/* ==========================================================================
   /faq page — sectioned Q&A with sticky TOC. Mirrors the trust-layer
   essay grid: dark hero band, sticky letter-indexed TOC on desktop,
   readable serif body in the column.
   ========================================================================== */

/* ----- Header ----- */
.faq__header {
  background: var(--surface-inverse);
  color: var(--ink-on-inverse);
  padding-block: clamp(var(--s-7), 12vw, var(--s-9)) var(--s-7);
  position: relative;
  overflow: hidden;
}
.faq__header::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    repeating-linear-gradient(0deg, transparent 0 39px, rgba(255,255,255,0.02) 39px 40px),
    repeating-linear-gradient(90deg, transparent 0 39px, rgba(255,255,255,0.02) 39px 40px);
  pointer-events: none;
}
.faq__header .eyebrow { color: var(--ink-on-inverse-muted); }
.faq__h1 {
  font-size: clamp(2.5rem, 7vw, 4.5rem);
  line-height: 1.0;
  letter-spacing: -0.03em;
  font-weight: var(--weight-bold);
  margin: var(--s-3) 0 var(--s-3);
  color: var(--ink-on-inverse);
  text-wrap: balance;
}
.faq__sub {
  font-family: var(--font-serif);
  font-size: clamp(1.125rem, 2.2vw, 1.5rem);
  font-style: italic;
  font-weight: var(--weight-regular);
  color: var(--ink-on-inverse-soft);
  margin: 0;
  max-width: 56ch;
}

/* ----- Body grid ----- */
.faq__body {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--s-7);
  padding-block: var(--s-8);
}
@media (min-width: 1024px) {
  .faq__body {
    grid-template-columns: 280px minmax(0, 1fr);
    gap: var(--s-7);
  }
}
@media (min-width: 1280px) {
  .faq__body {
    grid-template-columns: 300px minmax(0, 1fr);
  }
}

/* ----- Sticky TOC ----- */
.faq__toc {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
}
@media (min-width: 1024px) {
  .faq__toc {
    position: sticky;
    top: calc(var(--header-h) + var(--s-4));
    align-self: start;
    max-height: calc(100vh - var(--header-h) - var(--s-6));
    overflow-y: auto;
    padding-right: var(--s-3);
  }
}
.faq__toc-label { margin: 0 0 var(--s-3); }
.faq__toc-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.faq__toc-list a {
  display: grid;
  grid-template-columns: 2.25rem 1fr;
  align-items: baseline;
  gap: 0.5rem;
  padding: 0.55rem 0.6rem;
  border-left: 2px solid transparent;
  text-decoration: none;
  color: var(--ink-secondary);
  transition: color var(--t-fast) var(--ease-out),
              border-color var(--t-fast) var(--ease-out),
              background var(--t-fast) var(--ease-out);
}
.faq__toc-list a:hover,
.faq__toc-list a:focus-visible {
  color: var(--ink-primary);
  border-left-color: var(--ink-primary);
  background: var(--surface-elevated);
  outline: none;
}
.faq__toc-letter {
  font-weight: var(--weight-semibold);
  color: var(--ink-faint);
  letter-spacing: 0.1em;
}
.faq__toc-list a:hover .faq__toc-letter,
.faq__toc-list a:focus-visible .faq__toc-letter {
  color: var(--ink-primary);
}
.faq__toc-title {
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  letter-spacing: 0;
  line-height: 1.35;
  text-transform: none;
}

/* ----- Column ----- */
.faq__column {
  min-width: 0;
  max-width: 76ch;
}

.faq__prelude {
  font-family: var(--font-serif);
  font-size: 1.0625rem;
  line-height: 1.65;
  color: var(--ink-secondary);
  border-left: 2px solid var(--border);
  padding-left: var(--s-4);
  margin-bottom: var(--s-7);
}
.faq__prelude em { font-style: italic; }

.faq__empty {
  font-family: var(--font-serif);
  color: var(--ink-secondary);
}

/* ----- Section ----- */
.faq__section {
  scroll-margin-top: calc(var(--header-h) + var(--s-4));
  padding-block: var(--s-6) var(--s-5);
  border-top: 1px solid var(--border);
}
.faq__section:first-of-type { border-top: 0; padding-top: 0; }
.faq__section-header { margin-bottom: var(--s-5); }
.faq__section-letter {
  margin: 0;
  color: var(--ink-faint);
}
.faq__section-title {
  font-size: clamp(1.625rem, 3vw, 2rem);
  letter-spacing: -0.02em;
  margin: var(--s-2) 0 0;
  font-weight: var(--weight-semibold);
}

/* ----- Q&A list ----- */
.faq__qa {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--s-6);
}
.faq__item {
  scroll-margin-top: calc(var(--header-h) + var(--s-4));
}
.faq__item:target {
  background: color-mix(in srgb, var(--accent) 5%, transparent);
  outline: 1px solid color-mix(in srgb, var(--accent) 35%, transparent);
  padding: var(--s-3);
  margin-inline: calc(-1 * var(--s-3));
}
.faq__q {
  font-family: var(--font-serif);
  font-size: 1.375rem;
  line-height: 1.35;
  letter-spacing: -0.012em;
  font-weight: var(--weight-medium);
  color: var(--ink-primary);
  margin: 0 0 var(--s-3);
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.5rem 0.75rem;
}
.faq__q-no {
  font-size: 0.8125rem;
  color: var(--ink-faint);
  letter-spacing: 0.08em;
  font-weight: var(--weight-medium);
  flex-shrink: 0;
}
.faq__q-text {
  flex: 1 1 auto;
  min-width: 0;
}
.faq__q-anchor {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--ink-faint);
  text-decoration: none;
  opacity: 0;
  transition: opacity var(--t-fast) var(--ease-out), color var(--t-fast) var(--ease-out);
}
.faq__item:hover .faq__q-anchor,
.faq__q-anchor:focus-visible {
  opacity: 1;
}
.faq__q-anchor:hover { color: var(--ink-primary); }

.faq__a {
  font-family: var(--font-serif);
  font-size: 1.0625rem;
  line-height: 1.65;
  color: var(--ink-primary);
}
.faq__a p { margin: 0 0 var(--s-3); }
.faq__a p:last-child { margin-bottom: 0; }
.faq__a strong { font-weight: var(--weight-semibold); }
.faq__a em { font-style: italic; }
.faq__a a {
  color: var(--ink-primary);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
  text-decoration-color: var(--ink-faint);
  transition: text-decoration-color var(--t-fast) var(--ease-out);
}
.faq__a a:hover,
.faq__a a:focus-visible { text-decoration-color: var(--ink-primary); }
.faq__a ul,
.faq__a ol {
  margin: var(--s-3) 0;
  padding-left: 1.5rem;
}
.faq__a li { margin-bottom: 0.5rem; }
.faq__a code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--surface-elevated);
  padding: 0.1rem 0.35rem;
  border-radius: 3px;
}

/* Tables in answers (e.g. F8 mechanism comparison). */
.faq__a table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--s-4) 0;
  font-family: var(--font-sans);
  font-size: 0.875rem;
  line-height: 1.5;
  display: block;
  overflow-x: auto;
}
.faq__a table thead th {
  text-align: left;
  font-weight: var(--weight-semibold);
  font-size: 0.8125rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-secondary);
  padding: 0.65rem 0.75rem;
  border-bottom: 1px solid var(--border);
}
.faq__a table tbody td {
  padding: 0.65rem 0.75rem;
  vertical-align: top;
  border-bottom: 1px solid var(--border);
  color: var(--ink-primary);
}
.faq__a table tbody tr:last-child td { border-bottom: 0; }

/* ----- Epilogue ----- */
.faq__epilogue {
  margin-top: var(--s-7);
  padding-top: var(--s-5);
  border-top: 1px solid var(--border);
  font-family: var(--font-serif);
  font-size: 1rem;
  line-height: 1.65;
  color: var(--ink-secondary);
}
.faq__epilogue h2 {
  font-family: var(--font-sans);
  font-size: 1.125rem;
  font-weight: var(--weight-semibold);
  letter-spacing: 0;
  margin: 0 0 var(--s-3);
  color: var(--ink-primary);
}
.faq__epilogue a { color: var(--ink-primary); }

/* ----- Print ----- */
@media print {
  .faq__toc { display: none; }
  .faq__body { grid-template-columns: 1fr; }
  .faq__q-anchor { display: none; }
}