While it was commercially successful-selling 2.45 million units-critical reception was mixed.
Public anticipation for Sonic Unleashed was high, as video game journalists saw it as a possible return to Sonic's platforming roots.
Night-time levels see Sonic transform into the Werehog gameplay slows down to accommodate greater platform play, and involves combat against waves of enemies using the Werehog's brute strength. Daytime stages incorporate Sonic's traditional platforming and trademark speed, with a combination of behind-the-back third-person viewpoints and 2D side-scroller platforming gameplay seamlessly transitions between these two views. Gameplay features two distinct styles, with each being played either during daytime or nighttime.
Sonic Unleashed (known in Japan as ' Sonic World Adventure') follows Sonic as he attempts to restore the world after his nemesis Doctor Eggman shatters it with a powerful laser to unleash Dark Gaia, an ancient evil, while dealing with having become a 'Werehog', a werewolf-esque transformation, which he gains after coming into contact with the energy of Dark Gaia.