'' Sonic Generations '' was first revealed in August 2009 , when Sega accidentally leaked a press release including information about the game , then under the working title '' Sonic Anniversary '' . The company officially revealed the game on April 7 , 2011 , when they posted a teaser trailer on their Facebook page . The trailer depicted the two variants of Sonic running through Green Hill . It was initially announced for the Xbox 360 and PlayStation 3 ; the 3DS and Windows versions were leaked in a Sega Sammy Holdings financial earnings report . The 3DS version was confirmed in an interview with Iizuka published in '' Nintendo Power '' . A demo version featuring Classic Sonic 's version of Green Hill was released on June 23 , 2011 , the twentieth anniversary of the original '' Sonic '' game 's release . A second demo , featuring Modern Sonic 's Green Hill , was released on October 19 , 2011 . Demo versions of the game were also playable at E3 2011 and the New York Comic Con
E3 2011
E3 2011
Sonic Generations