Sonic And The Mystic Gems (previously known as Sonic 1 Harder Levels) is a hack made by Eduardo Knuckles and his team Harder Project of Sonic the Hedgehogon the Sega Mega Drive/Genesis. The hack adds to the game a lot of new features such as the three known main playable characters, a checkpoint monitor, customizable level music playlist, a sweet and clear save data select menu, difficulty selection, a unique music menu and some other additional menus and screens which gives to the game a completely new gameplay experience.