Gameplay in Zero Gravity is largely similar to its predecessor, with characters racing on different types of hovercraft called "Extreme Gear". In addition to the mechanics from the previous game, such as the trick system, Zero Gravity adds a new gameplay system based around gravity that replaces the predecessor's "fuel" system. During the race, performing tricks and other actions will increase a character's Gravity Points, or GP. If players have accrued enough GP, they can perform one of two maneuvers. A Gravity Dive will create a small black hole that points gravity forward down the track, giving the player a powerful free-fall boost that is further augmented by striking objects in the vicinity that the hole displaces, such as cars or signs. Alternatively, Gravity Control will alter the gravity of the course, allowing players to reach otherwise-inaccessible areas and shortcuts. Players can also use Gravity Control to more easily maneuver around sharp corners.
Building on the upgrade system from Sonic Riders, Zero Gravity features a new system called "Gear Change". Once players gain a certain number of rings during a race, they can choose to activate one of their Gear Parts. Gear Parts are predetermined based on the racer's equipped Extreme Gear, and will grant bonuses when activated, such as increasing a character's top speed or automatically accessing shortcuts that would otherwise require Gravity Control. In addition to the boards, skates, and bikes from the previous game, Zero Gravity also introduces three new types of Extreme Gear: air rides, yachts, and wheels. New Extreme Gear can be unlocked via the in-game shop, with different Gear providing different advantages and unique abilities.
Zero Gravity once again features two story campaigns, "Heroes" and "Babylon", which intersect with one another to create a single narrative. Three new game modes have also been added: Survival Mode, Survival Relay, and Survival Ball. Survival Mode entails each player to pick up missiles, then lock on and launch them at foes with Gravity Control, the winner being the last person standing. In Survival Relay, teams of two compete in a relay race, using their Extreme Gear as the baton. Survival Ball is a soccer-like minigame, in which players use Gravity Control to launch a ball through hoops. The game includes a total of 16 race tracks, spread across eight areas with two tracks each, which are unlocked via story progression.
