Sonic Regress is a fangame trying to follow the functionality of the classics of the 16-bit era, with the goal of being another classic Sonic adventure.

Another of Robotnik's plans has been prevented by the blue hero and his friends. Although they have restored peace, the evil Doctor is far from giving up... looking at the Master Emerald data he collected before losing it, he twirled his moustache as he thought up another brilliant plan... using the data, he realized he could try creating a Chaos Emerald prototype... to make sure his plans don't fall easily, he created two.

Being Master Emerald's data used, the prototype acts like a Chaos Emerald, making his machines more threatening.

Sonic and Tails with nothing to do, went for a ride on the Tornado, and they realize something familiar on an island, Death Egg under construction... both went to the island, but one of Robotnik's machines hit the Tornado and fell into the island, near a coast. It's now where a new adventure begins.