Sonic Unleashed is a platform game in which the player controls the titular Sonic the Hedgehog in two modes: fast-paced levels that take place during daytime, showcasing and using Sonic's trademark speed as seen in previous games in the series, and slower, night-time levels, during which Sonic transforms into the Werehog, and gameplay switches to an action-based, brawler style of play, in which Sonic battles Gaia enemies (those created by the main enemy in the game, Dark Gaia).[5][6] Each level takes place on a particular continent, each of which is based on a real-world location.[1] In sections of the Xbox 360 and PlayStation 3 versions of the game, the player may choose to advance the time of day in order to play as either Sonic or the Werehog; in the Wii and PlayStation 2 versions, time is advanced automatically.[7]
Daytime levels focus on Sonic's speed, and to this extent, sees the player control Sonic through fast-moving stages containing both 2D and 3D styles of gameplay.[8] 2D sections are reminiscent of the Mega Drive/Genesis-era Sonic games where the player controls Sonic in a side-scrolling fashion,[9] while 3D sections see the camera placed behind Sonic so the player may move in all directions. In addition to moves available in past games, such as the Homing Attack,[10] new moves are also introduced. For instance, a new sidestep feature known as the Quick Step is available, allowing Sonic to dodge left and right, and a Drift feature, which allows Sonic to make tighter turns without slowing down.[10] The game also features a gameplay mechanic previously used in the Sonic Rush series called the Sonic Boost, which greatly increases Sonic's speed, allowing him to smash through objects, destroy enemies instantly, or even access different level paths.[11] In the Xbox 360 and PlayStation 3 versions, an on-screen "Ring Energy" meter displays how much Boost is available.[11] The amount of Boost remaining may be increased by collecting more rings, and is decreased by using the Boost.[11] In contrast, the Wii and PlayStation 2 versions of the game represent available Boost using bars, which may be added by performing "Action Chains", destroying multiple enemies in quick succession through the use of homing attacks, or by collecting rings. Japanese game company Dimps helped design some of the stages.[12][13]