Line

There are four basic lines.

Each line if you were to give them thought represents a mood.

1. Horizontal - Calm, Relaxed, Quiet
2. Diagonal - Failing, Masculine, Aggressive, Powerful, Much more powerful than the vertical or horizontal
3. Vertical - Balanced Ordered & Upright.  Less stable than the horizontal.
4. Curved - The curve is an enclosure. It cups, holds and relates.

A composition should have only one dominant line.  You may have other subordinates.

A line begins with two points.  Often we can connect the dots, and not even draw a line.  Our mind does that naturally.

From the strait line we can draw a rectangle

From the diagonal line we can form a triangle.

and from the curve we can make a circle.

From the rectangle we can form a box

From the triangle we can form a cone or a pyramid.

From the Circle we can form a sphere.