Atompunk is like a specific esthetic. Imagine cold war era, but with the what they thought looked futuristic made real. Think themes around nuclear annihilation, global espionage, alternate-history and retrofuturism.
If you know the Fallout videogames, like that.
I just expect a popup in the game which says something like “Could not connect to server, some multiplayer features will be unavailable. Continue offline?”