Hey Ho (ヘイ・ホウ) -- The woodcutter bot... cuts wood. The machine starts at the top of a tree and chops his way down, sending segments of timber flying straight through the air or bouncing along the ground. When he gets to the last bit of trunk, the Hey Ho's attack changes depending on which character you're playing: if you're Sonic, the machine gets his hatchet stuck and ends up flying back across the screen. He promptly recovers, gives up on the remaining trunk, and moves forward to another tree. If you're Knuckles, the Hey Ho succeeds in cutting the last block, but loses his head in the process. His head flies across the screen, then jets itself back to its owner. The Hey Ho further harasses Knuckles by flying down to attack before moving on to the next tree.

Jet Mobile (ジェットモービル) -- When you come across a peculiar satellite transmitting to some unknown source, bust the machine with a spin and Eggman (or Eggrobo if you're Knuckles) will emerge from the wreckage and begin his escape through the forest. Chase him down through a series of arches strung with damage-inflicting mace chains. Eggman has no attacks, so the only challenge is to keep moving and attack while avoiding the maces. 8 hits later and Eggman smashes into a tree, but quickly recovers and escapes to his aerial fortress, which is conveniently flying low enough to jump onto.

Gapsule (ガプセル) -- This menacing machine awakens as soon as you jump on the yellow button on his head. The Gapsule is incapable of moving, but his flail-like arms can reach anywhere in the arena, and he would just love to smash you to pieces. When his eyes flash, he's homed in on your exact position and will promptly swing - so move out of the way fast, preferably with a Spin Dash. Fortunately, Eggman didn't spend too much on AI development for this particular contraption, and the Gapsule will smack itself upside the head if you happen to be standing on top when he swings. This is what you want to do, because there is no other way to damage him.

Hang Mobile (ハングモービル) -- Toward the end of Act 2, Eggman traps you in an arena with a moving laser blaster on the ceiling, very similar to the Wing Fortress boss from Sonic 2. The blaster chases you down while warming up, but pauses before unleashing the blast, giving you just enough time to run out of the way. With each blast, however, the width of the arena is shortened. You can jump and attack the blaster as much as you like, but it can't be destroyed. All you can do here is avoid the laser and wait for the overpowered blaster to destroy the whole stinking ship, then chase Eggman to an exterior platform. Eggman latches onto the platform from below and crawls along, spouting flame from the top of the pod everytime you play Jack-be-nimble and attempt to jump over. After a while, he'll swing upward four times - this is your only chance to attack. When playing as Knuckles, Eggman constantly spouts puffs of flame (regardless of whether or not you attempt a jump) and only swings upward twice in a row. Destroy Eggman's mobile and escape the plumetting fortress to land safely in...

Guardian (ガーディアン) -- The stone golem, like all the other sub-bosses so far, looks mean but is incredibly stupid. The rock monster jumps toward your character, one slow leap at a time. You can temporarily knock him out by hitting his head, but he'll pull himself back together and be none the worse for wear. You will note, however, that there is a pool of quicksand all the way on the left end of the arena. The object is to lure the Guardian to the pool and have him hop right in. He will sink like, well, a rock. Golem.

Egg Golem (エッグゴーレム) -- Eggman's latest contraption is encased in a sphinx-like shell. The machine trudges forward, firing laser blasts from its eye - if you let the machine chase you all the way to the edge of the screen, it will crush you like the small woodland creature you are. The object is to leap onto the Golem's hands and jump into its face, which will cause the brick armor to momentarily fly away, leaving Eggman vulnerable to attack. The window of opportunity is brief, however, for the ghostly bricks will return and reform the sphinx armor in just a few seconds. Crush the Golem and head even deeper into Angel Island's interior.

Heat Arms (ヒートアームズ) -- A giant, three-fingered hand reaches from the depths and attempts to squash you like a bug. The hand will pause just before attempting the blow, so get out of the way, but be sure to get back in time to land a hit before the freaky phalanges release their grip on the dirt and return to the abyss. Inbetween rounds of patty-cake, a pair of testicular orbs will arise from the darkness and wiggle in the air, each firing off a set of three flashing projectiles. The hand and both orbs must be destroyed before you can proceed. The hand takes 6 hits, the orbs take 4 each.

Hot Mobile (ホットモービル) -- Sonic alone must face this boss... Knuckles waltzes right through the end of this stage scott free (no capsule or anything). As you approach the site of the fallen Death Egg, Eggman launches a surprise attack, tearing up the platforms around you with missiles. Avoid the blasts and keep moving until you reach the magma falls. Proceed downward to the magma pool and Eggman pops up from the lava in a spiky, well-armored submarine. As soon as he emerges, the entire pool slopes downward toward his invincible machine, and whatever platform you're on slides directly into the sub and shatters. More platforms slide in from off-screen, so keep hopping and for the love of goodness, don't touch the lava. While you're performing your boiling ballet, Eggman attempts to disrupt your groove by firing off large landmines. The mines slide down the surface of the magma along with the platforms, and eventually return to the sub from whence they came - inflicting damage in the process. In short, your only challenge is to avoid the mines and hop platforms. Eggman eventually defeats himself with his own mines. The Hot Mobile is fairly sturdy, and takes 14 hits. (Note that a Flame Barrier makes this boss substantially easier.)

Knuckles the Echidna -- Knuckles fights with all his basic maneuvers: Spin Dash, spin jump, and a glide attack. He'll guard if you try to attack him from directly in front, so jump on him, Spin Dash him from behind, or knock him out of mid-glide from below. 8 smacks later and the red rival is out for the count. Immediately following his defeat, Knuckles is roused by some ruckus further in the chamber. He rushes to the Emerald altar directly ahead and is shocked to see the good Dr. Eggman making off with the Master Emerald. Knuckles latches on to the sacred stone in a very quaint attempt to drag it out of Eggman's grasp, but is electrocuted off by a pair of probing mechanical tentacles from Eggman's mobile. Eggman makes his escape just as Knuckles recovers from the shock, but now it's clear to the hard-headed echidna who the real villain is. Knuckles makes up for his stupidity by showing Sonic a hidden room with a teleportation orb that takes him directly to...

Sub-boss 1: - Mecha Sonic first attacks in a flail-swinging Egg Mobile reminiscent of the Green Hill Zone boss from Sonic 1. He takes a full set of 8 hits before retreating.

Sub-boss 2: - Mecha Sonic's second assault borrows the Flying Eggman boss from Sonic 2's Metropolis Zone. Once again, a full set of 8 hits is required for sending him along home.

Mecha Sonic (メカソニック) -- The robo rogue drops the Egg Mobile and faces Sonic/Knuckles head-on for the final encounter. Despite his rather edgy new appearance, though, his attacks are mostly unchanged from Sonic 2. He dashes from one side of the screen to the other, either in upright pose or in a spiky spin attack. He'll interrupt his attack pattern at random with a new backwards dash. He can only be damaged from the front and only when he's upright. 8 spins later and he collapses, allowing Sonic to move on to the Death Egg Zone. Knuckles, however, gets one more curve ball...

Mecha Sonic round 2 -- The fallen Mecha Sonic dashes over to the Master Emerald and absorbs its power, allowing him to transform into an invincible Super form. While under the influence of Master Emerald power, Mecha flies through the air and attacks by dashing down at the hapless echidna below. Occasionally he pauses to unleash a condescending belly laugh along with a trio of glowing orbs. This attack seems to drain his super strength, causing him to transform back into normal blue Mecha Sonic. He immediately spins toward the Master Emerald to replenish his energy. As he leaps onto the jewel, there's a brief window of opportunity to land an attack (or two if you're quick). After taking 6 hits, Mecha starts running out of gas, and even in Super form his attack pattern becomes more limited. He hovers slowly through the air, occasionally pausing to unleash a burst of shrapnel. After every couple of bursts, he momentarily loses super strength and dips toward the ground in normal blue form, offering another brief window for attack. 2 more hits (for a total of 8) and Mecha Sonic explodes with the rest of the crumbling ruins. This is the end of Knuckles' game.

Red Eye (レッドアイ) -- The Red Eye begins its assault stuck in a large column. 8 metallic orbs rotate around the column, guarding the eye. The orbs, however, periodically drop from their position and sweep the floor, leaving the eye vulnerable. Each time the eye takes damage, a single orb floats into the air and explodes into a burst of spikes. Once the eye is out of orbs (ie, 8 hits), it breaks free from the column and floats around in the air, orbited by a pair of platforms with spiky undersides. The eye won't do much to attack until it's been hit, then it flashes red and sweeps the ground with a large laser. During this phase, the platforms whip around the machine at high speed, so they're impossible to land on, but if you already happen to be standing on one, stay put and you'll be impervious to the laser attack. 8 more hits and the Eye is poked.

Death Ball (デスボール) -- The Death Ball doesn't have much in the way of offense, but due to the rotating shield bumpers that crawl along its surface, it's utterly impossible to hit. The Ball hovers slowly around the arena, and occasionally opens up its bottom to drop a rolling bomb. The bombs trod along the ground for a while and eventually explode into a trio of spikes. The Death Ball is impossible to hit with a normal spin, but it's possible to send the rolling bombs back up into the machine by stepping into one of the anti-gravity chutes on either end of the arena. As the gravity reverses, the bombs fly upward, and if you time your maneuver right, a bomb or two should land right smack into the vulnerable underside of the Death Ball. If your timing is off, the upside-down bombs can still be sent flying with a rolling attack. 8 hits later and the Ball is toast, opening the way to the real boss.

Kyodai Eggman Robo (巨大エッグマンロボ) -- Eggman's ultimate final mech, like the one from Sonic 2, is designed in his own glorious image, except this one is much, much bigger. The Doc begins his assault by simply trying to smush Sonic into hedgehog jelly with his two gigantic robot hands. Each hand has 3 fingers and each finger takes 3 hits. Once all the offending digits have been destroyed, the machine repositions itself on the left side of the arena, and chases Sonic down the platform. Occasionally he'll unleash a puff of flaming snot vapors from his nose... the flames sweep the ground and are easily jumped over. Venture a spin anywhere on Eggman's head and he'll open up his massive maw, revealing the Master Emerald within. Once exposed, the Emerald charges up for a huge laser blast that is extremely difficult to avoid, but the brief charging phase is your only opportunity to land a hit (careful not to fall over the edge). Manage 8 hits on the Emerald chamber and the Eggman Robo crumbles, but Eggman himself escapes in his Egg Mobile... with the Master Emerald in tow. The last line of business is to chase the escaping Eggman along the crumbling platform. It sounds easy, but it's a tricky business to spin the Doc without knocking yourself back over the edge. 8 hits later and Eggman drops the Emerald, but still manages to escape. If you have any less than all 7 Chaos Emeralds, the game ends here and you get the bad ending. If you do have all 7 Emeralds, however, Sonic transforms into Super Sonic and proceeds to...

Use the D-pad to maneuver Super Sonic up and down, and press any of the action buttons to shoot forward with a small burst of speed. Grab as many Rings as possible (there's plenty if you know where they are), but avoid the meteors, which slow your progress. Eggman fires missiles at Sonic, and while they obviously don't inflict damage, they will temporarily stun him which can be crippling when you need to keep Rings flowing through. After a short while, the meteor shower ends and you'll catch up with Eggman's space vessel. The machine fires flashing projectiles and homing lasers - either one will stun Sonic, and since they tend to hit in rapid succession, even a single hit can blow the fight. The object is to maneuver the homing missiles so they fly right back into the Eggman Robo's face. 8 hits and the shuttle falls into oblivion, but the relentless Eggman escapes once more in the old Eggman Robo (the one from Sonic 2). He's still greedily clutching the Master Emerald, and flies into another meteor shower firing fat bombs and tiny mines at the rampaging hedgehog behind him. All you have to do here is fly smack into the machine with your raging Super Sonic self. You'll be knocked back to the edge of the screen after each hit, but that's the only damage you can expect to take. 8 more hits and Eggman's number is (finally) up. Grab the Master Emerald and enjoy the good ending.