Skip to heading: The core premise | Zombie AI | Building the base | Tower defense | Forced autosave | More jank
They Are Billions is a steampunk-themed blend of real-time strategy, turn-based strategy, and tower defense, with some campaign maps also being pixel hunts, and it was developed by Numantian Games. I hated They Are Billions at first, second, and thousandth glance because of its jank, but I eventually found workarounds, and I grew to greatly enjoy my time with the game's extraordinarily complex mechanics, some of which are hidden beneath the surface, with the two of them, autosave and maphacking zombies, in plain sight due to how much frustration they cause. You won't be frustrated by them until the zombie numbers grow large, so I wouldn't blame you if you enjoyed the game for 20ish hours, started bashing your head against the wall when you encountered massive zombie hordes, and quit for good; I was on the verge of doing the same quite a few times at around 20ish hours into the campaign.
At first glance, They Are Billions is a proper real-time strategy, but the more you look into it, the more you'll realize that it appears to have suffered from feature creep, and that those added features have not been playtested or polished enough, which prevents it from being on par or surpassing a true RTS gem like Warcraft III. This is glaringly obvious if you play on higher difficulty levels, especially on the highest, which is how I played it, as it quickly ramps up zombie numbers to absurd levels (up to 50,000 per mission) that instantly reveal all the baffling design choices and the lack of many quality-of-life features that you need to enjoy handling that many zombies as a fresh player. If you can find workarounds for both, you'll minimize the frustration and actually enjoy the game's challenge of building and defending your base from swarms of zombies, and that's the intention of this text.
Like any other RTS game, They Are Billions rewards you for thinking ahead, greedily expanding, controlling resource nodes, taking key spots on the map, funneling your enemies into chokepoints, pumping out hundreds of units, flanking enemy units, and abundantly using withering fire. The turn-based part of the game happens when you press SPACE, and then the game stops. You can issue commands, sell and buy resources, and start constructing buildings, which you can cancel to get 100% of your resources back until you unpause the game. Finally, the tower defense part of the game is when your base grows enough to attract the zombies' attention and they first start trickling in and then swarming in, at which point the zombies will test the way you used your limited resources to set up towers that you can man with your units and that you can fortify with walls, automated defenses, such as ballistas and autogun turrets, and hazards, such as spike traps, barbed wire, and land mines.
They Are Billions plays perfectly fine during the real-time strategy part, and I don't have any issues with how it plays during the turn-based strategy part, but it's during the tower defense part that I guarantee you'll lose your fucking mind. I've uninstalled the game in frothing rage at least a hundred times because of how shittily the tower defense part is designed and how unpredictable it is. Just to give you an example, the developer hard-coded a restriction that you can't stack more than three layers of walls, but what constitutes a wall is not always clear, and what constitutes a layer isn't always known, and the game apparently considers wood towers and wood gates "walls." I've had instances where I couldn't place a wall because there was apparently a tower behind or a gate, or... (click the image for the 1.08 MB, 1489x846 JPG version)??
The practical consequence of this restriction is that you can't fully surround your buildings with defenses; you are forced to leave gaps, and these gaps will be used by zombies to infect your buildings. In the image below, you can clearly see and count 6 Wood Wall segments and 1 Wood Tower surrounding a Tesla Tower, and yet I am unable to place the final Wood Wall segment (click the image for the 971 KB, 1409x729 JPG version).
My best guess is that the restriction is due to a zombie type, the Harpy, that can jump over one or two layers of walls, but she gets stuck on three and her AI glitches out, so the developers created a "three layer check," but they didn't know how to properly implement it. I think the fact that the game uses an isometric perspective caused a lot of problems in making the "three layer check" work consistently and why it turned out so janky, but I noticed that the game inconsistently applies AoE splash ranges of special zombies to player structures as well, and again it seems it's because of the perspective. That ultimately means that in some locations, orientations, and combinations of structures, you'll not be able to build a complete defense there for no discernible or logical reason other than "you just can't," and when the special zombies appear and attack that gap with AoE damage from a certain angle, they'll infect adjacent structures and you'll instantly lose the mission, but you won't be able to recognize the danger until you actually start building there, at which point it's probably going to be too late to rethink your plans.
A thoroughly demented example of this problem comes courtesy of the Infected Mutant, a special zombie type who does low AoE damage that splashes to nearby tiles but attacks very quickly. When you see him heading to your base, you better be ready to instantly kill him or you'll suffer. In some circumstances, his attacks can splash way beyond what I would expect and hit buildings he shouldn't be able to. In the following image, you can see a situation where that happens and in which I thought I was ready for him, but his attacks immediately depowered my defenses because he infected a Mill way beyond his AoE range (click the image for the 169 KB, 884x547 JPG version).
In other circumstances, his attack felt more like a scratch and he went down easily. The next image shows an Infected Mutant attacking a Stone Wall right next to defense buildings, and none of those got damaged in the slightest. The only damage he did was to the Stone Wall he was hitting and the one next to it (click the image for the 186 KB, 822x652 JPG version).
Zombies in They Are Billions have two states: dormant and aggro. They are by default in the dormant state, in which they amble around, and if they see the player's unit or building, they enter the aggro state and move towards it. If it's a unit and it flees, the aggroed zombie will keep following it for a few seconds before going into the dormant state again. If you enter a zombie's sight range with your unit and go outside his sight range and then move in a zig-zag pattern, the zombie will follow that same pattern, and if you try that trick on a map where you have superior vision, you will clearly see how they move and how long it takes them to go dormant. Zombies can also hear the noise that a unit or a building made and aggro towards it without having a direct line of sight of the target tile. How much noise it takes to aggro a zombie and how far the zombie moves when in aggro state also appear to depend on the zombie's aggressiveness rating that seems to be ramped up on higher difficulty levels.
The zombies differentiate between "prey" and "inert objects," both of which can generate sound, but they will only actively pursue the former, and they may ignore the latter. For example, walls are inert objects, and zombies will attack any walls they encounter in their aggro state, but if they happen to go dormant near walls, they might just chill around them, allowing you to set up containment zones with walls. This is useful because, when one of your buildings is infected, it spawns zombies in the aggro state. They will immediately beeline to the nearest "prey," but if they can't see it because they're surrounded by walls, they will hit the walls for a bit and might give up, and if you happen to kill them right away, all the other zombies nearby might go back to chilling near the walls too.
None of this is explained in the game, by the way, though there are hints, such as in the Ranger's and the Wasp's description (click the above image for the 70.2 KB, 688x177 JPG version), and I did find some details of the noise mechanic on the unofficial wiki that aligned with my experience of the game. In short, as your base grows, the zombie noose will start tightening around it, and you'll be forced to defend against them, which will create more noise and attract more zombies. So, your base defense needs to be perfect, except that the developers made such janky mechanics that it's rarely possible to make it work the way you want it to.
When a noisemaking event happens, it assigns a noise rating to that and nearby map tiles — the higher the rating, the farther it ripples across the map. As the noise washes over zombies, the game makes a check using that rating against each zombie's aggressiveness rating; if the check succeeds, the zombie enters aggro state and moves towards the noisy tile. The noise rating also diminishes on its own over time, and occasional events on a single tile might not cause zombies to go aggro. So far, so good, but wait until you see what creates noise:
Basically, everything attracts zombies, but there is some RNG involved. Doing the exact same action in the exact same circumstances might attract 0, 5, 10, 15, or more zombies, and the direction from which they approach might vary slightly from attempt to attempt. This RNG-based mechanic can instantly torpedo a run because it is not limited by level topography. Zombies can "hear" you across the entire map and over mountains, forests, lakes, and rivers, which is absurd, but they might also ignore the noise completely and chill for no discernible reason. You can be fighting off a zombie horde on the east entrance to your base only to get swarmed by another horde coming to your west entrance in a little while, and if you replay the mission and start the same fight in the east, the west horde might never come or it might be miniscule. The problem is, as I said, in the tower defense part of the game that nudges you into unknowingly making subpar defenses unless you happen to have an exceptionally strong economy that can absorb the surprise attacks, which you likely won't have.
The zombie AI can be easily examined during the campaign by playing on the Frozen Lake level, where there are damaged Radar Towers near the Command Center. Moving close to them, supplying them with energy, and repairing them reveals a huge surrounding area, effectively giving you maphack, and showing you that zombies basically have that same vision of you at all times, and it's just that it gets disabled until there is some noise generated. In short, the zombies are rotten cheaters, and the game is designed to sabotage you without you realizing!
The biggest problem with the noise mechanic is when there are zombies behind an obstacle that you can't see over, such as a forest or a mountain. You might think you're safe, but, by placing a few buildings close to the barrier, you've actually generated enough noise to awaken any number of zombies, and you have sealed your fate because those zombies will stream to your base, pick up other zombies along for the ride, and create a massive horde that will come knocking on your door after a few minutes, and you'll get overrun without even knowing what happened or what you did wrong. Saving and loading the game also seems to mess with the zombie's aggressiveness ratings and/or noise levels, though I haven't definitively confirmed that, I just got the impression that loading a save can instantly trigger an attack wave without an obvious noisemaking trigger.
On one hand, this noise mechanic gives a lot of replayability, but on the other, that replayability comes with enormous frustration because it's constantly resulting in curveballs that hit you out of nowhere, and it's difficult to predict them or have a reliable strategy for dealing with them. The noise mechanic is just not consistent enough to create a satisfying challenge on higher difficulties, and whenever I've beaten a mission on maximum difficulty, I did it through workarounds that were in some cases basically exploits and should have been patched. The most obvious workaround is to avoid the noise mechanic altogether and instead intentionally trigger the zombies' aggro state by letting them see your unit and leading them away, Pied Piper style, into a kill zone that is as far away as possible from larger zombie hordes and that you can abandon if you need to. It's also a good idea to spread out your units to minimize wasted shots and the amount of noise assigned to a couple of tightly grouped tiles, as seen in this Ranger formation (click the image for the 1920x1080, 346 KB JPG version).
Another workaround is to research the Spike Traps upgrade and start building massive fields of them to kill zombies without much noise. Choose one or more entrances to your base, set up a few walls, and thickly layer spike traps there while sending your units elsewhere. You will need to repair those traps, and it's not possible to repair your buildings while there are zombies nearby, so you will eventually have to send some units there to help clear out the zombies, but the system works well enough. You can also combine the two: aggro small to medium zombie hordes and run in a zig-zag pattern across fields of spike traps while your other units decimate them with withering fire.
Each building the player can make in They Are Billions has a space requirement. Wall segments need 1 tile, Tents, Cottages, and Stone Houses that increase your population need 4 tiles in a 2x2 arrangement, and a Soldiers Center that creates troops needs 9 tiles in a 3x3 arrangement. Each building also has a spacing requirement, and these are baffling. Tesla Towers have to be spaced 4 or more tiles between each other, and so do Mills that provide energy for the colony, but Tesla Towers can be placed next to any other building, while Mills cannot because they have to have at least one free tile around them on all sides. Then again, population buildings can be stacked as long as they have a few free tiles around them, which is why I most often stack them in two adjacent rows.
There is no rhyme or reason as to why some buildings can be stacked or built together while others can't, but the practical effect is that you can easily run out of building space without even realizing it before it's too late. When the zombies swarm in and you give your units the command to reinforce the attacked part of your base, you will suddenly realize they are stuck and that you can't demolish the blocking buildings because the zombies are too close. Yeah, another restriction in the game is that you can't build, repair, or demolish any of your buildings if zombies are within 4 tiles. If you want to place a Saw Mill in a forest to get lumber, you might get cockblocked by that restriction through no fault of your own because there are zombies on the other side.
Even if everything goes as expected and there is not a single zombie near your colony, the fact that you have to imagine your base in your head 20 minutes into the future like this, "OK, here I will place a Mill, and let's see, 1-2-3-4 spaces, here I can place another, and 1-2-3-4, here a Tesla Tower, but wait, it covers 8 tiles, 1-2-3-4-5-6-7-8, here I can place another, no, that's not good enough, it doesn't cover the entire area, hmmm, maybe I can place it here" is just mindbogglingly idiotic. You must plan ahead because They Are Billions will not help you plan your base in the slightest, and the game won't give you much building space either. My estimate is that only about 50% of any given map in this game is buildable terrain, and that too can be pocked by random patches of unwalkable terrain or resource tiles that are too small to be worth mining and that you can't build over, causing you to have to spread out your base and your defenses too thin. A base-planning feature, such as the ability to place down free blueprints, seems obvious, and why it's not in the game is anybody's guess.
The best way to plan out your base is to use the game's Flat Mode (press F4 or middle mouse button), which minimizes the graphics and outlines tiles, helping you clearly see whether some terrain is buildable and walkable or not. After discovering the Flat Mode, I played the game exclusively like that, and you should too; it is simply too difficult to plan out your base otherwise and the game's graphics are just too distracting when things get crowded. One neat trick to check if a tile is pathable for your units is to see if the game will let you build a Wood Wall segment on that tile. If it won't, it's likely that the tile will be blocked for your units as well.
The backbone of your base in They Are Billions is the Tesla Tower, and it is arthritic. This pathetic building has wafer-thin defenses and can be infected by even the puniest zombie in a couple of hits, crippling entire parts of your base, and you need to build dozens of them to make a proper base. Their build and repair times are of geological significance, and you must build them to establish an "energy field" (visible when holding E) that lets your Command Center supply power to all other buildings. Without a Tesla Tower's coverage, you can't build or repair anything, not even Wood Towers, Spike Traps, and Wood Walls, and if a Tesla Tower is taken out, any other building in its energy field instantly loses power and won't work. Worse yet, Tesla Towers seem to be a priority target for every zombie, and starting their building process seems to have a massive noise rating. I can't count the number of times I had to concede the mission because I cleared an area of zombies and started building a Tesla Tower there only to get absolutely swarmed by zombies from all sides for no apparent reason. They couldn't have seen it, and it makes no sense why it should make so much noise, and yet that's how the game was designed to sabotage the player.
The above video shows the absurdity of the zombies' hard-coded hatred for Tesla Towers. This hulking monstrosity, the Infected Giant, can wipe out my defenses in an instant, and yet, he got so fixated on a Tesla Tower within his sight range but outside his reach that he couldn't stop moonwalking towards it in a vain attempt to reach it across unpathable terrain. You can't expand without placing Tesla Towers, so it's crucial to learn the size and shape of its energy field coverage and meticulously plan where and when to place it so that it is properly defended and that you can correctly expand, but now you also know that they are a magnet for zombies, especially when within their sight range, so you can exploit it by predicting their path to your base and distracting at least some of them with a decoy Tesla Tower. It is crucial that you defend your Tesla Towers, because zombies will take them out and that might spell doom for your mission if that Tesla Tower is powering your defenses. Note that the Giant in the above video was trying to reach the farther Tesla Tower rather than the infected one I had selected; zombies completely ignore infected buildings.
In another stellar example of lackadaisical video game development, They Are Billions lets you build and man towers but doesn't explain how to do it properly. You can place the three units you make in a Soldiers Center in towers to massively increase their attack and sight ranges. A Sniper, who by default has the attack range of 8 tiles, covers an area of r²π = 64π. Place him in a Wood Tower that adds 3 tiles to his range, and he now covers 121π, nearly doubling his coverage. Place him in a Stone Tower for a 4-tile range boost, and he covers an area of 144π! The problem is that both Wood and Stone Tower have a 1-tile spacing requirement, so you have to judiciously build them so that they support each other and minimize time-to-kill and wasted shots that generate needless noise.
Though 144π area coverage sounds amazing, a huge problem is that, even though your units placed in towers are shown as high above the ground, and they might be able to see over certain tiles, they might not be able to shoot over them because of a line of sight mechanic that is not explained at all, and you will likely not even realize that some of your units aren't shooting at anything until you've been playing the game for some 500 hours. Figuring out lines of sight is so important that, when I uncover any portion of the map in They Are Billions, I first identify which tiles give my units unobstructed line of sight of the path the zombies will take, then I figure out where to place my towers so that that path is under the most optimal damage distribution, and then I build my base in reverse to achieve that. Here's an approximation of what Soldiers in a Wood Tower can (blue lines) and can't shoot at (red Xs) (click the image for the 252 KB, 1,238x666 JPG version):
The above image comes from the time when I didn't know about line of sight, and it shows. What about the tiles that are neither touched by a blue line nor covered by a red X? Well, that's a good question. The game lists move speeds down to 1/20th of a tile, which indicates there are 20*20 = 400 spots that a unit can occupy in each tile. In short, the units in the tower have a 1/400 chance of being able to attack a unit in any of those tiles, and there is no reliable way to tell because a unit in a tower can also be slightly offset depending on which slot in the tower it takes. One trick I use to lines of sight is to put one of my units where I plan to place my tower and put another on the other side of a barrier, and then I have the former attack the latter. If it can't without moving, then it won't be able to attack a zombie standing there from the tower either.
A related problem is the player units' and buildings' targeting AI. You can't manually order your units in towers or your buildings to attack a target; you have to choose one of two targeting modes: Target Nearest or Target Highest Level. So, hold on, zombies have a "level" now? What is a "level" exactly and how does your unit or building determine the "highest" level of a zombie? I don't fucking know. I've been playing this fucking game for over 1,500 hours and I have no fucking clue how the latter targeting mode works. When I mouse over it, it simply says "attacks the most powerful zombie," and when I space out my towers and set some units in them to the latter mode, and there are no special zombies in range, they just attack some random zombie in the back. I hope you see the problem: if you put all your units on Target Nearest, they will waste their shots and generate too much noise by instagibbing the same zombie, and if you set them all to Target Highest Level, they will target zombies in the back, allowing other zombies to come near and destroy you, again generating noise.
Throughout each mission, you will get attacked by scheduled zombie waves, and the culmination of each mission is a massive wave of zombies coming at your Command Center, but the exact path these zombies take might differ depending on how you set up your defenses, and if there's unpathable terrain in their way, such as an Oil Pool, rocks, or a grove, the wave might also split around it differently, creating smaller groups that act autonomously. Imagine meticulously building out your colony for 2+ hours only for the game to spawn a zombie wave that takes a slightly different path than you expected, bypassing your defenses, knocking out your Tesla Towers, and wrecking your base while you watch helplessly.
Here's an example of what I mean that comes from a save file linked below that you can download, load, and test for yourself. The following screenshots are from the Campaign map "Noxious Swamp," where the player is swamped by Venoms, a special zombie type that can vomit bile in a 4-tile radius that does AoE damage in a 1-tile range, which is janky as hell too, though their attacks seem more manageable than the Mutant's because their attacks are slower. Anyway, in that map, I am warned that there is a wave of zombies coming from the south. My economy is booming; I can afford to build massive defenses there, and here's what I built (click the image for the 196 KB, 1,387x428 JPG version):
The rows of mines are at the edge of buildable terrain, but the map extends far beyond that, and that's where the zombie wave spawns before it heads to my base. The four buildings I have selected are Shocking Towers, and you might notice something strange: they aren't perfectly lined up and they seem to be focused on the left side of the gap. That's because I cheated too by loading the map multiple times to confirm whence the Venoms will arrive and discovered that they will hug the left side of the south path, which is why I optimized my defenses. As they enter the Shocking Tower's range, the Venoms will spread themselves thin and die before they get a chance to instakill any of my buildings. I didn't make any walls because I was too close to the mines, but the plan worked wonderfully regardless, and I learned more about the game's jank when it comes to AoE attacks (click the image for the 280 KB, 1,466x677 JPG version).
The Venoms' AoE attack, which is supposed to hit the target tile and all the nearby tiles, was actually hitting the Shocking Tower it was not supposed to, though the other one was undamaged. I was able to keep repairing any damage the Venoms were causing because of my optimized firepower distribution that kept them outside the 4-tile range. When the battle ended, I discovered that the rightmost Shocking Tower didn't even trigger once, and neither did the rightmost units in towers (note which Snipers are pointing their guns to figure out which were attacking). So, about 30% of my defenses there were completely useless, and I'd say that's the waste you can expect when you play the game, unless you know exactly what's going to happen. As for the land mines, only 10/30 triggered, and the rest were a waste of money, meaning I wasted 2,000 gold and 60 iron on them, which is a huge amount of resources that I could have invested into making units or Wasps.
A single Venom can obliterate entire rows of walls, but their AoE applied to walls only works orthogonally, not diagonally. Build your walls in cross-shaped patterns and you'll quickly regret it when a Venom shows up, but build your walls in x-shaped patterns and their AoE will be reduced to a puny 30 damage per attack to a single wall segment.
Based on Steam reviews of They Are Billions, forced autosave is the most infuriating feature of the game. In short, there is only one save slot, and every couple of minutes, the game will autosave and overwrite the previous save, and it will also autosave whenever you leave the mission or force-quit the game, such as by ending the process in Task Manager. If you make the tiniest mistake, such as by placing a Tesla Tower one tile away from where you should have placed it, it can be game-ending, but you won't even realize it until you've lost the game, and because there is no replay function, you'd have to be recording your screen to even come close to figuring out what happened. I think a major part of the appeal of RTS video games is the experimentation part, and the fact that They Are Billions intentionally discourages experimentation is a genuine tragedy.
You can be doing perfectly fine in a mission for an hour only for a stray zombie to infect one of your buildings and create a cascading zombie infection that completely annihilates your base in seconds, and there's nothing you can do other than leave the mission and try again, and if you decide to protect that part of your base the next time around, you might not have a zombie appear there at all. Well, if zombies cheat, so can we, and we can cheat better than them. It turns out that the game doesn't timestamp the save file or check its origin, so you can manually create a backup of the save file, and you can manually restore it to "load" it. For simplicity's sake, I copy the entire "Saves" folder.
To bypass the autosave feature in They Are Billions, do this:
This renamed copy is now your manual save. Keep playing the game and when wishing to load, do this:
This brings the game back to the same state it was in when the "Harpy Nest day 12" save was made. I also tested this with my saves from the GOG version of the game in February 2022; they were fully compatible with the Steam version, and the same trick also worked in the game's Survival mode. Making a copy of the "Saves" folder while in a mission is doable, but I advise leaving it to avoid file access and Steam sync issues. Thanks to the ability to manually save, you can now experiment with timings, unit combos, targeting modes, line of sight and attack ranges, unit and tower placement, different expansion strategies, and so on.
Thanks to the manual save trick, playing on the hardest difficulty becomes thoroughly satisfying, and the ability to save comes in particularly handy when playing hero missions during the Campaign, where a misclick can kill the hero and void the last 45+ minutes of gameplay. If endured, the highest difficulty will let you experiment on enormous swarms of zombies and enjoy your experiments rather than see them as a rage-inducing exercise in tedium. Whatever you choose, I recommend against playing on the lowest difficulty. It gives you ample time to set up a colony, but you are likely to explore the level very quickly, kill off all zombies, build the base, and get bored out of your mind waiting for the paltry zombie wave to finish the level.
Now that you have a way to manually save, you can have fun testing your unit combinations and building placements against some of the more dangerous zombies. Here are some of my saves, all Campaign missions on the highest, Apocalypse, difficulty:
I'm sure some of the missions weren't playtested at all on Apocalypse difficulty. In one Campaign Outpost mission later in the game, where you have limited resources and have to survive a swarm of zombies without a base, westbound zombies get stuck at a chokepoint, creating an undulating vortex that turns a tsunami into a trickle. It's mesmerizing, but it makes that level laughably easy. Later, I saw the same phenomenon on other Outpost levels, especially in the latter half of the game (click the image for the 2.4 MB, 4096x4096 JPG version).
In one of the early Campaign missions, Cape Storm, on Apocalypse difficulty, I built 300+ Soldiers and tight lines of walls to enclose them. The game spawned ~50,000 zombies to the north and sent them across the bridge and straight to my units. The zombies got stuck on my walls, punched through, pushed against my Soldiers, and eventually glitched out of bounds of walkable terrain. Some zombies literally teleported through my Soldiers, falcon-punching the buildings behind. This can happen in any map where the chokepoint is tight enough, and if it happens in a Survival mission, where the objective is to kill all zombies, you might get softlocked. If that happens to you, try placing your unit near the zombie and attacking your unit with an AoE attack of yours, such as a Thanatos or a Titan.
Rangers can easily glitch out. Order a Ranger to attack something, wait for her to lift her bow and, right after she shoots an arrow, press Q and left-click the same target. She will fire the original arrow and the second one immediately after, ignoring her attack cooldown, as shown in the video below.
Quickly cycling Q+left-click, Q+left-click can make a Ranger, which normally fires 1 shot per second (2 shots when Veteran), fire 10 or more shots per second. A group of Veteran Rangers manipulated this way can produce a frightening amount of arrows. This trick does work on Soldiers as well, though their range is a lot smaller and the target needs to basically be on top of them.
Some buildings can't be sold but they can be destroyed. If a Stone or Wood Workshop is destroyed, the player will lose access to buildings/units researched in them. If rebuilt, the research will have to be paid for again. The best course of action is keeping one of each of these research buildings inside the perimeter at all times, but if you no longer need anything it provides, feel free to destroy it by manually attacking it with your units.
Player units can use their enter/exit tower movement abilities to effectively blink through walls when towers are right next to them. This can make gates redundant, except for large troop maneuvers. Move the unit as close as possible to the tower and click on it.
During base-building Campaign missions, you will have a train arrive every day. The train is a solid, indestructible, inert object: zombies ignore it and can't attack or damage it, but it can block player units and block/squish zombies. Use a Ranger to lure the horde to the train tracks, step aside at the last moment and RUNRUNRUN to the colony. The train will squish the zombies on the train tracks, giving you money for each kill if the appropriate upgrade(s) are enabled. I even managed to lure a Giant in front of the train, which revealed the train does 500 damage (350 due to Giant's armor damage reduction). You can't build right next to the train tracks, with one exception — gates. Line the train tracks with gates and when the zombie horde arrives and starts gnawing at the gates, hold out until noon when the choo-choo daddy comes and rolls through them.
The Market is a mid-tier economy building that reduces the food need of nearby population buildings and lets you sell/buy resources for gold, letting you trade in common resources, such as Wood and Stone, for rare resources, such as Oil. This is the most broken building in the entire game, as it lets you ignore resource restrictions and gain access to things you shouldn't be able to have, allowing you to pump out defenses and keep building when you run out of money. Multiple Markets increase the exchange rates for both buying and selling in your favor, though their food-reducing effect does not stack.
Hotkey the Market to sell and buy resources as needed, and you can just keep stocking up in expectation of an attack, which is especially lovely when you have multiple Warehouses that increase your resource cap. My favorite way to abuse the Market is to build Wasps during prolonged zombie attackes because one Wasp only needs an active Stone Workshop, 1 energy, 320 gold, and 10 iron. During a Campaign mission, as long as I have the upgrade that gives me gold for zombie kills and enough energy supply, I can turn zombie numbers into gold, buy up all the Iron I need and boost my firepower. In theory, I can cover the entire map in Wasps, each of which only takes 6 gold for upkeep for the entire day.
In the Market, each click buys/sells 5 units of a resource, which can quickly turn into a chore when trying to buy/sell a lot of them and leads to strain on the wrist/hand. You can use a mouse macro to automate the clicking; I use AutoHotkey. For Autohotkey v1 scripts, the following code makes 20 fast clicks with 30ms delay between them upon pressing SHIFT+ALT+ENTER. Moving the mouse cursor while the script is running might lead to clicking on the wrong icon:
+!Enter::
Loop, 20
{
Send, {Click}
Sleep, 30
}
return
For Autohotkey v2 scripts, here is a script that only works while the They Are Billions window is active, and it makes 5 quick clicks in the same place upon pressing SHIFT+ALT+ENTER:
#HotIf WinActive("ahk_exe TheyAreBillions.exe")
+!Enter::Click 5
#HotIf
I also bound one of the extra keys on my mouse (Mouse6) to act as Enter in order to quickly access the building menu and to help with the script execution. Five clicks at a time doesn't seem like much, but it really cuts down on the mind-numbing clicking and lets you focus on the action.
I wish Numantian Games spent more time polishing They Are Billions, especially the tower defense part, to give us a timeless classic, a brilliant gem that could stand alongside the likes of Starcraft: Brood War and Warcraft III. There are workarounds for the jank, so if you are ready for it and think you can stomach the annoyances, I guarantee you'll enjoy the game as much as any other classic RTS.
The setting is phenomenal, the story is appropriately scary, and the action is tense. I recommend playing on Apocalypse difficulty, which is where the real fun begins. I witnessed endless zombie hordes shambling and scrambling at me, clawing, gnawing, and snarling for fresh flesh. I pushed them back with walls of wood, stone, fire, lightning, and lead. I explored the abandoned human settlements, cleansed the infected, and settled on the scorched ruins of the old world. This is my world now. I am not the prey — they are. And They Are Billions.