The perspective distance used by perspective() is specified by a <length> value, which represents the distance between the user and the z=0 plane, or by none. The z=0 plane is the plane where everything appears in a 2-dimensional view, or the screen. Negative values are syntax errors. Values smaller than 1px (including zero) are clamped to 1px. Values other than none cause elements with positive z positions to appear larger, and elements with negative z positions to appear smaller. Elements with z positions equal to or larger than the perspective value disappear as though they are behind the user. Large values of perspective represent a small transformation; small values of perspective() represent a large transformation; perspective(none) represents perspective from infinite distance and no transformation.