// create a regular point light source
light_source
{
  0*x // light's position (translated below)
  color red 1.0  green 1.0  blue 1.0  // light's color
// uncomment the next line to give the light source a visible appearance
//  looks_like { sphere { 0*x, 5 pigment { Yellow } } }
  translate <-20, 40, -20>
}