You can still find original discs on second-hand marketplaces like eBay or Amazon.
Since there is no official digital storefront (like Steam or GOG) where you can buy a "Sonic Riders Zero Gravity download," you must rely on physical copies or community tools to play on modern hardware. sonic riders zero gravity download
Unlike traditional racers, you can use "Gravity Control" to take sharp turns or "Gravity Dive" to launch yourself forward through air pockets. You can still find original discs on second-hand