style.css

@import url('https://fonts.googleapis.com/css2?family=Alegreya&display=swap');

body {
    margin: 0;
    padding: 0;
    font-family: "Alegreya", serif;
  }
  svg {
    position: fixed;
    top: 0;
    left: 0;
    height: 100%;
    width: 100%;
  }
  .node {
    stroke-width: 1.5px;
  }
  .link {
    stroke-opacity: 0.1;
  }
  .label {
    text-anchor: middle;
  }
  .controls {
    position: absolute;
    text-transform: uppercase;
    font-weight: bold;
    color: #0009;
    font-size: 10px;
    letter-spacing: 0.3ex;
    bottom: 1em;
    left: 1em;
    background: rgba(255, 255, 255, 0.8);
    z-index: 10;
    width: 50%;
    padding: 1em;
    border-radius: .8ex;
  }

  .controls label{
    display: block;
    vertical-align: middle;
    margin: 1ex 0;
  }

/*********** Baseline, reset styles ***********/
input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  background: transparent;
  cursor: pointer;
  width: 100%;
  max-width: 400px;
}

/* Removes default focus */
input[type="range"]:focus {
  outline: none;
}

/******** Chrome, Safari, Opera and Edge Chromium styles ********/
/* slider track */
input[type="range"]::-webkit-slider-runnable-track {
  background-color: #5c5c5c;
  height: 1px;
}

/* slider thumb */
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none; /* Override default look */
  appearance: none;
  margin-top: -7.5px; /* Centers thumb on the track */
  background-color: #808080;
  border-radius: 50%;
  height: 1rem;
  width: 1rem;
}

input[type="range"]:focus::-webkit-slider-thumb {
  outline: 3px solid #808080;
  outline-offset: 0.125rem;
}

/*********** Firefox styles ***********/
/* slider track */
input[type="range"]::-moz-range-track {
  background-color: #5c5c5c;
  height: 1px;
}

/* slider thumb */
input[type="range"]::-moz-range-thumb {
  background-color: #808080;
  border: none; /*Removes extra border that FF applies*/
  height: 1rem;
  width: 1rem;
}

input[type="range"]:focus::-moz-range-thumb{
  outline: 3px solid #808080;
  outline-offset: 0.125rem;
}