Here are some possibilities you might be thinking of:
* Sonic the Hedgehog (1991): This is considered the first main Sonic game, sometimes referred to as "Sonic 1."
* Sonic the Hedgehog 2 (1992): This is the sequel to the original game.
* Sonic the Hedgehog 3 (1994): This game was initially planned to be part of Sonic 2 but became a separate title.
* Sonic & Knuckles (1994): This game was designed to be played with Sonic the Hedgehog 3, creating a longer game with added content.
If you're thinking of a specific Sonic game, could you provide more information? For example, what platforms was it available on, what was the general storyline, or any specific characters that appeared in the game?