<P> Bungie initially conceived ODST as a small side project to produce in the lull between Halo 3's completion and Halo: Reach . Instead of featuring recognizable characters such as armored protagonist Master Chief, the developers focused on the ODSTs . Story director Joseph Staten penned a detective story utilizing film noir designs, settings, and characters . Composer Martin O'Donnell abandoned his previous Halo themes to create a quieter, jazz - influenced sound . During development, the planned expansion grew in scope to that of a full - sized game . Release marketing for the game included a tie - in comic, live - action trailers, and print and web advertisements . </P> <P> Upon release, ODST became the top - selling Xbox 360 game worldwide . The title received generally positive reviews from critics, who praised the atmosphere, music, and story approach . Reviewers were divided on whether the relatively short campaign and included extras were enough to justify the game's US $60 price tag . The game was the top - selling title in the United States in September 2009, and sold more than 3 million copies worldwide . Softpedia, Time, and Wired were among publications that declared the game one of the year's best . </P> <P> Halo 3: ODST is a shooter video game with most gameplay taking place from a first - person perspective . The game features an open world environment in the updated Kenyan city of Mombasa, referred to as New Mombasa . Although the gameplay of ODST bears a strong resemblance to that of previous Halo titles, the player does not assume the role of the enhanced human supersoldier Master Chief, protagonist of Halo 3 . Instead, the player controls human soldiers known as "Orbital Drop Shock Troopers" or ODSTs . Since ODSTs do not possess the Master Chief's advanced armor and reflexes, they cannot jump as high, move as fast, survive large falls, or wield two weapons at once . Instead of the Master Chief's damage - absorbing energy shield, the game uses a recharging stamina mechanic . After the player sustains damage, the screen flashes red and the stamina score decreases . If the player receives additional damage before the stamina can recover, the player's health is reduced . Loss of all health causes the player character to die and restart at the last saved checkpoint . Medical packs scattered around the game environment can restore the player's health . The player's head - up display (HUD) includes a "VISR" mode that outlines enemies in red, allies in green, and items of interest in either blue or yellow . </P> <P> The game's Campaign mode may be played alone or cooperatively with a maximum of three additional players . As a lone human soldier known as "the Rookie," the player's goal is to discover what happened to his missing teammates . After finding a piece of evidence left behind, such as a sniper rifle hanging from a power line, the player will enter a flashback mission, where they assume the role of the missing soldier six hours earlier . After the player has found the first piece of evidence, the choice of where to go next is left open; campaign levels may be played in any order . </P>

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