Dr. Robotnik's Mean Bean Machine is a Genesis game based on the Puyo Puyo franchise, and it's even referenced in Sonic Mania as a main boss. If you want to unlock a mode to freely play it you'd need to get 21 medals (silver or gold) from the bonus stages where you have to get the blue spheres and avoid the red spheres. The medals do stock for different playthroughs of the game.