Symmetrical nature of a video display creating vertical lines that run parallel up and down without bending or angling and creating horizontal lines that run side to side without bending or angling. Proper picture geometry assures that an image does not vary in size across the screen and that it does not bend or warp. Think of a perfect grid such as that found on graph paper or a perfect tic-tac-toe grid. On a video display such a grid should contain squares of equal size across the screen and feature lines that run straight and at 90-degree angles to the edges of the screen.