Stardust Speedway Zone is the sixth Zone of Sonic Mania, which is based on Stardust Speedway from Sonic the Hedgehog CD. The player is sent here from Press Garden Zone by the power of the Phantom Ruby at the hands of Dr. Eggman.
Act 1 is set in the Past version of the Zone, with elements of Marble Garden Zone present throughout much of the Zone such as pulleys, downward loops with pillars that the player spirals around, and wheels that open passageways when Spin Dashed into. Since Sonic CD, the flora around the stage has grown to cover more of the highways, and the Capsules containing the magic flowers of Little Planet are now littered across the Act. When destroyed, giant plants quickly grow to cover the surrounding area, spawning leaves that the player can use as platforms along with dangerous bio-mechanical heads that are harmful. The Zone is now more golden in appearance, decorated with things like pillars, ancient vases, stone griffins that carry Rings, and constellations in the sky depicting various things such as harps, Roman helmets and Sonic's head. There are also many fireflies swarming the Act, decorating the place with glowing orbs of light.
At the end of the first Act, the player automatically destroys one of Dr. Eggman's robot transporters and travels forward in time to Act 2, which is set in the Present version of the Zone, where everything is more urbanized and industrialized. Features include bungee cords that fling the player into the air, fireworks the player can ride on, and all kinds of neon lights and musical instruments, though the path-swapping system that was featured in the original version of the Zone is no longer present. The giant golden Eggman statue that was found midway through the Zone is now located at the end, serving as the setting for the battle with Metal Sonic.
As of v1.04, Stardust Speedway ends with a computer hologram that foreshadows a later Zone, with Eggman using the Phantom Ruby to send the heroes to Hydrocity Zone shortly afterwards.
In Encore Mode, the green highways and flora of Act 1 have become a yellowish colour, and the sky has changed to a crimson hue. Likewise, Act 2 changes the colour of the highways to a dark green colour and the urban buildings in the background becoming crimson, giving the entire Act a similar colour scheme to the original stage's Bad Future.
||Relax to the mellow funks of the past as Sonic and friends return to Little Planet's firefly-lit marble cityscape. But things aren't so simple as fauna has grown rather lush.
— Theme trailer description
References and Easter eggs