Progression in Sonic Unleashed is tied to collecting Sun Medals and Moon Medals. These are essential for unlocking new stages and advancing the main story. You'll find them in two primary locations:
- Within Stages: Both Sonic and Werehog stages contain a set number of medals. Some are out in the open, while others are hidden in secret paths or require specific actions to obtain. Replaying stages and exploring thoroughly is often necessary to collect them all.
- In Hub Areas: The explorable hub areas of each continent are also rich with medals. Look behind buildings, on rooftops, in hidden alleys, and interact with the environment. Some may require light platforming or puzzle-solving to reach.
Professor Pickle will often require a certain number of Sun Medals to unlock the next daytime stage and Moon Medals for the next nighttime stage. If you find yourself stuck, revisit previous stages and hub areas to hunt for any missed medals. The game provides a counter for how many medals are available in each area, so you'll know if you've found them all.