Easel is an automatic multiplayer game engine that I have been working on for three years. It's been a huge project, and I've had to discover many new ways of doing things to get the peer-to-peer rollback netcode to work as well as possible. I've had trouble explaining why it's not just another rollback netcode implementation, and this is the first time I've been able to articulate them all on a single page. I'm wondering if Hacker News has some other multiplayer networking/game engine/programming language geeks out there who love this kind of stuff too. Would love to hear more about your projects!