Here's how to unlock Super Sonic:
1. Complete the game: You must beat the game in any difficulty mode.
2. Collect all seven Chaos Emeralds: The Chaos Emeralds are scattered throughout the game, hidden in various levels. You'll need to collect all seven to unlock Super Sonic.
3. Enter the special stage: Once you have all seven Chaos Emeralds, you can enter the special stage by collecting 100 rings in any level.
Once you've done all that, you'll be able to transform into Super Sonic!