#volume {
  width: 40%; /* Width of the outside container */
}

/* The slider itself */
.slider {
  -webkit-appearance: none;
  width:  50%;
  height: 1.6em;
  background: #d3d3d3;
  outline: none;
  opacity: 0.7;
  -webkit-transition: .2s;
  transition: opacity .2s;
  font-size: 0.8vw;
}

/* Mouse-over effects */
.slider:hover {
  opacity: 1; /* Fully shown on mouse-over */
}

/* The slider handle (use -webkit- (Chrome, Opera, Safari, Edge) and -moz- (Firefox) to override default look) */
.slider::-webkit-slider-thumb {
  -webkit-appearance: none; /* Override default look */
  appearance: none;
  width:  2em;
  height: 2em;
  background: #000;
  cursor: pointer;
  font-size: 0.8vw;
}

.slider::-moz-range-thumb {
  width:  2em;
  height: 2em;
  background: #000;
  cursor: pointer;
  font-size: 0.8vw;
}