.slider {
  -webkit-appearance: none;
  height: 15px;
  border-radius: 5px;  
  background: #d3d3d3;
  outline: none;
  opacity: 0.7;
  -webkit-transition: .2s;
  transition: opacity .2s;
  margin: 10px 0px 10px 0px;
}

.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 25px;
  height: 25px;
  border-radius: 20%; 
  background: #31d2f2;
  cursor: pointer;
}

.slider::-moz-range-thumb {
  width: 25px;
  height: 25px;
  border-radius: 20%;
  background: #31d2f2;
  cursor: pointer;
}