They Are Billions review

They Are Billions is a colony builder and real-time strategy game where defense is everything. Numantian Games sets it on a post-apocalyptic steampunk planet: you build and fortify colonies against swarms of infected, and a single breach can spread through the base. The New Empire campaign has 48 missions and more than 60 hours of play, with more than 90 technologies and a hero who explores old fortresses. Survival Mode generates a random world with its own weather and infected population that you must hold for a set time. Real time with pause lets you place buildings and give orders while the game is stopped. It costs $29.99 on the US Steam store and includes a level editor and Steam Workshop. Only 80% of 19,051 English Steam reviews are positive, tied with Rogue Tower for the lowest share here, and it is single-player and Windows only.

Who it is for

RTS veterans who want hard, high-stakes base defense

Price

$29.99 one-time purchase on Steam (US store).

after the zombie apocalypse? $29.99 Buy on Steam
Quoted from the vendor pricing page on November 11, 2026.

Key features

• Campaign of 48 missions with more than 60 hours of play
• Survival Mode on randomly generated worlds
• More than 90 technologies to research
• Real time with pause for placing buildings and orders
• Level editor and Steam Workshop

Strengths and weaknesses

• Strength: Campaign lists 48 missions and more than 60 hours
• Strength: Pause at any time to plan, so reflexes matter less
• Strength: Steam Workshop and level editor
• Weakness: 80% of 19,051 English Steam reviews are positive, tied with Rogue Tower for the lowest share here
• Weakness: $29.99, the highest price on this list
• Weakness: Single-player and Windows only

Key facts

• Developer: Numantian Games
• Released on Steam: June 18, 2019
• Minimum RAM: 4 GB
• English Steam reviews: 80% positive of 19,051
• Campaign: 48 missions, 60+ hours

Where it ranks

They Are Billions is No. 10 in our Best Tower Defense Games verdict.