In order to incorporate multiplayer, the developers had to modify features that usually pause time such as the pipboy menu and the VATS system that lets players target individual body parts.

Titled New Vegas: Multiplayer, the project uses the game’s original Gamebryo engine but has modified it extensively to add multiplayer, with 91,041 additional lines of C++ code. Now it looks like fans may succeed where the development studios themselves have failed, as modders have managed to add online co-op functionality to the 2010 game Fallout: New Vegas. Fans of the Fallout series have been asking for an MMO or online game for years, and there was much disappointment online when the legal dispute between Bethesda and Interplay ended with the development of Fallout Online shutting down.