Answer:
Impressionism was a radical art movement that began in the late 1800s, centered primarily around Parisian painters.
To me, the golden spiral is the proportional basis that makes the most sense. In a landscape painting the views eye is automatically directed to the center of the spiral and can be used by the artist to put their subject in the eye of the viewer.
Shading will make parts that appear farther away DARKER.
For any art work, the parts that are nearer on the artwork will appear clear while the parts that are farther away will appear faint and light. The parts that are farther away can be shaded to make them them appear darker instead of faint.
