:root {
  --clr-terracotta: #A0522D;
  --clr-loess: #D2B48C;
  --clr-cream: #F5EFE6;
  --clr-stone: #708090;
  --clr-moss: #6B8E23;
  --clr-azure: #1E90FF;
  --clr-ink: #2F2F2F;
  --clr-umber: #3E2723;
  --clr-white: #FFFFFF;
  --clr-black: #000000;
  --clr-gradient-checker: rgba(62, 39, 35, 0.06);

  --font-heading: "Noto Serif SC", "Songti SC", "SimSun", Georgia, serif;
  --font-body: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", Arial, sans-serif;

  --font-scale: 1.25;
  --size-base: 1rem;
  --size-h1: calc(var(--size-base) * var(--font-scale) * var(--font-scale) * var(--font-scale) * var(--font-scale));
  --size-h2: calc(var(--size-base) * var(--font-scale) * var(--font-scale) * var(--font-scale));
  --size-h3: calc(var(--size-base) * var(--font-scale) * var(--font-scale));
  --size-h4: calc(var(--size-base) * var(--font-scale));
  --size-small: 0.875rem;
  --size-xs: 0.75rem;

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.5rem;
  --space-6: 2rem;
  --space-7: 3rem;
  --space-8: 4rem;

  --content-max: 1200px;
  --content-pad: 1.5rem;

  --radius: 4px;
  --radius-lg: 8px;
  --shadow-sm: 0 1px 2px rgba(47, 47, 47, 0.06);
  --shadow-md: 0 4px 12px rgba(47, 47, 47, 0.08);
  --shadow-lg: 0 8px 24px rgba(47, 47, 47, 0.12);

  --breakpoint-mobile: 767px;
  --breakpoint-tablet: 768px;
  --breakpoint-desktop: 1025px;
}

/* Reset & Base */
*, *::before, *::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-body);
  font-weight: 400;
  font-size: var(--size-base);
  line-height: 1.6;
  color: var(--clr-ink);
  background-color: var(--clr-cream);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.3;
  margin: 0 0 var(--space-4) 0;
}

h1 {
  font-size: var(--size-h1);
  font-weight: 900;
}

h2 {
  font-size: var(--size-h2);
  font-weight: 800;
}

h3 {
  font-size: var(--size-h3);
  font-weight: 700;
}

h4 {
  font-size: var(--size-h4);
  font-weight: 700;
}

p {
  margin: 0 0 var(--space-4) 0;
}

ul, ol {
  margin: 0;
  padding: 0;
  list-style-position: inside;
}

a {
  color: var(--clr-terracotta);
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
  transition: color 0.2s ease, background-color 0.2s ease, border-color 0.2s ease, text-decoration-color 0.2s ease;
}

a:hover {
  color: var(--clr-umber);
}

img, svg {
  max-width: 100%;
  display: block;
}

button {
  font-family: inherit;
  font-size: inherit;
  cursor: pointer;
  border: none;
  background: none;
  padding: 0;
  color: inherit;
}

:focus-visible {
  outline: 3px solid var(--clr-azure);
  outline-offset: 2px;
}

:target {
  scroll-margin-top: 120px;
}

/* Layout utilities */
.container {
  width: 100%;
  max-width: var(--content-max);
  margin-inline: auto;
  padding-inline: var(--content-pad);
}

/* Skip link */
.skip-link {
  position: fixed;
  top: -100%;
  left: 1rem;
  z-index: 1000;
  background: var(--clr-umber);
  color: var(--clr-cream);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius);
  font-weight: 600;
  text-decoration: none;
  transition: top 0.2s ease;
}

.skip-link:focus-visible {
  top: 1rem;
}

/* Header */
.site-header {
  position: relative;
  z-index: 100;
  background: var(--clr-cream);
  box-shadow: var(--shadow-md);
}

.site-header__inner {
  max-width: var(--content-max);
  margin-inline: auto;
  padding-block: var(--space-4);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

/* Branding */
.site-header__branding {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: var(--space-3);
  flex: 1;
  min-width: 200px;
}

.site-header__brand-cn {
  font-family: var(--font-heading);
  font-size: 1.875rem;
  font-weight: 900;
  color: var(--clr-terracotta);
  letter-spacing: 0.02em;
  line-height: 1.2;
}

.site-header__brand-en {
  font-family: var(--font-body);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--clr-stone);
  padding-left: var(--space-2);
}

.site-header__tagline {
  font-size: var(--size-small);
  color: var(--clr-stone);
  padding-left: var(--space-3);
  border-left: 3px solid var(--clr-loess);
  margin-left: var(--space-2);
  white-space: nowrap;
}

/* Navigation */
.site-nav__list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
  list-style: none;
  margin: 0;
}

.site-nav__link {
  display: inline-block;
  padding: 0.4rem 0.8rem;
  font-size: 0.95rem;
  font-weight: 500;
  text-decoration: none;
  color: var(--clr-ink);
  background-image: linear-gradient(to right, var(--clr-moss), var(--clr-moss));
  background-repeat: no-repeat;
  background-size: 0% 2px;
  background-position: left bottom;
  transition: background-size 0.3s ease, color 0.2s ease, background-color 0.2s ease, border-radius 0.2s ease;
  border-radius: var(--radius);
}

.site-nav__link:hover,
.site-nav__link:focus-visible {
  background-size: 100% 2px;
  color: var(--clr-umber);
  background-color: rgba(107, 142, 35, 0.06);
}

.site-nav__link[aria-current="page"] {
  background-color: var(--clr-terracotta);
  color: var(--clr-cream);
  background-image: none;
  font-weight: 600;
}

.site-nav__link[aria-current="page"]:hover {
  background-color: var(--clr-umber);
}

/* Nav toggle */
.nav-toggle {
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.3rem;
  padding: 0.5rem 0.75rem;
  background: var(--clr-terracotta);
  color: var(--clr-cream);
  border-radius: var(--radius);
  line-height: 1;
  transition: background-color 0.2s ease;
}

.nav-toggle:hover {
  background-color: var(--clr-umber);
}

.nav-toggle__icon {
  display: block;
  width: 1.25rem;
  height: 2px;
  background: currentColor;
  position: relative;
  transition: background-color 0.2s ease;
}

.nav-toggle__icon::before,
.nav-toggle__icon::after {
  content: "";
  position: absolute;
  left: 0;
  width: 100%;
  height: 2px;
  background: currentColor;
  transform-origin: center;
  transition: transform 0.3s ease, top 0.3s ease;
}

.nav-toggle__icon::before {
  top: -6px;
}

.nav-toggle__icon::after {
  top: 6px;
}

.nav-toggle__text {
  font-size: var(--size-xs);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.nav-toggle[aria-expanded="true"] .nav-toggle__icon {
  background: transparent;
}

.nav-toggle[aria-expanded="true"] .nav-toggle__icon::before {
  top: 0;
  transform: rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__icon::after {
  top: 0;
  transform: rotate(-45deg);
}

/* Footer */
.site-footer {
  background-color: var(--clr-umber);
  color: var(--clr-cream);
  margin-top: var(--space-8);
  font-size: 0.9375rem;
}

.site-footer a {
  color: var(--clr-loess);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.site-footer a:hover {
  color: var(--clr-moss);
  border-color: currentColor;
}

.site-footer__main {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr;
  gap: var(--space-6);
  padding-block: var(--space-7) var(--space-5);
}

.site-footer__brand-name {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 900;
  color: var(--clr-terracotta);
  line-height: 1.2;
}

.site-footer__brand-en {
  font-family: var(--font-body);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--clr-stone);
  margin-top: 0.25rem;
}

.site-footer__description {
  margin-top: var(--space-4);
  max-width: 40ch;
  line-height: 1.8;
  color: rgba(245, 239, 230, 0.85);
}

.site-footer__headline {
  font-family: var(--font-heading);
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--clr-terracotta);
  margin-bottom: var(--space-4);
  padding-bottom: var(--space-2);
  border-bottom: 2px solid rgba(160, 82, 45, 0.4);
}

.site-footer__list {
  list-style: none;
}

.site-footer__list li + li {
  margin-top: var(--space-2);
}

.site-footer__list a {
  display: inline-block;
  padding-block: 0.2rem;
}

.site-footer__contact {
  margin-top: var(--space-4);
  font-style: normal;
  color: rgba(245, 239, 230, 0.8);
}

.site-footer__contact p {
  margin-bottom: var(--space-2);
  display: flex;
  flex-direction: column;
}

.site-footer__contact a {
  color: var(--clr-loess);
}

.site-footer__meta {
  border-top: 1px solid rgba(245, 239, 230, 0.15);
  padding-block: var(--space-3);
  font-size: var(--size-xs);
  color: rgba(245, 239, 230, 0.6);
}

.site-footer__meta-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--space-2);
}

/* Back to top */
.back-top {
  position: fixed;
  right: 1.5rem;
  bottom: 1.5rem;
  z-index: 200;
  width: 3rem;
  height: 3rem;
  border-radius: 50%;
  background: var(--clr-terracotta);
  color: var(--clr-cream);
  font-size: 1.5rem;
  line-height: 1;
  box-shadow: var(--shadow-md);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.3s ease, transform 0.3s ease, visibility 0.3s ease, background-color 0.2s ease;
}

.back-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-top:hover {
  background-color: var(--clr-umber);
}

/* Common components */
.btn {
  display: inline-block;
  padding: 0.6rem 1.25rem;
  font-weight: 600;
  font-family: var(--font-body);
  text-decoration: none;
  border-radius: var(--radius);
  background-color: var(--clr-terracotta);
  color: var(--clr-cream);
  border: 2px solid var(--clr-terracotta);
  transition: background-color 0.2s ease, color 0.2s ease, border-color 0.2s ease, transform 0.1s ease;
}

.btn:hover {
  background-color: var(--clr-umber);
  border-color: var(--clr-umber);
  color: var(--clr-cream);
}

.btn--ghost {
  background-color: transparent;
  color: var(--clr-terracotta);
}

.btn--ghost:hover {
  background-color: var(--clr-terracotta);
  color: var(--clr-cream);
}

/* Breadcrumb */
.breadcrumb {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  font-size: var(--size-small);
  padding-block: var(--space-3);
  border-bottom: 1px solid rgba(47, 47, 47, 0.1);
}

.breadcrumb li {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.breadcrumb li + li::before {
  content: "/";
  color: var(--clr-stone);
}

.breadcrumb a {
  text-decoration: none;
  color: var(--clr-stone);
}

.breadcrumb a:hover {
  color: var(--clr-terracotta);
}

.breadcrumb [aria-current="page"] {
  color: var(--clr-ink);
  font-weight: 600;
}

/* Prose */
.prose {
  max-width: 70ch;
  margin-inline: auto;
  font-size: 1.0625rem;
  line-height: 1.8;
}

.prose h2 {
  margin-top: 2.5em;
  margin-bottom: 0.5em;
}

.prose h3 {
  margin-top: 2em;
}

.prose p + p {
  margin-top: 1.5em;
}

.prose ul,
.prose ol {
  margin-left: 1.25rem;
}

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

/* Section title */
.section-title {
  display: flex;
  align-items: baseline;
  gap: var(--space-3);
  font-size: 1.375rem;
  font-weight: 800;
  color: var(--clr-ink);
  border-left: 5px solid var(--clr-terracotta);
  padding-left: var(--space-4);
  margin-block: var(--space-6) var(--space-4);
}

/* Data card */
.data-card {
  background: var(--clr-cream);
  border: 1px solid var(--clr-stone);
  border-left: 4px solid var(--clr-terracotta);
  border-radius: var(--radius);
  padding: var(--space-4) var(--space-5);
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.2s ease, border-color 0.2s ease, transform 0.1s ease;
  position: relative;
  overflow: hidden;
}

.data-card::after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: 0;
  height: 0;
  border-top: 28px solid var(--clr-loess);
  border-left: 28px solid transparent;
  opacity: 0.4;
}

.data-card:hover {
  box-shadow: var(--shadow-lg);
  border-color: var(--clr-terracotta);
  transform: translateY(-2px);
}

.data-card__title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.0625rem;
  color: var(--clr-ink);
  margin-bottom: var(--space-2);
}

.data-card__value {
  font-family: var(--font-heading);
  font-weight: 900;
  font-size: 2.25rem;
  color: var(--clr-terracotta);
  line-height: 1.2;
  margin-bottom: var(--space-1);
}

/* Media containers */
.media {
  position: relative;
  background: var(--clr-stone);
  background-image: linear-gradient(45deg, rgba(255,255,255,0.05) 25%, transparent 25%, transparent 75%, rgba(255,255,255,0.05) 75%),
                    linear-gradient(45deg, rgba(255,255,255,0.05) 25%, transparent 25%, transparent 75%, rgba(255,255,255,0.05) 75%);
  background-size: 20px 20px;
  background-position: 0 0, 10px 10px;
  border-radius: var(--radius);
  overflow: hidden;
}

.media::before {
  content: "图";
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 1.5rem;
  color: rgba(255,255,255,0.5);
  font-weight: 700;
}

.media--16-9 {
  aspect-ratio: 16 / 9;
}

.media--4-3 {
  aspect-ratio: 4 / 3;
}

.media--1-1 {
  aspect-ratio: 1 / 1;
}

/* Accordion */
.accordion details {
  border-bottom: 1px solid rgba(47, 47, 47, 0.1);
}

.accordion summary {
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  font-weight: 600;
  padding: var(--space-4) 0;
  list-style: none;
  transition: color 0.2s ease;
}

.accordion summary::-webkit-details-marker {
  display: none;
}

.accordion summary::after {
  content: "+";
  font-size: 1.5rem;
  font-weight: 400;
  color: var(--clr-terracotta);
  transition: transform 0.2s ease;
}

.accordion details[open] summary {
  color: var(--clr-terracotta);
}

.accordion details[open] summary::after {
  content: "−";
  transform: rotate(180deg);
}

.accordion .accordion__content {
  padding-bottom: var(--space-4);
  line-height: 1.7;
}

/* Responsive */
@media (max-width: 767px) {
  :root {
    --content-pad: 1rem;
  }

  .site-header__inner {
    flex-direction: row;
    gap: var(--space-2);
  }

  .site-header__branding {
    flex: 1 1 auto;
    min-width: 0;
  }

  .site-header__brand-cn {
    font-size: 1.5rem;
  }

  .site-header__tagline {
    display: none;
  }

  .site-nav {
    order: 3;
    width: 100%;
    overflow: hidden;
    max-height: 0;
    visibility: hidden;
    transition: max-height 0.3s ease, visibility 0.3s ease;
  }

  .site-nav[data-open] {
    max-height: 80vh;
    visibility: visible;
    overflow-y: auto;
  }

  .site-nav__list {
    flex-direction: column;
    gap: 0;
    padding-top: var(--space-3);
    border-top: 1px solid rgba(47, 47, 47, 0.12);
  }

  .site-nav__item {
    border-bottom: 1px solid rgba(47, 47, 47, 0.06);
  }

  .site-nav__link {
    display: block;
    padding: var(--space-3) var(--space-2);
    border-radius: 0;
    background-image: linear-gradient(to right, var(--clr-moss), var(--clr-moss));
    background-repeat: no-repeat;
    background-size: 0% 2px;
    background-position: left bottom;
  }

  .nav-toggle {
    display: inline-flex;
  }

  .site-footer__main {
    grid-template-columns: 1fr;
    gap: var(--space-5);
  }

  .grid {
    grid-template-columns: 1fr;
  }
}

@media (min-width: 768px) and (max-width: 1024px) {
  .grid {
    grid-template-columns: 1fr 1fr;
  }

  .site-footer__main {
    grid-template-columns: 1.5fr 1fr 1fr;
  }
}

@media (min-width: 1025px) {
  .site-header__inner {
    flex-wrap: nowrap;
  }

  .site-nav {
    flex: 0 1 auto;
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition-duration: 0.001s !important;
    animation-duration: 0.001s !important;
    scroll-behavior: auto !important;
  }

  .back-top {
    transition: none;
  }
}