Proceed to the right. Some enemies will pop out of the asphalt and attack you with a flamethrower. The best way to take them out is to shoot low, so you can kill them before they can attack you. You will also find some banana peels, if you touch them you will be stunned for an instant. Climbing up, you can get two diamonds. A little further on, to proceed you will have to climb on a wheel, in order to pass unscathed the spikes further ahead. While the wheel is moving, however, you will have to keep running, or you will fall down. At some point, by jumping, you can grab onto a platform above and thus reach an Arrow Gas. It is advisable to keep this special weapon until the end of the level, if you want to grab some useful items. Then jump right overcoming the spikes, paying attention to the flying enemies.
Immediately after there is an uphill section, where you will have to climb by holding on to the lampposts and platforms. Nothing complicated, but keep an eye on the flying enemies and take them out as soon as possible. Along the way you will find two gold bars and a large first aid kit. There is also a Thunder Gas at the top, but you don't want to take it. Continue to the right. The next part is a little tricky. You will have to jump over the wheels again to get past the spikes, but you will also have to be careful not to fall into the void and to the flying enemies. Then enter the tunnel and follow the path.
You will encounter a new type of enemy: a turtle that throws its own shell at you. You cannot defend yourself from its attacks with the cloak. The turtle is only vulnerable as it throws its shell at you and it takes several gunshots to kill it. You will then have to jump quickly when it attacks you to avoid the shell and shoot it before the shell has come back, until you defeat it. At the top, there is a large first aid kit, but to reach it you must still be in possession of the Arrow Gas, using the arrows to climb. Go over and defeat another turtle. To overcome the next gap, you can grab onto the street lamps or repeatedly jump on the pump to inflate a balloon, which you can hang on to. On the next roof you will find another turtle and a Heavy Gas. Better not to take it. In front of you is another, longer precipice that you can overcome in the same way. On the other side, you can reach two Darkwing Dolls at the top, but only if you still have Arrow Gas. After you get them, you can go back for the Heavy Gas if you like. Move on. To defeat the inflatable puppet-like enemies, you'll need to hit them in the head, or they'll inflate again in an instant. From here on, the path is very linear. Keep moving forward by defeating the enemies. On a platform you will find a large first aid kit: you should take it, to restore your energy before the fight with the boss. Reach the glass building and enter the passage to face the boss.
BOSS FIGHT - WOLFDUCK
When the moon, on the top left, is uncovered, the boss is invulnerable and will attack you by throwing crates (which you can destroy with your gun) or by jumping from one side of the screen to the other. In these phases attacking it is useless, better just avoid it. On the other hand, when the moon is covered by clouds, the boss will quickly run from one side of the screen to the other. At this stage it is vulnerable and you can attack it with your gun, but you will still have to move so that it does not come at you. A good strategy is to duck in front of the step the boss is on when the moon covers itself. In this way, the boss will pass over you, without hitting you, after which you will be free to attack it from behind. Keep attacking it even as it comes back, then avoiding it with a jump. Special weapons won't be particularly useful to you in this fight. If you coordinate your movements well, you will soon defeat this boss.