This unofficial project ports back most of Sonic Unleashed's day levels from the Xbox 360 version into Sonic Generations on PC. It also includes any improvements that are deemed as necessary to accomodate to the better control scheme, higher resolution graphics, and a much smoother framerate.
This is the public hardware test uploaded on 13 May 2012. It's still available for download for anyone who wants to play through it. It's the tutorial level from Sonic Unleashed. It's merely a hardware test and in no way representative of the final product.