Goal

As custom in most computer games, each playable levels end with a goal to let the player know when they are finished with the level.

The ending goals of levels in Sonic games (respectfully known as Zones or Stages) have varied throughout the series through different representations. When Sonic or whomever the player is playing as have achieved the goal, there score is tallied with points from rings, enemies or how fast the level was completed. Usually bonuses are provied depending on speed and points.

Bonus Plate
The most early yet well known goals in the Sonic series appearing at the end of each Acts of almost every Zone, sometimes accompanied by a Warp Ring if Sonic has more than 50 rings, these large rings would teleport Sonic to the Special Zone. Usually a bonus is granted depending on your performance and representeded as a picture on the Bonus Plate.

Bonus Plates are not on the final Acts which is usually for boss battle. Opening the Egg Capsule after the boss fight officially finishes the Act.

Bonuses (16-bit)
In Sonic the Hedgehog 3 and Sonic & Knuckles you can play a sort of ""Keepie uppie" when the Bonus Plate spins down from above, keeping it up long enough earns Item boxes.

Chaos Emeralds
They are usually the goals of the Special Zone where once you collect enough rings they were yours but in recent Sonic games they are usually the goals of certain stages due to being part of the games story.

Egg Capsule
While originally they appeared at the end of third acts in Zones, in Sonic Adventure they would appear as the goal of Action Stages for Sonic and Tails. The animals that escape from the capsules are the same kind of animals used for raising chao, some of them would even go towards Sonic or Tails and be collected. Egg Capsules have not appeared in 3D since.

Goal Ring
Goal Rings also appear in recent Sonic games starting out in Sonic Adventure 2, they look like the Warp Rings from early Sonic games but serve as the goal at the end of the Stages. While they look like large rings they sometimes have the word "GOAL" in it's center but in Shadow's game they look like large sparkly rings, sometimes with a Chaos Emerald in it's center.

Ranking
Since Sonic Adventure 2 you were ranked for your performances, but no actual bonuses were granted until you completed everything with "S" Rank. Since Sonic the Hedgehog (2006) rings were rewarded depending on performance. The higher the rank, the more rings.
 * S (Best)
 * A
 * B
 * C
 * D
 * E (Worst)

In the Storybook Series instead of letters, it would be star rating where ★★★★★ is the highest and ★☆☆☆☆ is the lowest.

Other goals

 * Fish for Froggy.
 * Grab the balloon.
 * Destroy the E-100 Series robot.
 * Find 3 pieces of the Master Emerald. (Or 3 Chaos Emeralds, or 3 keys)
 * Complete the level in 5 minutes.
 * Collect a certain amount of rings.
 * Find the Lost Chao