The Mega Drive is a 16-bit fourth-gen home console developed and sold by Sega, released in Japan in 1988 and in Europe in 1990, it was released in North America in 1989 as the Genesis. The Mega Drive was adapted from Sega's System 16 arcade board, playing a library of more than 900 games created by Sega and a wide array of third-party publishers delivered on ROM-based cartridges. Several add-ons were released, including Master System Converter for backward compatibility and Mega Modem for online network service Sega Meganet. Contributing to its success were its library of arcade game ports, Sega's Sonic the Hedgehog series and several popular sports franchises with aggressive marketing. More than 30 million first-party Mega Drive units were sold worldwide before being discontinued in the late 1990s.