Guide the flame monster to the right.
Use the blue key to manipulate its path.
The flame will kill the skull monster.

Grab the purple color.
Let the skull monster fall down all to the bottom.
Meanwhile the flame monster is trapped in a circle.

Now set up a path to the left like in the image.
The flame will melt the ice block on the left.
Now you can reach the last purple fruit.

First trap the flame monster in a circle around a crate block.
When it goes up, break the crate so the flame is moving upwards.
It will follow the path the left and destroy the ice block with the mystery.