Sonic the Hedgehog 4: Episode I

Sonic the Hedgehog 4: Episode I is a side-scrolling platform game similar in gameplay and style to the 1990s Sonic the Hedgehog games for the Sega Genesis. The story begins shortly after the events of Sonic & Knuckles (1994). Sonic the Hedgehog parts with his friends, Miles "Tails" Prower and Knuckles the Echidna, to explore new territories on his own. However, series antagonist Doctor Eggman—who survived his defeat in Sonic & Knuckles—resurfaces, refines some of his past robots, and initiates a plan to get rid of Sonic. Sonic 4 is presented from a 2.5D perspective; although movement is restricted to a 2D plane, characters and objects are rendered in 3D. ==Development==

According to project head Takashi Iizuka, Sonic 4 was conceived in January 2009; development began four months later and lasted about a year and a half. Dimps, which had previously developed Sonic platformers for the Game Boy Advance and Nintendo DS, led development, with assistance from Sonic Team. Its proper title, Sonic the Hedgehog 4: Episode I, was revealed on February 4, 2010, alongside the debut of in-game footage. Brand manager Ken Balough stated that Sonic 4 was conceived following fan requests for a return to classic Sonic gameplay. He acknowledged the divide between older Sonic fans who played the Genesis games and younger ones who played more recent games like Sonic Unleashed (2008), and said Sega needed to cater to both demographics. While Balough said the game was always called Sonic 4, Kalata wrote that it was retitled Sonic 4 at the behest of Sega's American branch and made a multiplatform release, and noted that one of the game's levels still features signs that say Sonic the Portable. To stay faithful to the original Genesis games, the developers chose not to include voice acting. One new addition was Sonic's homing attack from Sonic Adventure; Iizuka said the team "wanted to add that excitement of performing continuous attacks" and felt it "add[ed] to the classic-style gameplay by providing a new means to discover routes in the sky". Iizuka said this decision was made because the team wanted both old and new fans to be able to enjoy the game. Senoue was involved with the project early on when Iizuka approached him to ask him to compose. Senoue said that he attempted to compose the tracks as if he had been composing them for the Genesis, using as few notes as possible. He did not use any FM sound tapes, although he did unsuccessfully attempt to find an old Genesis development kit. Senoue attempted to compose tracks "with a similar beat or similar tempo" to those from Sonic the Hedgehog and Sonic the Hedgehog 2. Senoue had fun working on Episode I and said his favorite track was the first level's, although Nagahara hated it and tried to persuade Senoue to compose a replacement tune. Eggman's theme was repurposed from an unused Sonic 3D Blast (1996) track. == Release ==

Episode I was originally scheduled for release in July 2010, a timeframe Sega announced in February 2010. Months before the game's release, a prototype version was made available to users of the Xbox 360's game testing service PartnerNet. Screenshots and footage were leaked and widely distributed across the internet, and PartnerNet had to be temporarily shut down as a result. fans reacted negatively. Iizuka later clarified that the delay was done so the developers could replace the mobile-exclusive levels with ones better suited for consoles. Other releases included a Windows Phone version on June 15, 2011; a Windows version via Steam on January 19, 2012; an Android version on January 25, 2012; and a BlackBerry Tablet OS version on July 20, 2012. Additionally, both Episode I and Episode II were released for the Android-powered Ouya on July 9, 2013. In April 2016, the iOS version was updated for the first time in three years to modernize it for newer devices. Changes included support for widescreen and Retina displays, more detailed character models, and refined textures. The iOS version was initially split into separate versions for iPhone and iPad; the update discontinued the iPad version and made the iPhone one a "universal" application, meaning it works across all iOS devices. Later in 2016, the Xbox 360 versions of Episode I and Episode II were added to the Xbox One's catalog of backward compatible games. ==Reception==

According to review aggregator Metacritic, the Wii version received "generally favorable reviews", while the both iOS and other console versions received "mixed or average reviews". On YouTube, hundreds of gameplay videos were posted by fans showcasing several oddities. The game was a commercial success, selling over a million copies across all platforms by 2011, according to Sega of America CEO Mike Hayes. ==Legacy==

Episode I was envisioned as the first installment of an episodic video game trilogy. Shortly before Episode I release, Balough confirmed that Sega had planned the entire Sonic 4 story. While he did not confirm the number of episodes, he said "[they] will definitely make up a larger game. After completing them all, you'll have experienced a larger overall story arc that lives up to the epic nature of earlier Sonics." Ahead of Episode II, Sega rereleased Sonic CD (1993) for modern consoles, and advertised it as a prequel to Sonic 4. Episode II, released in May 2012, reintroduces Tails and Metal Sonic, and follows Sonic and Tails as they attempt to prevent Eggman and Metal Sonic from relaunching the Death Egg. Fan input from Episode I played a significant role in the development of Episode II, as the developers worked to address aspects fans took issue with, such as the physics engine. Players who own both episodes on a single platform unlock the ability to play as Metal Sonic in Episode I levels. In 2015, Australian developer Christian Whitehead said that he had been offered the opportunity to develop Episode III with Sega Studios Australia before that division was shut down, and he instead worked on remasters of Sonic the Hedgehog and Sonic the Hedgehog 2 between 2012 and 2013. He said that while it was possible that Episode III could eventually be made, it was unlikely. Whitehead would go on to lead the development of Sonic Mania (2017), which, like Sonic 4, acts as a sequel to the Genesis Sonic games. Sonic 4 and Sonic Mania were frequently compared, with journalists viewing Sonic 4 unfavorably in contrast to Mania. In April 2025, an unused Episode II ending cutscene surfaced online; it depicts the Master Emerald rebooting the Death Egg after Sonic and Tails disable it during Episode II conclusion and features a cameo from Knuckles. ComicBook.com wrote that the cutscene suggests Episode III would have featured Eggman tricking Knuckles into helping him. ==Notes==