:root {
  --progressbar-width: 0;
}

.read-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 4px;
  background-color: #fff;
}

.read-progress::after {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: var(--progressbar-width);
  background-color: #c36f6f;
}

.chapter {
  width: 80%;
  max-width: 560px;
  margin: auto;
  margin-top: 100px;
}