Sonic Generations allows players to control both the pre-Sonic Adventure and post-Adventure designs for Sonic the Hedgehog and features remastered levels from Sonic's previous adventures. The game is divided into three eras: the Classic Era (pre-1998), the Dreamcast Era (1998–2005), and the Modern Era (2005 onwards). "Classic Sonic" plays through the levels from a 2D (or 2.5D) "classic" perspective; whereas "Modern Sonic" tackles them in a 3D and sometimes 2D perspective, similar to those of Sonic Unleashed and Sonic Colours.
The game was first announced in a teaser video posted by Sega on April 7, 2011 on Sonic's official Facebook page. The game was announced for both the Xbox 360 and PlayStation 3 and was scheduled for a 2011 release. An announcement of Sonic Generations for the Nintendo 3DS later appeared in an issue of the Nintendo Power magazine, paired with a November 2011 release date for all platforms. At E3 2011, SEGA revealed a trailer revealing City Escape from Sonic Adventure 2, with a further trailer appearing in mid-August detailing other levels. On October 11, 2011, Sega confirmed that Sonic Generations would also appear on the Steam platform for PC.
A fourteen-day demo was released to Xbox 360 and PlayStation 3 consumers on June 23, 2011, the official date of Sonic's 20th anniversary. A second demo was released on October 18 on Xbox Live, October 19 on the European PlayStation Network, and October 25 on the PlayStation Network in North America.
It was recently rediscovered that in 2010, prior to the game's official announcement, an anniversary game was announced for Wii, PlayStation Portable, Nintendo DS, and PlayStation 3, with negotiations for an Xbox 360 version in the works.
The gameplay is split into two separate gameplay styles, separated by the character used.
The Classic gameplay style is strictly 2D/2.5D. Sonic controls more like his Mega Drive/Genesis counterpart, including his ability to use the Spin Dash and Spin Attack to battle enemies.
The Modern gameplay style takes place in 3D, with occasional transitions to 2.5D. This gameplay style is akin to that developed in Sonic's more recent titles Sonic Unleashed and Sonic Colors, where you use the Sonic Boost and the Homing Attack to advance.
Homages to past games
Each level and boss in Sonic Generations is reminiscent of one previously appearing in the Sonic series.