Sonic Unleashed[a] is a 2008 platform video game in the Sonic the Hedgehog series. The story 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 his "Werehog" form, which he gains after coming into contact with the energy of Dark Gaia. Gameplay features two distinct styles, with each being played either during daytime or nighttime. 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. 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.