Like previous Ridge Racer titles, the focus of gameplay is on placing first out of 14 in numerous 3-lap races across several tracks and numerous cars. In most races, the player can earn up to three nitrous boosts by successfully drifting around corners without crashing, which can then be used to give the player a short burst of speed. Some races are labelled as "no-nitrous", which prevent the player from earning any nitrous during the race, though the player can optionally enable nitrous. If the player wins using this option, the race is considered complete, but noted for breaking the no-nitrous rule. Some races are also Duels between the player and a single computer opponent, who is usually equipped with a much better car than the player can select from.
Ridge Racer 6 introduces a career-mode "World Xplorer", a branching-tree arrangement of races in which the player can only attempt races next to a race that has already been successfully completed. The layout of the races in the Xplorer is such that the position of a race will indicate what class of car can be used (horizontal position) and the difficulty of the course (vertical position). Rewards can be obtained by completing certain races or completing all races that enclose an area on the Xplorer, and usually offers new cars but also include additional variations of the tracks (mirroring and reverse) or new branches added to the tree. A player can also engage in quick races and time challenges for any track and car that has been unlocked.
Source: Wikipedia, "Ridge Racer 6", available under the CC-BY-SA License.