SEGA has announced that a demo of Sonic Generations will finally be available from tomorrow, to celebrate the twentieth anniversary of the blue hedgehog, waiting for the game. The demo will include the classic version of Green Hill Zone, at the opening of the very first Sonic the Hedgehog, in order to provoke nostalgia effect on all players. SEGA has also stated that the demo will be available only until July 12, will remind you that Sonic Generations will arrive by the end of 2011.