The plot focuses on Sonic the Hedgehog joining a resistance movement formed by his friends, alongside its rookie and his misplaced past self.

With the game's title chosen to signify its themes of power and teamwork, it was intended to have a darker tone compared to previous entries in the franchise and the character creation system was inspired by Sonic fan art the developers had come across over the years.

[3] The Avatar is created from a base of seven animal types, which each possess a unique ability; they also wield a grappling hook and can equip weapons known as Wispons, including flamethrowers, whips, and hammers.

[7] Players must complete each level while fighting waves of enemies, and (with the exception of Classic Sonic) seamlessly shift from side-scrolling to third-person perspectives.

[8] Stages are filled with features such as spring boards, rails, and boost pads, and obstacles such as spikes, bottomless pits, and robots.

Knuckles the Echidna forms a resistance movement with Tails, the Chaotix, Amy Rose, Silver the Hedgehog, Rouge the Bat and a survivor of Eggman's attack who is only referred to as "The Rookie".

Back in the city, Tails is attacked by Chaos, but is saved by Classic Sonic, who has become marooned in the present by the Phantom Ruby's power.

Tails infiltrates Eggman's computer network and finds the Phantom Ruby's weakness: the gemstone is directly powered by the Death Egg and will be rendered useless without it.

However, Eggman has a backup power source hidden in his empire's fortress, and as the resistance make their final charge toward it, he has Infinite enact his endgame: creating an asteroid-like second sun over the planet that will eliminate everything in its path upon impact.

Sonic and the Rookie then battle Infinite and defeat him, but Eggman unveils yet another backup plan, moving the Phantom Ruby into his Death Egg Robot and fighting the resistance directly.

Shadow heads into the city towards enemy territory on Rouge's command, but E-123 Omega ends up causing chaos despite the fact that the mission is meant to be recon.

Unable to handle the pain of being called "weak", he covers up his past and gains the power he uses now from the Phantom Ruby, rechristening himself as Infinite.

The game was produced in commemoration of the series' twenty-fifth anniversary and the title was chosen to signify its themes of power, teamwork and armies.

[12] The game was intended to give a darker perspective to the world of Sonic, in contrast to the fantasy-based themes of previous entries,[14] and expand upon the modern-style gameplay from Unleashed and Colors.

[14] At one point in development, the series' traditional ring-based health system was abandoned to balance the game's difficulty, and for designing the Classic levels, the team looked to Generations and Mania as a reference.

[15] Sonic Team head Takashi Iizuka explained that for years, he had seen many fan-made characters and wanted to give players the opportunity to play as their own.

[19][20] The soundtrack was primarily composed by series sound director Tomoya Ohtani and performed by the London Symphony Orchestra, with additional music from Naofumi Hataya, Kenichi Tokoi, and Takahito Eguchi.

[33][34] A tie-in racing game for iOS and Android devices, Sonic Forces: Speed Battle, was released in select regions in September 2017.

[39] The story acts as a prequel, focuses on Shadow the Hedgehog and his friends Rouge the Bat and E-123 Omega, and explores the origins of Infinite.

In contrast to Parish, Kemps enjoyed the "quite strong" bosses, particularly one fought "among the winding coils of a giant snake," although she wished they were more plentiful.

Alexandra panned the Avatar stages as "disjointed and confused" due to a lack of flow and an excessive reliance on trial and error.

[8] Ben "Yahtzee" Croshaw of The Escapist panned it for not exploring the potential of its ideas and lambasted the story for its attempt at a more mature tone.

The open-world Frontiers was designed to be lengthy, with an emphasis on exploration, puzzles and combat to address the criticism that Forces received for its short length.

[65] The story of Forces influenced the plot of IDW Publishing's Sonic the Hedgehog comic book series, with its narrative beginning shortly after the game's events.