Basically, it's an alternate timeline where you get the bad ending in Sonic Mania.
After being defeated in the Titanic Monarch, Dr. Robotnik tries to study the power of the Phantom Ruby, "The power of this stone is far beyond anything I imagined, as if it could surpass every boundaries possible, my metallic experiments ended up in mediocrity, it's time I level up my game...".
He locked himself up underground in a bunker working with what was left of his plans and most important machines. He finally created the first being powered by the phantom ruby, using Sonic and his friends' DNA, Meta the Eternal, the most powerful Eternal in the universe; Eternals are incredible beings that never ages and are virtually indestructible. This new creation was learning at an insane rate and its intelligence nearly matched Robotnik's, her awareness surpassed the 12th level and she began looking for beings capable of fighting equally against her.
She eventually learned about the existence of Sonic, a blue hedgehog Eggman seems to hate deeply. After months of intense planning, he discovered where the phantom ruby originated. From The Supreme Ruby, something with truly unlimited power, something that controls the mere existence of the multiverse.
Meta and Eggman were finally ready to conquer the planet, no, the universe, but Meta, being free-willed, wanted something more, she wanted to battle "Sonic the Hedgehog", but the only way to do that was to kidnap every person standing in her way, so she decided to trap Sonic's friends in solid capsules.
Sonic will have to free his friends to take down Meta at any cost... but how?
About the game
It's unsure if the game will be ever completed one day, but we sure hope so!
In this game, there are two zones, with 1 level to play with each, and a boss level. Each Act 1 levels end with a Mini-Boss battle, and Act 2 levels end with a Big Boss battle.
You got 3 playable characters, the same as Mania: Sonic, Tails, and Knuckles. They all have a new ability if you press the special button. Sonic got the Homing Drive, where he can go higher and faster with it. Tails can defend himself easier when flying with his new Tail Whip. Knuckles can finally go faster with his Mega-Punch, where he can destroy enemies while running.
It may not work on some computers, for old computers, it will do the d3dcreateservice() error and another error that I don't know why it happens, but it happens on some computers.