Magnet Man stage
Typically, this is the first level that players will play, although it is possible to start on any level. Obviously, the magnet theme is prevalent and many enemies and obstacles involve Mega Man being drawn towards something via magnetic attraction. Proto Man also makes an appearance early on in this level.
Magnet Man has three actions. He can jump twice to the other side of the room (here, the slide is useful for avoiding contact), he can jump very high and fire three Magnet Missiles, which will make a single 90° turn towards Mega Man, or he can generate a magnetic field that will make him invulnerable and draw Mega Man towards him. He is weak to the Needle Cannon primarily, but also takes damage from the Spark Shock. Defeating him grants Mega Man the Magnet Missile, which is identical to the ones that Magnet Man himself fires. Also, he is weak against the attack that you receive from Sparkman, if you didn't kill this guy first.
Hard Man stage
Hard Man's stage is quite similar to Guts Man's stage. Mega Man will travel through excavated tunnels, dealing with construction robots as well as giant bees that drop a cluster of smaller bees to attack. Proto Man also makes an appearance in this level, and is a bit harder to deal with due to the layout of the room.
Hard Man is much simpler than Magnet Man. He will fire two fists that will go towards Mega Man for a distance, then return back to Hard Man. He will then jump into the air above Mega Man and land head first into the ground, causing a shaking that freezes Mega Man. However, he will not attack while Mega Man is frozen as he is stuck in the ground, so this is more of a superficial effect. Since his body is made of many layers of hard metal, the Magnet Missile can be devastating. Defeating him will give Mega Man the Hard Knuckle, similar to the ones Hard Man used. A large knuckle appears in front of Mega Man and fires straight ahead, moving slowly at first, then accelerating. It can be controlled slightly by holding up or down on the directional pad.
Top Man stage
This stage earns points for uniqueness. The level is very grassy and features a few top-themed obstacles, notably at the end where Mega Man must jump between spinning tops that are traveling vertically over a pit.
Top Man is quite straightforward. He begins by throwing three tops into the air that suspend for a moment, then converge on Mega Man's position. He then starts spinning quickly which makes him invulnerable, then dashes across the room to the other side. He repeats this strategy over and over again. The Hard Knuckle makes short work of Top Man, apparently by throwing off his momentum. Defeating him earns Mega Man the Top Spin. This weapon is unique in that Mega Man does not fire anything. However, by pressing B while Mega Man is in the air, he will spin for a moment, damaging enemies who come in contact with him.
Shadow Man stage
Set in what appears to be some sort of smelting facility (because of the "lava"), Shadow Man's stage has many pits into what appears to be lava. There are also special light bulbs on the ceiling that turn the entire room dark when they appear on screen. Proto Man appears in this level in a situation almost identical to his appearance in Magnet Man's stage.
Shadow Man is very agile. He slides and jumps around the room throwing shuriken. This makes him quite dangerous, as he will attempt to damage you as much as possible in a little amount of time. However, by using Top Man's Top Spin attack, Shadow Man is quick to defeat, though Mega Man will probably take quite a bit of damage himself. Defeating him equips Mega Man with the Shadow Blade, which is identical to Shadow Man's shuriken attack. A large shuriken can be fired in three directions (forward, up, and diagonal) and it will return to Mega Man if it does not make contact with an enemy.
Spark Man stage
Spark Man dwells in an industrial-themed stage, which contains flashing lights and a background of numerous cogs which are reminiscent of Metal Man's stage from Mega Man 2. Rocket-powered platforms attempting to smash Mega Man into spikes on the ceiling and blocks of compacted metal which form barriers to block the way are some of the obstacles faced in this stage.
Spark Man himself is a simple foe if Mega Man is equipped with the Shadow Blade. The room in which the battle takes place has an irregularly shaped floor, so the slide technique is almost useless. Spark Man attacks by shooting sparks from his head in eight directions, followed by a large spark shock directed at Mega Man. Upon his defeat, the Spark Shock is awarded, which stuns some enemies (even if they are in midair) and damages others.
Snake Man stage
Most of this stage is spent navigating a nest of pipes, which sometimes terminate in mechanical snakes both large and small which attack Mega Man. After climbing to the top of this area, Mega Man climbs a tower into the clouds and must hop across flying platforms in the sky in order to reach the boss's room.
Snake Man attacks by running around the room, pausing periodically to jump into the air and fire a couple of snakes. The snakes he fires slither across the floor, also climbing vertical surfaces until they contact Mega Man. Avoiding these snakes can be difficult while also avoiding a collision with Snake Man. The Shadow Blade is an effective weapon to use against Snake Man, although it doesn't do as much damage as against Spark Man. The awarded weapon is identical to the snakes fired by Snake Man. If you can't kill Snake Man normally, get a health container to help push the fight in your favor. This guy hits really hard and the shadowblade doesn't really do too much damage as opposed to hitting other bosses in the game with their weakness. This guy is actually one of the hardest of the first eight bosses you'll have to fight, if not the hardest.
Gemini Man stage
This otherworldly stage begins in what appears to be an Arctic region, with Mega Man running across ice crystals while being attacked by mechanical penguins. Proto Man appears to open Gemini Man's cavernous fortress for Mega Man, but he does not attack as he does in his other appearances. After proceeding underground, the remainder of the stage is spent in a cavern made of multicolored rocks, inhabited by flying tadpoles and more mechanical penguins. Near the end of the stage, the Rush Marine can be used (although it is not necessary) to traverse the water.
Gemini Man begins the battle by releasing a duplicate of himself. The two foes circle the room by jumping in an arc to one side and then running across to the other side, all the while firing the Gemini Laser. The laser bounces off the walls at angles until it contacts Mega Man, or until it disappears after a few seconds. By using the weapon acquired from Snake Man, one of two Gemini Men can easily be destroyed. When only one remains, the attack pattern changes abruptly to a simple running and jumping while firing the laser. The same weapon will finish him off quickly. The Gemini Laser, which is gained after this battle, is the same as that used by the boss.
Needle Man stage
This stage appears to take place in a metropolitan area, and is rather short to complete. Mega Man faces robotic hedgehogs which fire needles from their backs, and later he must slide to avoid being hit by telescopic needles which extend from the ceiling.
Needle Man jumps vertically into the air, firing his needle cannon at Mega Man. He also runs across the ground, pausing to attack Mega Man with the needles attached to his head. By using the Gemini Laser, a speedy defeat is assured, as even if the laser misses the target, it will reflect off the walls to hit him later. The Needle Cannon, which is awarded upon his defeat, fires needles quickly in a straight line.
Doc Robot (Mega Man 2 revisited)
Spark Man stage
Waiting in the Spark Man stage is Metal Man and Quick Man. Metal Man, being metal, is vulnerable to magnets. You can make quick work of him with Magnet Missiles.
Quick man is another story. If you remember, it was easy in Mega Man 2 to use the Flash Cannon which drained half his life before the battle even began. You don't get this luxury. Logic says that Gemini Laser would be the best thing, but that's not the case here. Use the snake cannon to get rid of him quickly, but be wary, as running into Quick Man drains your life quickly.
Needle Man stage
Coming up in the Needle Man stage is Air Man and Crash Man. Air Man is very vulnerable to Spark Shocks, if you can get them past his tornadoes of death. And running into him does severe damage, so avoid that. Crash Man seems like the grandfather of Hard Man, as their weapons do much the same thing. Use Hard Knuckles on him, he'll be quick work.
Gemini Man stage
In Gemini Man's stage, Flash Man and Bubble Man are hiding out.
Flash Man's stage is full of platforms, much like it was in Mega Man 2. This would make you think that Gemini Lasers might be good. But because of the platforms, the laser will bounce all over the place, rarely hit him and you'll die before the second one gets him. Needle cannon seems to be the best thing to get him.
The thing about Bubble Man is that the ceiling is covered in spikes. Spikes means instant death, so there isn't much room for jumping. This guy can be easy if you use Shadow Blades. It's helpful when Bubble Man is jumping to fire them overhead, too.
Shadow Man stage
Finally, in Shadow Man's stage awaits Wood Man and Heat Man.
Wood Man is, ironically enough, very vulnerable to the Needle Cannon. The timing is different with his leaf shield, as well, from Mega Man 2, so be wary of jumping over it too quickly.
Heat Man appears vulnerable to Shadow Blades as well. The problem of course being that Heat Man throws his molten whatever at you from across the room, and Shadow Blades only go so far. Be careful of his movement – he moves slower than you might remember from Mega Man 2, and thus is a little harder to jump over.
Finally, you'll meet Break Man. There's no real secret to defeating him, just keep shooting him and slide underneath him when he jumps, because he'll only shoot in one direction. After that, he pops up and you follow, and then you move on to Wily's castle.