.range-slider {
  width:300px;
  height:20px;
  margin:0 auto 1em;
  position:relative;
  cursor:e-resize;
}
.range-slider:before {
  content:"";
  display:block;
  position:absolute;
  top:9px;
  left:0;
  width:100%;
  height:2px;
  background-color:black;
}
.range-slider span {
  display:block;
  height:inherit;
  position:relative;
  z-index:2;
  background-color:red;
  cursor:inherit;
}