Speed
The emphasis of the entire game is speed. Some parts of levels require a good amount of speed to make the jumps from platform to platform. Missing a platform might not necessarily kill Sonic, but it will usually make the level longer and a bit more difficult to complete. Some sections do require slowing down in order to make the jumps, but these usually only make up a small part of the level. Going back to get a power up or coins that were missed is typically not a good idea.
Power Ups
There are a few power ups in the game that are received through TV boxes. The image on the screen indicates what item is inside. This can be 10 coins (coin), a speed boost (shoes), a shield (blue shield), invincibility (sparkle), or an extra life (Sonic). The shield will let Sonic be hit once without any loss of coins. Invincibility renders Sonic invincible to most pitfalls and enemies in the game. Invincibility will not save Sonic from falling death or being crushed.
Coins
Coins are very commonly scattered around the level and play an important role in the game. If Sonic gets hit, he will not die if he has coins. Instead, the coins he is carrying will be scattered, and it is possible to recover some of them before they disappear. Sonic dies if he is hit but has no coins left. Getting 100 coins will give Sonic an extra life. Coins also raise the score, which gives Sonic an extra life when he gets 50,000 points. Having 50 coins at the end of an act will cause a giant ring to appear. Going into this ring allows Sonic to enter the Special Stages.
Special Stages
There are five special stages in the game, each containing a Chaos Emerald. The stages take place in a rotating passageway with a variety of different blocks that alter how the passages rotate. "R" blocks will reverse the direction of the rotation. "Up" and "Down" blocks alter the speed of the rotation. Star bumpers will cause Sonic to bounce if he touches one. The Goal blocks are not actually the goal of the stage and should be avoided. The purpose is to get the Chaos Emerald. This will be inside a group of blocks that disappear after Sonic touches them a few times. Getting all of the Chaos Emeralds results in a different game ending.