If you're wondering what the difference between Normal and Difficult is, all the bosses take less damage from special weapons and some enemies take more shots to destroyed.
With that taken care of, on with the show.
Instead of six Robot Masters to deal with, you have eight Robot Masters this time around. Once again, you can start with any Robot Master you want. Since I'm covering everything in the order NCS does it, we're starting with Bubble Man.
Bubble Man
Bubble Man is perhaps the easiest to deal with if you have just the Proto Buster, so let's go ahead and do that.
The frogs shoot miniature clones out of its mouth. Take out the source, then stand still to kill off all the underlings.
The robots with the red shells go faster when you shoot their shells off. Either hit them directly from a lower point or jump out of the way!
When you jump into the water, you'll jump higher than usual. Keep that in mind so you don't accidentally drift upwards into the spiked ceiling.
To destroy the big angler fish, just shoot at the angler on its head. The shrimp that come out of its mouth and lunge towards you can give you power-ups (and come in quite handy if you're playing this later in the game), so shoot them down as you take out the big fish. Unlike the last game, the health power-ups come out much more often from destroyed enemies, and you no longer have those pesky point icons to deal with. You can also get extra lives off of enemies if you're lucky.
Watch out for the jellyfish. Not only do they come down rather slowly, they also start following you shortly after they reach your level and explode upon contact.
Once you get out of the water, you'll start seeing crabs falling down the waterfall in the background. If they hit the platforms, though, they're not very fast and they go down in one shot.
To beat Bubble Man, walk under the bubbles and jump over the bullets, and shoot him as he slowly comes back down to the ground. He just keeps doing this while going from one side of the room to the other, so he's really not that hard at all.
When you beat Bubble Man, you'll get Bubble Lead.
Flash Man
I always did this guy first. Seriously, he's even easier than Bubble Man in an all-Proto Buster run.
The robots that look like gas canisters shoot both straight and at an angle. They take a short break from shooting before they switch between the two angles, so use that as opportunity to get some extra shots in on him. The straight shots have a bit of range and speed, so be careful.
As you go through this level, you'll be going through a maze of sorts. There are only a few dead ends, but if you take certain paths, you may be able to get extra lives or an Energy Can. (More on those later.) The floor also has quasi-ice physics, so you'll be sliding around for about a second after you come to a stop.
The walls that are comprised of squares with smaller squares in them can only be destroyed with the Crash Bomb, which you won't get until you beat Crash Man.
As you start going down the vertical portion of this stage, you'll meet
MM2's version of the crusher robot. It's a Sniper Joe in a two-legged mecha, and he shoots at you in five angles. Even if you can (very easily) take this robot out, you'll still have the Sniper Joe to deal with. At least he can't move
and he's got a pattern this time around.
The enemy that looks like a stack of cans can only be shot in the portion with eyes. If you're playing on Difficult mode, he takes two hits instead of one, and after that first hit, the other portions fly off of his head and come straight at you with no warning.
If you can stay on the top of the screen and manage to make it across all the small platforms at the end of the vertical portion, you'll be able to get an Energy Can. These cans can be used to completely refill your energy in the midst of a difficult situation (preferably boss battles), and you can carry up to four.
Flash Man is hilariously easy. Just shoot at him with the Mega Buster and stay out of his way. Stay in the air he pulls his arm cannon out. There's a good chance you might avoid his firepower completely.
When you beat Flash Man, you'll get the Time Stopper. You'll also get Item 3.
Metal Man
Metal Man not only has one of the most awesome weapons in
Mega Man history, he's also got one of the better BGMs and level designs in the franchise as well. Gears spinning in the background, the earliest uses of conveyor belts, and one of the most frantic pieces of video game music from the late '80s.
The pink arrows that flash at the ends of the conveyor belt tell you which direction the conveyor belt you're on is going at a glance. One of the first that goes left has an Energy Can at the end, which is easily attainable.
The spiked crushers take out almost a third of a full energy bar, so avoid these at all costs. You can jump through the chains that hold them, but I wouldn't recommend it.
The drills come out in certain section of stages, they take a few hits before they go away, they give out a lot of power-ups if you go slowly, and they don't stop coming at all until you reach the end of said section. They can also hit you by surprise, so go slowly.
If you have one of the items near where the vertical portion begins, you can get the 1-up on the top conveyor belt at the end.