Sonic the Hedgehog is a videogame character who was first introduced in 1991 with his appearance in Sonic the Hedgehog from Sega. There have been a number of Sonic the Hedgehog games over the last 20 years and Sonic has had cameos and special appearances in a number of other games as well. He has also appeared in a number of animated series and in a variety of comics. Sonic Generations commemorates Sonic the Hedgehog's 20th Anniversary. It was developed by Sonic Team and lets players play in both a classic mode and a modern style of game play.
The basic game theme is that Sonic's world has been thrown into chaos because a new power (Time Eater) begins to create time holes that take Sonic and his friends back to different times and places in the past. While in the past, he runs into a variety of characters from previous games including a younger version of himself. He and the younger version of himself as well as Tails race around trying to find all of their friends that are scattered throughout the world so they can put everything right again. Once they find out who is behind the Time Eater, they need to defeat him and send everyone back to their correct time.
Sonic Generations is an arcade style game. You travel through the game by running, jumping, and rolling from level to level. You collect rings by running into them and run, jump, and otherwise maneuver around enemies. There are nine different zones or levels that you play in that are based on previous games (Green Hill, Chemical Plant, Sky Sanctuary, Speed Highway, City Escape, Seaside Hill, Crisis City, Rooftop Run, and Planet Wisp). Each of the nine zones has a main challenge along with ten smaller challenges that you need to accomplish. As you beat the challenges, you accumulate points that you can use to unlock upgrades like abilities, shields, or the original Sonic the Hedgehog Genesis game. You can also unlock special artwork and music as you beat the challenges and find the five special red rings hidden in the zone.