/* Fives — "The spine": mobile wayfinding for the long pages.
   Hand-authored (no .jsx sibling). Progress hairline + "On this page"
   sheet. Mobile-only (<=759px, also matchMedia-gated in spine.js).
   Reduced motion honoured in CSS + JS. */

/* Mobile gate: the FAB + sheet render only at <=759px. The progress bar
   is site-wide (all viewports) — it is NOT hidden here. */
@media (min-width: 760px) {
  .spine-fab,
  .spine-sheet-root { display: none !important; }
}

/* Part 1 · reading-progress hairline */
.spine-bar {
  position: fixed;
  top: calc(65px + var(--safe-top));
  left: 0;
  height: 2px;
  width: 100%;
  background: var(--fives-accent);
  transform: scaleX(0);
  transform-origin: left;
  z-index: 180;                 /* below the nav (200), above content */
  opacity: 0;
  transition: opacity var(--fives-t-standard) var(--fives-e-settle);
  pointer-events: none;
  will-change: transform;
}
.spine-bar.is-visible { opacity: 1; }

/* Part 2 · "On this page" — trigger button */
.spine-fab {
  position: fixed;
  right: max(20px, var(--safe-right));
  bottom: calc(20px + var(--safe-bottom));
  z-index: 180;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin: 0;
  padding: 10px 16px;
  background: var(--fives-primary);
  color: #F5EFE1;
  font-family: var(--fives-body);
  font-size: 13px;
  font-weight: 600;
  line-height: 1;
  border: 0;
  border-radius: var(--fives-r-md);
  cursor: pointer;
  opacity: 0;
  transform: translateY(6px);
  transition: opacity var(--fives-t-standard) var(--fives-e-settle),
              transform var(--fives-t-standard) var(--fives-e-settle);
  pointer-events: none;
}
.spine-fab.is-visible {
  opacity: 1;
  transform: none;
  pointer-events: auto;
}
.spine-fab:active { transform: scale(0.97); }
.spine-fab svg { display: block; flex: 0 0 auto; }

/* Sheet root, scrim, panel */
.spine-sheet-root {
  position: fixed;
  inset: 0;
  z-index: 400;
  visibility: hidden;
}
.spine-sheet-root.is-open { visibility: visible; }

.spine-scrim {
  position: absolute;
  inset: 0;
  background: rgba(42, 36, 24, 0.4);
  opacity: 0;
  transition: opacity var(--fives-t-standard) var(--fives-e-settle);
}
.spine-sheet-root.is-open .spine-scrim { opacity: 1; }

.spine-sheet {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  max-height: 70vh;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  padding: 20px max(24px, var(--safe-right))
           calc(20px + var(--safe-bottom)) max(24px, var(--safe-left));
  background: var(--fives-bg);
  border-top: 1px solid var(--fives-line);
  border-top-left-radius: var(--fives-r-lg);
  border-top-right-radius: var(--fives-r-lg);
  transform: translateY(100%);
  transition: transform var(--fives-t-standard) var(--fives-e-settle);
}
.spine-sheet-root.is-open .spine-sheet {
  transform: translateY(0);
  transition: transform 300ms var(--fives-e-settle);
}

.spine-sheet-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 4px;
}
.spine-sheet-title {
  margin: 0;
  font-family: var(--fives-body);
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--fives-muted);
}
.spine-close {
  width: 44px;
  height: 44px;
  margin: -10px -12px -10px 0;   /* 44px hit area, edge-aligned */
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  background: transparent;
  border: 0;
  cursor: pointer;
  color: var(--fives-text);
}
.spine-close:active { transform: scale(0.95); }
.spine-close svg { display: block; }

.spine-list { display: block; }
.spine-item {
  display: block;
  width: 100%;
  margin: 0;
  padding: 14px 0;
  text-align: left;
  font-family: var(--fives-body);
  font-size: 16px;
  line-height: 1.4;
  color: var(--fives-text);
  background: transparent;
  border: 0;
  border-top: 1px solid var(--fives-line);
  cursor: pointer;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity var(--fives-t-standard) var(--fives-e-settle),
              transform var(--fives-t-standard) var(--fives-e-settle);
}
.spine-item:first-child { border-top: 0; }
.spine-item.is-in { opacity: 1; transform: none; }
.spine-item:active { color: var(--fives-accent); }
/* the section the reader is currently in (set on open by spine.js) */
.spine-item.is-current {
  color: var(--fives-primary);
  font-weight: 600;
  box-shadow: inset 2px 0 0 var(--fives-accent);
  padding-left: 12px;
}

/* Jumped-to heading clears the sticky nav + hairline */
.spine-anchor { scroll-margin-top: calc(80px + var(--safe-top)); }

/* Reduced motion (belt; the JS is the braces) */
@media (prefers-reduced-motion: reduce) {
  .spine-bar,
  .spine-fab,
  .spine-scrim,
  .spine-sheet,
  .spine-item {
    transition-duration: 0.01ms !important;
    transition-delay: 0s !important;
  }
  .spine-item { opacity: 1 !important; transform: none !important; }
  .spine-fab.is-visible { transform: none !important; }
}