They Are Billions is an Early Access PC strategy game about trying to build a city while fighting off hordes of zombies. It's surprisingly fun and polished, but also incredibly brutal. If you want to have any chance of not dying right away, I have some tips for you.
If you've played an RTS such as The Settlers or Age of Empires before, you'll feel right at home in They Are Billions' setup. A central command building gives you extra resources at regular intervals that you can then use to construct more buildings and grow even more. Even if you're new to the genre, developer Numantian Games' take on it is a little more approachable with very little to actually micromanage except whatever fighting units you create to march around and keep your city safe. The rest pretty simple: Build a thing, earn resources from the things, and then use those to build another thing.
Once you get comfortable with the controls and menu layout (remember to press "Tab" in order to rotate buildings before you place them or double-click a specific one in order to select all the others like it), you're ready for the more complicated parts of the game.
Here are some things to keep in mind if you want to survive as long as possible and potentially even make it through to the end.
Double stack your walls, always, no matter what, seriously just do it.
There are two types of walls in the game: Wood and stone. The former will do well enough early in the game, but unlocking the stone walls in the tech tree should be a priority. That upgrade alone will more than double the strength of your defences. How can you double them even beyond that? Literally build a second wall. They Are Billions only lets you build two walls back-to-back. If you want to start making another set ,you'll need to space them farther apart, which is something I sometimes do depending on the situation. Walls aren't cheap, especially the stones ones. If you're trying to wall in large areas you might be tempted to skimp, at least for a little bit. Don't! If anything, not being able to afford double walls means you rethink how you've positioned the perimeter of your base.
Keep your resource levels balanced.
The economy of They Are Billions revolves around money, workers, food and electricity. Then there's a second set of resources which are primarily for building: Wood, stone, iron and oil. Those commodities can be bought and sold at the market (once you build it) and are harvested from placing mines, sawmills and the like next to certain parts of the map.
One of the biggest obstacles to survival outside of the zombies themselves is managing resource bottlenecks. For example, you might need more electricity in order to power the new mine you want to build. However, the mill that would give you the electricity requires additional workers. In order to get those additional workers you need to build more houses, but more houses requires more food, so before you do anything you'll need to construct a fishing rig, hunters' hut or farm.
In the bottom right corner of your screen the game keeps track of what you're netting in each of these resources. The best thing you can do is develop evenly and make sure that none of them ever gets too low. There's nothing worse than being short on a particular resource and having no immediate way to harvest more right as the next zombie wave is about to hit.
Always be building.
On the outside They Are Billions is a strategy game about turtling, but on a more basic level it's a race to see how fast you can build a colony, maximise its economy, and stock up on defensive structures and powerful units. In order to be making top-tier Thanatos and Titan units by the end, and these are the ones you'll want to prioritise, you're going to need to reach the oil age and have a lot of housing supported by multiple banks to be making enough cash.
When the game starts, begin building houses and a sawmill. Then expand with hunters' huts and fishing until you have enough food to make more housing. Add a mill for more electricity and keep repeating until you're in a position to save for a barracks, wood workshop and warehouses. While you'll need to maximise wood, stone, iron and eventually oil production to keep filling out your technology tree, workers and money are the two resources you'll always be looking to come back to and maximise the most.
Keep a small force available for scouting and thinning the horde.
While you're busy expanding your base and preparing your defences, it's also important to put together a small band of fighters (mostly archers and snipers; soldiers aren't really worth it) to patrol the map and slowly kill as many of the ambient zombies as possible. You don't want the final wave to hit and have twice as many to fight all of the sudden.
Keeping a roving band of fighters moving around is also a good way to train them. After killing a certain number of zombies, fighters will turn gold and become veterans, boosting their stats and making them much more lethal. Your mobile death squad also helps out during zombie waves, allowing you to plug a particular hole in your defences if say, you forgot to double the walls like you were supposed to. Plus, a force of elite snipers and archers, somewhere between 20-40 strong, will be needed in order take out the zombie villages on the outskirts of the map before the final wave. While the number of zombies these villages spawn is finite, you can keep them from ever coming into this world to begin with by clearing them once you have the military might available.
Make sure to set units' priorities.
While we're on the topic of micromanaging your fighting squad, it's also important to set their priorities. In addition to moving fighting units around and being able to set patrols, you can also decide whether they target the nearest enemy or the strongest. You'll want a mix of different types of units prioritising different things. For the watchtowers you put behind walls at each choke point (you are doing this, right?) two snipers and two archers is a good, affordable mix. From there, you should make sure the snipers are prioritising the most dangerous enemies since they have longer range and deal more damage, making it easier for them to take down bigger zombies while they slowly approach as your archers focus on the grunts already at your doorstep.
The pause button is your friend.
Did you know that if you press the spacebar, you can pause the game? That makes the spacebar the most useful button in the game other than your right-click. Early on you might feel free and relaxed as you manage your base in real time, but if you really want to be prepared for the later phases, you'll need to use every second. Nothing happens in the game when it's paused, but you can still assign orders and place buildings, which will begin construction once you unpause.
Pausing often is not only helpful for taking stock of a situation and planning out your next phase of development, it's also great for battles when you need to quickly shuffle units back and forth between different parts of your base while compensating for the less-than-great unit pathfinding. It might feel like cheating, but it isn't. You might as well start doing it now, as opposed to three lost games later.
Always be looking for better choke points.
Zombies can't walk through trees, climb over mountains, or swim. As a result, the game's randomly generated maps will always present you with opportunities to use natural barricades for free. It's a simple thing to keep in mind, but it grows more complex when you have to decide whether it's worth it to expand and set up a new choke point versus staying closer to the defences you've already built.
A long wall isn't always harder to defend, since the zombies almost always all attack in one specific area rather than spreading out. Long walls let you take advantage of the full area of effect of electric towers, ballistas, and the fighters in your towers, as opposed to needing to build all of those things separately at each new choke point. If you're trading one long wall for three or more very small choke points, it probably isn't worth it.
Make sure each building is producing as much as it can.
Buildings such as sawmills, mines and farms produce new resources at a set rate based on the terrain in their area. As you build out your base and things start to get tight, it can be appealing to just throw in the next building wherever it fits. With a little bit of thinking and planning ahead, you can usually get a lot more for a lot less.
If you have houses on grassy land, get rid of them and put your farm there instead. If you have a fishing rig on a lake, see if there isn't a way you can spread it out farther and fit two or even three instead. And never, ever, place a sawmill or mine in a suboptimal spot. Wood and stone are two of the most important resources in the game, and you won't encounter a ton of forests or big mineral deposits in the wild. Above all else, you should be giving those types of buildings top priority when it comes to placement. If your starting map area doesn't have at least a few solid wooded areas and mineral deposits, you should immediately start over.
Don't be afraid to destroy your own buildings.
This is a zombie game, so when things get killed they don't just die, they become zombies. Houses, farms and barracks can all become deadly once the enemy horde gets their hands on them. That's why the game won't allow you to delete certain units when enemies get too close. You'll have to think ahead and not be afraid to just destroy a whole section of your base if zombies are about to get through and infect it. You get half your spent resources back, and it destroying buildings can wind up being a good opportunity to fine-tune the layout of your base.
Set small goals and enjoy the learning curve.
Come to terms with the fact that you're not going to win a game of They Are Billions on your first try. Or your second. Or maybe even your tenth. Fortunately, the game makes it easy to learn from each failure. Were you taking too long to develop? Did you expand too quickly, before you had enough resources to adequately defend? Or maybe you got to the final wave and it kicked your arse because you didn't believe everyone who told you how hard it would be? Whatever happened, stay calm and enjoy the process.
Instead of trying to straight up win every game at first, focus on things that are more readily achievable. Maybe spend a playthrough trying simply to get to the final stage of technological development. Or even just to survive the first zombie wave. Either way, there's plenty of learn and grow as a zombie-fighting city planner. The game's still in Early Access, so there's plenty of stuff that's likely to change or get added down the road.