The game takes place during the events of Halo 2 and Halo 3. Recognizable characters, such as Master Chief, are nowhere to be found, leaving the player to explore a different style of story. The design of the game has a detective feel, with jazz-influenced sound and film noir settings, designs and characters. When it was released, Halo 3: ODST became the top-selling game worldwide, selling more than 2.5 million units despite the relatively short campaign and the full-game price tag. The game includes Halo 3's multiplayer on a separate disc, including the original 11 maps in the 24 map package. It also includes a new cooperative game mode called firefight where players take on waves of enemies and see how long they can last.