Chemical Plant made its first appearance as the second zone in Sonic the Hedgehog 2. Here, you race along chemical-filled pipes, and may even end up submerged in chemicals, in which case you must escape before drowning. You can also travel through pipes and change direction at intersections, a feature added to the zone for Sonic Mania.
Act 1[edit]
When the path splits, take the lower path. Continue forward until you reach a spring and jump over it to avoid being sent back in another direction. Eventually, you should see two floating blocks above a drop to the right. Take the drop down to a lower level, then drop further down off another drop to the right (below the blocks that form steps in the chemical-filled water). Before the blocks below that set of blocks can form steps leading upward, Spin Dash into the wall to the right to find the giant ring. After the Special Stage, return to the left and climb up the blocks. Continue to the right, avoiding some enemies and obstacles along the way, into the loop-de-loop. Hop over the spring to be launched into a chute. Upon emergence, destroy the Grabber Badnik before it can grab you and continue forward. You should reach some blocks, but before ascending them, drop down to the bottom and again, before the blocks can form steps, Spin Dash to the right to find the second giant ring. After the Special Stage, take your time ascending the blocks to higher ground.
Ride the platforms floating above the water to the other side. The ground at the end of the path here will attempt to flip you back into the water, so make sure to jump over it or step on it when the yellow layer is on top. Take the floating platforms up and continue forward until you reach a spring, which you can once again jump over. Keep going until you reach the boss, which will submerge itself into the chemicals below upon your arrival. Hit it when it isn't surrounded by the harmful blue goop to defeat it.
Act 2[edit]
The second act introduces a new feature to Chemical Plant in the form of syringes that, when stepped on, give the substances nearby different properties (such as making them much bouncier, allowing Sonic to reach heights he couldn't before). However, upon reaching the first one, it's best to have Tails fly you up to the layer above so as to not jump too high. Go left, dodging the Grabber, and hop onto the sticky platform that slides along the wall. Use it to get to the next level, then continue forward until you land in another sticky platform. Hop off of it into a bubble, which will ascend into another area. Continue left until you come across some tubing topped off by what looks like a spring; hop inside to be sent to another area down below. Continue forward to land in another sticky platform, then hop off to the ground below (time your jump so as to avoid the hazards). Continue left to the spring, then forward to the Star Post.
Past the Star Post is a spring. Jump on it, then step onto the giant syringe in front of you. Jump on the nearby substance, now green and bouncy, to be taken to an area high above. Continue left into another sticky platform, and then another in order to avoid some spikes. Hop off and continue into another syringe that you can step off, after which you can hop on the bouncy substance to be sent to higher ground again. Continue down the path, off some more sticky platforms and into some tubing. The tubing will send you into a sticky platform on the ceiling; jump off and continue forward, to the Star Post and into the bubble. Take the sticky platform on the ceiling to the left, then stop on the syringe and bounce onto the green substance into some tubing to the left. Continue forward, into another bubble and down some slopes, until you come to a stop.
Wait for the blocks up above to form some steps that you can reach, then climb up to the left and up another set of blocks. To the left of this area is the seventh giant ring. If you've successfully cleared all Special Stages, you can now enter Super mode after collecting fifty rings. You can exit the area through the tube to the left. The path will lead you to a Star Post and another sticky platform on the ceiling. Jump off into the tube to the right and prepare for a unique boss fight.
Connect four puyos of the same color to eliminate them. This shouldn't be too difficult as long as you move quickly; Dr. Eggman will send some garbage puyo your way every now and then in order to impede your progress. For the achievement/trophy, you'll have to make a triple-chain combo. You can do this easily by following the format in the image to the right, or by setting up three lines of three puyo, identical vertically and different horizontally. On top of each line should be a single puyo, the same color across all three columns. Above this horizontal line of three should be a single puyo, each the same color as those puyo below the horizontal line. If you're able to eliminate the horizontal line by connecting it with a puyo of the same color, this will set off the chain of three, earning you the achievement/trophy and defeating Eggman.
After defeating Eggman at his own game, jump into the tube above you and free the animals from the capsule to clear the zone and move onto the next.