Sonic 3D: Flickies' Island

Doctor Robotnik discovers mysterious birds called Flickies that live on an island in an alternate dimension. He learns that they can travel anywhere using large rings, so he decides to exploit them by turning them into robots to help him search for the Chaos Emeralds. Sonic arrives at the island only to discover the presence of Robotnik, and he is tasked with saving the Flickies and defeating his nemesis. Sonic travels through the island, saving the Flickies and clashing with Robotnik in his various machines. If the player collects all the Chaos Emeralds, Sonic proceeds into a black void, where he engages in a final battle with Robotnik, who pilots a large robot. Sonic manages to destroy the robot's weapons and defeats Robotnik, freeing the Flickies. If the player fails to collect the Emeralds, Robotnik escapes in their possession.