Mystic Woods
This introductory level features short acts for easy hunting. Climb branches, run through tunnels, and jump down from treetops to find emeralds, and get a feel for your radar as it reacts to nearby emeralds. Conveyors serve as a way to speed up and as a hindrance when heading the opposite direction. The level is derived from Wood Zone from Sonic 2 prototypes.
Cascade Valley
Based off of Emerald Hill Zone, this level features plenty of paths to explore and simple badniks to destroy. The zone changes from a coastal area to a large waterfall as you progress from act to act. Ziplines, various loop designs, and brief underwater areas make speedy movement a must, but exploration is the name of the game and you'll need to look high and low for emeralds in order to progress to the next zone.
Chemical Plant
While the sheer amount of steep downhill slopes and speed boosters makes getting from start to finish a cinch, learning which of the tangled paths gets you there fastest takes some time. Switches control the water level in the second act, and the floating platforms that move with it are key to collecting emeralds or navigating the trickier passages.
Frosty Peak
This cold modification of Hill Top Zone inexplicably houses lava sure to punish misjudged jumps. Passages on the mountain's surface tend to be straightforward, but the caves underneath are labyrinthine and susceptible to magma flows. Badniks here are well-protected, so think twice before planting a homing attack onto a shield of fire.
Casino Night
With architecture straight from prototype versions of the original Casino Night Zone, this zone is less a platforming challenge and more a pinball machine. Bumpers, flippers, and giant springs are activated using the A, B, and C buttons. Badniks are scarce here, so score attacks are largely based on how quickly you can grab large collections of rings and bring them to the finish.
Metropolis
It's all upstairs from here, as the one act in this zone is twice as tall as the others so far. All of the familiar traps from the original Metropolis Zone return here, with some areas forcing you to use moves you didn't have back in 1992 just to progress. With no more locked doors between you and the finish, this zone's missions are entirely optional.