/*
 * Home page scrollytelling: a request travels through the stations while the visitor scrolls.
 * main.js sets --story-progress (0 to 1) on .story and marks the active step with .is-active.
 * Without the "motion" class the stage stays hidden and the steps read as a plain numbered list.
 */
.story {
  margin-top: var(--space-9);
  /* Inactive steps sit slightly to the right; that offset must never widen the page on phones. */
  overflow-x: clip;
}

.story__intro {
  max-width: 40rem;
  margin-bottom: var(--space-6);
}

.story__intro h2 {
  font-size: var(--text-2xl);
}

.story__intro p {
  color: var(--color-muted);
  font-size: var(--text-md);
}

.story__stage {
  display: none;
}

.story__steps {
  display: grid;
  gap: var(--space-4);
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: none;
}

.story__step {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: var(--space-1) var(--space-4);
  padding: var(--space-5);
  border: 1px solid var(--color-line);
  border-radius: var(--radius-lg);
  background: var(--color-surface);
}

.story__step-index {
  grid-row: span 3;
  color: var(--color-accent);
  font-size: var(--text-lg);
  font-weight: 800;
  font-variant-numeric: tabular-nums;
  line-height: 1.2;
}

.story__step h3 {
  margin: 0;
}

.story__step p {
  max-width: 65ch;
  margin: 0;
  color: var(--color-muted);
}

.story__step-code {
  justify-self: start;
  max-width: 100%;
  margin-top: var(--space-2);
  overflow-wrap: anywhere;
  font-size: var(--text-xs);
}

/* With motion: sticky stage left, long scroll track of steps right. */
.motion .story__body {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr);
  gap: var(--space-7);
  align-items: start;
}

.motion .story__stage {
  position: sticky;
  /* Vertically centred in the space below the header. */
  top: max(calc(4.25rem + var(--space-5)), calc(50vh - 8rem));
  display: grid;
  gap: var(--space-6);
  padding: var(--space-6);
  /* The edge keeps the dark panel apart from a dark page. */
  border: 1px solid var(--color-line-strong);
  border-radius: var(--radius-lg);
  background: var(--color-terminal);
  color: var(--color-terminal-ink);
  box-shadow: var(--shadow-lifted);
}

.story__rail {
  position: relative;
  padding-top: var(--space-2);
}

/* Track and fill share one line through the node centres. */
.story__rail::before,
.story__rail-fill {
  content: '';
  position: absolute;
  left: calc(100% / 14);
  right: calc(100% / 14);
  top: calc(var(--space-2) + 0.55rem);
  height: 2px;
  border-radius: 2px;
  background: color-mix(in srgb, var(--color-terminal-dim) 35%, transparent);
}

.story__rail-fill {
  background: var(--color-accent-on-dark);
  transform-origin: left;
  transform: scaleX(var(--story-progress, 0));
}

.story__packet {
  position: absolute;
  top: calc(var(--space-2) + 0.55rem - 0.4rem);
  left: calc(100% / 14 + (100% - 100% / 7) * var(--story-progress, 0) - 0.4rem);
  width: 0.8rem;
  height: 0.8rem;
  border-radius: 50%;
  background: var(--color-accent-on-dark);
  box-shadow:
    0 0 0 5px color-mix(in srgb, var(--color-accent-on-dark) 25%, transparent),
    0 0 18px var(--color-accent-on-dark);
}

.story__nodes {
  position: relative;
  display: grid;
  grid-template-columns: repeat(7, minmax(0, 1fr));
  margin: 0;
  padding: 0;
  list-style: none;
}

.story__node {
  display: grid;
  justify-items: center;
  gap: var(--space-2);
  color: var(--color-terminal-dim);
  font-size: var(--text-xs);
  text-align: center;
  transition: color var(--duration-base) ease;
}

.story__node-dot {
  width: 1.1rem;
  height: 1.1rem;
  border: 2px solid color-mix(in srgb, var(--color-terminal-dim) 60%, transparent);
  border-radius: 50%;
  background: var(--color-terminal);
  transition:
    border-color var(--duration-base) ease,
    background-color var(--duration-base) ease,
    transform var(--duration-slow) var(--ease-spring);
}

.story__node.is-passed {
  color: var(--color-terminal-ink);
}

.story__node.is-passed .story__node-dot {
  border-color: var(--color-accent-on-dark);
  background: var(--color-accent-on-dark);
}

.story__node.is-active .story__node-dot {
  transform: scale(1.35);
}

.story__node-label {
  overflow-wrap: anywhere;
  hyphens: auto;
}

/* All lines share one grid cell, so the box grows with the longest line instead of letting it spill out. */
.story__readout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  align-content: start;
  min-height: 7.5rem;
  padding: var(--space-4);
  border: 1px solid color-mix(in srgb, var(--color-terminal-dim) 30%, transparent);
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
}

.story__readout::before {
  content: '';
  grid-row: 1;
  display: block;
  width: 2.5rem;
  height: 0.5rem;
  margin-bottom: var(--space-3);
  background: radial-gradient(circle, var(--color-terminal-dim) 0 0.22rem, transparent 0.25rem) 0 0 / 0.85rem 0.5rem
    repeat-x;
  opacity: 0.6;
}

/* Only the active line is shown; it types itself out. */
.story__code {
  grid-row: 2;
  grid-column: 1;
  padding: 0;
  background: none;
  color: var(--color-terminal-ink);
  font-size: inherit;
  overflow-wrap: break-word;
  opacity: 0;
  clip-path: inset(0 100% 0 0);
}

.story__code.is-active {
  opacity: 1;
  animation: type-in 0.9s steps(24, end) forwards;
}

.story__code.is-active::after {
  content: '';
  display: inline-block;
  width: 0.55em;
  height: 1.1em;
  margin-left: 0.15em;
  vertical-align: text-bottom;
  background: var(--color-accent-on-dark);
  animation: caret 1s steps(1) infinite;
}

@keyframes caret {
  50% {
    opacity: 0;
  }
}

.motion .story__steps {
  gap: 0;
}

/* Each step gets a screen's worth of scroll so the stage has time to play. */
.motion .story__step {
  min-height: 62vh;
  align-content: center;
  border-color: transparent;
  background: transparent;
  transform: translateX(calc(var(--move, 1) * 16px));
  transition: transform var(--duration-slow) var(--ease-out);
}

/* Steps out of focus step back in colour, not in opacity, so their text keeps its contrast. */
.motion .story__step h3,
.motion .story__step .story__step-index {
  color: var(--color-muted);
  transition: color var(--duration-slow) var(--ease-out);
}

.motion .story__step.is-active {
  transform: none;
}

.motion .story__step.is-active h3 {
  color: var(--color-ink);
}

.motion .story__step.is-active .story__step-index {
  color: var(--color-accent);
}

.motion .story__step h3 {
  font-size: var(--text-xl);
}

.motion .story__step-code {
  display: none;
}

@media (max-width: 60rem) {
  .motion .story__body {
    grid-template-columns: minmax(0, 1fr);
    gap: var(--space-4);
  }

  .motion .story__stage {
    top: calc(3.75rem + var(--space-2));
    z-index: 5;
    /* A collar in the page colour hides the text scrolling past between header and stage. */
    box-shadow:
      0 calc(-1 * var(--space-3)) 0 var(--space-2) var(--color-bg),
      var(--shadow-lifted);
    gap: var(--space-4);
    padding: var(--space-4);
  }

  /* In one column the sideways step-back reads as a layout jump, so only the colour changes. */
  .motion .story__step {
    min-height: 48vh;
    transform: none;
  }

  .story__node-label {
    display: none;
  }

  .story__readout {
    min-height: 4.5rem;
    font-size: var(--text-xs);
  }
}