.content-nav-rail {
  position: fixed;
  z-index: 3;
  top: 50%;
  right: 16px;
  width: max-content;
  transform: translateY(-50%);
}

.content-nav {
  --content-progress: 0;
  width: max-content;
  padding: 20px;
  border-radius: 12px;
  background: hsl(0 0% 0% / 0);
  visibility: hidden;
  opacity: 0;
  pointer-events: none;
  transform: translateX(20px);
  transition:
    opacity 300ms ease,
    transform 300ms ease,
    visibility 300ms step-end;
}

.content-nav.is-visible {
  visibility: visible;
  opacity: 1;
  pointer-events: auto;
  transform: translateX(0);
  transition:
    opacity 300ms ease,
    transform 300ms ease,
    visibility 0s;
}

.content-nav ol {
  position: relative;
  display: flex;
  margin: 0;
  padding: 0;
  flex-direction: column;
  gap: 20px;
  list-style: none;
}

.content-nav ol::before,
.content-nav ol::after {
  position: absolute;
  top: 10px;
  bottom: 10px;
  left: 3px;
  width: 2px;
  z-index: 0;
  content: "";
}

.content-nav ol::before {
  background: hsl(216 19.6% 20%);
}

.content-nav ol::after {
  background: hsl(120 100% 20%);
  transform: scaleY(var(--content-progress));
  transform-origin: top;
}

.content-nav li {
  position: relative;
}

.content-nav a {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 8px max-content;
  align-items: start;
  gap: 10px;
  color: hsl(0 0% 100% / 0.5);
  font-size: 0.875rem;
  font-weight: 400;
  line-height: 1.45;
  white-space: nowrap;
  transition:
    color 160ms ease,
    opacity 100ms ease;
}

.content-nav-dot {
  display: block;
  width: 8px;
  height: 8px;
  margin-top: 6px;
  border-radius: 50%;
  background: hsl(216 19.6% 20%);
  transition: background-color 220ms ease;
}

.content-nav .is-past a,
.content-nav .is-active a {
  color: var(--text);
}

.content-nav .is-past .content-nav-dot,
.content-nav .is-active .content-nav-dot {
  background: hsl(120 100% 40%);
}

.content-nav .is-active .content-nav-dot {
  animation: content-nav-pulse 1800ms ease-in-out infinite;
}

.content-nav a:focus-visible {
  border-radius: 4px;
  outline: 2px solid var(--focus-ring);
  outline-offset: 5px;
}

.content-nav a:active {
  opacity: 0.7;
}

.content-block {
  scroll-margin-top: clamp(24px, 3vw, 48px);
}

@media (hover: hover) {
  .content-nav a:hover {
    color: var(--text);
  }
}

@media (max-width: 1750px) {
  .content-nav-rail {
    display: none;
  }
}

@keyframes content-nav-pulse {
  0%,
  100% {
    box-shadow: 0 0 0 0 hsl(120 100% 40% / 0.24);
  }

  50% {
    box-shadow: 0 0 0 7px hsl(120 100% 40% / 0);
  }
}

@media (prefers-reduced-motion: reduce) {
  .content-nav,
  .content-nav.is-visible {
    transition-duration: 0.01ms;
  }

  .content-nav .is-active .content-nav-dot {
    animation: none;
  }
}