function initVML() {

    /* Utility function to create a VML tag */
    function vml(tag, attr) {
      return createEl('<' + tag + ' xmlns="urn:schemas-microsoft.com:vml" class="spin-vml">', attr)
    }

    // No CSS transforms but VML support, add a CSS rule for VML elements:
    sheet.addRule('.spin-vml', 'behavior:url(#default#VML)')

    Spinner.prototype.lines = function(el, o) {
      var r = o.length+o.width
        , s = 2*r

      function grp() {
        return css(
          vml('group', {
            coordsize: s + ' ' + s,
            coordorigin: -r + ' ' + -r
          }),
          { width: s, height: s }
        )
      }

      var margin = -(o.width+o.length)*2 + 'px'
        , g = css(grp(), {position: 'absolute', top: margin, left: margin})
        , i

      function seg(i, dx, filter) {
        ins(g,
          ins(css(grp(), {rotation: 360 / o.lines * i + 'deg', left: ~~dx}),
            ins(css(vml('roundrect', {arcsize: o.corners}), {
                width: r,
                height: o.width,
                left: o.radius,
                top: -o.width>>1,
                filter: filter
              }),
              vml('fill', {color: o.color, opacity: o.opacity}),
              vml('stroke', {opacity: 0}) // transparent stroke to fix color bleeding upon opacity change
            )
          )
        )
      }

      if (o.shadow)
        for (i = 1; i <= o.lines; i++)
          seg(i, -2, 'progid:DXImageTransform.Microsoft.Blur(pixelradius=2,makeshadow=1,shadowopacity=.3)')

      for (i = 1; i <= o.lines; i++) seg(i)
      return ins(el, g)
    }

    Spinner.prototype.opacity = function(el, i, val, o) {
      var c = el.firstChild
      o = o.shadow && o.lines || 0
      if (c && i+o < c.childNodes.length) {
        c = c.childNodes[i+o]; c = c && c.firstChild; c = c && c.firstChild
        if (c) c.opacity = val
      }
    }
  }
Internal method that adjusts the opacity of a single line.
Will be overwritten in VML fallback mode below.