have Cover spaced and positioned such that advancing safely and efficiently was impossible at certain points. (The highway maps were particularly terrible about this; I'm intensely glad XCOM 2 never tried to make its own highway maps)

Whereas XCOM 2 is a lot more consistent about spacing adequate amounts of Cover adequately close that consistent, safe advancement is almost always possible. It's difficult to communicate what a massive improvement this piece alone is.

This is particularly surprising given one of the grander changes made; where in EU/EW, there was a list of completely fixed maps (Which was really obvious with eg Battleships, since they used so few maps compared to how often you might down them), in XCOM 2 maps are procedurally generated. Procedural generation is usually where this kind of tuning goes wrong, because devs don't know how to implement the design rules into the procedural generation directly, and don't think of how to use other rules to effectively arrive at the needed design anyway.

Indeed, the procedural generation of maps is one of XCOM 2's most impressively competent elements in general, and a huge boost to replayability. It's also one of its elements that's easy to overlook if you only play a handful of runs total, in the sense that EU/EW wasn't too terrible on repetitiveness within a single run due to how many maps it had vs how many missions a run expected to do in total (Unless you were playing Long War, of course...) and it's easy to assume XCOM 2 employs a similar solution rather than recognizing that it's employing procedural generation, but if you play 6+ runs it becomes very appreciated.

Said procedural generation being a notable part of what this post is delving into.

So first of all is what the game internally calls plot types. Broadly speaking, this can be compared to how EU/EW had map 'pools', where a given map was assigned to one or more mission types as a valid possibility; it's a big part of how the game ensures maps end up coherent visually/narratively, as assorted sub-components of map generation have assigned plot types to make sure everything is in 'theme'. eg City Centers have potted-plant trees that are clearly pruned and whatnot to get a specific, uniform look, whereas wilderness environments have wilderness trees growing straight out of the ground with a variety of exact appearances, and you won't find a given tree in the other environment where it would look out of place.

A lot of the implications of plot types are chiefly aesthetic, but there's actually a number of gameplay implications that are useful to keep in mind, hence part of why this post exists.

So let's start with XCOM 2's most iconic plot type, the one the game always introduces you to:

City Center

Okay, I say the game starts out by introducing you to this plot type, but that's a bit misleading given the Tutorial mission is a fixed map that includes elements you'll never see in a procedurally-generated City Center map... but non-Tutorial Gatecrasher is properly using procedural generation, and the tutorial is mostly using map elements City Centers use. (Though you'll never see a City Center map happen to generate the Tutorial mission layout)

Anyway, the City Center plot type of course represents densely urban ADVENT-controlled territory. Well, in practice it more represents the portion of an urban city more at the edges; high-rise buildings are visible in the distance of City Center maps, but a map will never have actual gameplay buildings more than three stories tall; with the scale XCOM 2 operates at, a single high-rise would be an entire map unto itself, and quite a large one at that.

Anyway, as such the City Center plot type is thus restricted to missions striking into ADVENT City Centers -which is very few. Only Gatecrasher and VIP-related missions use the City Center plot type; the second-to-last mission conceptually takes place in a City Center, but it doesn't actually use the City Center plot type. In the base game you'll thus see the City Center plot type once a month like clockwork, except for the first month where Gatecrasher adds a second case. War of the Chosen adds three new mission types for VIP missions, none of which use the City Center plot type, so it's noticeably rarer in War of the Chosen -especially since the very first VIP-related mission is, in War of the Chosen, forced to be an intro on Lost, and so in War of the Chosen your first VIP mission will never take place in a City Center!

As for actual mechanical stuff...

Well, first of all, City Centers are by far the most consistent plot type about having security towers. I'm pretty sure City Centers are actually forced to place security towers on the map. Furthermore, City Centers tend to generate such that security towers are actually interfering with the most direct route to the objective; other plot types that can have security towers are much more prone to placing them such that retaining squad Concealment doesn't require Hacking them or taking a more roundabout route. So ideally you'll bring Specialists into City Center maps; in War of the Chosen, a Reaper is also notable once you have Reaper Infiltration so they can scout directly through security towers.

Second, City Centers are strongly prone to scattering civilians about. For most purposes you don't really care about civilians if you're not in a Terror mission, but there are three reasons to care: the Infestation Dark Event, the Alien Infiltrator Dark Event, and the fact that civilians actually have a detection radius!

Alien Infiltrator for the obvious reason; if it's active, there will be Faceless in City Center maps, and you should keep your distance from civilians, especially in the base game where they can attack the same turn they reveal themselves. Infestation because Chryssalids are willing to attack -and thus infest- civilians even if the civilians are supposed to be ADVENT loyalists! (And this or a Beastmaster Chosen summoning Chryssalids are the only ways to see Chryssalids in City Center missions; no, Savage isn't a qualifier, since Sitreps can't trigger on VIP-related missions)

As for the civilian detection radius, it's... a bit awkwardly handled. You mostly don't actually care about it; the detection radius on civilians is tiny and civilians rarely generate at or near chokepoints or key Cover locations. So most of the time the fact that they have a detection radius is basically a cute detail, not something that actually matters.

Buuuut there's a couple notable qualifiers that are liable to ambush a learning player -or even an experienced player, honestly.

The first of these qualifiers is the consideration of dropping from high ground while Concealed; your soldiers atop a building can't actually see civilians who are inside the building just on the other side of a window, but will be spotted by said civilians as they drop, breaking squad Concealment. You can work around this a few different ways, such as having a 'spotter' who stays at ground level to keep an eye out for civilians, or making an effort to never drop down next to windows... but it's janky regardless, and it's incredibly frustrating to activate a pod prematurely because a cute detail suddenly actually mattered in a specific edge case.

The second qualifier is the consideration that clusters of High Cover can block line of sight to civilians, and the game's 'fog of war' doesn't actually fade such spots appropriately. This makes it very easy to advance someone to a location that looks like you can see into it just fine and it has nothing in it, but whoops it actually has some civilians just barely close enough to spot a soldier taking Cover! This is exacerbated by the game's step-out mechanics working against you, as civilians won't be visible if they're standing on the other side of High Cover because they don't use Cover and so don't use step-out mechanics, but will still be able to spot a soldier who takes Cover near them because of the soldier using step-out mechanics. (In general, step-out really shouldn't have contributed to detection radius in this way; I don't use it, but I totally understand why a mod exists to make corners safe to approach. For the base game, too!)

Less obvious and, thankfully, much less frustrating is that civilians do have some limited post-Concealment relevance, as they 'yell' when fleeing from your forces approaching them. This can be heard by nearby pods and put them into the 'yellow alert' state, potentially drawing them to your location and making them slightly less vulnerable to Concealment abuse; it barely matters, but at least it never breaks in a frustrating, mildly nonsensical way to screw you over.

Layout-wise, City Centers are generally a bit flatter than most plot types if one ignores destructible terrain. That is, the actual solid ground is generally primarily or exclusively all one Z-level, where eg Wilderness will often have clifftop regions of solid ground giving high ground advantage, and in fact will often have three layers of such. (Whether that's high ground atop high ground, or valleys of especially low ground in addition to high ground clifftops) It's not unusual for there to be two such Z-levels in a City Center map, but when it does exist it tends to either be a clear boundary that provides only limited opportunity for the high ground Aim bonus to matter (Because you go up or go down and then move on from the meeting of Z-levels) or for it to be a brief stretch of highways crossing over a 'valley' of low ground, once again giving limited opportunity for the high ground Aim bonus to matter. It's mostly buildings that will provide high ground -and they're very destructible.

City Centers are also where you'll see vehicles regularly, though thankfully never as the primary Cover option like some EU/EW maps. The actual handling is slightly silly, in that the streets are organized as if time was stopped in the middle of ordinary daily traffic, but a more realistic framework would probably have been a huge pain to implement and would definitely have been maddening to play (You'd, what, have a random chance to be hit by a car when trying to cross a street?), so whatever. In any event, this handling means vehicular Cover is often relevant, but if you don't want to take the risk, it can usually be avoided -City Center streets generally have Cover objects on each side of the road, and the roads themselves aren't very wide, where it's feasible to jump from Cover on one side of the road to the other. Vehicles themselves are also much less horrible of bombs than in the prior game; for starters, the visuals for whether they're going to detonate soon or not are much clearer (Fire billowing out of the engine area, as well as a very distinctive sound effect when it first starts), and for another it's much rarer for weapons fire to instantly detonate them. Generally, even multiple missed shots clipping a vehicle will still lead to a delayed detonation, not an immediate one.

This is good, because 3/5ths of the standard mission types that use the City Center plot type have the objective mandate interacting with a vehicle on a road.

That said, do be wary once you're in the very late game. Andromedons, Sectopods, and Gatekeepers (When they elect to fire...) are all capable of instantly detonating a vehicle with a missed shot, and Andromedons that throw a punch will instantly detonate every vehicle around them. They also all have Wall Smash, and this can lead to them detonating vehicles just by walking near them. Taking cover against a truck is reasonably safe for most of a run, as even multiple missed shots from Troopers, Officers, Vipers, etc, will generally not detonate a vehicle immediately -and a lot of enemies are reluctant to fire their firearm anyway, like Codices. But in the late game, it's pretty dangerous; I personally just make a habit of avoiding using vehicles as Cover if possible, period, to avoid habit getting me in trouble in the late game.

Anyway, City Centers also tend to be made of several quite large buildings. With the vast majority of such buildings, the rooftop is very accessible, with multiple climb points spaced all around the edges, and sometimes including ladders (Or, more rarely, stairs) inside to get up top. Grappling -and SPARK and Icarus Armor mobility- are still very nice to have, of course, but where EU/EW were inconsistent about letting you access roofs at all and tended to have only a handful of widely-spaced climb points when the roof was possible to climb to at all, in XCOM 2 being near a building virtually always means you're at worst within a Dash of the building's rooftop. There's a few uncommon building designs that break this rule -which can be an unpleasant surprise if you've gotten used to assuming that ready rooftop access is a given- but you can go entire runs without ever having this matter. So Grapple access is a little less significant than you might be used to coming in from EU/EW.

It should be noted that Turrets are possible in City Centers, but surprisingly rare. Turrets are primarily associated with ADVENT infrastructure, and ADVENT facilities are actually quite rare in City Centers. Of the five standard mission types that use the City Center plot type, three of them can't have ADVENT facilities at all. One of them -Neutralize Target- forces an ADVENT facility of some kind, but the other -Rescue VIP From ADVENT Cell- actually usually has the cell in question tucked inside a non-ADVENT building. As in, they will literally be locked up in a department store, that kind of thing. And Gatecrasher will never have Turrets.

Usually if you see Turrets in a City Center plot type, they're attached to an ADVENT checkpoint, which can be plopped down almost without regard to mission type. So if you spot ADVENT barricades, be aware that Turrets might be nearby. (But probably aren't)

Overall, City Centers are one of the better plot types about showing off XCOM 2's procedural generation. If you play enough, you'll start recognizing individual buildings, but only a few layout pieces are sufficiently large and rigid for recognizing them to really let you draw conclusions about terrain your squad doesn't have sight on. It's really nice!

On a different note, I have slightly mixed feelings about the exclusivity of the City Center plot type: from a narrative perspective, it's very much a good thing, as X-COM is supposed to be waging guerrilla warfare on a global superpower with superior technology, inhumanly tough soldiers, and myriad other advantages. It would be pretty terrible if the majority of missions were striking deep into firmly ADVENT-controlled territory, running strongly contrary to the narrative placing the player as the underdog.

On the other hand, the City Center plot type is overall my favorite plot type to play in, if we ignore the complicating factor of what missions are tied to City Centers. (Which I tend to dislike, unfortunately) The aesthetic is distinctive and great, the tuning of Cover spacing and whatnot is almost always good (And when it's bad, it's only a little bad), XCOM 2's use of verticality is in full force as something to engage with in a substantive way, and it's very rare for any two City Center maps to end up feeling like basically the same thing as each other. No other plot type is so consistently great in so many ways.

It's a little sad XCOM 3 is extremely unlikely to make City Centers a bigger part of gameplay. Indeed, I won't be surprised if they go away entirely... heck, Chimera Squad is supposed to take place in a city center, but diverges significantly from the City Center aesthetic.

Alas.

Small Town

'Small Town' is one of the more interesting plot types to me on the level that the procedural generation tends to end up producing what feels convincingly like an implied little story that varies quite a bit.

Sometimes, as the image I used here points to, a Small Town map comes across like an area of ex-resistance or ongoing resistance, where the locals are rejecting ADVENT and ADVENT is using force to pressure them to reconsider their stance. Smashed buildings, little or no civilian presence, a general state of disrepair suggesting essential services like trash collection have been cut off... that kind of thing.

Other times, a Small Town seems to be in the middle of transition, with ADVENT modular construction and security towers popping up inside an otherwise small town sort of environment. It's easy to imagine that groundwork is being laid to convert the area into a more City Center-type environment, with checkpoints and security towers and whatnot as the earliest construction in the process.

Still other times, a small town seems to be tied into the larger ADVENT regime in its current form, such as by being a place ADVENT trains can stop to refuel at, or having an ADVENT facility right alongside the residential buildings, suggesting local civilians probably work at the facility you're raiding.

I'm not 100% sure these different apparent narratives are really intentional, but it's an interesting outcome regardless, and unusual -other plot types don't tend to lend themselves to a variety of procedurally-generated implied stories.

Anyway, mechanically, Small Town often has security towers and civilians, but neither is guaranteed. They're also only rarely actual problems -civilians in Small Town maps tend to be clustered in the open, highly visible, meaning they're very unlikely to get your squad Concealment broken unless you're careless in general, and they're also only rarely positioned to block off access to Cover you might care about. By a similar token, security towers in Small Town maps tend to be only mildly inconvenient: there's rarely real chokepoints, and security towers aren't particularly prone to getting placed near any chokepoints that do exist. (eg alleys between houses) They might block off access to some High Cover while you're in squad Concealment, but that's usually the worst you'll see.

High ground tends to be common across a Small Town map, but it also tends to be dubiously useful for non-SPARKs, as a lot of it is the roofs of houses, with nearly no Cover and said Cover being poorly-placed, like solar panels toward the middle that struggle to get line of fire on nearby enemies at ground level. There's usually an ADVENT facility on the map with Cover around the edges, but it also is typically where your objective is, limiting the usefulness of this high ground. So Small Town maps are one of the more subtle reasons to consider SPARKs... though keep in mind that Small Town infrastructure tends to be frail, such that a SPARK standing on a house's roof is basically guaranteed to take fall damage if even a weak Frag Grenade is tossed their way. Maybe don't take to high ground with your SPARK if you aren't going to be firing the cannon that turn.

Sometimes you'll get high ground in the form of cliffs, but usually this is specifically a valley; you might find a pod in the valley and successfully ambush it with height advantage, but it's not something to count on, and you're very unlikely to get high ground against multiple pods from such. It mostly will be from civilian buildings and maybe ADVENT infrastructure.

Sometimes, you'll get a Small Town map with more or less no relevant high ground at all; there's a few Small Town-exclusive segments that don't include high ground, or where the high ground can easily end up irrelevant or is extra-dubious for non-SPARKs, such as a graveyard layout that has only a mausoleum for high ground, where the graveyard is large enough that someone standing on the mausoleum needs Squadsight to be able to target the further parts. (And also the mausoleum has no climb points and its Cover situation is pretty horrible up there) This doesn't happen too often, but you shouldn't assume you'll get high ground.

Outside that, Small Town tends to be one of the best plot types for sniping; there's often only one or two exceptionally tall buildings on the map, and the non-building portion of things tends to be fairly flat. As such, a Sharpshooter climbing atop an extra-tall building is surprisingly likely to have clear lines of fire to almost the entire map. Mind, Squadsight penalties adding up limits the viability of this strategy, but the point is that most plot types have much messier line-of-fire situations, where a Sharpshooter taking a good-looking chunk of high ground is distressingly likely to end up unable to draw a bead on pods the rest of the squad activates. This is much rarer of a problem in Small Town maps.

Anyway, I mentioned ADVENT barricades and security checkpoints and all, and that means Small Town is another plot type where Turrets can be found lying about, away from the actual objective. It's not particularly common, but it can happen. So maybe be cautious if you spot ADVENT barricades, as a Turret or two might be in the area. (But probably isn't) Not that Turrets are a big threat in the first place, but if you're already engaged with a pod, they can be an additional complication you don't need.

Overall, while Small Town isn't as consistently great as City Center, it's still a plot type with a solid amount of real variety. I tend to enjoy missions using it to an above-average extent.

Wilderness

'Wilderness' is one of the most common plot types for any given run to encounter -which isn't necessarily intuitive, as Supply Raid variants are the only standard mission type that use Wilderness, and they only occur every other month!

Nonetheless, Wilderness gets used for all three plot missions -the Blacksite, Forge, and Psi Gate missions- as well as both Avenger Defense variants, and Avatar Project Facilities, and rescuing captured soldiers. So you'll see it quite a bit more often than every other month. If you have the Tutorial on, your second mission is also a Wilderness mission, for that matter.

Wilderness is also a bit misleading of a name in practice, as it's actually pretty uncommon for a Wilderness map to be dominated by... well, wilderness. Most missions using the Wilderness plot type are isolated and secret ADVENT facilities that sprawl quite a bit; the Psi Gate, Avenger Defenses, and some Supply Raid variants are legitimately occurring in basically-untouched wilds with at most a road or train track passing through. (Also the second mission for a Tutorial-enabled campaign) 

And even with all of those, the game is perfectly happy to plunk down cabins, rusted transformers, and other human infrastructure. Generally it appears to be abandoned, yes, but my point is it's entirely possible to have a Wilderness map that's about as urban as a Small Town map, even when it's one of the missions that doesn't force in significant ADVENT infrastructure. To the point I suspect some players think Wilderness and Small Town are the same plot type.

Anyway, in spite of the tendency for ADVENT infrastructure to show up on Wilderness maps, you'll actually never see a security tower on one. Which makes sense given that it's hinted they're really there to scan civilians in city centers; if there's not supposed to be civilians around, no need for a civilian-scanner. It does feel weird in conjunction with the holographic wall bits reacting to units passing through them but not functioning as any kind of security system, though.

Oh, and as I just alluded to, you will normally not see civilians on Wilderness maps. They can be forced by Sitrep, but regular civilians don't happen. No hunters wandering the woods, no hikers out for a jog, nobody out collecting mushrooms... it's actually a little silly if you think about it, but whatever. XCOM 2 does drop hints of explanations for bits and pieces of this, but more importantly it's clear flavor and mechanics -and anyway Wilderness maps are often supposed to be taking place in areas ADVENT wouldn't want civilians getting anywhere near anyway. Simpler to just not have civilians on the plot type at all.

In terms of terrain, Wilderness is the plot type heaviest on indestructible high ground, via sheer cliffs of solid ground. In particular, it's the plot type most prone to the indestructible high ground being positioned so it's persistently relevant -for example, Supply Raids on trains or convoys quite often have the train or convoy bracketed by indestructible high ground, with rocks and trees intermittently placed right at the edge of the high ground, with enemies tending to patrol down near the train or convoy. Thus, you can fight multiple pods in a row from high ground, while retaining Cover access, with said high ground being safe. (In the sense that a grenade won't add in fall damage) This will sometimes happen on other plot types, but it's much rarer.

Interestingly, a lot of Wilderness-specific elements are destructible, but tough enough it's easy to think they're actually indestructible. Rocks in particular tend to be quite durable -which is then made even less clear by the presence of rocks that are indestructible, without necessarily looking particularly different. This probably could've been handled better.

On a related note, Wilderness is fond of its huge High Cover trees -some of them are multi-tile affairs, even- and they are... weirdly janky. Destroying them when an enemy is taking cover against them often results in the game on almost every level conveying the enemy is in the open -their Cover icon turns into a yellow shield, they switch idle animations from 'in cover' to 'exposed', and so on- but if you try to line up a shot it's aggravatingly common for the High Cover benefits to nonetheless be applying as if the tree were still standing.

I'm not sure why it's trees in specific. I've only ever seen this from trees in Wilderness, and potted trees in City Centers; other High Cover objects that can be fully destroyed behave as expected. My best guess is it has to do with trees having the semi-unusual property of being able to degrade when taking damage -most objects flip straight from 'fine' to 'destroyed' with no in-between graphic, where trees will lose their leaves and often have other apparent changes when initially taking damage. (Like splitting open down the middle)

In any event, as a result I personally basically treat trees as indestructible objects, in the sense that I'm not going to try to blow up their Cover to get a clear shot, but rather am going to try to flank, pull the target out, etc.

Wilderness is also one of two plot types strongly prone to having mechanically-relevant water. That is, City Centers are quite fond of having stuff like decorative pools of water, but these are not only decorative in an in-universe sense but also a gameplay sense: you can't actually send soldiers through such patches of water. Shallow rivers, meanwhile, are reasonably common on Wilderness maps, can be walked through by soldiers, and are an example of water tiles that will cause units walking through them to stop burning, as well as causing units standing in them to be impossible to set alight.

Mind, purely-decorative water can still occur on Wilderness maps. You'll see deep rivers that cannot be passed through except by flight or Grappling, the edge of the map can be delineated by hitting impassable ocean, waterfalls can occur and the waterfall per se is simply impassable terrain... don't assume water is mechanically water just because it's in Wilderness.

It's also worth pointing out that explosive vehicles are more common than you might intuitively expect of the Wilderness plot type. Multiple mission types that use Wilderness force explosive vehicles to be present, and still others don't force it per se but can have such present. (Avatar Project Facilities will sometimes have a road with cars on one side of the building, for example) Even when the mission type doesn't include such, derelict cars are still valid to be placed, and in spite of being ancient rusted hulks that probably have little or no gas inside they still will go off like a bomb if shot at. Never mind that cars don't actually explode when shot in the first place...

Overall, Wilderness is actually one of my least favorite plot types, which is a bit of a surprise given I overall preferred EU/EW's maps set in wilderness to its other maps, generally speaking. Among other points, Wilderness is the plot type from the base game most prone to feeling same-y, where the map isn't actually a clone of the last two Wilderness maps you saw but it doesn't actually feel particularly different from either of them. Which makes it a bit unfortunate that it's the plot type you'll encounter most consistently throughout a run...

Shanty

Shanty is a bit of a weird plot type, as it's technically extremely exclusive -it's only used for Retaliation missions- but it overlaps so heavily with Wilderness it's easy to assume Retaliation missions are just using the Wilderness plot type. The Resistance camp setpieces -camper vans, overgrown buildings used as makeshift housing, and all the other stuff representing civilians living in the woods, away from ADVENT- are the only parts that are Shanty-exclusive, and it's not unusual for them to take up only a relatively small portion of the map. The new Retaliation variant added by War of the Chosen is particularly prone to having just a couple clusters of Shanty-specific objects surrounded by Wilderness components, but even in the base game this kind of thing can happen.

Of course, one can point out that maps using the Wilderness plot type generally have ADVENT terrain of some kind, where Shanty has only a limited selection of ADVENT elements it's willing to use. You'll never find an actual ADVENT building on a Shanty map; at most there'll be a parked ADVENT convoy. (Which, bizarrely, can include the Chosen artillery gun if you're talking War of the Chosen)

Indeed, as far as the terrain itself goes, it really is largely accurate to think of Shanty and Wilderness as equivalent, as there's civilian infrastructure pieces in Wilderness maps, and they tend to be very similar to Shanty civilian infrastructure in tactical implications.

Of course, the lack of ADVENT elements is mechanically notable right away due to ADVENT Turrets: in the Wilderness plot type, Turrets are common. Not guaranteed by the plot type, but you'll see them more often than not. Shanty, meanwhile, can only generate Turrets in the uncommon event of generating an ADVENT convoy on the map -and even when such a convoy generates, it's not guaranteed to include Turrets.

Shanty also has some genuinely unusual pieces. Probably my personal favorite is a landed UFO that's apparently been gutted, boarded up, and is being used as a fortified location by the camp. I'd personally expect its internals to be used as a shelter from the elements and all, but still, I do like the idea that occasionally a camp has formed around an abandoned UFO and repurposed it in the very basic way of treating it as just a chunk of sturdy terrain.

Anyway, as a concrete example of Wilderness overlap, Shanty is the other plot type that regularly has mechanically-relevant water via shallow streams. I'd say this is a reason to not bring Flamethrowers or Hellfire Projectors into Retaliation missions, but while it's technically true it's not really relevant given they're inherently bad and are a hazard to civilians and all... you shouldn't be bringing them for much better reasons, is the point.

It's also worth pointing out that Shanty buildings are more consistent about having widespread Cover along the roof's edge than non-ADVENT Wilderness buildings. As civilians tend to spawn near said buildings, destructible high ground with Cover is relevant more consistently in Shanty than Wilderness. Indeed, Shanty is one of the plot types Grapples are most prone to really shining in. Just beware grenade-carrying enemies.

Aesthetically, I'm unsure how to feel about Shanty. My first response was to be pretty unhappy with it -Shanty is a depiction of the Resistance, the people providing X-COM Supplies, and in the base game presumably where you're buying personnel from when purchasing them from the Resistance HQ... and said Resistance lives in literal shantytowns. Meanwhile, the player faction of X-COM flies around in the shiny, futuristic Avenger, has a standardized Star Trek-ish uniform in good condition for people aboard the Avenger, is kitted out with increasingly advanced technology produced entirely internally, and... still needs to badger literal shantytowns into giving to the cause, even though there's no way they can spare much. In particular, rescuing civilians actually raises your income; you somehow leverage a brutal attack on a literal shantytown into the shantytown giving up more to the cause!

This feels a bit like playing a CEO jetting around in their personal plane and begging the poorest segments of the population to please donate to me. ie completely horrible. Only it's more like a CEO jetting into a warzone and asking people who just last week had bombs dropped on them to please donate, so even worse than my first example sounds.

War of the Chosen helped noticeably in a few different ways. The introduction of multiple Resistance factions, who seem to be doing better than living in literal shantytowns, helps fill out the world such that it's more plausible to assume that Shanty isn't 'this is what everyone resisting who isn't aboard the Avenger looks like'; I can now readily assume ADVENT is targeting the most vulnerable camps, and in turn assume the Supply drop-off is funded more heavily by people who aren't in such a bad situation.

The introduction of a new Retaliation type where the shantytown being attacked has its own defenders also helps a lot, as it logically implies the camps have a bit more to spare than the base-game Retaliation suggests.

Also notable is the Retribution action on Chosen: the game still retains the ick factor of ADVENT raiding shantytowns being good for your bottom line by virtue of causing the Resistance to give more in spite of having been attacked, but at least now there's a form of crackdown that negatively impacts your Supply drop, thus showing a recognition that the Resistance's capacity to give is in part affected by how much they have.

The addition of Covert Ops, and specifically Supply Runs, also helps, giving X-COM a bit less reliance on being funded by generous donors. Indeed, in War of the Chosen Supply drops are often a relatively token payout; even on Commander difficulty, I sometimes skip picking them up for a month because 98 Supplies (Or worse) is not a great investment of scanning time. In conjunction with VIP missions no longer being consistently provided by the Spokesman, in War of the Chosen it doesn't feel like X-COM is funding itself almost exclusively through generous donations by an oppressed population that has little to give. (The Black Market is a minor portion of your funding, and is attached to the broader Resistance, and Excavating the Avenger isn't that large a chunk of your income; the only other income sources are the ambiguous Supply payout from completing various mission types, and the much clearer payout from Supply Raid, which are uncommon and not that large a payout in Supplies)

It's not perfect -it's still incredibly gross to get funding increases through Retaliation missions occurring- but it does make me less bothered by the Shanty plot type's aesthetics...

... but I do think it would've been better for something more like Small Town to be the visuals for Retaliation missions. Or at least a possibility for them, instead of Shanty being the only possibility.

I'd say something like 'I hope they get this right in XCOM 3', but honestly, XCOM 3 will likely have a radically different context with no possibility of repeating this particular bit of awful. Like, EU/EW having rescuing civilians increase your income was a little weird, but in their context it could be argued that there were members of the Council of Funding Nations who were fence-sitters who absolutely could spare more for the X-COM Project but weren't really taking the alien invasion seriously, and who were convinced to give more by your effectiveness at fending off a brazen assault by clearly hostile aliens. By a similar token, if XCOM 3 is an interdimensional alien invasion, and returns to 'you are defending Earth and funded by nations who aren't necessarily fully behind your project', then repeating this exact mechanic won't repeat XCOM 2's problems that are tied up in the mechanic.

... though if XCOM 2 ever gets a remastering or similar, I'd certainly hope this element would get reworked to stop being gross.

Slums

Slums are broadly like City Center maps in their mechanical implications, with lots of buildings to climb or duck inside, security towers to Hack, civilians more or less always present, and very similar distributions of Cover and whatnot. They're alike enough I actually didn't realize they were separate plot types at all until until I was assembling these mission-related posts!

I wish the distinction was better communicated to the player, because how the game distributes these two plot types is pretty telling: where City Center is exclusively used for missions where you're rescuing or kidnapping a high-profile ADVENT individual who appears to be of higher education (Given that friendly VIPs will always be Engineers or Scientists), Slums are exclusively used in Guerrilla Ops, with all other plot types used by Guerilla Ops unambiguously being cases of ADVENT having comparatively limited control over the area.

This strongly suggests the Slums are, in fact, meant to be neglected by ADVENT all-around, with much lesser security than the City Center plot type represents. This is also consistent with mechanical details; with City Center missions, you have a hard time limit to evac, with Bradford indicating the reason why is that fighter craft are scrambling, and the Skyranger has to leave in that time limit or risk being shot down, and anybody still on the ground when time is up is simply lost. With Slums, timing out will fail the objective, but your team can (Going by mechanical implications) still kill all the enemies, drag their bodies to the Skyranger, and leave at a relatively leisurely pace.

This also suggests that broadly the citizens in the Slums are somewhere on the range of 'apathetic' to 'actively hostile' to the ADVENT authorities, implying civilians in the Slums at minimum aren't trying to call ADVENT 'peacekeepers' in on X-COM, and possibly are actively colluding with X-COM! Which in turn also indicates that the game isn't holding itself to a simple binary of 'ignorant citizens who think everything is great' vs 'people actively rejecting and resisting the occupation', but something a bit more nuanced.

This kind of thing is a big part of why it frustrates me it's not more clearly communicated. Among other points, a big part of what the game does to make Slums look bad is to give them dimmer lighting than City Centers... which is then hidden by the game actually having the day/night cycle tracked on the Geoscape and applying appropriate lighting to the tactical battle with no mechanical implications. A City Center plot type at night and a Slum during daylight have relatively similar lighting, and with no mechanics attached there's no reason for the player to pay attention to whether things are currently dark because it's night or dark because the plot type just defaults to being dark. (I can contrast this with classic X-COM, where night fights constricts player unit vision; you're not going to stay confused for long on whether a map's palette is just naturally dark or if it's dark from being in a night fight)

There is a way to draw a clear line between 'dark due to innate lighting' vs 'dark due to night'; your soldiers all have flashlights mounted on their guns that aren't used in response to a darker default lighting... but honestly, I didn't actually notice this until I ran into a mod that restores flashlights on ADVENT forces, where the mod talks about the flashlights your troops have. Nor is it necessarily obvious what triggers flashlights. And in War of the Chosen, underground maps force the flashlights to be on regardless of time of day...

All of which is to say I suspect not realizing City Center and Slum are distinct is actually pretty common. And unfortunate, given the narrative elements hinted at by the handling.

This also actually ties into me ultimately being less grossed out by the Shanty plot type: with actually recognizing that Slums are a distinct plot type, and the implications of how the game organizes it, this actually directly suggests a non-trivial portion of X-COM's support comes from citizens in Slums. Still the poorer part of the population, yes, but not so desperately poor as Shanty civilians, and a popular revolt against authorities does by default mean the rebels are the underclass; my issue with X-COM getting support from poor folks isn't that it's a thing at all, but the conjunction of X-COM being well-off with Shanty being the Retaliation map type painting a picture where the non-X-COM portion of the Resistance is primarily in severe poverty we're nonetheless extracting Supplies from.

And it actually makes sense that you don't get Retaliation missions set in Slums. ADVENT is presumably oppressing the Slums, yes, but also presumably it takes a more defensible form; rounding up people as 'criminals' and hauling them off to jail (And possibly secretly executing them at that point), that kind of thing, not rolling an army through the streets shooting everybody. It would actually be pretty weird for a Slum to suffer such an open assault -it would be bad public relations, after all. (Where murdering a camp in the middle of nowhere, with no witnesses not part of your regime, is only bad public relations if you miss someone with a camera or something to actually get the news out)

On a more mechanical note, something you'll see in Slums but not City Centers is raised highways that tower up above even the tallest buildings on the map. These have their support pillars all act as indestructible climb points, and the road itself is indestructible as well, so these are unusually safe high ground to take to as far as that goes. Though if a pod is up there, it can be hard to get good Cover from them...

Abandoned City (I almost always refer to these as 'Old World' cities across this site, as that's what players will hear them called by the game)

The new plot type War of the Chosen most heavily tries to showcase, and the most developed one as well, with a decent amount of map randomization -still not as much as the base game plot types, unfortunately, but more than the other new plot types.

Broadly speaking, it's semi-accurate to draw comparisons to City Centers or Slums: high ground is largely in the form of fully destructible buildings, explosive cars show up a decent amount in the streets, not to mention there are distinct roads, similar sorts of spacing on Cover, etc.

Of course, there's a bunch of fairly significant divergences. For one thing, abduction pods show up scattered about, and much like in Enemy Unknown these are always indestructible, and usually are High Cover features -though they're larger than in Enemy Unknown, tending to be 2x2 tile features, and in XCOM 2 they're not always upright. If they're on their side, generally the tapering end portion is only Low Cover.

For another, security towers and civilians are never present in Old World cities, unless one counts VIPs I guess, but that's a little different. That's a pretty big contrast with City Centers and, to a lesser extent, Slums.

Surprisingly, Old World buildings also tend to be sturdier than City Center infrastructure. Fire escapes are a notable exception that disintegrates bizarrely easily, but outside that taking to infrastructure-based high ground is actually a little safer than in City Center or Slum maps. Conversely, in the unlikely event of enemies hiding up inside a building, you shouldn't assume a single Frag Grenade will tear the ground out from them; you'll need at least Plasma Grenades or Rockets for it to be a reliable thing.

Though it really is unlikely to see enemies in the upper floors of buildings in Old World city maps. They will never start the map on such high ground, period, and inactive pods will more or less never patrol up into such areas -it's only active pods that are particularly realistic to take to high ground, and I've emphasized repeatedly that the AI is bizarrely quick to go down once active. This is a pretty stark contrast with City Centers and Slums, where enemies still shy away from upper floors and rooftops once activated, but can absolutely spawn on them or patrol up to them. (Well, Sectopods can't patrol up to rooftops, but they're still perfectly happy to spawn up there. Somehow)

Also unusual with Old World city maps is that the game cheats a little with building heights: buildings generally only have two distinct floors in mechanical terms, but visually clearly keep going up, out of bounds. This also sometimes messes up mechanics, as you'll occasionally see Supply Extraction spawn a crate up in this space you're not supposed to go, or a Psi Transmitter repeater get placed up in that space, and when considering Grapple targets you'll sometimes be offered as targets tiles up in this out-of-bounds zone. (I've not experimented with Grappling up there, myself, so I don't know what weird nonsense might result from trying. It'd probably be bad, though)

These maps are also unusually flat when to comes to the indestructible foundations, even more so than City Centers: with almost every other plot type, significant Z-level differences where each floor is indestructible are possible, and typically common. Old World city maps are extremely flat if you ignore all the destructible terrain; the only exception is that there's often a raised train track -or two of them- and much like raised highway segments in Slums these have their support pillars as indestructible climb points and the portion you walk on can't be destroyed, making these fairly safe high ground to use. Unlike Slum highways, they actually have respectable ability to take Cover from enemies up there with you... and also pods don't normally end up atop them in the first place. Outside Lost waves, basically, who you don't need Cover against.

Speaking of, Lost are pretty inextricably intertwined with this plot type; any mission that can roll this plot type, Lost will always be present if this plot type triggers. (Which can make The Horde and Lost Sitreps seem more common than they actually are, since they'll be announced as Sitreps in such a case) That's pretty notable in its own right -plot types don't normally interact with stuff like enemy composition, except in the indirect sense that eg Faceless, Berserkers, and Chryssalids are very constricted in mission type by default and so by extension normally cannot show up in several plot types.

Anyway, this in turn has knock-off implications; the assorted vehicles scattered around consistently have the implication that them exploding will accelerate Lost waves, for example. It also means that even though security towers and civilians aren't a thing, it's generally actually easier to get squad Concealment broken, because Lost are scattered all over the place and have the standard detection radius instead of the reduced radii found on security towers and especially civilians. (Not that you care in a The Horde mission, mind) Reapers are particularly appreciated for navigating these maps without unexpectedly breaking squad Concealment, though you can just be careful in your movements, especially when the mission doesn't actually have time pressure.

It makes me wonder if XCOM 3 is going to make an effort to tie unit types to areas as a bit broader of a trend. That would fit with my suspicions XCOM 3 is going to be more Apocalypse-like in terms of multiple factions that each have their own territories and all, for one.

In any event, Abandoned City has a great aesthetic, but is held back a bit by its tendency toward repetitive maps (If you play the game enough, you will get very familiar with the limited range of maps used for Rescue Stranded Resistance Agents, and the less limited but still limited range used for Gather Survivors From Abandoned City), and also held back by imperfect design in several regards. Among other points, I've run into problems where opening a door inside the upper parts of a building somehow lets an enemy on the ground spot someone when no line of sight should be possible.

It's too bad it seems unlikely XCOM 3 will return to this plot type. A more polished version would be great.

Sewer

War of the Chosen's new plot types are generally a bit poor on map variability, but Sewers are probably the worst offender. Which makes it unfortunate War of the Chosen seems to have a bias toward using the plot type overall, particularly early in a run. It gives War of the Chosen an unusual propensity for repetitiveness in the early game, and also contributes to jank like seeing ADVENT Generals in sewers a lot. It's bad enough I totally understand the existence of a mod that removes the Sewer plot type entirely. I haven't used it myself as of this time of writing... but honestly, I probably will default to it eventually.

Regardless of that unfortunate element, the Sewer plot type is one of two plot types representing a new type of map in War of the Chosen: underground maps. This is notable because underground maps have the very significant implication of expanding the reinforcement list, where it's not just ADVENT units that can reinforce it, but also most alien types.

This isn't huge in and of itself, but it's interesting how War of the Chosen has a trend of connecting plot types to mechanical implications a bit more intentionally than the base game. The base game's plot types have mechanical implications and trends, as I've been covering, but I suspect the impact on gameplay was largely not deliberate. Certainly, it's not designed to be obvious to a player.

Anyway, moving on to other mechanics stuff...

First of all, Sewer maps are some of the more mechanically segmented maps, with solid walls breaking the map into distinct sections. The walls in question are surprisingly fragile, easily broken through with one Frag Grenade, including even basic weapons tend to punch holes in combat, so they're not a serious obstacle to getting from point A to point B, but they do mean Sewers is one of the easier plot types to pace your pod activations. Rangers and Templar tend to perform especially well (assuming you aren't recklessly sending them through unexplored doorways as part of a melee attack) since Sewers lends itself to situations where you know they can melee a target with zero risk of being spotted by a pod just out of sight, much more so than most plot types.

Second, high ground is something of a premium. It mostly occurs as isolated little platforms, where if you don't fight a pod in a fairly narrow area that particular high ground is useless. In conjunction with the solid walls blocking off lines of fire, Sharpshooters rarely get opportunities to snipe in Sewers, and you generally shouldn't even try. Said high ground also tends to have awkwardly-placed and easily-destroyed Cover, and the steel walkways in particular are distressingly frail and prone to collapsing entirely, making Sewers high ground dangerous to make use of if you aren't 100% confident you'll wipe out every enemy before they can attack. (With some qualifiers like 'a lone Codex isn't going to leverage these issues, because they'll be too busy launching Psionic Bomb instead')

Sewers also often -though not always- have 'rivers' that you might as well treat as infinite pits, because your soldiers -and your enemies- completely refuse to drop down into and wade through the sewage. Which. I can't blame them. But! My point is these create segmentation of a different kind, where you can't get from point A to point B by walking even though they're easily within a single move's worth of tiles because a 'river' is in the way. This actually makes Rangers and especially Templar a bit erratic on Sewers maps, where they might not be able to melee anything on a given turn if you activate a pod while it's across one of these from your squad.

This issue is constrained some by the tendency for steel walkways to appear intermittently along the 'river', but some variants will place such bridges quite far apart. On the plus side, these steel walkways are made of a much sturdier steel than high ground steel walkways, by which I mean they're completely indestructible and you don't have to worry about a bridge being taken from you. (Or worry about people being dropped into sewage) So that's nice, albeit probably another example of War of the Chosen having been rushed.

Another way Rangers and Templar tend to stand out in Sewers is that indestructible High Cover is a common feature throughout: steel structural columns appear regularly throughout Sewers maps, and are always completely indestructible, and a few forms of less common high ground platforms function as indestructible High Cover. As such, it's not unusual for an enemy to take cover against something you simply can't blow up, at which point a melee attacker is great to have -or a flanker supreme, which still describes Rangers once they have Run And Gun.

Also, as one might expect of literal sewers, you will never find security towers in them, and civilians will only occur if a Sitrep forces civilians to spawn. I mean, it wouldn't be that out there for there to be civilians hiding in the sewers as a semi-normal thing, but whatever, point is that's some clear mechanics stuff.

Oddly, while high ground is generally dubious to leverage in a direct sense, Grapples are often very useful on Sewer maps anyway, as high ground tends to be spaced decently across the map, and the gaps in walls in particular usually include a high ground area right above them, including a hole in the wall so you can Grapple in from either end. So you can often Grapple closer to where you're trying to go, where Grappling in eg Slums is often taking you parallel to your objective rather than toward it.

On a more aesthetic note, I very much enjoy the dark lighting of Sewers. (With one qualifier: it really exacerbates the 'is that a Trooper or a Stun Lancer?' problem) I tend to prefer how XCOM 2 looks at night in general -and honestly, I'd expect, with the whole guerrilla resistance thing, for night missions to be more explicitly a default- but the extremely dark underground environments provide a lot of fun visual contrast, and especially show off a lot of details that are more easily overlooked in other plot types -I didn't actually notice that Sectoids have a glowing chest until I saw one underground in War of the Chosen, for example, because the glow is pretty low-key. So broadly I like the addition of underground maps in War of the Chosen, even though the execution really needed more polish.

But overall, I kind of wish Sewers wasn't a plot type that got made, especially given all the general rushing and all. (It doesn't help that Neutralize Field Commander can use this plot type, which is just baffling) I'd rather more attention got put on...

Subway

The Subway plot type is the other underground plot type. It's also somewhat prone to repetitive map design, but much less so than Sewers. I personally think its maps tend to be better-designed and more interesting, to boot.

It doesn't help that it overlaps heavily with Sewer in its map design and attendant implications: there's the High Cover steel structural columns you can't destroy, the map being segmented by stretches of infinitely tall walls that are actually pretty easily destroyed, the not-very-useful high ground platforms that are painfully frail...

... there are differences, but there's enough overlap it's possible to get a Subway map that's basically indistinguishable from a Sewer map.

As one difference, there's no rivers of sewage, not only in the obvious sense, but in the deeper sense that there's no lengthy stretches of impossible-to-walk-through terrain in Subway maps.

More obvious is the presence of subway trains, which is... a bit of a mixed bag, unfortunately. There's exactly one on-the-ground subway train chunk the game can plunk down, and it's overall an interesting little setpiece, but it shows up often enough it's easy to get sick of encountering it, it dominates a good chunk of real estate, and it's a case where XCOM 2's line-of-sight rules fall down on the job pretty regularly. There's places inside the train that have much more limited ability to get line of sight on them than one would intuitively expect, leading pretty readily to cautiously advancing, seeing nothing, then starting on using up everybody's action points and whoops when you're more than half-done you activate a pod and now the squad is in trouble. Less egregious and easier to account for is the tendency for a pod to hang out atop the train, which once again is harder to get line of sight on than you'd intuit and lends itself readily to activating a pod when you were sure you'd determined it was safe.

The doors on the train are probably the most egregious piece, in that they visibly have windows set inside them, but still completely block line of sight -even though XCOM 2 can, in fact, set doors to be seen through while closed. This is at least not too difficult to deal with once you know what the issue is; you can treat the area between the doors as the blind spot it, in fact, is, for one, and for two you can actually set someone next to the door, open it, and then close it if there is a pod in there, without this activating the pod if your squad is still Concealed. Still, it's pretty bizarre this door got handled this way in the first place.

There's also subway station areas, what I assume are train maintenance areas, and a few other things that don't show up in Sewers, but the mechanical distinctiveness of these areas is mostly pretty low. I actually like the maintenance area and wish it spawned more regularly, but it's just a solidly-tuned little space, not anything that makes for a striking change of pace. The station areas are more notable, primarily because they have the rather bizarre quality of having knee-high fences in some parts your soldiers refuse to vault over. Which is probably more 'War of the Chosen was rushed' stuff...

But yeah, pretty similar to Sewers, and mostly better-tuned.

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A sub-element of some plot types is biomes: this is the game's internal terminology for stuff like whether you're wandering through a green forest or a snowy forest. It's... pretty light, mechanically, still, let's get into it.

Temperate

Temperate is your green, forest-y sort of environment; green grass, scattered trees, large rocks, etc. It's actually weirdly barren if I'm honest -there's never flowers, the trees aren't particularly dense, etc- but that's probably for the best as far as things like visual clarity and mechanical design go.

I tend to think of it as the 'default' biome type, due to things like Enemy Unknown defaulting to green forest-y environments for crashed and landed UFOs, and Lost Towers taking place in a green forest sort of environment. I'm not sure how meaningfully accurate this thinking is in practice, though -I feel like I actually see the other biomes more commonly overall, for example.

Regardless... biomes are, oddly, a lot more visible in their different-ness than some of the plot type sets, but actually pretty low-impact on the mechanical level. They're also only used by the Wilderness, Small Town, and Shanty plot types, meaning you're not going to see wintery city centers or the like, which is a little sad. (At least it can rain in city centers...)

I'm honestly not sure the Temperate biome has any mechanical implications unique to it, which is another reason I tend to think of it as the 'default' biome. Not that biomes matter much, but still.

Arid

Even though 'Arid' seems to be pulling primarily from United States deserts, the game is perfectly happy to run rivers through Arid maps. So that's one possible mechanical implication of biomes that simply... isn't.

The only mechanical implication I am aware of unique to Arid is that cacti are exclusive to them, and are unusually frail High Cover objects. You don't need to worry about your soldiers dehydrating in the blazing sun (Or freezing to death during the freezing desert nights), the trees look different but function the same as Temperate, even quite large rivers can be plunked into an Arid map. So... yeah. Biomes continuing to matter little.

I actually like the Arid aesthetic the most, out of base-game biomes. It probably wouldn't actually be good for the game for it to be, say, the only biome used, as a number of enemies clearly were designed with different lighting in mind -the red-and-black of ADVENT Officers gets a little washed out in the Arid biome's lighting, reducing the contrast, as one example- but I enjoy the color palette of Arid maps, and actually like how a fair few enemies look in it, such as Vipers. Same for a lot of player tools, for that matter. It also helps that it's a bigger change of pace from Temperate than our next biome...

Tundra

Tundra is basically Temperate, but it's currently winter. The name makes me think it's really more meant to represent skulking about in places like Alaska, Siberia, etc, but if so the aesthetic doesn't do much to reflect such an idea. It really just comes across like winter weather... which gets a little weird with a run of XCOM 2 being expected to take less than an in-game year, as no, the game does not correlate usage of Tundra to which portion of the year you're in.

You might expect your soldiers to need cold weather gear or something, but nah, your shirtless Mad Max refugees don't have to worry about frostbite or anything. Bit of a clash in aesthetic decisions there.

Sadly, there's no frozen rivers or snowmen Low Cover objects or anything else interesting to set this apart from Temperate. It really is basically Temperate, just... snow everywhere. I don't think it has any unique features. Which is weird; icy environments are usually an area video games excel in making distinctive. (Even if players often complain about the ways icy environments get made distinctive, like slipperiness in platformers)

Not that I'd want frozen rivers for Mutons to instant-kill my soldiers by a Plasma Grenade sending them straight into the icy depths, but still...

Xenoform

I love Xenoform's aesthetic, but it continues the trend of not having mechanical meaning. Alas.

It's added by War of the Chosen, by the way. It builds on several things that existed in the base game -the bits around the Psionic Gate, and the plant things you can see in the Alien Fortress- but the biome did not per se exist in the base game.

The expanded Xenoform aesthetic is a big part of what contributes to my 'aquatic Chryssalids' interpretation/speculation, actually. Xenoform is a very wet environment, placing (purely decorative) puddles at random across the ground (This doesn't happen with other biomes), and furthermore the Xenoform plant (?) life bears a striking resemblance to undersea -especially deep sea- life. There's High Cover objects that resemble glowing anemones, decorative objects carpeting the ground that calls to mind sea-floor tubular life-forms while having the glowing elements seen a decent amount in deep-sea life...

... the trees having cancerous growths like a Blossom Tree out of the Command & Conquer games and having their leaves all dead is the only part of the Xenoform biome that doesn't feed pretty directly into the vibe of an alien ocean floor encroaching upon the Earth's surface. And the tumorous growths still share the glow of a lot of Xenoform possibly-plants, like the ground-level glowing life is parasitically overtaking the Earth trees.

The only mechanical bits to note is that wet-looking patches of ground in Xenoform maps don't actually put out fires, and that the glowing anemone High Cover bits are surprisingly sturdy. They can be destroyed, but just chucking a Plasma Grenade or Rocket will generally leave the alien anemone alive while vaporizing all the other destructible terrain in the area.

Oh, and that Xenoform in general doesn't really do visible destruction-in-stages on its distinctive bits. Where other biomes have their trees visibly suffer damage the first time they're hit by explosives, even if they're mechanically fine, Xenoform trees and anemones show no change until they're gone; it can be easy to lose track of whether you've damaged a given chunk of a Xenoform environment or not, and thus easy to be left unsure whether a given application of explosives is liable to blow something up or leave it yet standing.

But overall... not much mechanical impact.

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Also, it should be pointed out that assorted non-standard missions ignore plot types and biomes entirely. I also haven't covered the Chosen Stronghold plot type even though it has a unique plot type because I'd rather cover it when we get to that mission type. So this isn't remotely everything major to do with map generation.

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Next time, we move on to specific mission types, starting with Retaliations.

See you then.