Mods are popular enough to sustain substantial online communities, and when it comes to modding communities, there are few that can rival the one for Bethesda games. Mods (short for “modification”) allow players to tweak the game, from things as minor as interface tweaks to more substantial additions like new characters and locales. While some play on console systems like the Xbox and PlayStation, many are playing it on PC, because that version offers mod support. You may already own it: Bethesda Softworks, the game’s publisher, announced that they had shipped 12 million units of the game “representing sales in excess of $750 million” (shipping, it should be noted, is a different metric from sold). You may already know this, since the game has been the subject of a pretty heavy media blitz before launch. Fallout 4, the newest blockbuster role-playing video game, came out last week.