     // night
     if (sun_z < nighttime) {
         color = nightblue_color;
-        // color = vec3(phi_diff, 0,0 );
-
     // night to sunrise OR sunset to night
     } else if (sun_z > nighttime && sun_z < sun_start) {
         float size = sun_start - nighttime;

        float percent= diff/size;
        color = (sunset_color + (high_noon_color - sunset_color) * percent);
        color = mix(color, nightblue_color, phi_diff);
        // color = vec3(phi_diff, 0,0 );

        // color = mix(vec3(1,0,0), vec3(0,1,0), phi_diff);

    // high_noon
    } else if (sun_z > high_noon_start) {
        color = high_noon_color;
        // color = vec3(phi_diff, 0,0 );

    }



}

    // varies from [PI..0] respectively
    // But because this is only functional for the upper hemisphere,
    // the phi for the lower hemisphere is calculated in the if statement

    float phi = acos( (unit_vector.x) / sqrt(unit_vector.x * unit_vector.x + unit_vector.y * unit_vector.y) );
    if (unit_vector.y < 0) {
        phi = 2*PI - phi;
    }
