Code your colony
Screeps: World is an open source MMO strategy sandbox where you play by writing JavaScript. Your code controls units called creeps, which harvest resources, build structures, mine, defend, and conquer territory. The world is a huge persistent open map where every player's units coexist in real time and follow the same rules. Your scripts keep running 24/7, so your creeps keep working while you are offline. Territory control matters: as you expand your footprint, your influence and ability to grow with it increase, and competing players may push back on the same land.
Playing with a group
The server is open source, so you can host your own instance and set your own rules. That lets you and your friends play together over LAN or over the internet, and you can run a private server at a faster tick rate to develop and test your scripts. On the official server, all players share one real-time world, so your group can cooperate or compete for the same territory. There is also a standalone world shard where CPU-locked players compete on equal terms.
Before you start
Basic programming skills are enough to get going, but experienced developers can push their code hard. You can edit scripts in the in-game editor or in your own external IDE, and WebAssembly support opens the door to C/C++, Rust, TypeScript, Go, C#, F#, Kotlin, Swift, D, Pascal, Zig, and more. The game is deliberately slow-paced, ticking every 2 to 5 seconds depending on the shard, which gives you room to debug scripts against the live world. The starter package includes permanent MMO access with a 20 CPU limit; you can unlock your full CPU later through an in-game CPU Unlock item bought with in-game credits, or skip that and stay on the CPU-locked shard.