This route is peculiar in a couple of ways. It extends off the top of the map screen and contains two separate branches. Whether you arrive from the left, or the right, you are force to jump up a large number of platforms in an effort to scale the mountain and reach the top. The left side is actually longer than the right, so it's faster to reach the top if you approach from the right side. The map above does not show the extent of either side.
However, if you're following along in the walkthrough, you'll have to climb the longer left side to reach the top. For the first portion of the climb, you are attacked by birds who fly straight across until they are above you and then drop down. When you get a bit higher up, you are attacked by bouncing bugs. Don't forget that if you are running low on energy and have enough Force power, you can use the Energizer ability to regain your health. Keep climbing high enough and the bugs are replaced by the enemies who fly across the screen in a wave-pattern.
There is one portion of the left climb that makes it particularly difficult to reach the top. There is a single ledge on the left where a unique enemy lives, who likes to jump into the air and land on the ledge. When he does, it does somedamage to Bang, and causes him to lose his grip and fall. You can't destroy this enemy with any weapon, and you can't even Jet Pack past him. The only thing you can do is let this enemy jump five times before he ultimately defeats himself. After his fifth jump, he will fall to his death, allowing you to continue your ascent and reach the top.
The top region of the mountain is occupied by two humanoid enemies, but of whom shoot at you, but are otherwise easy to eliminate. You must journey to the middle of this section until you find a gap in the ceiling that you can jump through. When you do, and reach the screen above, Bang will be surprised by how empty it is, wondering if there is no enemy camp at all. However, there is more than meets the eye on this screen. Expand the box below to learn the location of the base.
In the base
As soon as you enter, you will encounter a ruffled Bopper. He explains that you can't get any farther without all of the medallions, and then he attacks you. He is without his vehicle now, so all he does is pace back and forth on the floor, jumping occasionally. He shoots a machine gun at you that sprays bullets in a variety of directions. When you arrive in the room, you are standing on a platform. They safest way to defeat Bopper is to remain on the platform and squat down. From this position, you can consistently shoot him in the head. You will get hit from time to time with bullets, so be prepared to eat food or use the Force power Energizer if necessary.
Once Bopper is defeated, he will drop the final medallion. Collect it to restore all of your health. Then climbup the right wall to the screen above. When you reach the next level, two humanoids in suits will be shooting at you. Clear them away and fall down to the floor. Shoot continuously as you walk to the left until you reach the end of the room where Professor Plum is waiting in a cell. You will release him, and he confesses that he finished the bomb. Bang asks him how to use the medallions and he tells you to come near him. This, however, is a trap. It's a fake professor who is rigged to explode. Get away from him before he blows up. Then climb up the left wall to the screen above.
You will arrive in a room with a giant contraption on the ceiling. Bang will demand that the enemy appear. The boss will reveal himself. Bang tries to ask about the professor, but the boss says its his business and proceeds to attack you. The machine he is in will launch orbs of energy at you. You can shoot them with your own gun. The spheres on either side are your first target. The left orb is easy to strike, since you can climb up the left wall and shoot it.
The right orb is a bit more difficult since you can't grab onto a wall to destroy it. You'll need to use another type of weapon to destroy it. The Powerball is very effective here, especially since you can fire it upward by holding when you press . Use any weapon that you like to destroy the right sphere. A new target will appear in the middle, shooting bullets at you. Once again, you can climb up the left wall and position yourself so that you have an easy shot at it, and shoot it until it is destroyed, triggering an explosion in the chamber where the boss is. He falls out and exclaims that he's had it. He explains that the bomb will go off when he dies.
Now climb up the left wall to the screen above, remove the enemy waiting there, and continue climb up to the screen above that. Jump off the wall and over to the floor on the right. Walk over and you will encounter a tall alien. He explains that he is part of a group that made humans a millenium ago, and it might have been a mistake. He reasons that mankind will kill itself. Bang is determined to stop the bomb. Keep going right and drop down the gap in the floor. Fall to the floor below, and crawl through the narrow tunnel. Shoot the one remaining enemy, and the bomb mechanism will slide down to the floor. Approach it to defuse the bomb.
At this point, you have a limited amount of time, and five attempts to place the medallions into the bomb in the correct order. If you fail to do this in the time limit, or the number of tries, the bomb will explode and the game will immediately end, giving you the bad ending. The order that the medallions need to be is always random, so you must guess it each time. Any medallions that you do guess correctly will remain in place, and the remaining medallions are returned to you to try again.
The best strategy is to simply try placing each one in the order that they are presented. The ones which are right will stay in place. When the remainder are returned to you, start with the medallion to the right of the one you started with perviously, and try them all in order again. Keep doing this until every medallion has been placed in the right order, and you are almost assured of getting it right before you run out of tries. It won't work every time, so there is a small amount of luck involved, but this method rarely fails to find the right solution.
If you successfully place the bombs in the right order, you will then be treated to the good ending. The aliens will explain that they're giving up on you, to which Bang replies that's fine. Walk to the right to find the exit from the room, and the Hermit will appear on a cloud. He will offer to make you his apprentice, but you decline. Then he whisks you to the bottom of the mountain where you reunite with your friends. Congratulations!