While previous games have been very linear, ODST shakes things up a little. When playing as the Rookie, you must explore the ruined streets of New Mombasa at night in what is a sandbox of sorts. It basically serves as a hub world for activating each level as you seek out beacons, ranging from a broken sniper rifle to a bashed helmet, to trigger the flashbacks in which you play as one of your missing comrades. More areas of the city are unlocked as you progress through the game. Scattered throughout the city are audio logs which tell the story of a citizen's bid to escape the city during the invasion, and collecting these helps towards unlocking various supply points which contain valuable weapons and ammo, as well as a mongoose or two – very helpful for quickly travelling from one end of the city to the other.