Go right and pick up the Thunder Gas you will find. You will also find a diamond, immediately after. In the meantime, you will encounter some enemies, try to kill them quickly, before they can attack you. To continue, you will have to hold on to a lever, in order to lower an iron beam from above. Continue to the right and hold on to the hook to reach a suspended platform, on which you will find another diamond. Pull another lever to bring down an iron beam and continue. Cling to the hooks at the top and continue jumping from one hook to the other, to the right. You will come to a small platform, above which is a Darkwing Doll. Grab it and continue, being careful not to fall into the gaps. You will now have to overcome a climbing part. Climb higher and higher, holding on to the platforms and being careful not to fall. There is also a diamond on one platform. Try to take out the bats without getting close before they can attack you.
Once at the top, continue to the right. You will have to overcome a long stretch suspended in the void, jumping from one hook to another. Towards the end you will be attacked by two bats. If you can't take them out with your weapons, just avoid them. It is important not to end up against them, risking to fall. At the end of this stretch, try to take the narrow lower passage. Just jump against the wall and press Right on the Control Pad. You will find a gold bar. Continue and grab the pulley at the end of the path to go back upstairs. Now you will have to overcome another area without floor, jumping from one pulley to the other. It is important to jump at the right time, before falling. When the third pulley is about to fall, jump to the right to avoid the spikes. To continue, you will have to drop two more iron beams, as described above. Then go down into the gap on the right and follow the path.
By holding on to a hook, you can catch a Heavy Gas on a ledge in the upper left. Continuing on, you will encounter some though enemies with a green cloaks. Their cloak is resistant to your attacks and you can only attack them while they shoot you. But you too can parry their bullets with your cloak. So dodge their attacks and shoot them quickly, before they can protect themselves again. Climb over the precipice by holding on to the hooks and you will come to an area with many suspended platforms. You can reach them easily by holding on. You will find two more gold bars. You will find other enemies with green cloaks, take them out as described above. There are also some slugs on the floor, but these shouldn't bother you. On the last platform you will find a large first aid kit. Grab it and go right to meet the boss.
BOSS FIGHT - QUACKERJACK
The screen is divided horizontally into three levels. You can easily switch from one to the other by jumping or dropping. QuackerJack just walks back and forth, but if you get to the same level he is, he will quickly move up or down to escape your attacks. The main danger, however, is a small guy at the top of the screen, in an area you can't reach. This guy will try to match your horizontal location and drop some banana peels trying to hit you. You will then have to keep moving to dodge them. The basic strategy for defeating QuackerJack is to quickly get to the level he is in and shoot him before he can change positions. If you are quick, you will certainly be able to land at least one hit. If you have the Thunder Gas, things will be simpler. This weapon allows you to hit the boss even without being at the same level as him. Heavy Gas can also be useful to you: you can hang on to a platform and throw it to hit QuackerJack if he is below you. However, always keep an eye on the guy who drops the banana peels and move immediately if he approaches. Do not rush too much to attack the boss, coordinate the movements well and act with timing. Eventually you will defeat him.