Sonic Unleashed

"The difference is night and day."

- Tagline

Sonic Unleashed (ソニックワールドアドベンチャー) is a game in the Sonic the Hedgehog series developed by Sonic Team Japan and published by Sega for the PlayStation 2, PlayStation 3, Wii and Xbox 360. This is the first main series Sonic game on the Wii and last for the PlayStation 2. The game follows Sonic the Hedgehog as he attempts to restore the world to normal after his nemesis, Doctor Eggman, splits the world's continents into pieces with a powerful new ray weapon and the power of the Chaos Emeralds to harness the power of Dark Gaia, as well as his struggles with his new beast form generated by Dark Gaia's energies, Sonic the Werehog. Whilst incorporating Sonic's traditional platforming and trademark speed, the gameplay style for this game is notably different, focusing on 2D side-scrolling platform gameplay rendered with 3D visuals, as well as behind-the-back, third-person stages; gameplay seamlessly transitions between these two styles. This radical change in gameplay, coupled with the focus on extreme speed and boosting (during the day stages), makes this game considered the first "modern" Sonic game, a style that was later represented in Sonic Colors, Sonic Generations and partially Sonic Lost World.

Gameplay
Gameplay primarily consists of two modes. The first is 2D side-scrolling platform gameplay, rendered with 3D visuals (as found in the Sonic Rush and Sonic Rivals series), with seamless shifts to behind-the-back, third-person stages. Concepts returning from past games include Sonic's trademark high-speed gameplay, as well as improved lock-on for automatically targeting and hitting enemies. In the 2D gameplay, sliding across the ground also returns, and a new feature, Drift allows Sonic to slide around a corner at high speed. Players will also be able to perform a new side-step maneuver known as Quick Step, allowing Sonic to instantly dodge obstacles to the left or right. As the player goes through the game and Sonic gains more experience points, the player is able to upgrade and gain new abilities for Sonic and Sonic the Werehog.

An on-screen Ring Energy meter can be filled by collecting rings, which is used to activate a temporary speed increase known as Sonic Boost, during which time the camera uses a fish-eye effect and motion blur; hitting enemies and obstacles will reduce the meter. Action Chaining allows the player to collect energy more quickly, by collecting rings faster or by stringing together sets of actions, including button input sequences, some of which will be in midair. Repeated action chains will allow the player to perform special moves or access different routes in the level. Shield pick-ups from previous games will make a return, protecting Sonic from various hazards.

The second is 3D beat-em-up style gameplay with platforming and puzzles thrown in. During night sections of the game, Sonic transforms to his alternate Werehog form, and gameplay shifts from fast-paced action to a slower, more platform-oriented style of gameplay. The Werehog form allows Sonic a great deal of strength, and gameplay involves smashing enemies and destructible environments, whilst his stretchy arms will allow him to reach high platforms and perform special attacks. The Ring Energy meter changes to two bars, Unleashed and Vitality; the Vitality Bar acts as a health bar and replenishes by collecting rings, whilst the Unleashed Bar activates with a button to increase attack strength, decrease vitality loss from enemy attacks, and enables special moves, and replenishes by defeating enemies and destroying objects.

Levels
Nine levels exist in the game on seven continents, all of which are based on real-world locations. Each stage is placed on a different continent on Earth. These locations include:


 * Apotos (Windmill Isle): This level is the first level in the game and serves as the backdrop to most of the tutorials in the game. Its architecture is influenced by Greek Mediterranean architecture, like the real Greek island of Chora, Mykonos Greece. It also looks similar to the Greek city of Santorini.
 * Spagonia (Rooftop Run): A level influenced by western European architecture, like the real Italian city of Siena.
 * Mazuri (Savannah Citadel): The sandy, desert-like level inspired by Africa . This is present in the Xbox 360/PlayStation 3 version as a hub world, day and night stages, on the Wii/PS2 version it is only playable for the boss battle against the Egg Beetle and as a hub world.
 * Holoska (Cool Edge): An icy location, most likely based on Alaska (due to the name).
 * Chun-nan (Dragon Road): A level inspired by China's architecture. It includes a run along what looks like the Great Wall.
 * Shamar (Arid Sands): A stage designed to resemble a Middle Eastern desert landscape, probably Petra, Jordan.
 * Empire City (Skyscraper Scamper) A location based on New York City where Sonic is shown to run between skyscrapers. This stage is only available on the PlayStation 3/Xbox 360 version.
 * Adabat (Jungle Joyride): A level inspired by Angkor and Southeastern Asia themes. It contains many flowing rivers and high cliffs.
 * Eggmanland (Eggmanland/Crimson Carnival (Japan)): Eggman's empire, based on an island near the fifth continent. The stage is combination of an amusement park and a factory. It resembles a fusion of Circus Park, Lava Shelter, Hot Shelter and Final Egg.

Levels have been designed so that the two aforementioned modes of 2D and 3D gameplay will be switched between roughly every fifteen to thirty seconds. In addition, the game features a day-and-night system; some parts of the action stages have been specially built so that time will pass, and these can be played as either Sonic or his werehog form, while others are only built for one specific form, and during these areas, time will not pass. The player is easily able to advance time manually during the areas allowing either form, should they prefer one or the other.

The game also features town stages, or "hub-worlds", that are set in the same environments as the action stages and players also are able to walk around the environment freely and speak to townspeople, even gaining items from them. However, this "overworld" can be completely ignored, should the player prefer to simply play through all the stages. Optional side-quests are also available from these stages, for instance, using Tails to fly the Tornado plane; side-quests will be the only time characters other than Sonic will be playable. Such side quests are only available for the PlayStation 3/Xbox 360 version of the game.

Console Differences
Due to the different power and capabilities of the consoles of the PS3/Xbox 360 compared to the Wii/PS2, there are significant differences between the two versions of the game released. Note that there is an additional mobile phone release developed by Gameloft that sports completely different gameplay, so it is not considered here.
 * In the Wii/PS2 version, when you run into a specific part of a stage or hit a question mark in the action stages, Chip speaks and reads the words on the screen. In the PS3/Xbox 360, they are only read rather than spoken.
 * The hub world in the Wii/PS2 version consists of selecting an area to go than exploration. Also, the time of day is only changeable after the continent has been restored.
 * In the daytime stages, Sonic doesn't get an extra life after getting 100 rings in the Wii/PS2 version (nor are there extra life items), however, in the PS3/Xbox 360 version, he does (and there are).
 * In the Wii/PS2 version, lives work differently and are "permanent". Sonic, by default, always starts levels with 3 lives. For example, if Sonic lost 2 lives in a night act, he would regain them by the start of the next level. To obtain more lives, Sonic must visit areas in Gaia Gates that contain extra life items, which will permanently increase the number of chances Sonic has to complete a single level.
 * In the PS3/Xbox 360 version, Homing Attack and Grab lock-on reticules are green, while in the Wii/PS2 version, they are red.
 * The Mazuri levels were removed, as well as Empire City in its entirety, from the Wii/PS2 version (except for Mazuri's boss).
 * Sonic begins with all his abilities in the Wii/PS2 version, while he must acquire them in the PS3/Xbox 360.
 * Sonic the Werehog is the only one who levels up and what he gains is predetermined when he acquires a certain number of orbs in the Wii/PS2 version. He also has significantly fewer moves than in the PS3/Xbox 360, and in the Wii/PS2 version, he collects Dark Gaia Force instead of Chaos Orbs in order to improve his abilities.
 * Sonic's top speed and Sonic Boost gauge can't be leveled up permanently and are determined by rings gathered in the stage on the Wii/PS2 version. If Sonic takes damage, he levels down by one bar of boost. The PS3/Xbox 360 version allows these to increase in level for the rest of the game.
 * In the 360/PS3 version, the Sonic Boost is performed by holding down the boost button. It works continuously, and can be filled by collecting Rings and can be leveled up to increase the bar length. In the Wii/PS2 Version, the Sonic Boost works by pressing the boost button and the boost lasts for 2-3 seconds. It's filled by collecting Rings, performing Action Chains, and drifting. It costs one square of the bar to use a single boost and the bar can be increased by collecting Rings from a total of three bars to six.
 * Action Chains are a feature found only in the Wii/PS2 versions. When Sonic strings together certain types of combos, he can create an Action Chain. The more moves Sonic does, the more Boost power he gets.
 * Action Chains must be initiated with destroying 2 enemies consecutively. They can be continued by destroying more enemies, touching speed pads, starting grinding, and ring dashing. However, they cannot be continued by boosting, drifting, stomping, using jump pads (and their blue springs), or using pulleys.
 * Sonic must find Medals in the PS3/Xbox 360 version in order to access new levels. In the Wii/PS2 version, Sun and Moon tablets are used to access levels; the Medals are determined by rank or gathered automatically after certain missions, and they're used to unlock Secret Areas at Gaia Gates.
 * Gaia Gates are not present in the PS3/360 version. Instead, those versions feature fully explorable hub worlds.
 * In the Wii/PS2 version, the Gaia Gates serve as the hub worlds. In them, Sonic can use his medals to open up various puzzles, which are home to a variety of extras (including extra life items). Their only other function is to serve as a simpler level select.
 * Sonic's rank in the PS3/Xbox 360 version is determined by score and its worst ranking is E. On the Wii/PS2 version, regular Sonic's ranks are determined by completion time while Sonic the Werehog's are judged on three factors: level-up orbs gathered, completion time and number of rings gathered and the worst ranking of this version is C.
 * For boss battle rankings, the PS3/360 version is determined by score. The Wii/PS2 version uses time as its sole factor and has no ranks aside from S, which earns a medal and C, which doesn't award any bonuses.
 * Eggmanland is one long stage where Sonic switches forms in the PS3/Xbox 360 version. In the Wii/PS2 version, it starts with the daytime stage and missions before switching to 5 night-time levels. However, there is no explorable Gaia Gate.
 * In the "Jungle Joyride" stage on the PS3/Xbox 360 version, Sonic is seen running on the water, but in the Wii/PS2 version, Sonic appears to surf when he runs on it. This is also seen in a later game, Sonic Generations (3DS).
 * On the Wii/PS2 version, the Sky Chase minigames have been completely removed.
 * In the Wii/PS2 version, it is possible to Spin Dash. Sonic spins automatically whenever he boosts and encounters a speed pad. Also, at the beginning of the level, if the player presses the boost button or swings the Wii Remote, just as the countdown ends, Sonic will not only start off with a Spin Dash, but he will also get one free boost. If the player presses the button or swings too late, Sonic will trip and fall over for a few seconds.
 * Sonic has fewer voice clips in the Wii/PS2 version. For example, he only has one clip for boosting, while there are at least 3 in the PS3/360 version.
 * The Levels in the game are much more challenging in the PS3/Xbox 360 versions, and are much longer, while in the Wii/PS2 version, the levels are much shorter, and offer easier gameplay. Also, the PS3/Xbox 360 version is the only version in which the day stages have 3 acts for every continent.
 * On the PS3/Xbox 360 versions, the "Hedgehog Engine" is used. This is used to reflect light off everything on screen to produce CGI quality graphics in-game. As you would expect, the PS3/Xbox 360 versions of the game received more praise on the graphics front, however the Wii/PS2 versions were commended also. This engine is also used to load levels while you play them. This is needed to keep up with the incredible speeds Sonic reaches in the daytime stages of the game without encountering too many framerate or slowdown issues. It can allow Sonic to reach in excess of 300 MPH (483 km/h). Since the Wii/PS2 consoles cannot handle the capabilities of the Hedgehog Engine, the daytime stages were created by Sonic Team in cooperation with Dimps to supply alternative but similar gameplay.
 * In the nighttime stages, Sonic appears to run faster when dashing in Wii/PS2 versions compared to the PS3/Xbox 360 versions. His speed also seems to be less controllable and can shatter objects by running into them. Also, the "aura" on his attacks are blue in the Wii/PS2 version (and also red, green, and yellow), while it is purple on the PS3/Xbox 360, which is another thing to note at the graphical differences. Interestingly, the auras turn blue when Sonic activates his Unleashed Mode in the PS3/Xbox 360 versions.
 * In the Xbox 360/PS3 versions, the Star Posts or Checkpoints appears in the daytime and nighttime acts as well. But in the Wii/PS2 versions, the Star Posts appears exclusively in the Time Attack missions during the daytime sections, and they add time.
 * The Wii/PS2 versions of Unleashed are the last main-series Sonic games to feature item capsules in levels. In the night stages, these hidden objects hold extra Gaia force, Unleashed force, or hidden extras. In day stages, they only hold hidden extras. In Gaia Gates, they can hold hidden extras, extra lives, or unlock missions.
 * They behave slightly differently than other item boxes in the series. They cannot be destroyed by homing attacking, but can instantly be destroyed when touched.
 * They resemble the item boxes of the Sonic Rush series, and the design reappears in Sonic and Sega All-Stars Racing.
 * In the Wii/PS2 version, the night acts have names, and Apotos, Spagonia, Holoska, and Chun-nan each have three, Shamar and Adabat both have four, and Eggmanland has five. In the 360/PS3 version, each world (except for Eggmanland) have two acts (called Act 1 and Act 2).
 * The Wii/PS2 versions of the final boss (Perfect Dark Gaia section) has Super Sonic fight it by himself while the PS3/360 versions the Gaia Colossus fights Perfect Dark Gaia along with Super Sonic.
 * The PS2 version also has some differences between the Wii version. In the PS2 version, Sonic's looks and renderings are similar to his Adventure style. His quills also don't move like the Wii version. He even has a darker blue in the PS2 version.
 * On the Wii/PS2 version, Tricks can only be performed one button at a time, while in the PS3/360 version, all buttons can be performed simultaneously.
 * The Wii/PS2 versions have backward compatibilities to their successors (PS3 except for Slim and Super Slim models for the PS2 version and Wii U for the Wii version). The PS3/Xbox 360 Version are incompatible with their successors (PlayStation 4 and Xbox One, respectively due to hardware compatibilities) although their is no word if Sony, Microsoft and in some cases SEGA, will be able to return the game in the near future.
 * As of April 2014, the PS3/Xbox 360 version is downloadable and also sold as a disc while the PS2/Wii Version is only sold as a disc.
 * In the Wii/PS2 versions, Sonic appears to slow down when Sonic begins to side scroll but in the PS3/Xbox 360 versions, Sonic retains his speed.

Plot

 * For the script of the storyline, see Sonic Unleashed/Script.

At the beginning of the story, Sonic is confronting his nemesis, Doctor Eggman, on Eggman's flagship. Eggman then activated the ships defense systems, activating the cannons and bringing forth a horde of Egg Fighters. After seeing the obstacles, Sonic boosted forward and began dodging the batteries fired from the cannons. bounding across the flagship, Eggman brought forth his Mech and unleashed a flurry of machine gun fire. After running across the ceiling while dodging missiles, Sonic ran through the Flagship's hallway. Eggman fired his Mech's grappling hook-like arm and grabbed Sonic. After being pulled to Eggman in the Mech's grasp, Sonic summoned the Chaos Emeralds from within himself and became Super Sonic in order to stop him, destroying Eggman's mech, Eggman fled in his Egg Mobile and fled from his Flagship. after chasing Eggman through space and destroying have of his fleet, they finally arrived at Eggman's Research Facility and knocking Eggman himself to the ground. As a trap, Eggman pretends to plead for mercy. When Sonic is close enough, he activates the Chaos Energy Cannon, which traps Sonic in the center and begins drawing the Chaos energy out of Sonic and the Emeralds in a fashion that is clearly extremely painful for him.

After the weapon is charged, Eggman fires a laser at the Earth to wake a monster known as Dark Gaia, splitting the planet. The dark energy of the Emeralds is brought out by the ray, transforming Sonic into a monstrous version of himself and rendering the Chaos Emeralds gray and powerless. Eggman then opens an airlock which sucks Sonic and the drained Emeralds out into space and down to Earth. While Sonic is saved from a fatal landing due to an unknown energy source, he still ends up taking a heavy fall. After pulling himself out of the dirt, Sonic encounters a flying dog-like creature. Sonic then asks the creature what his name was and the creature couldn't remember his own name or history (which Sonic thinks he landed on him, causing the memory loss). Sonic agrees to help Chip restore his memory during their journey.

After exploring the city of Apotos, Sonic names the creature Chip and the two run into Tails at night. Tails immediately recognizes Sonic even though he is in his Werehog form and reveals that Professor Pickle of Spagonia University may be able to help them on their adventure. Once they reach Spagonia, they discover Dr. Eggman has kidnapped Professor Pickle for his knowledge on Dark Gaia. After traveling to Mazuri and freeing him, Professor Pickle explains the nature of Dark Gaia and reveals that restoring power to the Chaos Emeralds via the Gaia Temples would help the planet return to normal. Sonic then sets out to the seven Gaia Temples to restore the Emeralds and reassemble the planet. In Spagonia, Sonic and Chip run into Amy at night, who doesn't recognize Sonic in his Werehog form. He later saves Amy from Dark Gaia's influence and she, upon learning her savior's identity, decides to help Sonic and Professor Pickle. All the while, Dr. Eggman makes plans to reassemble Dark Gaia and finish Eggmanland.

During the restoration of the sixth Chaos Emerald and continent, it's revealed that Chip is in fact Light Gaia, the opposite of Dark Gaia, and he lost his memories because, like Dark Gaia, he was prematurely awakened by Eggman's laser when Eggman started the Time of Awakening, where Chip and Dark Gaia was meant to awaken, too early; likewise, Dark Gaia has not yet been fully reborn due to his premature awakening, and Sonic must stop Eggman before Dark Gaia's full powers return to its normal state.

At this point, Sonic travels to the location of the last temple, over which Eggman has built Eggmanland using an extraction of Dark Gaia's power. While Sonic is able to restore the last emerald and defeat Eggman's newest mech, Dark Gaia becomes complete, by draining the dark energy that Sonic had that turned him into Werehog, knocking Dr. Eggman out of the way to keep the power for itself. Sonic is too weak to move so Chip uses the Gaia Temples to form a body called Gaia Colossus to combat Dark Gaia with, Sonic recovers on the Gaia Colossus and helps Chip fight Dark Gaia. Chip and Sonic hold off the beast, but Dark Gaia manages to drown the planet in darkness, achieving its fully-matured form in the process. Sonic then transforms into Super Sonic using the seven Chaos Emeralds and takes Perfect Dark Gaia down with the help of Gaia Colossus, but the battle leaves him too drained of his energy to escape. As the final continent moves back into place, Chip flings Sonic back onto the surface while he remains behind. After Sonic wakes up, Chip's necklace and some parting words are found on the ground. Sonic then picks it up and puts on the necklace as a bracelet to remind them of their adventures together. The game ends as Sonic runs off with Tails, who is in the Tornado, towards another adventure.

Characters
While these characters were confirmed to appear in the game, Sonic is the only playable character (although the player does take control of Chip for brief sections during one boss battle). However, optional mini-games were going to be available, during which time another character was planned to be used in order to complete them. Tails also controls the Tornado plane in missions similar to that of Sonic Adventure, but can only be played in the PlayStation 3 and Xbox 360 versions
 * Sonic the Hedgehog
 * Super Sonic
 * Sonic the Werehog
 * Chip (Light Gaia)
 * Gaia Colossus
 * Amy Rose
 * Miles "Tails" Prower
 * Professor Pickle
 * Doctor Eggman
 * Dark Gaia
 * SA-55 (Orbot)

Development
The development of Sonic Unleashed was announced in April 2008. Unleashed was originally intended to be the third installment of the Sonic Adventure series and subsequently, at an early development stage, had the working title Sonic World Adventure, complete with work-in-progress logo. However, the development team began to introduce enough new innovations to separate it from the Sonic Adventure titles, and so a new title, Sonic Unleashed, was decided upon. It was then later revealed that the game's name in Japan would in fact remain Sonic World Adventure for its release there.

The title was first brought to public attention when the Sonic Unleashed name was trademarked by SEGA on 12 March 2008. Screenshots of cut scenes, artwork, and a video were leaked ten days later; the title was then officially confirmed by SEGA on 3 April 2008 with a small selection of screenshots and an updated video.

The game was being developed internally by Sonic Team. It is a multiplatform release on the Wii, PlayStation 2, PlayStation 3,and the Xbox 360. There are two development "silos" that work on two separate builds of the game: one for the Xbox 360 and PlayStation 3 version, and one for the Wii and PlayStation 2 version. The Xbox 360 and PlayStation 3 versions run on SEGA's "Hedgehog Engine", which has been in production for three years and produces a frame rate of 30 frames per second. The Wii and PlayStation 2 versions do not take advantage of the Hedgehog Engine, instead using a modified version of an existing, internal SEGA engine.

The Wii version of the game has been developed specifically to take advantage of its controller's capabilities, with notable differences in gameplay. The game uses the Wii Remote and Nunchuk option; whilst character movement and basic actions are assigned to buttons, certain actions will benefit from physical movements. It supports the GameCube controller, and also the option of using the Classic Controller. The levels, whilst sharing the same styles, themes and motifs as the Xbox 360 and PlayStation 3 versions, are different to those shared between the Wii and the PlayStation 2 versions, and Dimps was only involved with design of the daytime stages for these versions.

Initially, it was stated that Unleashed was to be intended solely as a single-player experience, and would not offer any multiplayer or online modes. This was then cast into doubt when references to online modes were alluded to around E3 2008, but a later interview re-iterated that Unleashed would have no online modes at all. A demo was said to be available on the PlayStation Store and on Xbox Live near to the game's release, and was released recently.

On 12 March 2009, a Downloadable Content (DLC) pack was released for the Xbox 360 called the "Chun-nan Adventure pack"; the expansion includes four new daytime stages and two new Nighttime stages. A framerate patch was also included to fix framerate issues on areas and levels in the game such as the hub-worlds and Adabat. The package cost US$3.13 to download for the Xbox 360 and US$1.99 on the PlayStation 3, while the framerate patch comes free. On 26 March 2009, an additional expansion was released called the "Spagonia Adventure Pack". Just like the pack before it, it contains four new daytime stages and two new nighttime stages. Later, a "Holoska Adventure Pack" and a "Mazuri Adventure Pack" were released on 9 April 2009 and 30 April 2009 respectively, also containing four daytime levels and two nighttime levels. On 21 May 2009, another DLC Pack was released including extra levels for Apotos and Shamar, including five daytime levels and four nighttime levels between the both of them. In 11 June 2009, yet another DLC pack was released that included extra levels for Empire City, and Adabat, including five daytime levels and four nighttime levels between the both of them, and it was also said to be the last DLC content for Sonic Unleashed. On 2 April 2009 the "Chun-nan Adventure Pack" was released for the PlayStation 3 on the PlayStation Network, with all other DLC from the Xbox 360 Version were released to PSN later on.

Music
The game's theme song is "Endless Possibility" by Jaret Reddick. The song seems to take Sonic's point of view as to the events of what happens within the game. The themes of the various continents are developed with the region in mind. Each stage features instruments that are synonymous to the real-world area that the levels are based off, with the exception of Eggmanland, which uses synthesizers to emulate the technology theme. The ending theme, "Dear My Friend", is about the brief but touching friendship between Sonic and Chip. The game also has an orchestral theme called "The World Adventure" that plays during the credits and on the title screen. Most of the soundtrack was composed by Tomoya Ohtani, who has done works for soundtracks from Sonic Adventure 2, Shadow the Hedgehog, and most recently, Sonic Lost World.

The game's soundtrack was released as the album Planetary Pieces.

Other Media
Archie Comics stated that they had plans for an adaption of Sonic Unleashed, and made one a few months later. The adaption was simply titled "Sonic Unleashed" and featured the scene where Super Sonic changes into the Werehog, but with some minor changes. Such as the Gaia Manuscripts never being mentioned and Chip being nowhere to be seen. A Japanese magazine has also released a manga adaption of Sonic Unleashed. This manga was the first sighting of Chip.

Close to the game's release, SEGA revealed a trailer for an upcoming short animated film tilted Sonic: Night of the Werehog. The film, starring Sonic and Chip, has no dialogue, except for two instances where Sonic says "whoa" and "oops." The film is about 10 minutes long and was released in November 2008 alongside the game.

Reception
Sonic Unleashed received mixed reviews. Initial anticipation when the first media for Unleashed was revealed was high, as the demonstration videos hinted at a possible return of Sonic to his traditional platforming roots, especially after the decrease in the series' popularity and critical success after Sonic's transition to three-dimensional gameplay and a number of poorly received titles in the franchise that preceded it, such as the 2006 games, Sonic the Hedgehog and Sonic the Hedgehog Genesis. However, critical reception to Unleashed was mixed, with Metacritic aggregate scores of 54 and 60 out of 100 for the PlayStation 3 and Xbox 360 versions respectively and 66 out of 100 for the Wii and PlayStation 2 versions. GameSpot gave the Xbox 360 and PS3 versions each a 3.5/10 while giving the Wii version a 7.0/10. The added element of motion controls for the Werehog sections, as well as text-based hub worlds and better Werehog level design and camera system, were reasons cited for the higher review scores for the Wii version of the game, though a few review websites, such as 1UP, gave the Wii version a lower score than its Xbox 360 and PS3 counterparts.

Positive elements of Unleashed remarked upon by reviews include the environments, such as the "postcard-perfect architecture" and the graphics, with stages looking "absolutely gorgeous" and being "very pretty and lovingly animated", with one reviewer comparing them to a playable Pixar film. Praise was given to the technical competence of SEGA's new Hedgehog Engine as a whole on the Xbox 360 and PlayStation 3 versions, with "bright cartoonish graphics that fly by without a stutter"; however, some complaints were raised about frame rate reduction when large numbers of enemies appeared during the Werehog sections. Although the Wii and PlayStation 2 versions do not use the Hedgehog Engine, graphics for these platforms were still praised for their high quality, with the title being nominated for Best Graphics Technology for the Wii by IGN in its 2008 video game awards. The soundtrack to the game was also praised as being an improvement on more recent installments in the series; use of an orchestral score, rather than rock as in more recent games, was appreciated.

An overwhelmingly negative reaction was given by critics to the Werehog concept and corresponding night-time sections, which contributed greatly to the lower-than-expected review scores. Complaints stemmed from the game's change of speed, from high-speed daytime sections to the slower, night-time sections; the "pace-breaking combat levels" were described as "plodding", as well as "lethargic" and "combat-heavy". Further to the change of pace, the new style of gameplay that accompanies the night-time levels was widely criticized, involving "frustrating" platform elements and combat described as not "terribly interesting" and "boring", some reviewers felt that the Werehog as a concept did not mix well with the daylight areas and traditional Sonic gameplay; GamePro's review described them as "dreadfully out-of-place", while IGN stated that they have "nothing to do with Sonic whatsoever", feeling that the Werehog was "being slapped on" to the Sonic experience.

In stark contrast to the Werehog sections, many reviewers found the daytime levels to be enjoyable, especially the "exhilarating" sense of speed they provide; with "the most satisfying gameplay of any Sonic title in years", the game "perfectly captures the feel of classic Sonic". Many also enjoyed the mixture of, and transition between, 2D and 3D sections. Indeed, many reviewers remarked that they would have appreciated the game more had it comprised solely of, and expanded upon, the daytime levels. However, GameSpot's reviews for the Xbox 360 and PlayStation 3 versions argued that the controls were "unresponsive" in the daytime levels and that most of them were "horribly designed", instead describing the Wii version as a "vastly superior experience", with its daytime levels praised for better control and design.

Aside from the criticism of Werehog levels, further aspects of the game were criticized, contributing to the mixed review scores. The quests that players must undertake in hub-towns were described as "inane" and "tedious", where "figuring out what happens next involves aimlessly wandering through towns and speaking to citizens, only to discover that most of them don't know what we're looking for". The story and overall tone of the game, including the new character Chip, were criticized, some remarking that it was too juvenile, or comparable to that of a Saturday morning cartoon. Most reviewers also felt that the English voice acting for characters was poor. Some fans however feel that this is one of Jason Griffith's best roles as Sonic in a long time.

Despite most reviewers preferring the Wii/PS2 versions of the game over the Xbox 360/PS3 versions, some members of the fanbase feel the complete opposite, criticizing things such as the limit on the boost gauge, the bland levels and inferior graphics.

Trivia

 * Sonic Unleashed is the third Sonic game with the rating of E10+ (fourth, counting Sega Superstars).
 * The game's art direction and cut-scenes are widely inspired by animations of the Pixar Studio.
 * Between the HD games, the PlayStation 3 version runs faster at 60fps rather than a capped 30fps, but also contains more noticeable framerate dips (though it also drops in the Xbox 360 release in certain areas). Certain special effects such as Sonic's speed dust particles are also enhanced on PlayStation 3, though miscellaneous details such as windmills in the distance are missing. Character models are very slightly enriched on the PlayStation 3, while the Xbox 360 employs smoother shading. The transition between day and night was also changed to be a silent screen showing the medals (PS3) rather than Sonic's transformation. Between the SD games, the Wii release is generally regarded as superior, as the PlayStation 2 version has less polygons and dimmer lighting.
 * The Ghost photographers from Sonic: Night of the Werehog appear in the game, in the first scene at Eggmanland and in the missions of "Tower Terror" and "Fright Fight".
 * Knuckles and Shadow were planned to appear in the game, but they were later scrapped for unknown reasons.
 * When booting up the PS3 version of this game, some of Sonic's sprites from Sonic the Hedgehog are used before the SEGA motto loads up.
 * The achievement "I ain't fraid of no ghosts" is a reference to "Ghostbusters".
 * This is the first Sonic game where Sonic can collect at least 1,000 rings in a stage (daytime) as other games' ring cap limit is 999.
 * In the opening cinematic, a SEGA Dreamcast can be spotted when Eggman pushes the button to fire the laser. It is seen again later when the Egg Dragoon is defeated. In the cutscene where Sonic loses his Werehog transformation, a SEGA Dreamcast can be seen to the left of Eggman. The Dreamcast also makes an appearance in the scene after the Egg Dragoon is defeated, when Eggman is seen attempting to command Dark Gaia to destroy Sonic, the Dreamcast, along with a controller and a game case (with Dr. Eggman's 2D art for Sonic Rush as the cover) can be seen to the right of Eggman.
 * In the PlayStation 3 and Xbox 360 versions of the game, in the nighttime Spagonia HUB to the right in a small lane, a person in the shower can be heard whistling the theme from the teaser trailer.
 * In the PlayStation 3 and Xbox 360 versions, in the nighttime Mazuri hub, elephants can be spotted. However during the day, two zebras can be spotted.
 * This is the first game in the main series to be known by a different name in Japan, where it goes by the name Sonic World Adventure. The next is Sonic Generations, which was given subtitles.
 * In PlayStation 3 and Xbox 360 versions of the game, Mazuri is a playable level, but in the Wii and PlayStation 2 versions, it only features a boss battle. Similarly, the entire Empire City level was cut from the Wii/PS2 version.
 * The Daytime stage theme for Mazuri is actually a remix of the ending credit theme of Sonic the Hedgehog, Game Gear version.
 * This is one of the only four Sonic games to have a fully explorable 3D hub world. The other three are Sonic Adventure, Sonic the Hedgehog (2006) and Sonic Rush Adventure.
 * This is the second Sonic game where Sonic transforms into Super Sonic at the beginning of the game, the first one being Sonic the Hedgehog 3.
 * Despite the divided opinions, this game sold 2.45 million copies in little time.
 * The music in the Adabat day stages is a remix of the background tune in the level Regal Ruin in Sonic R.
 * This is the first Sonic game from the main console series since Sonic Adventure not to have Crush 40 perform the theme song.
 * This is the first main series game to not feature Knuckles the Echidna since Sonic the Hedgehog 3 and the first console game to not feature Shadow the Hedgehog since Sonic Adventure 2.
 * If you look at the news stand in the Empire City HUB closely enough, you can see a picture of the cover of Sonic The Hedgehog (2006) on a newsletter. This picture is also visible when looking over the shoulder of someone reading the newspaper in the background.
 * In Skyscraper Scamper Act One, at the beginning of this stage you can see highway signs that show some locations which are named after some characters that don't appear in the game. These include:
 * S.Shadow Avenue, Rouge St., E-123 Omega Rd, Blaze Rd, Silver Beach, Seaside Park, Chao Garden, West Park, Chao Beans, Soleanna Hotel, and Pachacamac Parking.
 * There are some levels that weren´t released in the last version,however they are in the game (Xbox360) doing glitches, here are some explains of were they are and the description and some other secrets:
 * Jungle Joy Ride Act 1 (Night):After the Goal Ring in Jungle Joyride's main Night stage, there is a sealed door. By using the wall-walking glitch, it is possible to cross through this door. There is a large, unused, empty chamber within. If accessed from the ghost mission instead of the main level, the door will be open, and there will be objects within. There is a tree which can be knocked down and used as a bridge, floating platforms, and switches that raise the water level. The platforms and the kill zone raise, but the room's unique water level puzzle is clearly unfinished- the water graphics remain in place. At the top of the room, there is a door. Beyond the door is an ornately detailed chamber containing the original Goal Ring.
 * Arid Sands Act 1 (Night): After the Goal Ring in Arid Sands' main Night stage, there is a sealed door. By jumping onto it from a well-positioned water barrel and using the uppercut, followed by the midair Y-Y-A combo, you can fall into an unused canyon area. It's empty, but you can open the sealed door from the other side. Bring water barrels to the bottom of the chasm, stack them, and do an uppercut-grab to go on. There is a huge chunk of level which is empty. Go on through it. There are, among other things, two pillars you can knock down, which don't appear elsewhere. Eventually, you will reach a pit, which is uncrossable without objects to bridge the gap. Beyond it is a fairly large stretch of level, leading up to the Gaia Temple.
 * Tails, Amy and Professor Pickle do not seem to have been affected by Dark Gaia. The Professor even remarks that he knows his assistant is affected by Dark Gaia, and that he must do something to help him.
 * The manual incorrectly states that the LT and RT (Xbox 360)/L2 and R2 (PS3) are not used in the day stages although they are used to perform Sonic Drift. Also in day stages section of the manual, if Sonic doesn't reach the goal within 10 minutes he'll lose a life which isn't true in the game itself, meaning the player can take as much time as needed to clear a day stage. (This is a reference to the classic Sonic games and also Sonic the Hedgehog 4 where the player has to finish each act within 10 minutes).
 * One cutscene contains a reference to the ending of Sonic CD. The cutscene plays after the first exorcism of the game. During the cutscene, Sonic (in his Werehog state) is seen carefully putting Amy on the ground after having saved her, with her eyes closed, then quickly leaving by swinging across buildings when she opens her eyes and turns to look at him. Much like how in the ending of Sonic CD, he put Amy on the ground, and then, while her eyes were still closed, he carefully backed away and then ran off just as she opened her eyes.
 * In 2007, the AOKI company revealed a scrapped concept art of the upcoming Sonic Unleashed, but by that time no-one actually knew about the game, perhaps it wasn't going to be Sonic Unleashed (these concepts were revealed privately).
 * Examining the contents of the game disc reveals what some of the regions intended names were before they were swapped for their current names. It seems some of them were named after actual locations on Earth.
 * Apotos - Mykonos, Greece
 * Mazuri - Great Mosque of Djenne, Djenne, Mali, Africa
 * Holoska - Alaska, Greenland, Antarctica
 * Spagonia - Siena, Tuscany, Italy, Spain
 * Chun-nan - Great Wall of China, Yanqizhen, Huairou District, Beijing, China
 * Shamar - Petra, Jordan, Iran, Iraq
 * Empire City - New York City, New York, USA (with Central Park as the hub world), Chicago, Illinois, USA
 * Adabat - Angkor Wat, Angkor, Cambodia (location); Thailand (flag),
 * Eggmanland - Disneyland
 * This is the first time Sonic has been tricked by Dr. Eggman who actually succeeds in it, as it is usually Knuckles the Echidna who falls for his made-up stories.
 * A common misconception is that Sonic Unleashed relates to the anime series Sonic X, although it does not.
 * On the 360/PS3 version when you get an A-Rank on a daytime stage (or complete a day mission) and on the Wii/PS2 version when you get an S-Rank, Sonic's pose accurately resembles that of his pose on the title screen and character select screen of Sonic Advance.
 * In the Xbox 360 version, after Perfect Dark Gaia is defeated and the Earth is returning to normal, Chip says "Sonic, You must live." The subtitles say "Sonic, You have to live."
 * This is the only Sonic game where Sonic never loses the Chaos Emeralds throughout the game.
 * On the official website the rating in the trailer showed is E10+ but the audio is the "E for everyone" rating clip.
 * In the Wii/PS2 version, the player can access the Spin Dash move by either pushing the boost button at the right times during takeoff in day stages or boosting shortly before or after running onto a dash panel or in certain areas, such as right before a loop.
 * The jump animation in the Wii/PS2 version is much looser than the one in the PS3/360 version, the latter being carried over to Sonic Colors and both versions of Sonic Generations.
 * This is the third Sonic game with an E10+ rating. The 2 previously ones were Shadow the Hedgehog and Sonic the Hedgehog (2006).
 * When Dark Gaia transforms in his perfect form, green blood can be seen when four arms grow from his sides, which is one of the main reasons why the game was rated E10+ by the ESRB, and 7+ by the PEGI.
 * On Sonic and SEGA All-Stars Racing for iPod Touch, iPhone and iPad, there is a mission called Sonic Unleashed. Inside the mission you play as Sonic, destroying wolf-like robots, possibly representing Sonic's struggle with his Werehog form.
 * In the PlayStation 3 and Xbox 360 version, there are two achievements named after songs from the British band, The Beatles.
 * This is the final Sonic game on the PlayStation 2 as well as the last Sonic Game to be released on a 6th Generation Console.
 * This is the first console Sonic game that used the Sonic Boost. Sonic the Hedgehog (2006) and Sonic and the Secret Rings had a similar move, but it was not officially the true Boost while in Sonic Rush and Sonic Rush Adventure. it was under the name Super Boost.
 * This is the second game to have a different level entrance screen than the rest of the Sonic games. The first was Sonic Adventure.
 * In the Demo version of Sonic Unleashed on the Xbox 360 the game will read Sonic World Adventure, the Japanese title and give a Japanese URL.
 * The Eggman bosses are based on animals of some sort, as Egg Beetle and Egg Lancer are both based on beetles, Egg Devil Ray is based off a fish, and Egg Dragoon has features similar to a dragon.
 * In the Wii/PS2 version of the game, the day/night times in the cities were a point and click static map which included the Gaia Temple, which was the exploration world and level select with its own "level" music. However, in the PS3/X360 version, this was removed to bring the "hub worlds" in.
 * For some reason, when Eggman split the Earth open, none of the oceans fell into the core.
 * The back cover of the Xbox 360 version doesn't mention that the game supports downloadable content, but it is possible that SEGA considered adding DLC for the game at the last minute. Strangely, this wasn't corrected in the Platinum Hits re-release.
 * Dr. Eggman's artwork for this game has the same pose as his artwork in Sonic Channel.
 * If you look around "BONNY'S KITCHEN" in the Empire City HUB closely enough, there is a magazine named "WORLD TREASURE" the cover appears to be Shamar.
 * During nighttime stages in the Wii/PS2 version, when Sonic picks up a box, the box's shadow won't show up but Sonic's shadow continues to show.
 * The Wii/PS2 version of Sonic Unleashed notably has more blood than the HD versions, as shown in multiple instances other than Dark Gaia's transformation listed above. During the fight with Dark Moray, green blood sprays out of the monster every time one of his warts is destroyed. And during the running sections of the Dark Gaia fight, droplets of green blood fly into the air after Sonic attacks one of his eyes.