They Are Billions

It is a fine game, but there is no mid-level save. I'm a working adult and I have limited time and this is by far the worst decision. Just such a dumb decision. Bad decision. Bad dumb stupid decision. You can just manually copy and past the saves folder on your computer to perform your own manual saves, but I shouldn't have to. I decided to play through the campaign because I do like RTS games and zombie survival games and this is a pretty cool combo. I do love how easy it is to get swarmed by one missed zombie making it into your base. This does not work well with no mid-game saves.
pros:
- challenging zombie mechanics that make protecting your bases from all sides very important
- zombies
cons
I would like to reiterate that it is a very bad, dumb, poor, stupid decision by the devs to not have a mid-game save. Like, the worst thing you can do in a single player game. Just so stupid. I thought that 1 hour in and I still think that 100 hours in.
The unit path-finding isn't great, plenty of times units start walking into walls or buildings. It works out fine most of the time, but it can be greatly improved.
The required spacing between buildings is such a pain. Like, houses should be able to be stacked and your units should be able to just walk though them. Spacing quarries and sawmills is so tedious and difficult to get "right" and optimize placement.
There are Hero mission that only give you research points, you don't get to use a hero on the normal levels. I don't get it. It is an RTS, not a point and click adventure game. So there is a whole skill tree for your hero that doesn't affect anything in the main game. It'd be more acceptable to me if you actually used the hero on your missions, or if you could train a "hero-unit" that gets increased stats from your hero skill tree.
there is no way to speed up the game. Most level require you to last a certain amount of days and I'm prepared to win and hold off attacks by halfway through. If I could speed it up or even skip to the next day, that would be so much better.
Conclusion
Its just a fine game. I'm not going to play it again anytime soon and its hard to recommend to anyone who values their time. I kind of regret buying it, but overall is a well made game. Just a lot of decisions made that disrespect my time. I wouldn't have spent so much time on it if I didn't just want to give an honest effort.
and a last note:
It is such a bad choice to not have a mid game save. Such a bad, bad, bad decision.

After playing the game for over 200+ hours and completing the whole campaign on the highest difficulty (800 % Apocalypse), my thoughts about the game are as follows:
Pros:
- A very fun and engaging gameplay loop;
- Nice art style with well-designed maps, units, and buildings (except for Crystal Palace, which looks terrible, out of place and has an unnecessarily large footprint);
- A nice and relaxing soundtrack;
- A good variety of zombies and units, even though some are more useful than others;
- The noise system – As your colony grows, nearby zombies will start coming after you. If you attack them too long from one tile, you generate too much noise and attract more zombies, therefore you want to constantly move your units in the early game and attack from different places. If you don’t pay attention to this mechanic on higher difficulties, you’ll have a very hard time;
- The wave system – Every now and then the game throws at you wave of zombies. It's very satisfying and fun to blow them up;
- The snowball system – Even one zombie can ruin your run. If a zombie infects a building, all colonists inside turn into zombies that quickly go to infect the nearest building, creating a chain reaction that's hard to stop. Although this can be frustrating, it adds urgency, excitement, and challenge to the game.
Cons:
- Obligatory Ironman mode – The game forces an Ironman mode on all players in all difficulty settings, even in the campaign (!). The game saves regularly and you can exit anytime you want, but you won’t be able to load the game if you lose. The devs even made the effort to perform game save when you Atl+F4. Players can technically perform their own saves (copying the save files from the game folder), but they shouldn’t have to;
- Lack of proper tutorial – The game barely explains any of its mechanics, units, or buildings. Given the fact that there is only one way of playing the game (see reasoning below) this is a huge problem;
- Poor unit pathing – AI pathing for your units is atrocious. Sometimes a handful of units can navigate through your town, but others get stuck. Also, unit formations are completely non-existent;
- Building restrictions – You can’t build houses in a row more than 2+, you can’t place more walls than in a row 2+, you can’t place attack towers next to each other, you can’t place resource generation buildings in certain range of each other (you need to carefully plan building layout in such a way to get most of the resources available);
- Confusing building health bars – Structures have 2 health bars (green and yellow). The green one represents the overall health and is important only regards to walls/watch towers. Zombies will never touch the green health bar of buildings, and they are incapable of destroying them. They can however infect them and therefore disable them – this is where the yellow bar comes in. The yellow bar is usually 10 % to 50 % of the building’s overall health and if zombie depletes it, the building becomes infected;
- No easy permanent health bar toggle option – By default, you don’t see health bars of your units and zombies. This makes tracking the zombies wandering into your base very easy to miss. The game gets significantly easier with health bars permanently on but the option to toggle them permanently is not one convenient button – you need to keybind health bars to a number on your numpad, then hold the button and toggle NumLock;
- Only one way to play – The game has a specific way to play it. It is solely a singleplayer game, you need to build the sustainable economy, expand and fortify the spawn/choke points. You can’t opt for any early game push, “tower rush” or other. Because of this, the game can get a bit boring after a while (it’s still the same);
- Campaign tech tree – In the campaign, you get technology points to spend on upgrades and unlocking new units/buildings. A good portion of the tech perks are just basic things, that should be available right from the start or at least from the certain mission automatically. In other well-known RTS games tech tree serves the purpose to compliment or alter players specific playstyle. In TAB the tech tree is often times to make the game even playable in the first place. Since any of the tech choices you do are irreversible (!!!) it is absolutely possible to soft-lock yourself from completing any of the future missions. One example for all is “Farm tech” – it is undeniably impossible to play later than first 4 missions without farms (building that provides precious food resource 3x more than other buildings in the same category). I can’t fathom why this limiting “feature” is present in the lowest of difficulties for casual players – if you make bad tech decisions, all that remains is to restart the whole campaign (losing many hours of gameplay);
- Campaign mission variety – There are three types of missions in the game: building missions, scout/hero missions and swarm missions. Every single one of the missions in any of the aforementioned category plays exactly the same without exceptions. The building missions have in total around 5 objectives: “reach x amount of population”, “resist all swarms of infected”, “destroy all villages of doom”, “reach a gold production of x”, “finish in x days”. No innovations or originality is present;
- Campaign mission difficulty indicator – Each campaign mission gets a difficulty rating (1-5) meant to show how hard it is. Often it doesn’t represent the real difficulty of the mission (e.g. Lowlands rated 2 but is the second hardest mission in the game);
- Campaign “scout/hero” missions – These missions, especially on higher difficulties, can feel a bit tedious as there are literally hundreds of zombies and you (most of the times) need to kill them one by one (!). The heroes don’t have any abilities to ease these missions, grenades are scarce and scattered. Completing these missions is often just question of time you invest in it (lots of kiting, shooting and pixel hunting most generic looking items on the ground), here and there the devs throw a curveball at you in a form of surprising superfast zombies (harpies) which can end your mission run in an instance;
- Campaign “swarm” missions – Often the progression to any of the main missions is gatekept by swarm missions. Here you need to “plan” your defence for the incoming swarm. These missions require almost no micro (except few swarm missions – e.g. only giants etc.) and most of the time you just hurdle your units into one big blob and wait for the end;
- Campaign loss count – In the campaign game tracks the number of tries it took you to beat the map. Doesn’t impact the gameplay (only victory points for achievements) but it is an obnoxious way to tell the player how much he sucks;
- Campaign story – The story is barebones in the literal sense of the word. There are like 4 total monologue cutscenes with the emperor. The lore is almost non-existent, every map has like 10 lines of text of description and that’s it. Your units don’t talk or explain anything about the mission. Don’t expect any interesting or intriguing story;
- Campaign’s last mission – The last mission of the campaign unexpectedly and without warning throws special zombie waves at you from a certain day. If it’s you first playthrough and you don’t know that a harpy wave is coming, you will very probably lose your first attempt at the last mission;
- Insanely grindy achievements – “Infected killer level 10” wants you to log 100 million zombie kills, which would take hundreds (maybe thousands) of hours without specialized custom maps.
Summary: The foundations are very solid. Unfortunately, the game is littered with poor design decisions that can often make you feel that the devs actively hate you. I still give it a thumbs up as I wouldn’t invest so much time into something I didn’t enjoy, but there is no way to overlook the multitude of flaws that significantly diminish the game’s overall appeal.

Play mission, lose, get reset back to the beginning. Play same mission, lose, get reset back to the beginning. Play same mission, lose to population goal, get reset back to the beginning. Close game, uninstall, never play again. Reinstall, open game, get reset back to the beginning.

This game scratches a particular itch that is hard to find. It's a turtler's dream - Build your base, capture every resource you can and climb that tech tree, because the game knows who you are and it's going to throw everything it's got at you and you better be ready. And frankly you wont be ready and that makes it so much more rewarding when you succeed.

The killer feature of this game is (to my surprise) a pause button. If you're anything like me, trying to control hundreds of little units and navigating a mini map can get disorienting when the chaos hit. Being able to quickly pause to make some decisions and then unpause to see your plan spring into action is brilliant.

"They Are Billions" has 2 main game modes. The survival mode works well and is addictive. 4 played hours feel like 1. Replayability is high because the maps are randomly generated.
The campaign mode doesn’t work well and is more tedious than fun. There are 3 types of missions:
Base building missions are like survival game mode, but on pre-built, fixed maps and often with long waiting times until the final wave.
Horde missions are just base defense with a limited number of units, which usually means placing your units and going AFK for 10-15min because micro isn't required.
Hero missions in which you control a single unit and have to retrieve an artifact. It theory it has great potential to bring variety and story in to the campaign mode, but in practice you spend 98% of your time killing and kiting zombies with your hero and 2% searching for items. This is simply boring.
Both game modes also have 2 problems:
Bad unit balance: Out of 7 unit types, you only really need 3, the other 4 are just nice to have.
Tedious base building: Finding space for your buildings can be a real pain in the a** because space is usually very limited and most buildings require empty space next to them for access.
Conclusion: Only buy "They Are Billions" if you are interested in the survival game mode. The campaign mode is not worth the money.

Almost 500 hours I've played. Part RTS, part tower defense. Super addicting. Super hard. All it takes is one zombie to sneak in and destroy your whole base. You can spend 3 hours building a secure base but in the final wave have it all destroyed. I end up losing most games in the last day, but I don't consider loses a waste of time, but rather a learning experience. When I win, I move up the difficultly level and do it again. This is one of my all-time favorite games.

They Are Billions is made for a specific kind of person, and that person is me: it's an RTS where turtling is not only encouraged but essential, where mistakes are severely punished and your base can be destroyed in the blink of an eye. And perhaps most importantly, this game lets you pause. There is no element of dexterity here, you can take as much time as you need to issue orders to your troops and micromanage every aspect of your play. If you lose despite this advantage, you have only yourself to blame... They Are Billions is not for the faint of heart. The title is accurate and you will be shocked by how many zombies that can spawn at once, and if even one of them gets into your residential district the infection will spread out of control. The stakes are higher than ever but that only makes victory all the more sweet when it is finally achieved. Two thumbs up from me, this is a game I will gladly revisit time and again.