A large set of greenery ruins set flying high in the clouds amongst dangerous gusts of wind and a lethally violent tornado, Windy Valley is located inside a cave within the Mystic Ruins. The level is split into three main parts: the windy hills at the beginning, the tornado, and the aerial spiraling tracks. Sonic goes through all three, while Tails goes through only the third, and Gamma goes through only the first. Windy Valley was the only level that went through the biggest visual changes between the announcement of the game on August 22, 1998 and its release in December. Though still broken up into three parts, the layout and textures for each were completely redone. The prototype images can be viewed below.
In Sonic's story, Windy Valley is the second level. Here, he and Tails attempt to track down a Chaos Emerald to stop Chaos from collecting them all.
Level C - Get the Chaos Emerald!
Level B - Collect 50 rings and destroy the capsule!
Level A - Destroy the capsule within 3 minutes.
Windy Valley is Tails's first level, where he must race Sonic to the Chaos Emerald at the end. Interestingly, because the whole level moves downward, Tails can fly from the beginning to the end of the level without touching the ground.
Level C - Find the Emerald before Sonic!
Level B - Collect 50 rings and beat Sonic!
Level A - Beat an even faster Sonic!
Windy Valley is Gamma's third level. Here, Gamma searches for E-103 Delta to free him after being banished from the Egg Carrier. Like his other levels, enemies and other structures must be destroyed to increase the time limit.
Level C - Destroy "E-103"!
Level B - Collect 50 rings and destroy "E-103"!
Level A - Destroy "E-103" with more than 150 seconds remaining!