How Old Light uses delta encoding to sync multiplayer game state efficiently

Old Light is a browser-based strategy game designed to run for days, requiring an efficient method to keep each player's game state accurate without resending the entire world. The server sends lightweight 'world delta' messages describing only what changed — such as players joining, leaving, or sectors going stale — rather than full state snapshots. Because the server broadcasts identical delta messages to all connected clients, it avoids the costly process of tracking each client's individual state. All values in a delta represent absolute totals, making patches idempotent and resilient to missed or duplicate messages. To handle privacy, the server generates two different patches from a single game event — a scrubbed public version for all players and a detailed private version only for the affected empire's owner.