Story: sonic was running through green hill zone and he stop by to visit tails suddenly there's that Universe Eater (just like the time eater, and is not classic and modern eggman in there.) and Teleport Sonic and Tails to The Other Universe, when sonic falls down on the land (just like others ones you know) when sonic gets up he sees the world of The Valley Sonic Checks it out (tails be somewhere in this place, so i don't yet) sonic met up with Fone Bone and his friends so they tell him about this place and they team up to save the world (and rescue tails) and defeat the Universe Eater.
Sonic The Hedgehog
Tails Miles Power
(more characters here
(more levels soon)
The Universe Eater (final boss)