Numantian Games spent over two years in early access refining They Are Billions before its full release in 2019, and the community response tells a clear story: the survival mode is exceptional, the campaign is not, and the gap between those two experiences defines how most players feel about the game. Set in a steampunk post-apocalyptic world overrun by billions of infected, the game asks you to build and defend a colony against increasingly massive zombie hordes.
Player sentiment runs positive overall, but almost every conversation splits along the same line. Those who came for the survival mode and stayed there tend to rate the experience highly. Those who expected the campaign to deliver a comparable experience walked away frustrated. The tension between what They Are Billions does brilliantly and what it fumbles creates a lopsided but memorable strategy game.
The Ruthless Art of Colony Defense
The survival mode is where They Are Billions earns its reputation. You start with a command center, a handful of soldiers, and a map crawling with wandering infected. From there, you build outward: walls, housing, resource buildings, military structures, all while managing an economy that needs to grow fast enough to field an army before the next wave hits. The pacing creates a constant push and pull between expansion and fortification that keeps every session feeling urgent.
What separates this from most tower defense or colony survival games is how unforgiving the infected are. A single zombie slipping through a gap in your walls can infect your colonists, who then turn and infect others, creating a cascading chain reaction that can consume an entire colony in under a minute. Hours of careful building, wiped out because one wall segment was placed a tile too far from a chokepoint. Players describe these moments with equal parts rage and admiration. The game respects your time only insofar as it expects you to respect its rules.
Map generation keeps the survival mode fresh across dozens of runs. Each map offers different terrain, resource layouts, and infected density, forcing you to adapt your strategy rather than repeating a single build order. The difficulty settings scale dramatically, and the highest levels demand a near-perfect understanding of timing, economy, and military composition. Veteran players spend hundreds of hours chasing clean victories on the hardest settings, which speaks to how tight the core mechanics are.
The unit variety, while not enormous, covers distinct tactical roles well. Rangers for scouting and early defense, soldiers for holding walls, snipers for thinning crowds at range, and late-game units like Titans and Thanatos that can turn the tide against the final wave. Getting the right mix matters, and overcommitting to one unit type is a reliable way to lose.
Where the Campaign Stumbles
The campaign mode launched with the 1.0 release after the survival mode had already built a dedicated player base during early access, and the contrast was not kind. Players expected a narrative-driven experience that would build on the survival formula, and what they got was a series of mission-based maps with restrictive rules, uneven difficulty spikes, and a story that few found compelling. The hero unit system introduced in the campaign feels undercooked, with leveling and abilities that don’t add the depth they promise.
Mission design is the core issue. Many campaign missions lock you into specific strategies or impose limitations that strip away the freedom that makes survival mode so engaging. Instead of building your colony your way, you’re often funneled into a prescribed approach. Players who tried to apply survival mode thinking to campaign maps found themselves hitting walls that felt more like design oversights than intentional challenge.
Late-game variety in survival mode, while strong enough to sustain many runs, does eventually plateau. Once you’ve mastered the economy and learned the optimal defensive structures, the strategic decisions narrow. The game doesn’t offer the depth of unit or tech progression that would keep the meta shifting over hundreds of hours the way some strategy games manage to.
Performance can struggle in the late game when thousands of infected are on screen simultaneously. The final wave, which is the climactic moment every run builds toward, is also where frame rates take the biggest hit. It rarely makes the game unplayable, but it can make the most exciting moments feel sluggish on older hardware.
A Game That Punishes Perfectionists and Rewards Them
The defining quality of They Are Billions is how it treats failure. This is not a game where you can recover gracefully from a major mistake. A colony breach doesn’t give you time to mount a defense. It cascades. And that cascade, that chain reaction of infection spreading through your carefully built settlement, is simultaneously the most frustrating and the most thrilling thing the game does. Players who bounce off the game almost always cite this mechanic. Players who love the game almost always cite the same one.
That design philosophy creates a specific kind of tension that few strategy games replicate. Every quiet moment while you’re building and expanding carries the knowledge that all of it can end instantly. The pause button becomes your best friend. Scouting every corner of the map becomes critical not for strategic advantage but for survival. The game trains you to be paranoid, and that paranoia is the experience.
Should You Play They Are Billions?
If you want a colony builder where the stakes feel truly dangerous and where a single mistake can cascade into total collapse, this is one of the best options available. Strategy players who enjoy survival scenarios, high difficulty, and the satisfaction of finally cracking a map that’s been beating them for hours will find a lot to love here. The survival mode alone justifies the purchase for this audience.
Skip it if you need a strong campaign or narrative to drive your strategy games forward. The campaign mode is broadly considered a disappointment, and if that’s your primary mode of engagement with this genre, you’ll likely feel the same way. Players who get frustrated by punishing failure states where hours of progress vanish should also think carefully before diving in.
The Verdict on They Are Billions
They Are Billions built its reputation on a survival mode that delivers tension, challenge, and replayability in a package that few colony builders can match. The infected cascade mechanic is divisive by design, and it works precisely because it refuses to be fair. A lackluster campaign and eventual repetition in survival mode keep it from reaching the top tier of the genre, but the core experience is distinctive enough to stand on its own. For strategy fans who want to feel truly threatened by the things clawing at their walls, this delivers.