Warzone 2100 is a free, open-source real-time strategy game from 1999 where you don’t pick units from a menu, you design them. Pick a body, bolt on a propulsion system and a weapon, and your factory starts turning out the tank you just invented. Twenty-seven years later the base-building loop still holds up, and the game is still getting updates.
Why Warzone 2100 still holds up
Pumpkin Studios made Warzone 2100 and Eidos released it in 1999 on Windows and the original PlayStation. Support ended a few months later, and in 2004, after a fan petition, the source code was released under an open-source license. Volunteers have kept it going ever since as the Warzone 2100 Project. The current version, 4.7.0, came out in April.
The hook is the unit designer. Research unlocks new bodies, propulsion, and weapons from a tech tree of more than 400 technologies. Halftracks or hover, machine guns or artillery, light body or heavy, you decide what rolls out of the factory, and you can redesign it the moment research hands you something better. Add cyborgs and VTOL aircraft and your army ends up looking like your answer to the map, not the designer’s.
The base is where that plays out. Factories, research facilities, power generators, and defensive lines spread across the map as the game goes on, and a good research path matters as much as a good attack. There’s a full single-player campaign about rebuilding after a nuclear war, skirmishes against AI bots, and online or LAN multiplayer with cross-platform play.
Get it at wz2100.net. It runs on Windows, macOS, and Linux, needs about 150MB without the campaign videos, and runs fine on integrated graphics. The Windows installer has a checkbox to grab the campaign videos too, and they’re worth it.
Games that push the base-building idea further
These six newer games each take one piece of the Warzone 2100 loop, whether it’s scale, terrain, building freedom, or a classic base and tech climb, and push it hard.
Tempest Rising
Tempest Rising is the most direct modern take on the classic base-building RTS. Slipgate Ironworks released it in April 2025, and it plays like the late-90s and 2000s games it’s openly modeled on: build your base, harvest resources, climb the tech tree, and save up for one of two superweapons per faction. The Global Defense Forces and the Tempest Dynasty each get an 11-mission campaign, and skirmish lets you field up to 500 units per side.
The third faction, the alien Veti, got its own 11-mission campaign with The Veti’s Wrath on September 29 ($19.99), and a free official map editor with Steam Workshop support arrived in July. Tempest Rising isn’t on GOG. It’s $39.99 on Steam.
Beyond All Reason
Beyond All Reason goes for a bigger base and a bigger war. It’s a free, community-built game inspired by Total Annihilation, with team games up to 8v8 and thousands of units on the map at once. Every projectile is simulated, explosions reshape the terrain, and mountains block radar, so the ground you build on matters. Your economy grows exponentially, and the game is about turning that growth into factories faster than the other side.
It’s labeled alpha, but it plays like a finished game and updates constantly. It’s free at beyondallreason.info for Windows and Linux (no Mac), and it wants at least 12 GB of RAM. A Steam release is planned with no date yet. If you’d rather play the original that inspired it, Total Annihilation: Commander Pack is $0.99 on GOG right now.
Zero-K
Zero-K comes from the same Total Annihilation lineage and leans harder into terrain. You can dig canals, raise ramps, and sculpt the land into a fortress. It has more than 100 units and a 70-plus mission campaign you can play solo or co-op, with no paid advantages. The Zero-K Team released it on Steam in April 2018, and it’s free on Steam for Windows and Linux.
Age of Empires IV
Age of Empires IV is the polished, historical version of the build-up-then-break-out loop. You gather, expand, and advance through the ages, and each civilization builds and fights differently enough that learning a new one feels like learning a new game. It launched in 2021, but it’s still getting big expansions. Raiders of the North came out October 29 with the Vikings and the Scots, and Dynasties of the East added four variant civilizations last November.
It isn’t on GOG. The Anniversary Edition is $39.99 on Steam, and Raiders of the North is $19.99.
Cataclismo
Cataclismo takes Warzone 2100’s design-it-yourself idea and applies it to walls. Instead of placing a prebuilt fortress, you build it piece by piece from wood and stone, design blueprints ahead of time, or use ones other players made. Then night falls and the Horrors come, and you find out whether your chokepoints and towers were as clever as you thought. Between sieges you send units out to gather the resources for the next expansion.
Digital Sun released it in March 2025 with Hooded Horse publishing. It’s on GOG for $8.99 (regularly $29.99) and $29.99 on Steam.
Diplomacy is Not an Option
Diplomacy is Not an Option is base-building at its most stubborn. You run a medieval town, build walls and an economy, raise an army, and then hold off waves that can top 25,000 enemies. Every arrow and catapult stone is physically simulated, so the fights look as chaotic as they sound, and an active pause lets you give orders without panicking.
It left early access in October 2024 with a story campaign, endless, challenge, and sandbox modes, plus a map editor. It’s on GOG for $11.99 (regularly $29.99) and $29.99 on Steam.
Where to get them
GOG’s strategy sale prices end Wednesday, November 4 at 11:59pm PT. Prices were checked on October 29.
| Game | Where | Price | Regular |
|---|---|---|---|
| Warzone 2100 | wz2100.net | Free | Free |
| Beyond All Reason | beyondallreason.info | Free | Free |
| Zero-K | Steam | Free | Free |
| Cataclismo | GOG | $8.99 | $29.99 |
| Diplomacy is Not an Option | GOG | $11.99 | $29.99 |
| Tempest Rising | Steam | $39.99 | $39.99 |
| Age of Empires IV: Anniversary Edition | Steam | $39.99 | $39.99 |
Start with Warzone 2100, since it costs nothing and shows you fast whether designing your own army is your thing. Then pick the modern game that matches how you like to build: Tempest Rising for the classic base and tech climb, Beyond All Reason for scale, Zero-K for reshaping the map, Cataclismo for building the walls yourself, Diplomacy is Not an Option for holding them against a flood, and Age of Empires IV for history with a long road of expansions ahead.