Halo 3: ODST takes place around the same time as events in Halo 2 and at the start of Halo 3 . The game tells the story of the Covenant's invasion of Earth in 2552 from the perspective of Orbital Drop Shock Troopers, focusing on the war-torn city of New Mombasa. The player controls various members of the ODST squad, with a main character known as The Rookie who can be seen as the protagonist.
The gameplay in Halo 3: ODST is different from previous games in the series. It's more open-ended and features exploration, rather than linear levels. The new VISR visor system helps players identify friends and foes, provides map data, and links up with AI systems controlling the city. Unlike before, player stamina and health are key factors, with reduced speed and jump height.
The game includes a Firefight mode, a four-player cooperative game where the focus is on the campaign. This mode takes inspiration from film noir and jazz elements in its soundtrack. The Halo 3: ODST package also comes with an additional version called Halo 3: Mythic , which is a stripped-down, multiplayer-only experience featuring all downloadable maps from Halo 3 , including new and previously unreleased maps.