Adrian Zeyfang: Probably Impossible: NecroDancer's network code

A technical overview of Crypt of the NecroDancer's unique approach to online multiplayer, based on the principles of rollback, while replacing the conventional frame-based timeline by a turn-based system. Bringing online multiplayer to a rhythm game in which players can directly interact with the world and each other poses many challenges that aren't typically encountered while working on other network games - all while preserving the emergent, quirky mechanics that the game's community grew to love. This talk introduces a conventional rollback approach, then gradually shapes it into the architecture found in NecroDancer today, describing and resolving edge cases along the way. Follow the journey of how online multiplayer, a feature once dismissed as "impossible", was implemented!