Sonic and his long-time sidekick Tails must team up with Doctor Eggman, normally their enemy, to stop the Deadly Six, leading to conflicts among the three parties.

While the gameplay is typical of the Sonic series in some ways, it adds parkour mechanics and features largely cylindrical level design with an emphasis on alternate pathways.

The main antagonist of the series, Doctor Eggman, is a mad scientist who seemingly turns over a new leaf to help Sonic stop the Deadly Six.

Also serving as the main antagonists and boss characters are the Deadly Six, a group of the world's indigenous Zeti race consisting of the hyperactive Zazz; the obese and dim-witted Zomom; Master Zik, the elderly founder of the tribe and Zavok's teacher; the flirtatious and self-absorbed Zeena; the diminutive and pessimistic Zor; and Zavok, the tribe's leader.

[14] Sonic and Tails pursue Doctor Eggman, who has captured several of their animal friends with the intention of using them to power his robot army.

They then start to use one of Eggman's machines to siphon energy from Sonic's world below, planning to drain all of its life force until there is nothing left and use it to power themselves up.

Reluctantly, Sonic agrees to work with Eggman, believing that he needs his help to stop the machine, though this seems to cause some distrust between him and Tails.

Upon reaching the machine and finding it already switched off, Eggman reappears, having faked his death and used the energy harvested to power his latest giant mech.

Sonic defeats Eggman, sending him falling to the planet's surface, and he and Tails restore the stolen energy to the world below before returning home.

In a post-credits scene, Orbot and Cubot find Eggman, who has survived his fall, and they dig him out of a soft spot of dirt he landed on.

Upon realizing that half of his mustache is missing, Eggman throws another tantrum, prompting Orbot and Cubot to run away in fear.

[3] Sonic Team sought to streamline the controls,[20] increase the length,[19] and add more diverse levels compared to previous entries in the series.

[3] The parkour mechanic was introduced to maintain a more fluid sense of movement, in contrast to previous Sonic games where running into a wall would force the player to a complete stop.

[22] The design of the new "Deadly Six" villains was based on that of an ogre, and each one's appearance was intended to reflect a certain key characteristic of their personality, which the developers hoped players could see "just by looking at them.

[8] A downloadable demo of the game's first stage was made available for both consoles on October 9 in Japan[31] and in mid-November in North America and Europe.

[38] A patch for the Wii U version was released on December 10, 2013, adding additional features such as button controls for some Wisps and the traditional extra life reward for collecting 100 rings.

"[62] Mark Walton (GameSpot)[66] and Chris Scullion (Computer and Video Games)[48] singled out the candy-themed "Dessert Ruins" level as a visual highlight.

[63] Vince Ingenito (IGN) was favorable to the "pleasant" art direction and stable framerate, but criticized the "subdued" color palette.

[68] Schilling singled out the multi-lock homing attack, writing that while it usually worked "perfectly well", it appeared to "inexplicably fail" on occasion.

"[71] However Justin Towell (GamesRadar) defended the control scheme, explaining that while it had a learning curve, it also "modernize[s] environmental traversal" and "provide[s] a distinct safety net".

[58] However, Turi criticized Sonic's "odd sense of momentum" and imprecise jumps,[62] stating that switching between two speeds is "jarring" and produces "touchy platforming".

[63] Schilling excoriated the "profoundly frustrating" controls as the worst in the series, explaining that "Sonic's too sluggish while walking, and too skittish to cope with the trickier platforming bits when running".

[72] Stephen Totilo (Kotaku) stated that the 3DS version does a better job of teaching the controls,[82] although Turi derided its "constant, lengthy tutorial text".

[68] Otero praised the 3DS version's "better levels" as "competently made race tracks full of alternate pathways", but called the "trial and error" required to complete the "slower-paced 3D stages" "incredibly frustrating".

"[52] Edge noted that "Sonic games, and platformers in general, have always been about memorizing the lay of the land, but rarely have mistakes been so costly or heavily punished.

Daniel Cairns (VideoGamer.com) and Castle highlighted the level where Sonic becomes a giant snowball as "genuinely excellent"[79] and "a cool riff on Monkey Ball",[71] whereas Turi and Ingenito described it as "atrocious",[62] "uncontrollabl[e]" and "the exact opposite of fun".

[67] Totilo preferred how the Wisps were implemented in the 3DS version,[82] but Towell stated that while they were "more integral" to the design, they tended to interrupt "the free-form gameplay" with "clumsy mechanic[s]".

"[62] EGM Now observed that the inclusion of the Deadly Six subverted the familiar Sonic-versus-Dr. Eggman concept, but questioned whether the plot was a clever self-parody or had been “scrawled together by a couple of grade-schoolers”.

"[83] James Stephanie Sterling of Destructoid said it "can wildly swing from brilliant to horrific at the drop of a hat, but when one steps back and takes a look at the whole production, one sees far more to love than hate.

[73] David McComb (Empire) called it "A cheap, cruel, crushing disappointment in the wake of Sonic Colors and Generations.