Nested category CartoCSS for polygons

style.mss

/* start */
#vttowns_wgs84 {
    polygon-opacity:0;
    line-width: 0.4;
    line-dasharray:3,6;
    line-color: #555;
    line-opacity: 0.5;
    [springfloods=true] {
      ::line1 {
        line-width: 5;
        line-color: #2E5387;
        line-opacity: 1;
        line-offset:0;
        line-join:round;
        line-clip:false;
      }
    }
    [priority=true] {
      ::line2 {
        line-width: 5;
        line-color: #FF9900;
        line-opacity: 1;
        line-offset:4;
        line-join:round;
        line-clip:false;
      }
    }
    [sigimpact=true] {
      ::line3 {
        line-width: 5;
        line-color: #0A460C;
        line-opacity: 1;
        line-offset:9;
        line-join:round;
        line-clip:false;
      }
    }
    ::labels {
    [springfloods=true],[priority=true],[sigimpact=true] {
      text-face-name:'unifont Medium';
      text-size: 14;
      text-fill: #000;
      text-allow-overlap: true;
      text-halo-fill: #FFF;
      text-halo-radius:1;
      text-name:[townnamemc];
    }
  }
}
/* end */