An alternate reality game (ARG) is an interactive narrative that uses multiple media to tell a story and requires user participation to advance the plot. ARGs have been used since the late 1990s to promote movies, TV shows, and products. They embed narrative elements in the real world and across different online and real-life platforms, with no single medium containing the entire story. Players must collaborate to piece together clues and solve puzzles, with the game masters adapting the narrative based on player actions and theories.