Screeps: World is an open source MMO RTS sandbox game for programming enthusiasts, wherein the core mechanic is programming your units AI. You control your colony by writing JavaScript which operates 24/7 in the single persistent open world filled by other players on par with you.
It appears that there is a 50% discount on Screeps World during the summer sale
Garbage collection in, garbage collection out. (Unpredictable gc is the bane of my life).
People code in rust, c++, C# etc via wasm