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Xcom Enemy Within Tech Tree

In most cases, new research projects are unlocked after getting a new alien artifact (weapons, pieces of UFOs construction, alien bodies or living aliens), but some of them, such as the armor for soldiers, require the invention of the items. The following tech tree has been divided into several groups to facilitate the reading:

Xcom Enemy Within Tech Tree


Nothing gets a soldier killed more quickly than walking around a corner into the guns of an enemy fire team. XCOM enforces a fog of war perspective, which means that you can only see what is within your soldier's line of sight. The interiors of rooms, areas beyond a certain distance, and even the other side of a closed door can all conceal lethal ambushes.

XCOM: Enemy Unknown is a great game but the tech tree left me terribly confused. The existing tech trees graphs ( on which i based mine ) helped a bit, but i thought there was plenty of room for improvements.

Long War is a partial conversion mod originally developed for XCOM: Enemy Unknown. After the release of Enemy Within, development of the mod switched to Enemy Within.[11] The mod makes changes to many of the game's existing features, adds entirely new features, and brings back concepts from X-COM: UFO Defense.[12] Changes include the ability to send a larger number of soldiers into battle, additional soldier classes, psionic abilities, weapons, and items, and an expanded technology tree. In the mod aliens and EXALT conduct their own research and get stronger over the course of the game, a process that speeds up or slows down based on the player's success in stopping missions launched by the hostile forces.[13][14][15][16] The mod was heavily praised by Enemy Unknown lead designer Jake Solomon and producer Garth DeAngelis.[17]

Why? That's a question I've asked myself often - including during a recent spate of long nights with XCOM 2 - and never been entirely sure of the answer. Is it the Skinner box hook of all those random number generators, and of the climb up a tech tree which keeps on throwing rewards at me? I don't think that can be overlooked, and similarly neither can the awareness that XCOM essentially loops the same compulsive experience over and over again. I think that's the most meaningful difference between it and the olden X-COM, really: the original always felt like a frightening foray into the unknown, whereas XCOM is more of a puzzle-box. I have these pieces, where do I put them all and in which order?

Requiring the Cybernetics Lab (workshop for adjacency bonus), the journey to MEC Trooper fun begins with a soldier of at least Squaddie rank going through augmentation. The process takes three days and strips him or her of any previous gene mods and class abilities, but it does grant you a new tech tree and access to a unit that can really soak up some damage.

The use of tech trees in 4X games is quite different. Tech trees typically do not have an on-map representation. They are a function of the empire itself. In such games, each empire's cities (or equivalent) provides some portion of research that is pooled until the civilization researches a particular technology. The rewards for a tech are improvements for "cities", new units or unit equipments, bonuses for a civilization researching them, or other such things.

Tech trees are one of the big points where historians pick at games. It's a hierarchical view of science, research, and history. When compared with actual history, tech trees are wrong. On the other hand, the few attempts at doing something different have wound up pulled from any final version, with good reason.

  • XCOM: Enemy Unknown is an amazing game, and this post is about how to choose optimal skill tree for various character classes in XCOM, but really it's just using that as a game design exercise. I'll be explaining what they did right and what they did wrong in designing skill trees, and then I'll summarize design points at the end of the point. It's just much easier to discuss this with a concrete example than on purely theoretical terms.XCOM character progressionFirst, the basics in case you never played it. You get a bunch of 0xp soldiers, who don't even have character classes. Then as they get XP they get levels, and on each level they get HP, Aim, and Will bonuses, plus one skill, either mandatory or one of two to choose from.Rookie - no class

  • Squaddie - character gets their randomly assigned class, one class-defining skill

  • Corporal - two skills to choose from

  • Sergeant - two skills to choose from

  • Lieutenant - two skills to choose from

  • Captain - two skills to choose from

  • Major - one skill

  • Colonel - two skills to choose from

  • All levels also get attribute bonuses depending on class, and they're a bit higher on squaddie and colonel than on other levels.Even before seeing individual class trees, there's a lot of very interesting design going on here.Random classesFirst - you can't choose class your rookies are going to get, so pushes the player towards a balanced team. It's even more interesting, since classes are random with same chances, except your first four rookies will always all get different classes (if it was left completely up to chance, you'd most likely get some duplicates only 9.375% would be all-different).Later in the game if you really want to have all-Heavy team you definitely can - either by hiring and training a lot of rookies until you get all the Heavies, or buying an officer school upgrade that makes all new recruits start at squaddie (with a class you want already).But early game the path of least resistance most new players will take is a balanced team - which happens to be pretty decent strategy (not obvious, in a lot of strategy games spamming one or two unit types is optimal, and some are clearly awful), and get the player to enjoy more game elements than if they had full choice.This random assignment can also increase frustration. If your only soldier of a class you need gets killed or wounded (and will require long hospital stay), you won't have any replacement easily available. You have ways to deal with this frustration - by training more rookies, or investing in Officers Training School, or going for missions where you get a higher level soldier as a reward, and slightly unbalanced team can still deal with most missions - but this random assignment just keeps on giving.Fortunately they didn't overdo it - since there are only 4 classes and you have enough outs, you'll eventually be able to get the kind of squad you want. Random game elements are aSkill treesAnother really neat design gem is with xp levels. Some levels are much more valuable than others - especially getting a Squaddie matters since then the soldier gets their class - and then depending on class different levels might have more or less important skills to choose from. Soldiers mostly get xp for participating in missions and killing aliens - and the way it's tweaked is that one mission participation (60xp) plus one alien killed (30xp, more for some high level aliens) is exactly the amount (90xp) needed to get that first promotion. This makes it really important to get rookies on the front lines, not just keep them behind farming mission participation xp while high level soldiers do all the work - but even without much luck all rookies will get their promotion on the second mission.And there's a reason why some levels don't give you a choice. Some skills are class-defining - you have to pick them, or other skills dependent on them won't work (see Heavy class for details of that). And some skills are basically must-haves - so powerful it would be stupid to take anything else over them. Unfortunately here XCOM doesn't do a very good job (see Sniper class for details).SniperI feel Sniper has by far the worst designed skill tree of all classes, so let's start with it.The difference between Sniper and other classes is that Sniper uses Sniper Rifle (or one of its upgrades based on alien technology) and can't fire it after moving. They can still fire a pistol, but that's a pretty miserable choice.Skills for the first two levels are:Squaddie - Headshot - fires shot with +30% critical hit and extra damage, 2 turn cooldown

  • Corporal - Snap Shot - can fire after moving with -20 aim penalty

  • Corporal - Squadsight - can fire at anything any ally sees (if there are no walls in the way)

  • This is just awful. Headshot is a nice to have, not a big deal, so it shouldn't go into mandatory slot.Squadsight on the other hand is absolutely critical for any Sniper - since you can't shoot anything after moving and you are relatively weak, as a Sniper you should stay behind on high grounds with unblocked view of most of the battlefield and shoot aliens the rest of your squad finds.Now Snap Shot would be interesting choice, but since Squadsight is a must have, Snap Shot never sees any action! What's worse - Squadsight and Snap Shot have interesting interactions. Sniper with both could move to flank a newly discovered alien, and then shoot it from a direction where they are not covered (low cover gives -20, high cover -40 to aim, so it might be worth Snap Shot penalty - and shooting alien completely in the open also gives huge critical hit %). But of course they're mutually exclusive so that never happens.What this trees should instead look like is:Squaddie - Squadsight - it's a must-have skill and a class-defining ability

  • Corporal - Snap Shot - nice to have

  • Corporal - Headshot - nice to have (or even more it much further down the skill tree, and put something else here)

  • In Enemy Within they reduced Snap Shot penalty and nerfed Squadsight a bit - but that still doesn't change the fundamental fact that Squadsight is still a must-have. Reordering these skills would be the only right thing to do, not tweaking stats.And on top of all the problems with this - Squaddie Sniper with neither Squadsight nor Snap Shot is usually weaker than Rookie in a fight, since they need to stay close to aliens, but can't move then shoot to flank them while staying covered.Anyway, let's pretend close combat Sniper (Snap Shot instead of Squadsight) is a thing in further discussion, since the skill tree was clearly designed with this assumption in mind, even though that never actually happens in real games.The tree doesn't get any better later on:Sergeant - Gunslinger - +2 bonus with pistols

  • Sergeant - Damn Good Ground - +10 aim and +10 defence against enemies at lower elevation, in addition to the usual elevation bonuses

  • Gunslinger is just really awkward here. If you go for Squadsight sniper as you should, you will find yourself using pistols in desperate situations sometimes (when a wall blocks your shot, and someone absolutely has to shoot the enemy this turn), but such situations are hopefully rare, while you'll be at high elevation most of the time. So it's a weak bonus vs strong bonus.And even if you go for Snap Shot Sniper for some crazy reason - Gunslinger just does almost nothing since you can shoot your sniper rifle after moving just fine. And Damn Good Ground also does almost nothing since you'll mostly be facing nearby aliens at similar elevation. So it's very weak bonus vs weak bonus.Either way, Gunslinger is always a bad pick.Lieutenant - Disabling Shot - can fire a shot that causes target's primary weapon to malfunction until reloaded, but can't critical hit, 2 turns cooldown.

  • Lieutenant - Battle Scanner - can throw scanning device that extends your vision for 2 turns, 2 uses per battle

  • Disabling Shot is just fairly weak - Snipers have high chance of critical hits against most aliens, and if you hit something you usually want to finish it same turn, not let it wander around and fire. There are some aliens who can't be killed in one shot, but this only affects primary weapon, and such aliens often have secondary weapons like grenades or melee attacks. Overall, a very weak skill.For Squadsight Sniper you usually want to stay behind in safe elevated position, so you can't throw a battle scanner as far as you'd like. For Snap Shot Sniper, I don't even know if they could shoot at aliens revealed by battle scanner since they can't see them directly.Battle scanners would be awesome for your close combat troops - since you know where aliens are, but they can't see you, why not ambush them? Except that won't really work since the moment you move within their range aliens get a free move to run to cover.So maybe this should be redesigned by moving battle scanners to Support class instead, and making aliens seen this way not able to run for cover when triggered? For now even awkward battle scanners are still a lot better than nearly useless disabling shot.Captain - Executioner - +10 aim against targets with less than 50% health

  • Captain - Opportunist - eliminates aim penalty for overwatch shots, and allows them to cause critical hits

  • This is probably the closest Sniper gets to actual skill choice, everything else being autopick. I'd say Opportunist is significantly stronger than Executioner, but Executioner is still a very nice bonus, if it was somewhere else. If this bonus was +20 aim or +10 aim and +10% critical hit, that would be a serious consideration.Major - Low Profile - makes partial cover count as full

  • And this gets to be a forced pick? For a Squadsight Sniper this is fairly close to completely worthless. Your cover is being too far behind for aliens to be able to see you - and if they somehow ambushed you, you might just as easily have no cover whatsoever rather than partial cover.For Snap Shot Snipers I can imagine this having some value, but not terribly much.But you know for whom this bonus would be absolutely awesome? Assault class. Or any class other than Sniper.Colonel - In The Zone - killing a flanked or uncovered target with sniper rifle does not cost an action

  • Colonel - Double Tap - can use both actions for shooting (including Heatshot and Disabling Shot), 1 turn cooldown

  • This is a Double Tap autopick, but for interesting reasons. Double Tap is a high reward low variance pick - you get to shoot 3 times / 2 turns instead of 2 times / 2 turns - greatly increasing your damage output no matter what.In The Zone sounds like it could potentially shoot a lot more times than two, but this will rarely happen. Triggered aliens run straight to cover, and they tend to stay in cover - and you can't move to flank them. Melee aliens tend to avoid cover, but they tend to be hard to kill in one shot.There are some uses - if there's a pack of multiple aliens one of your soldiers could throw a grenade at them, weakening them and destroying their cover. Then an In The Zone Sniper could finish them all off without using an action. I'm sure this happened sometimes, but as a player you should generally go for solid low variance choices (Double Tap) over choices which can occasionally be amazing but most of the time do nothing (In The Zone).Now this isn't the worst part of the tree, since many players find high variance exciting - check "Timmy" player archetype in this article.HeavyFor a much better design let's take a look at Heavy.Squaddie - Fire Rocket - fires a rocket using rocket launcher, cannot be used after moving, can be used once per battle

  • This is what mandatory skills should be like. Heavies have rocket launcher as a class characteristic, and many skills further down the road enhance either rocket launcher, or all area effects (and that's the only one you have here).Corporal - Bullet Swarm - can use both actions to fire primary weapon

  • Corporal - Holo-Targeting - shooting at or suppressing enemy gives allies +10 aim against that enemy

  • Anything that doubles damage output is great, especially with no cooldown. The problem here is how fast you'll run out of ammo here. So it looks like they're both viable choices. But once you perform a Muton autopsy and get Ammo Conservation in a Foundry, your ammo will double, and this problem will go away, moving bullet swarm from about as good as Holo-Targeting to way better.Sergeant - Shredder Rocket - fire a rocket that causes all enemies to take +33% damage from all sources for next 4 turns, but has weaker blast

  • Sergeant - Suppression - special shot that makes target suffer -30 aim, and grants free reaction fire against it (and also uses a lot of ammunition)

  • So many interesting things about this level. Suppression is the only ability that's available for multiple classes - Support Lieutenants also get it - and it's mostly useful for trying to capture aliens. In case you never tried it, the way it usually works is that your Heavy will suppress an alien, your Assaults (with Lightning Reflexes and maybe Resilience to protect against enemy fire) or Supports (with Sprinter for faster movement) will move towards it, and then maybe a Support will throw a Smoke Grenade to give your approaching and exposed soldiers some extra cover. Suppressed alien is likely to just stay under cover and often doesn't even try shooting, since AI prefers to save ammo rather than try shots with very low chance of succeeding.And Shredder Rocket ability shows why Fire Rocket had to be mandatory. If Fire Rocket was optional, then if you didn't take it then, you couldn't take Shredder Rocket now.Overall, Suppression is much better here. It's extremely useful for capturing aliens alive, it's somewhat useful in regular battle, and its main downside of going though a lot of ammo goes away with Ammo Conservation. But once you've captured all the aliens you'll ever want, Shredder Rocket is a serious consideration.Lieutenant - HEAT Ammo - +100% damage against robots (nerfed to +50% in Enemy Within)

  • Lieutenant - Rapid Reaction - second reaction shot on overwatch if first one was a hit

  • Since most of your nastiest enemies are robots - HEAT Ammo is a really really good choice. Interestingly it also combos with a rocket not just primary weapon. After the nerf it's not as clear what's the better choice.Rapid Reaction is not as good as it sounds early game, since Heavies go through a lot of ammo, and if you don't have enough ammo to shoot twice it won't work. Late game you'll have Ammo Conservation, but then you'll also have Cyberdisks and Sectopods trying to murder you.HEAT Ammo was an interesting design as a safety valve. Balancing everything about the game is pretty much impossible, but you can put some elements like that in it instead. If robotic aliens end up being too powerful, players will pick HEAT Ammo more often making robots less menacing. On the other hand if robotic aliens end up being relatively weak (relative to what player has at that point of the game, other aliens etc.), players will tend to pick Rapid Reaction, and that will make robots stronger in relative terms.Since robots turned out to be really powerful, HEAT ammo is the way to go.Captain - Grenadier - can carry 2nd grenade in inventory slot

  • Captain - Danger Zone - increases area of effect of rocket attacks and suppression by 2 tiles

From design point of view Grenadier requires specific inventory item to be useful - and that means you won't be carrying any of the alternatives like SCOPE, or Chitin Plating. How good it is depends on how good you think grenades are, and that very strongly depends on difficulty level, aliens you face at tha

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