/* ============ Header ============ */
.site-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.82);
  backdrop-filter: saturate(160%) blur(14px);
  -webkit-backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid var(--c-border);
  height: var(--header-height);
  display: flex;
  align-items: center;
}

.site-header__inner {
  width: var(--content-max);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: var(--space-5);
  height: 100%;
}

.site-header__brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--c-ink);
  font-weight: 700;
  font-size: var(--fs-4);
  border: 0;
  letter-spacing: -0.01em;
}

.site-header__brand:hover {
  color: var(--c-primary);
}

.site-header__brand .logo {
  width: 36px;
  height: 36px;
  flex: 0 0 36px;
  transition: transform var(--t-base);
}

.site-header__brand:hover .logo {
  transform: rotate(-6deg) scale(1.05);
}

.site-header__title {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}

.site-header__title small {
  font-size: var(--fs-1);
  color: var(--c-ink-muted);
  font-weight: 500;
}

.site-nav {
  margin-left: auto;
  display: flex;
  gap: var(--space-2);
  align-items: center;
}

.site-nav a {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-2);
  color: var(--c-ink-soft);
  border: 0;
  font-weight: 500;
  font-size: var(--fs-2);
  transition: background-color var(--t-fast), color var(--t-fast);
}

.site-nav a:hover {
  background: var(--c-surface-tint);
  color: var(--c-primary);
}

.site-nav a[aria-current="page"] {
  background: var(--c-primary-50);
  color: var(--c-primary);
}

.site-nav__icon {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.site-nav__toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--c-border);
  border-radius: var(--radius-2);
  padding: 8px 10px;
  cursor: pointer;
  color: var(--c-ink);
}

@media (max-width: 880px) {
  .site-header__title small { display: none; }
  .site-header__title strong { font-size: var(--fs-3); }
  .site-nav__toggle { display: inline-flex; margin-left: auto; }
  .site-nav {
    position: absolute;
    inset: var(--header-height) 0 auto 0;
    flex-direction: column;
    align-items: stretch;
    padding: var(--space-3);
    background: var(--c-surface);
    border-bottom: 1px solid var(--c-border);
    box-shadow: var(--shadow-2);
    transform: translateY(-110%);
    transition: transform var(--t-base);
    z-index: -1;
  }
  .site-nav.is-open {
    transform: translateY(0);
  }
  .site-nav a { width: 100%; }
}

/* ============ Footer ============ */
.site-footer {
  margin-top: auto;
  background: linear-gradient(180deg, transparent, rgba(59, 58, 140, 0.04));
  border-top: 1px solid var(--c-border);
  padding: var(--space-7) 0 var(--space-6);
}

.site-footer__inner {
  width: var(--content-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: minmax(260px, 1fr) 2fr;
  gap: var(--space-7);
}

.site-footer__about p {
  color: var(--c-ink-muted);
  font-size: var(--fs-2);
  max-width: 48ch;
}

.site-footer__sections {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-5);
}

.site-footer h3 {
  margin: 0 0 var(--space-3);
  font-size: var(--fs-2);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--c-ink-muted);
}

.site-footer ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.site-footer li + li { margin-top: var(--space-2); }
.site-footer a {
  border: 0;
  color: var(--c-ink-soft);
  font-size: var(--fs-2);
}
.site-footer a:hover { color: var(--c-primary); }

.site-footer__base {
  width: var(--content-max);
  margin: var(--space-6) auto 0;
  padding-top: var(--space-4);
  border-top: 1px solid var(--c-border);
  display: flex;
  justify-content: space-between;
  color: var(--c-ink-muted);
  font-size: var(--fs-1);
  gap: var(--space-4);
  flex-wrap: wrap;
}

@media (max-width: 880px) {
  .site-footer__inner {
    grid-template-columns: 1fr;
    gap: var(--space-5);
  }
  .site-footer__sections {
    grid-template-columns: 1fr;
  }
}

/* ============ Hero ============ */
.hero {
  text-align: center;
  padding: var(--space-7) 0 var(--space-6);
}

.hero__logo-wrap {
  display: flex;
  justify-content: center;
  margin-bottom: var(--space-5);
}

.hero__logo {
  width: clamp(120px, 18vw, 180px);
  height: auto;
  filter: drop-shadow(0 12px 28px rgba(59, 58, 140, 0.18));
  transition: transform var(--t-slow);
}

.hero__logo:hover {
  transform: scale(1.04) rotate(-2deg);
}

.hero h1 {
  margin: 0 auto var(--space-4);
  max-width: 20ch;
  background: linear-gradient(120deg, var(--c-primary), var(--c-accent-teal) 70%, var(--c-accent-indigo));
  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
}

.hero__lede {
  max-width: 66ch;
  margin: 0 auto var(--space-4);
  color: var(--c-ink-soft);
  font-size: var(--fs-4);
}

.hero__ctas {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  justify-content: center;
  margin-top: var(--space-5);
}

.cta {
  --cta-color: var(--c-primary);
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-5);
  background: var(--c-surface);
  color: var(--c-ink);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-pill);
  font-weight: 600;
  box-shadow: var(--shadow-1);
  transition: transform var(--t-base), box-shadow var(--t-base), border-color var(--t-base);
}

.cta:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-2);
  border-color: var(--cta-color);
  color: var(--cta-color);
}

.cta__icon {
  width: 28px;
  height: 28px;
  border-radius: var(--radius-2);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: color-mix(in srgb, var(--cta-color) 14%, white);
  color: var(--cta-color);
  flex: 0 0 28px;
  transition: transform var(--t-base);
}

.cta:hover .cta__icon {
  transform: rotate(-8deg) scale(1.06);
}

.cta__icon svg {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

/* ============ Card grid (sections) ============ */
.section-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-5);
  margin: var(--space-6) 0;
}

.section-card {
  --accent: var(--c-primary);
  position: relative;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  padding: var(--space-5);
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-3);
  box-shadow: var(--shadow-1);
  color: var(--c-ink);
  border-bottom: 0;
  transition: transform var(--t-base), box-shadow var(--t-base), border-color var(--t-base);
  overflow: hidden;
}

.section-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
  background: linear-gradient(90deg, var(--accent), color-mix(in srgb, var(--accent) 30%, var(--c-accent-indigo)));
  opacity: 0.85;
}

.section-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-3);
  border-color: color-mix(in srgb, var(--accent) 40%, var(--c-border));
}

.section-card__icon {
  width: 44px; height: 44px;
  border-radius: var(--radius-2);
  background: color-mix(in srgb, var(--accent) 16%, white);
  color: var(--accent);
  display: inline-flex; align-items: center; justify-content: center;
}

.section-card__icon svg {
  width: 22px; height: 22px;
  stroke: currentColor; fill: none;
  stroke-width: 2; stroke-linecap: round; stroke-linejoin: round;
}

.section-card h3 {
  margin: 0;
  font-size: var(--fs-5);
}

.section-card p {
  margin: 0;
  color: var(--c-ink-soft);
  font-size: var(--fs-3);
}

.section-card__link {
  margin-top: auto;
  font-weight: 600;
  color: var(--accent);
  border: 0;
  display: inline-flex; gap: 6px; align-items: center;
}

.section-card__link svg {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
  transition: transform var(--t-base);
}

.section-card:hover .section-card__link svg {
  transform: translateX(4px);
}

/* ============ Breadcrumbs ============ */
.breadcrumbs {
  font-size: var(--fs-2);
  color: var(--c-ink-muted);
  margin: 0 0 var(--space-4);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  align-items: center;
}

.breadcrumbs a {
  border: 0;
  color: var(--c-ink-soft);
}

.breadcrumbs a:hover { color: var(--c-primary); }

.breadcrumbs__sep {
  color: var(--c-border-strong);
  user-select: none;
}

/* ============ Page header ============ */
.page-header h1 {
  background: linear-gradient(120deg, var(--c-primary), var(--c-accent-indigo) 65%, var(--c-accent-teal));
  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
}

.page-header__intro {
  color: var(--c-ink-soft);
  font-size: var(--fs-4);
  max-width: 64ch;
}

/* ============ Prose layout ============ */
.prose {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-5);
}

.prose__body {
  min-width: 0;
}

.prose__body h1,
.prose__body h2,
.prose__body h3,
.prose__body h4,
.prose__body h5,
.prose__body h6 {
  position: relative;
}

.prose__body a.header-anchor {
  border: 0;
  margin-left: var(--space-2);
  opacity: 0;
  color: var(--c-accent-indigo);
  font-weight: 500;
  transition: opacity var(--t-fast);
}

.prose__body h2:hover a.header-anchor,
.prose__body h3:hover a.header-anchor,
.prose__body h4:hover a.header-anchor,
.prose__body h5:hover a.header-anchor,
.prose__body h6:hover a.header-anchor {
  opacity: 1;
}

/* Page title H1: never show the anchor symbol — the URL is the canonical link. */
.prose__body h1 a.header-anchor {
  display: none;
}

@media (hover: none) {
  .prose__body a.header-anchor { display: none; }
}

.prose__body figure,
.prose__body table,
.prose__body pre,
.prose__body .mermaid,
.prose__body .table-wrap {
  max-width: none;
}

/* ============ Code blocks ============ */
pre.codeblock {
  position: relative;
  background: var(--c-code-bg);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-3);
  padding: var(--space-4) var(--space-5);
  padding-right: 4.5rem;
  overflow-x: auto;
  font-family: var(--ff-mono);
  font-size: 0.9rem;
  line-height: 1.55;
  color: var(--c-code-ink);
  box-shadow: inset 0 0 0 1px rgba(255,255,255,0.6);
  margin-block: var(--space-4);
}

pre.codeblock code {
  font-family: inherit;
  background: transparent;
  padding: 0;
  font-size: inherit;
  color: inherit;
  border: 0;
}

.copy-btn {
  position: absolute;
  top: 10px;
  right: 10px;
  background: var(--c-surface);
  color: var(--c-ink-soft);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-2);
  padding: 4px 10px;
  font-size: var(--fs-1);
  font-family: var(--ff-sans);
  font-weight: 500;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: background-color var(--t-fast), color var(--t-fast), border-color var(--t-fast);
}

.copy-btn:hover {
  background: var(--c-primary-50);
  color: var(--c-primary);
  border-color: var(--c-primary-soft);
}

.copy-btn.is-copied {
  background: color-mix(in srgb, var(--c-success) 14%, white);
  color: var(--c-success);
  border-color: color-mix(in srgb, var(--c-success) 30%, var(--c-border));
}

.copy-btn__icon {
  width: 14px; height: 14px;
  stroke: currentColor; fill: none;
  stroke-width: 2; stroke-linecap: round; stroke-linejoin: round;
}

/* Inline code */
:not(pre) > code {
  font-family: var(--ff-mono);
  background: var(--c-code-inline-bg);
  color: var(--c-code-ink);
  padding: 0.08em 0.4em;
  border-radius: 5px;
  border: 0;
  font-size: 0.9em;
}

/* ============ Tables ============ */
.table-wrap {
  width: 100%;
  overflow-x: auto;
  border-radius: var(--radius-3);
  border: 1px solid var(--c-border);
  background: var(--c-surface);
  margin-block: var(--space-4);
  -webkit-overflow-scrolling: touch;
}

table {
  border-collapse: collapse;
  width: 100%;
  font-size: var(--fs-2);
}

th, td {
  text-align: left;
  padding: 12px 16px;
  border-bottom: 1px solid var(--c-border);
  vertical-align: top;
}

th {
  background: var(--c-surface-tint);
  font-weight: 600;
  color: var(--c-ink);
  position: sticky;
  top: 0;
}

tr:last-child td { border-bottom: 0; }

tbody tr:hover { background: color-mix(in srgb, var(--c-primary-50) 50%, transparent); }

/* ============ FAQ accordion ============ */
.faq-item {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-2);
  margin: 0 0 var(--space-3);
  overflow: hidden;
  transition: box-shadow var(--t-base), border-color var(--t-base);
}

.faq-item[open] {
  border-color: var(--c-primary-soft);
  box-shadow: var(--shadow-2);
}

.faq-item > summary {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  font-weight: 600;
  cursor: pointer;
  color: var(--c-ink);
  list-style: none;
}

.faq-item > summary::-webkit-details-marker { display: none; }

.faq-item > summary::after {
  content: "";
  margin-left: auto;
  width: 12px;
  height: 12px;
  border-right: 2px solid var(--c-ink-muted);
  border-bottom: 2px solid var(--c-ink-muted);
  transform: rotate(45deg) translate(-2px, -2px);
  transition: transform var(--t-base);
}

.faq-item[open] > summary::after {
  transform: rotate(-135deg) translate(-2px, -2px);
}

.faq-item__body {
  padding: 0 var(--space-4) var(--space-4);
  color: var(--c-ink-soft);
}

.faq-item__body > *:first-child { margin-top: 0; }
.faq-item__body > *:last-child { margin-bottom: 0; }

/* ============ Task lists ============ */
ul.contains-task-list,
ol.contains-task-list,
.task-list {
  list-style: none;
  padding-left: 0;
}

li.task-list-item {
  list-style: none;
  display: flex;
  gap: var(--space-3);
  align-items: flex-start;
  padding: 6px 0;
}

li.task-list-item::marker { content: ""; }

li.task-list-item input[type="checkbox"] {
  appearance: none;
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  border: 1.5px solid var(--c-border-strong);
  border-radius: var(--radius-1);
  background: var(--c-surface);
  cursor: pointer;
  margin-top: 4px;
  flex: 0 0 18px;
  display: inline-grid;
  place-content: center;
  transition: background-color var(--t-fast), border-color var(--t-fast);
}

li.task-list-item input[type="checkbox"]::before {
  content: "";
  width: 10px; height: 10px;
  transform: scale(0);
  transition: transform var(--t-fast);
  background:
    linear-gradient(45deg, transparent 45%, white 45% 55%, transparent 55%) center / 100% 2px no-repeat,
    linear-gradient(-45deg, transparent 45%, white 45% 55%, transparent 55%) center / 2px 100% no-repeat;
  /* fallback checkmark via clip-path */
  clip-path: polygon(14% 44%, 0 65%, 50% 100%, 100% 16%, 80% 0, 43% 62%);
  background: white;
}

li.task-list-item input[type="checkbox"]:checked {
  background: var(--c-primary);
  border-color: var(--c-primary);
}

li.task-list-item input[type="checkbox"]:checked::before {
  transform: scale(1);
}

li.task-list-item.is-checked > *:not(input):not(.copy-btn),
li.task-list-item input:checked ~ label,
li.task-list-item input:checked + label {
  text-decoration: line-through;
  color: var(--c-ink-muted);
}

li.task-list-item.is-checked {
  text-decoration: line-through;
  color: var(--c-ink-muted);
}

/* ============ Mermaid ============ */
.mermaid {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-3);
  padding: var(--space-4);
  margin-block: var(--space-4);
  overflow-x: auto;
  text-align: center;
}

.mermaid svg { margin: 0 auto; max-width: 100%; height: auto; }

/* ============ KaTeX adjustments ============ */
.katex { font-size: 1.02em; }
.katex-display {
  padding: var(--space-3) 0;
  overflow-x: auto;
  overflow-y: hidden;
}

/* ============ Related links ============ */
.related {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-3);
  padding: var(--space-5);
  margin-top: var(--space-7);
}

.related h2 {
  margin-top: 0;
  font-size: var(--fs-4);
  color: var(--c-ink);
}

.related ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--space-3);
}

.related a {
  display: block;
  padding: var(--space-3);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-2);
  background: var(--c-surface);
  color: var(--c-ink);
  font-weight: 500;
  font-size: var(--fs-2);
  transition: transform var(--t-base), border-color var(--t-base), box-shadow var(--t-base);
}

.related a:hover {
  transform: translateY(-2px);
  border-color: var(--c-primary-soft);
  box-shadow: var(--shadow-1);
  color: var(--c-primary);
}

/* ============ Section index list ============ */
.article-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-4);
  list-style: none;
  padding: 0;
  margin-top: var(--space-5);
}

.article-list li { margin: 0; max-width: none; }

.article-list a {
  display: block;
  padding: var(--space-4);
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-3);
  color: var(--c-ink);
  font-weight: 500;
  transition: transform var(--t-base), border-color var(--t-base), box-shadow var(--t-base);
}

.article-list a:hover {
  transform: translateY(-3px);
  border-color: var(--c-primary-soft);
  box-shadow: var(--shadow-2);
  color: var(--c-primary);
}

/* ============ Misc ============ */
.callout {
  background: var(--c-accent-amber-50);
  border-left: 4px solid var(--c-accent-amber);
  padding: var(--space-3) var(--space-4);
  border-radius: 0 var(--radius-2) var(--radius-2) 0;
  margin-block: var(--space-4);
}