Sonic and his friends are just hanging out on a peaceful sunny day, finally having time to relax after Eggman's most recent defeats. However, Sonic closes his eyes for a second and opens them to see his friends are being abducted by Dr. Eggman! He rushes to stop him, but gets knocked out and sucked in like his friends...
When Sonic wakes up, he finds himself in Eggman's lab, and rushes through to find the evil madman. He finds Eggman, along with a machine with his friends trapped inside! He tries to fight Eggman, but the battle quickly causes the machine to self-destruct, scattering 10 crystals across the world. Sonic wakes up in Garnet Valley Zone and heads out to stop Eggman and find out what's happening.
From what is known, the gameplay is a mix of Generations and Lost World, featuring the tiered running and parkour of Lost World but with elements from Generations being equally prevalent. New to the series are the Prisms, which act as permanent power-ups Sonic collects throughout the world and can use at any time in a level. There are 10 confirmed, and using them allows him to use the powers of one of his friends, such as using Tails' flight, Knuckles' digging, Amy's hammer, or other traits. There is also going to be a Prism upgrade system, where defeating enemies and getting rings will help you gain Credits to buy upgrades that increase the duration, range, power or speed of the abilities from the Prisms. There will be at least 5 zones, each structured like the ones from Colors, with many Acts, and Unleashed-style hub worlds Sonic can explore.