This is one of those rare games that just play perfectly and every bit of it is just a classic
Overall This game has an interesting opening video(the first sonic game I believe to have had an opening video) with a catchy song performed by Pastiche*. Then once at the start screen Sonic looks very similar to Sonic 1 on the Genesis. Which is quite interesting, and surprised me at first. The options in the main menu are New Game, Continue, Time Attack, and RAM Data.
The first level in Sonic CD is Palmtree Panic which is similar to Emerald Hill Zone just with a different layout and different characters. All of the levels in this game are fun to play and the boss battles, while frustrating, are some of the best ever in a sonic game. There is the added ability to either time warp to the past or future, and the best part is you control whether it's a good future or a bad one. The levels in this game are(1 level has 3 Zones):
-Palmtree Panic
-Collision Chaos
-Tidal Tempest
-Quartz Quadrant
-Wacky Workbench
-Stardust Speedway
-Metallic Madness
Then comes the audio section in my review. This game, even the North American version, has the BEST music I have EVER heard in a game. It's so unique and fits this game's style. All sound effects sound right, explosions, everything in this game's audio is perfect honestly.
Final Verdict: This is the classic Sonic experience you will never get again. The ability to time warp adds even more unique variety to this ever aging game. Any way you can play this, find a way, it is worth every second.
*lyrics and info at http://www.sega-16.com/Song%20Lyrics-%20Sonic%20CD%20(US).php