Sonic CD is the ultimate Sonic Game
This game looked amazing and you could keep track of your progress with the small amount of memory that the Sega CD came with.
The Sega CD only gave you enough memory to save the progress of one game at a time. Then you had to delete the saved game when you wanted to save your progress on another game. One of the Sega's Cd worst features.
Sonic Cd had great graphics and sound. The Graphics were clean and colorful. The music was well composed and had good beats. I liked how the music would change from stereo to mono in different parts of the game.
Sonic has the ability to travel through time. The graphics and sound reflect that. They seem to get choppier in the past and so does the music. You need to play this game several times through to see all of the levels since you may not always be able to pick up enough speed to time travel.
Overall it was the Best Sonic game I have played.