After you get some more upgrades, you head farther into the depths of Zebes.

Get the Brinstar Map

Go downward until you see two doors. Shoot the left door with five missiles to open it. Go through. Go to the left to enter the dead end, then use a bomb to open a tunnel. Roll through it and use another bomb to open the end. Go through the door on the left and get the Brinstar map.

Get More Missiles

Exit the map room and kill the Zeela (you have to do this to unlock the door). Jump onto the ledge and bomb the wall, roll through the tunnel, and use a bomb at the other end. Kill all of the enemies in the room to unlock the door on the right, then go through the door on the right.

Shoot the door on the right with five missiles to open it. Go through. Get on the upper ledge and go to the right, and allow yourself to fall down through the pit blocks. Get the missiles, then bomb the left wall, and leave this room the way you came in.

Get the Charge Beam

Go downward and you can optionally shoot the door on the left with five missiles to open it, then go through the door to use the save room. Exit the save room, then go down to the bottom of the room to find two doors facing each other. If you would like to recharge your missiles, shoot the door on the left with five missiles, and go through. In this room, avoid bumping into or killing the Firefleas, because the room will get darker each time you kill one. After you get through the Fireflea room, you will find a room with a missile recharger. Exit the missile recharge room and go up the ledges, then go to the right, and go through the door on the right.

Now shoot the door on the right with five missiles and go through. Make your way to the right, then use bombs to break through the wall on the right, then hold the Dash button to run to the right to get past the Metarees on the ceiling that try to hit you. Go through the door.

Go to the bottom-left corner of this large room to find a missile tank. Then use bombs on the base of the wall to the right and you will break open a hole. Go into the tunnel and you will fall down below to a room with a Chozo Statue. It is holding the Charge Beam. Take it. You can hold the beam button to charge up a more powerful shot. Also, if your beam is fully charged, you can spin jump into enemies to damage them. It doesn't work on all enemies, however. You can turn this on and off from the pause screen if you press R to view your equipment.

Go to a Mini-Boss

Go back up through the hole in the ceiling and go left and up. When you can't go farther up, go to the right side of the room. From there, go up until you see metal blocks in the ceiling on the left. If you are proficient in wall jumping, you can go to the left and wall jump up the structure on the left to get a Missile Tank. Then you can go down from the structure and walk on the floor in that area to fall through some pit blocks, then go to the right. Or instead of falling through the pit blocks, you can go to the right and wall jump up the wall.

Go upward on the platforms on the right side of the room, then when you can't go farther up, go to the left. At the door, go up. You can kill the Zebs that come out of the pipe to refill health and items. Then go to the right until you can't go any farther, then go up, then left. Go up through the opening. You can roll into the tunnel in the upper-left corner and bomb the wall to reach a hidden door, which leads to a save room.

Then exit the save room and go to the right to reach a door. Shoot it with five missiles to open it. Go through. Go to the right, killing all of the Green Kihunters with charged shots or missiles. Then go to the right side of the room and you will see a blinking door in the ceiling. (If it's not blinking, there are still Kihunters in the room that you need to kill.) Go through the blinking door and you will encounter a mini-boss.

Spore Spawn

Small spores will float down from the ceiling. These will hurt you if they hit you, so shoot them with your beam before they can hit you. They will become energy and missiles if you need them.

Spore Spawn will swing from side to side. You can stay safe by crouching in the lowest part of the room and shooting the spores or moving out of the way of them. The far corners of the raised ledges are also safe while rolled into a ball.

When Spore Spawn opens up, shoot a charged shot or missiles at the center to damage it. Normal beam shots will not work. Charged Shots deal the most damage.

After you have done enough damage, Spore Spawn will become darker and will start swinging around more quickly. Keep hitting the inside of its mouth until it dies. Pick up the energy and missile refills that it leaves behind, then go up through the ceiling to a door. Go through it.

Get Super Missiles

Go to the right side of the next room and jump onto the green pipe. It will break open and you will fall for a while, then you will land in front of a Chozo Statue that holds Super Missiles. This will allow you to reach lower Brinstar.