You're on top of Dr. Cossack's place now, and you have to be careful - the long fall down will spell instant death if you're not careful!
This stage is unlike any other in the game because there are scrolling sections. During these sections, you need to keep moving forward, dodging and killing enemies all the while. It's pretty self-explanatory, just don't get left behind or fall to your death.
Golden bricks will appear in the second scrolling section. When you stand on them, they sink slowly, but jump off or above them, and they'll travel upward rapidly. Use these to your advantage when you can.
At the end of the level, you'll find a seemingly-unreachable Energy Tank. Use the Balloon item to get high enough to slide through the opening and get it.
Two spider robots wait in the boss lair of this stage. You'll fight two of them, one at a time. Stay on the platforms and don't fall onto the bed of spikes, but at the same time be vigilant and dodge the attacks. Unload on them with the Drill Bomb and you'll win this fight in no time flat. Even without the Drill weapon, it's not too tough a fight, but it will speed up the experience.