[Rohansi]

> Every developer on videogames has some kind of offline mode already implemented, because its necessary to be able to playtest the game builds on the developer machines.

Not guaranteed. Many just run a local server, either in-process or externally. Minecraft's singleplayer mode actually runs a server in-process internally. This simplifies development because singleplayer is conceptually the same as playing alone on a server.

This gets more complicated when there are infrastructure servers in the mix for things like player state, matchmaking, etc. You would bypass that in development but they are required for normal play while being external to the game server.