The game is a spin-off and a prequel to the Sonic series following the adventures of Sonic's trusty sidekick Miles "Tails" Prower as he tries to save an island from Wendy Witchcart, who turns anyone opposing her into crystals with her magic and also before meeting Sonic.
The gameplay of Tails' Skypatrol is less in line with the familiar platforming style of the traditional Sonic games. There are no rings or emeralds to be collected, Dr. Robotnik is entirely absent and Tails is constantly "suspended" in flight mode and clears each stage simply by completing each course from left to right. The screen is fixed and constantly moves along with him. Should Tails fall, bump into objects or touch the ground, he loses a life.
Across each stage Tails carries a golden ring with him which he can throw as a projectile to defeat enemies or break walls. Using the Ring, he will also latch on to any number of devices the player will encounter in each stage, ranging from gymnastics bars to railcarts.
In order to stay afloat, the player must constantly watch Tails' flight meter, which slowly drops to zero. Scattered across the map are Mint Candies which Tails can collect in groups of either one, two or three to replenish his stamina.
Source: Wikipedia, "Tails' Skypatrol", available under the CC-BY-SA License.