These are product advertisements placed in various media to promote the release of Sonic the Hedgehog CD.
This two page advertisement mentions the games QSound ability and the 63 levels found in the game.
This ad comes from the "Welcome to the Next Level" booklets Sega included with its games during the slogan's lifetime.
A full-page advertisement for Sonic the Hedgehog CD used in Korea.
An advertisement featuring Sonic CD and the Mega CD console as a whole. From the Japanese publication Beep!