Sega Game Toshokan (セガゲーム図書館?), literally translates to Sega Game Library is a game service exclusively released in Japan distributed along with Mega Modem addon for the Sega Mega Drive, in a form of a special cartridge.
With the cartridge in the slot, Mega Modem connected, and a Sega Meganet subscription, owners of the systems could download and play select Mega Drive games exclusively available through the service, which were released between 1990 and 1992.
List of Sonic the Hedgehog games
Only two Sonic-related video games released on the service. One of them later received a physical media release outside Japan.