Brainsnag Level 18 answer: Squeeze the Cloud
The level says: “Water the plant”
Hints first (no spoilers)
Hint 1Clouds are full of water.
Hint 2How do you get water out of a sponge?
Hint 3Pinch the cloud inward with two fingers (scroll down over it on a computer) to wring the rain out.
Show the full solution
The cloud is a sponge. Pinch it inward with two fingers (mouse wheel down on desktop) to squeeze it. Rain falls on the plant and it perks up.