*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.65;
  color: var(--color-text);
  background:
    radial-gradient(1200px 600px at 90% -10%, rgba(21, 108, 106, 0.06), transparent 60%),
    radial-gradient(900px 500px at -10% 110%, rgba(201, 104, 43, 0.04), transparent 60%),
    var(--color-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.site-main {
  flex: 1;
}

.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 clamp(16px, 3vw, 40px);
}

a {
  color: var(--color-primary);
  text-decoration-color: rgba(21, 108, 106, 0.3);
  text-underline-offset: 3px;
  transition: color var(--t-fast), text-decoration-color var(--t-fast);
}
a:hover {
  color: var(--color-accent);
  text-decoration-color: var(--color-accent);
}
a:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: 2px;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--color-primary);
  color: #fff;
  padding: 8px 12px;
  border-radius: 0 0 6px 0;
  z-index: 100;
}
.skip-link:focus {
  left: 0;
}

/* ============ HEADER ============ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(248, 247, 242, 0.86);
  backdrop-filter: saturate(160%) blur(14px);
  -webkit-backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid var(--color-border);
}
.site-header__inner {
  display: flex;
  align-items: center;
  gap: 20px;
  min-height: var(--header-height);
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--color-text);
  font-weight: 700;
  letter-spacing: -0.01em;
}
.brand:hover { color: var(--color-primary); }
.brand__mark {
  display: block;
  transition: transform var(--t-med);
}
.brand:hover .brand__mark { transform: rotate(-6deg) scale(1.04); }
.brand__name { font-size: 18px; }

.nav-toggle {
  display: none;
  margin-left: auto;
  width: 42px;
  height: 42px;
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  cursor: pointer;
  padding: 10px;
  flex-direction: column;
  justify-content: space-between;
}
.nav-toggle span {
  display: block;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform var(--t-fast);
}

.primary-nav {
  margin-left: auto;
}
.primary-nav ul {
  display: flex;
  gap: 6px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-link {
  --nav-accent: var(--color-primary);
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: 999px;
  color: var(--color-text-muted);
  text-decoration: none;
  font-weight: 500;
  font-size: 14.5px;
  position: relative;
  transition: color var(--t-fast), background var(--t-fast);
}
.nav-link svg { color: var(--nav-accent); }
.nav-link:hover {
  color: var(--color-text);
  background: var(--color-bg-tint);
}
.nav-link.is-current {
  color: var(--color-text);
  background: linear-gradient(0deg, var(--color-bg-tint), var(--color-bg-tint));
  box-shadow: inset 0 0 0 1px var(--color-border);
}
.nav-link.is-current::after {
  content: "";
  position: absolute;
  left: 16px;
  right: 16px;
  bottom: 2px;
  height: 2px;
  background: var(--nav-accent);
  border-radius: 2px;
}

@media (max-width: 820px) {
  .nav-toggle { display: inline-flex; }
  .primary-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--color-bg-alt);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
    transform: translateY(-12px);
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--t-fast), transform var(--t-fast);
  }
  .primary-nav.is-open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .primary-nav ul {
    flex-direction: column;
    padding: 12px clamp(16px, 3vw, 40px);
    gap: 4px;
  }
  .nav-link {
    width: 100%;
    border-radius: var(--radius-md);
  }
}

/* ============ FOOTER ============ */
.site-footer {
  margin-top: 64px;
  background: linear-gradient(180deg, transparent, var(--color-bg-sunken));
  border-top: 1px solid var(--color-border);
}
.site-footer__inner {
  display: grid;
  grid-template-columns: 1.4fr 2fr 1fr;
  gap: 32px;
  padding: 40px 0 32px;
  align-items: start;
}
.site-footer__brand {
  display: flex;
  align-items: center;
  gap: 12px;
}
.site-footer__name { font-weight: 700; }
.site-footer__tag {
  color: var(--color-text-muted);
  font-size: 13.5px;
  max-width: 28ch;
}
.site-footer__nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px 16px;
}
.site-footer__nav a {
  text-decoration: none;
  color: var(--color-text-muted);
}
.site-footer__nav a:hover { color: var(--color-primary); }
.site-footer__meta {
  color: var(--color-text-subtle);
  font-size: 13px;
  text-align: right;
}
@media (max-width: 720px) {
  .site-footer__inner {
    grid-template-columns: 1fr;
    text-align: left;
  }
  .site-footer__meta { text-align: left; }
}

/* ============ HERO / HOME ============ */
.hero {
  padding: clamp(36px, 6vw, 80px) 0 clamp(24px, 4vw, 48px);
  text-align: center;
}
.hero__logo {
  display: block;
  width: clamp(160px, 22vw, 240px);
  height: auto;
  margin: 0 auto clamp(20px, 3vw, 32px);
  filter: drop-shadow(0 14px 30px rgba(15, 79, 77, 0.18));
  transition: transform var(--t-med);
}
.hero__logo:hover { transform: translateY(-3px) rotate(-1.5deg); }
.hero__title {
  font-size: clamp(32px, 4.2vw, 52px);
  line-height: 1.1;
  margin: 0 0 16px;
  font-weight: 700;
  letter-spacing: -0.02em;
  background: linear-gradient(120deg, var(--color-primary), var(--color-accent) 70%, var(--color-blue));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero__lede {
  max-width: 68ch;
  margin: 0 auto 14px;
  color: var(--color-text-muted);
  font-size: clamp(16px, 1.4vw, 19px);
}
.hero__lede strong { color: var(--color-text); font-weight: 600; }

.cta-row {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  max-width: 960px;
  margin: 36px auto 0;
}
.cta {
  --accent: var(--color-primary);
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 10px;
  text-align: left;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 22px 22px 24px;
  text-decoration: none;
  color: var(--color-text);
  box-shadow: var(--shadow-sm);
  transition: transform var(--t-med), box-shadow var(--t-med), border-color var(--t-fast);
  position: relative;
  overflow: hidden;
}
.cta::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, transparent 60%, color-mix(in srgb, var(--accent) 14%, transparent));
  opacity: 0;
  transition: opacity var(--t-med);
}
.cta:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: color-mix(in srgb, var(--accent) 35%, var(--color-border));
  color: var(--color-text);
}
.cta:hover::before { opacity: 1; }
.cta__icon {
  width: 44px;
  height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: color-mix(in srgb, var(--accent) 12%, transparent);
  border-radius: 12px;
  position: relative;
}
.cta__title {
  font-size: 18px;
  font-weight: 600;
  margin: 0;
  position: relative;
}
.cta__desc {
  color: var(--color-text-muted);
  font-size: 14.5px;
  margin: 0;
  position: relative;
}
.cta__more {
  margin-top: auto;
  color: var(--accent);
  font-weight: 600;
  font-size: 14px;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  position: relative;
}

@media (max-width: 820px) {
  .cta-row { grid-template-columns: 1fr; }
}

/* ============ HOME OVERVIEW ============ */
.overview {
  padding: clamp(28px, 4vw, 56px) 0;
}
.overview__title {
  font-size: clamp(22px, 2.4vw, 30px);
  margin: 0 0 6px;
  color: var(--color-text);
}
.overview__lede {
  color: var(--color-text-muted);
  max-width: 72ch;
  margin: 0 0 28px;
}
.overview__grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}
.overview__card {
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 22px;
  box-shadow: var(--shadow-sm);
  transition: transform var(--t-med), box-shadow var(--t-med);
}
.overview__card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); }
.overview__card h3 {
  margin: 0 0 8px;
  font-size: 17px;
}
.overview__card h3 a {
  text-decoration: none;
  color: var(--color-text);
}
.overview__card h3 a:hover { color: var(--color-primary); }
.overview__card p {
  margin: 0 0 12px;
  color: var(--color-text-muted);
  font-size: 14.5px;
}
.overview__card ul {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 14.5px;
}
.overview__card ul a { text-decoration: none; }
.overview__card ul a:hover { text-decoration: underline; }

/* ============ CONTENT LAYOUT ============ */
.content-page {
  padding: clamp(20px, 3vw, 40px) 0 clamp(40px, 5vw, 64px);
  display: grid;
  grid-template-columns: minmax(0, 1fr) 240px;
  gap: 56px;
}
@media (max-width: 1100px) {
  .content-page { grid-template-columns: 1fr; }
  .toc { display: none; }
}

.breadcrumbs {
  margin: 0 0 16px;
  font-size: 13.5px;
  color: var(--color-text-subtle);
}
.breadcrumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  padding: 0;
  margin: 0;
  list-style: none;
}
.breadcrumbs li::after {
  content: "/";
  margin-left: 6px;
  color: var(--color-border-strong);
}
.breadcrumbs li:last-child::after { content: ""; }
.breadcrumbs a {
  text-decoration: none;
  color: var(--color-text-muted);
}
.breadcrumbs a:hover { color: var(--color-primary); }

.prose {
  max-width: none;
  width: 100%;
  min-width: 0;
}

.prose h1 {
  font-size: clamp(28px, 3.4vw, 40px);
  line-height: 1.15;
  margin: 0 0 24px;
  letter-spacing: -0.02em;
  background: linear-gradient(120deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  scroll-margin-top: calc(var(--header-height) + 16px);
}
.prose h2 {
  font-size: clamp(22px, 2.4vw, 28px);
  margin: 40px 0 14px;
  color: var(--color-primary-strong);
  letter-spacing: -0.01em;
  scroll-margin-top: calc(var(--header-height) + 16px);
  position: relative;
  padding-left: 14px;
}
.prose h2::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.2em;
  bottom: 0.2em;
  width: 4px;
  border-radius: 2px;
  background: linear-gradient(180deg, var(--color-primary), var(--color-accent));
}
.prose h3 {
  font-size: clamp(18px, 1.7vw, 22px);
  margin: 28px 0 10px;
  color: var(--color-text);
  scroll-margin-top: calc(var(--header-height) + 16px);
}
.prose h4 {
  font-size: 17px;
  margin: 22px 0 8px;
  color: var(--color-text);
  scroll-margin-top: calc(var(--header-height) + 16px);
}
.prose h2 a.header-anchor,
.prose h3 a.header-anchor,
.prose h4 a.header-anchor {
  text-decoration: none;
  color: inherit;
}
.prose p {
  margin: 0 0 16px;
}
.prose strong { color: var(--color-text); }

.prose ul, .prose ol {
  padding-left: 1.4em;
  margin: 0 0 16px;
}
.prose li { margin-bottom: 6px; }
.prose li::marker { color: var(--color-primary); }

.prose blockquote {
  border-left: 4px solid var(--color-accent);
  background: var(--color-accent-soft);
  margin: 20px 0;
  padding: 12px 18px;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  color: var(--color-text);
}

.prose hr {
  border: 0;
  border-top: 1px solid var(--color-border);
  margin: 28px 0;
}

/* Inline code */
.prose :not(pre) > code {
  background: var(--code-bg);
  color: var(--code-text);
  padding: 0.1em 0.35em;
  border-radius: 4px;
  font-family: var(--font-mono);
  font-size: 0.9em;
  font-weight: 500;
  border: 0;
}

/* Code block figure */
.code-block {
  margin: 20px 0;
  background: var(--code-bg-block);
  border: 1px solid var(--code-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  position: relative;
  box-shadow: var(--shadow-sm);
}
.code-block__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 6px 10px 6px 14px;
  background: linear-gradient(180deg, var(--color-bg-sunken), var(--code-bg));
  border-bottom: 1px solid var(--code-border);
  font-size: 12px;
}
.code-block__lang {
  font-family: var(--font-mono);
  color: var(--color-text-subtle);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-size: 11px;
}
.code-block__copy {
  appearance: none;
  background: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font: inherit;
  font-size: 12px;
  padding: 4px 10px;
  border-radius: 999px;
  cursor: pointer;
  transition: all var(--t-fast);
}
.code-block__copy:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: var(--color-primary-soft);
}
.code-block__copy.is-copied {
  border-color: var(--color-green);
  color: var(--color-green);
}
.code-block pre {
  margin: 0;
  padding: 16px 18px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 13.5px;
  line-height: 1.55;
  background: transparent;
}
.code-block code { font-family: var(--font-mono); }

/* Tables */
.table-wrap {
  overflow-x: auto;
  margin: 20px 0;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
}
.prose table {
  width: 100%;
  border-collapse: collapse;
  background: var(--color-bg-alt);
  font-size: 14.5px;
}
.prose th, .prose td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--color-border);
  text-align: left;
  vertical-align: top;
}
.prose th {
  background: var(--color-bg-tint);
  font-weight: 600;
  color: var(--color-primary-strong);
}
.prose tbody tr:nth-child(even) td { background: rgba(232, 236, 233, 0.4); }
.prose tbody tr:last-child td { border-bottom: 0; }

/* Task lists */
.prose ul:has(> .task-item) {
  list-style: none;
  padding-left: 0;
}
.prose .task-item {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  transition: background var(--t-fast);
}
.prose .task-item:hover { background: var(--color-bg-tint); }
.prose .task-item input[type="checkbox"] {
  appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 5px;
  border: 1.5px solid var(--color-border-strong);
  background: var(--color-bg-alt);
  cursor: pointer;
  position: relative;
  margin-top: 4px;
  flex-shrink: 0;
  transition: all var(--t-fast);
}
.prose .task-item input[type="checkbox"]:hover {
  border-color: var(--color-primary);
}
.prose .task-item input[type="checkbox"]:checked {
  background: var(--color-primary);
  border-color: var(--color-primary);
}
.prose .task-item input[type="checkbox"]:checked::after {
  content: "";
  position: absolute;
  left: 4px;
  top: 1px;
  width: 5px;
  height: 10px;
  border: solid #fff;
  border-width: 0 2px 2px 0;
  transform: rotate(45deg);
}
.prose .task-item.is-checked,
.prose .task-item:has(input:checked) {
  color: var(--color-text-subtle);
}
.prose .task-item:has(input:checked) {
  text-decoration: line-through;
}

/* FAQ accordion */
.prose details.faq {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  margin: 10px 0;
  background: var(--color-bg-alt);
  overflow: hidden;
  transition: box-shadow var(--t-fast);
}
.prose details.faq[open] {
  box-shadow: var(--shadow-md);
}
.prose details.faq > summary {
  list-style: none;
  cursor: pointer;
  padding: 14px 18px;
  font-weight: 600;
  color: var(--color-primary-strong);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}
.prose details.faq > summary::-webkit-details-marker { display: none; }
.prose details.faq > summary::after {
  content: "+";
  font-size: 20px;
  line-height: 1;
  color: var(--color-accent);
  transition: transform var(--t-med);
}
.prose details.faq[open] > summary::after { content: "−"; }
.prose details.faq > .faq__body {
  padding: 0 18px 14px;
  color: var(--color-text);
}

/* Mermaid */
.prose .mermaid {
  margin: 20px 0;
  text-align: center;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 16px;
  overflow-x: auto;
}

/* TOC */
.toc {
  position: sticky;
  top: calc(var(--header-height) + 20px);
  align-self: start;
  font-size: 14px;
  max-height: calc(100vh - var(--header-height) - 40px);
  overflow-y: auto;
  padding-left: 16px;
  border-left: 1px solid var(--color-border);
}
.toc__title {
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-subtle);
  margin: 0 0 10px;
}
.toc ol {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.toc ol ol {
  margin-top: 6px;
  padding-left: 12px;
  gap: 4px;
}
.toc a {
  text-decoration: none;
  color: var(--color-text-muted);
  display: block;
  line-height: 1.4;
}
.toc a:hover { color: var(--color-primary); }
.toc a.is-active {
  color: var(--color-primary-strong);
  font-weight: 600;
}

/* Related pages */
.related {
  margin-top: 48px;
  padding-top: 28px;
  border-top: 1px solid var(--color-border);
}
.related__title {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-subtle);
  margin: 0 0 16px;
}
.related__grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 14px;
}
.related__card {
  display: block;
  padding: 14px 16px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: var(--color-text);
  transition: transform var(--t-fast), border-color var(--t-fast), box-shadow var(--t-fast);
}
.related__card:hover {
  transform: translateY(-2px);
  border-color: var(--color-primary);
  box-shadow: var(--shadow-sm);
  color: var(--color-text);
}
.related__card-kind {
  display: block;
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-subtle);
  margin-bottom: 4px;
}
.related__card-title {
  display: block;
  font-weight: 600;
  color: var(--color-primary-strong);
}

/* KaTeX adjust */
.prose .katex { font-size: 1.02em; }
.prose .katex-display {
  margin: 18px 0;
  padding: 10px;
  overflow-x: auto;
}

/* Print */
@media print {
  .site-header, .site-footer, .toc, .code-block__copy { display: none; }
  body { background: #fff; }
  .content-page { grid-template-columns: 1fr; }
}