r-image-repeat: stretch round;
      /*
      "
      The first keyword applies to the horizontal scaling and
      tiling of the top, middle and bottom parts, the second to
      the vertical scaling and tiling of the left, middle and right parts
      "
      https://www.w3.org/TR/css-backgrounds-3/#border-image-repeat
      */
      border-image-slice: 64 fill; /* the center will be black */
      border-image-source: url("support/4bicolor-squares.png");
      display: inline-block;
      image-rendering