Sonic Unleashed, released as Sonic World Adventure in Japan, is a 2008 video game in the Sonic the Hedgehog series developed by Sonic Team and published by Sega for multiple platforms in 2008. The game follows Sonic the Hedgehog as he attempts to restore the world to normal after his nemesis, Doctor Eggman. The game also focuses on Sonic's 'werehog' form, which he gains during the beginning after coming into contact with the energy of Dark Gaia. Gameplay features two distinct styles, with each being played either during daytime or night-time. 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.