Sonic CD is a classic 2D platformer game that was first released in 1993 for the Sega CD console. The game features Sonic the Hedgehog, the iconic blue anthropomorphic hedgehog who can run at supersonic speeds, as he travels through different time periods to save the world from his arch-nemesis, Dr. Eggman.

The gameplay of Sonic CD is similar to other classic Sonic games, with players controlling Sonic as he runs through levels filled with enemies, obstacles, and collectibles. The game also introduces some new features, such as the ability to travel through time and alternate versions of each level.

In Sonic CD, each level has a past, present, and future version, and the player can travel through time by running past signposts that indicate the time period. Each version of the level has different enemies, obstacles, and paths to explore, and the player's actions in the past can affect the future version of the level.

The game also features special stages that can be accessed by collecting enough time stones throughout the levels. In these stages, Sonic must run through a 3D environment and collect rings while avoiding obstacles.

Sonic CD is known for its fast-paced gameplay, vibrant graphics, and catchy soundtrack. The game features animated cutscenes that add to the story and give the game a unique style. The game also introduced Sonic's sidekick, Amy Rose, who makes her first appearance in the series.

Sonic CD has been re-released on various platforms over the years, including as part of the Sonic Gems Collection, on mobile devices, and on modern consoles such as the PlayStation 4, Xbox One, and Nintendo Switch. The game remains a beloved classic among fans of the Sonic series and retro gaming in general.