Celebrate Sonic's 20th birthday with him and his friends.
In the celebration of the blue hedgehog's 20 years, extraordinary events occur in his world: a mysterious force opens a hole in time and transports Sonic and his friends to the past. There, Sonic meets his former self, as he was in 1991. Together, they will once again take on the task of bringing order to the world. Modern Sonic and classic Sonic must face new threats, save their friends, and discover what lies behind the mysterious time holes.