float area_light_small(vec2 uv) {
  // dot(uv, uv) is the same as (uv.x*uv.x + uv.y*uv.y)
  return 1. / dot(uv, uv);
}


void mainImage( out vec4 fragColor, in vec2 fragCoord ){
    vec2 uv = ( fragCoord - .5*iResolution.xy ) / iResolution.y;

    float v = area_light_small(uv) / 1200.;
    v = pow(v, 1./2.2); // gamma mapping

    fragColor=vec4(v);
}