styles.css

body {
  font-size: 14px;
  margin: 0;
}

h1, h2, h3 {
  font-weight: normal;
}

.underlying {
  opacity: 0;
  pointer-events: none;
  max-width: 20em;
  margin: 1em auto;
}

.overlay {
  position: absolute;
  top: 0;
  left: 0;
}

.overlay span {
  position: absolute;
}

svg {
  position: absolute;
  z-index: -1;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  overflow: visible;
}

canvas {
  position: absolute;
  z-index: -2;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  opacity: .2;
}

button.permission {
  position: absolute;
  right: 1rem;
  bottom: 1rem;
}

@media screen and (min-width: 320px) {
  body {
    font-size: calc(14px + 8 * ((100vw - 320px) / 960));
  }
}
@media screen and (min-width: 1280px) {
  body {
    font-size: 22px;
  }
}

@media screen and (max-width: 500px) {
  svg, canvas {
    display: none;
  }
}