Halo 3: ODST is a first-person shooter that covers the events leading to Halo 3. Instead of the Master Chief, players take control of a rookie Orbital Drop Shock Trooper (ODST) caught in the chaos of New Mombasa following the aftermath of a massive shockwave caused by the retreat of an invading Covenant ship.
The campaign mode which covers the story can be enjoyed in singleplayer or multiplayer co-op with up to three other players. Campaign missions are branching and can be played in any order once the appropriate objectives are reached.
Halo 3: ODST's multiplayer modes meanwhile are accessed from a separate disc, featuring 21 maps from Halo 3 and 3 new maps. A new cooperative multiplayer mode called Firefight pits up to four players against waves of enemies in timed survival matches where new abilities and handicaps are introduced after a set number of rounds.