:host {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  display: block;

  height: 5px;
  z-index: 100;
}

span {
  display: block;
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  right: attr(progress percentage);
  background-color: #5f7fc3;
  transition: right 0.2s linear;
}