Sonic Mania/Stardust Speedway

Stardust Speedway is the sixth zone in Sonic CD, and as indicated by the name and stage design, there is an emphasis on speed here even more so than the other zones. Shoot through the many tracks in the stage in order to progress forward, but beware of the enemies, strategically-placed so as to trip you up when traveling at high speed. As the achievement/trophy of this zone requires you to get through the second act in under a minute, practice in the game's time trial mode may be helpful in memorizing enemy locations. Remember that you don't necessarily have to clear the stage, but simply reach the boss in time. The second act's walkthrough details the quickest path through, though if you still find yourself having trouble, you can stand around and wait for a Time Over after passing a Star Post midway through the act. This will reset the timer, allowing you to continue through the rest of the stage from that Star Post with a significant time advantage.

Act 1
The first act is based off of the past version of the area, and thus bears the appearance of some ruins taken over by plant life. Let the springs guide you forward; the highest path is recommended here as the path of least resistance, so try to climb as high as you can before shooting forward into a track. Once you land, you should see a Hyper Ring Item Box to the left, and some vines to the right. While these vines appear to be part of the background, you can hop onto their leaves, so follow them forward, hopping on leaves whenever necessary to avoid the hazards. You should then make it to some catapults that will show you out in either a fixed direction or one you can choose. When given the first option, choose to shoot out to the right. A spring hidden in the floor can send you up to a rung that you can grab onto, lifting you up to higher ground and the first Star Post. Ignore the spiked lifts and simply continue forward through the speedway. When you slow down, jump over whichever spiked ball is in the foreground and Spin Dash into the wheel buried into the ground to lower some platforms. When given the option, catapult yourself into the highest path, then when given another option, catapult yourself to the right to land in another catapult. Finally, catapult yourself into some rings to set yourself on the right track, at which point you can let the springs do the work. Once you slow down, you'll have to avoid some more spiky hazards, after which you can speed up again. Grab onto a rung to the right after you stop moving and hop on a spring to head to a higher level. Proceed forward to the right and once again, let the springs do the work, only adjusting your course direction to the right at one point to avoid being bounced back and forth. The boss fight consists of one large Hotaru Badnik that summons small Hotaru Badniks, fireflies that shoot lasers. Avoid the lasers they form and get eight hits in on the large Hotaru to defeat it and proceed to the next act.

Act 2
For the next act, you are transported to the present, changing the look of the zone but not the function; there are still plenty of tracks to zoom through. To go through the zone on the quickest path: If you're not playing the game's time trial mode, you'll still have a battle with Metal Sonic to face. The first phase of this battle will consist of simply dodging Metal Sonic's rolls and charges as you run along the track. Once you've reached his lab, you'll have Silver Sonic to deal with; Spin Dash into him when he rolls in order to get him to ricochet off the walls and into Metal Sonic. For the third phase, you'll have to dodge more of his attacks while running along the track; if there's a good time to enter Super mode, it's now. Eventually, a spiked wall will form and Metal Sonic will race to avoid it alongside you, attempting more of his attacks in the process. After dodging his attacks, attack him back to cause damage. In Sonic Mania Plus, this boss fight has been altered to resemble the final boss of Knuckles' Chaotix. Avoid his attacks and attack his chest, which encases the Phantom Ruby, in order to defeat him.
 * Take the highest track available to you. Be prepared to jump over a gap in the track partway through. Getting the timing right on this jump may take some practice.
 * When you latch onto the rocket, jump off when it reaches its highest point, leaning forward slightly. This should give you a head start on the ground below, though be careful to avoid some hazards. This includes a Dango that rolls around; as dealing with it would take too much time, simply jump over it, as well as a spring that would take you backwards.
 * Let a couple of springs send you upward and continue forward from there, doing nothing to alter your course. This includes landing in a catapult; as its position is fixed, simply shoot out into the track below.
 * Once rolled up inside the track, take a right turn, then another right turn, then straight up, then right once more. Let the spring on the left send you into the spring on the right, which should in turn send you up to a higher platform.
 * Climb up to the next platform, jumping over a Dango and hopping onto a spring to be sent into a catapult. Catapult yourself to the bottom-right twice to end up back on the ground.
 * After racing forward a bit, you should end up on a bungee cord. Use it to bungee up to a catapult to the top-right, which you can then use to end up back inside a track. This track will lead you to the finish.

Regardless of the Metal Sonic you've faced, defeating him will allow you to free the animals of Stardust Speedway and move on to the next zone.