Sonic CD is a port of the 1993 Sonic game made for the Sega CD / Mega CD Sega Genesis / Mega Drive add-on to Windows.
There was actually two versions of this port this being the later one. There was an older one that was released as part as bundled software for various computers in 1995 which used the DINO graphics libraries instead of DirectX.
This is the re-release version from Expert Software.
