:root {
  --brand-primary: #0b1a2e;
  --brand-accent: #e6b422;
  --brand-accent-soft: rgba(230, 180, 34, 0.14);
  --brand-accent-glow: rgba(230, 180, 34, 0.35);
  --brand-gradient-start: #0b1a2e;
  --brand-gradient-mid: #12305a;
  --brand-gradient-end: #1f4f8f;
  --bg-base: #f4f6fb;
  --bg-elevated: #ffffff;
  --bg-soft: #eef2f9;
  --bg-glass: rgba(255, 255, 255, 0.72);
  --bg-glass-strong: rgba(255, 255, 255, 0.88);
  --text-primary: #17233b;
  --text-secondary: #4a5875;
  --text-muted: #7b87a3;
  --text-invert: #ffffff;
  --border-soft: rgba(23, 35, 59, 0.08);
  --border-medium: rgba(23, 35, 59, 0.14);
  --shadow-sm: 0 2px 8px rgba(11, 26, 46, 0.06);
  --shadow-md: 0 10px 30px rgba(11, 26, 46, 0.1);
  --shadow-lg: 0 22px 55px rgba(11, 26, 46, 0.16);
  --shadow-glow: 0 12px 32px rgba(230, 180, 34, 0.28);
  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --radius-xl: 32px;
  --radius-pill: 999px;
  --transition-fast: 0.22s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-smooth: 0.42s cubic-bezier(0.22, 1, 0.36, 1);
  --header-height: 72px;
  --max-width: 1200px;
  --font-sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
}

html[data-theme="dark"] {
  --brand-primary: #e8eefb;
  --brand-accent: #f0c542;
  --brand-accent-soft: rgba(240, 197, 66, 0.16);
  --brand-accent-glow: rgba(240, 197, 66, 0.4);
  --brand-gradient-start: #060d18;
  --brand-gradient-mid: #0b1a2e;
  --brand-gradient-end: #163a66;
  --bg-base: #070c16;
  --bg-elevated: #0f1728;
  --bg-soft: #121c30;
  --bg-glass: rgba(18, 28, 48, 0.72);
  --bg-glass-strong: rgba(18, 28, 48, 0.9);
  --text-primary: #eaf0fb;
  --text-secondary: #a7b4cd;
  --text-muted: #7684a0;
  --text-invert: #06101f;
  --border-soft: rgba(234, 240, 251, 0.08);
  --border-medium: rgba(234, 240, 251, 0.16);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 10px 30px rgba(0, 0, 0, 0.5);
  --shadow-lg: 0 22px 55px rgba(0, 0, 0, 0.62);
  --shadow-glow: 0 12px 32px rgba(240, 197, 66, 0.22);
}

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

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

body {
  margin: 0;
  padding: 0;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  color: var(--text-primary);
  background-color: var(--bg-base);
  background-image:
    radial-gradient(1200px 600px at 12% -8%, rgba(31, 79, 143, 0.16), transparent 60%),
    radial-gradient(900px 520px at 92% 4%, rgba(230, 180, 34, 0.12), transparent 62%);
  background-attachment: fixed;
  overflow-x: hidden;
  transition: background-color var(--transition-smooth), color var(--transition-smooth);
}

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

a {
  color: var(--brand-accent);
  text-decoration: none;
  transition: color var(--transition-fast), opacity var(--transition-fast);
}

a:hover,
a:focus-visible {
  color: var(--brand-primary);
  opacity: 0.92;
}

ul,
ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

h1,
h2,
h3,
h4 {
  margin: 0 0 0.6em;
  line-height: 1.3;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--text-primary);
}

h1 {
  font-size: clamp(1.75rem, 4.4vw, 3rem);
}

h2 {
  font-size: clamp(1.4rem, 3vw, 2.1rem);
  position: relative;
  padding-bottom: 0.5em;
}

h2::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 64px;
  height: 4px;
  border-radius: var(--radius-pill);
  background: linear-gradient(90deg, var(--brand-accent), rgba(230, 180, 34, 0));
}

h3 {
  font-size: clamp(1.1rem, 2.2vw, 1.35rem);
}

p {
  margin: 0 0 1em;
  color: var(--text-secondary);
}

strong {
  color: var(--text-primary);
  font-weight: 700;
}

::selection {
  background: var(--brand-accent);
  color: var(--brand-primary);
}

.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

:focus-visible {
  outline: 3px solid var(--brand-accent);
  outline-offset: 2px;
  border-radius: 6px;
}

::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-track {
  background: var(--bg-soft);
}

::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, var(--brand-gradient-mid), var(--brand-gradient-end));
  border-radius: var(--radius-pill);
  border: 2px solid var(--bg-soft);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--brand-accent);
}

/* ============ HEADER ============ */
#site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--bg-glass);
  backdrop-filter: blur(18px) saturate(180%);
  -webkit-backdrop-filter: blur(18px) saturate(180%);
  border-bottom: 1px solid var(--border-soft);
  box-shadow: var(--shadow-sm);
  transition: background var(--transition-smooth), box-shadow var(--transition-smooth), border-color var(--transition-smooth);
}

#site-header.is-scrolled {
  box-shadow: var(--shadow-md);
  background: var(--bg-glass-strong);
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
  min-height: var(--header-height);
  display: flex;
  align-items: center;
  gap: 18px;
  flex-wrap: wrap;
}

.logo-area {
  flex: 0 0 auto;
}

.logo-area a {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: var(--text-primary);
  font-weight: 800;
}

.logo-area a:hover {
  opacity: 1;
}

.logo-area svg {
  border-radius: 12px;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-smooth), box-shadow var(--transition-smooth);
}

.logo-area a:hover svg {
  transform: rotate(-6deg) scale(1.06);
  box-shadow: var(--shadow-glow);
}

.brand-name {
  font-size: 1.28rem;
  letter-spacing: 0.02em;
  background: linear-gradient(120deg, var(--brand-gradient-mid), var(--brand-gradient-end), var(--brand-accent));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
  transition: filter var(--transition-fast);
}

.logo-area a:hover .brand-name {
  filter: brightness(1.18);
}

#main-nav {
  flex: 1 1 auto;
  display: flex;
  justify-content: center;
}

#main-nav ul {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}

#main-nav a {
  display: inline-block;
  padding: 8px 14px;
  font-size: 0.94rem;
  font-weight: 600;
  color: var(--text-secondary);
  border-radius: var(--radius-pill);
  position: relative;
  transition: color var(--transition-fast), background var(--transition-fast), transform var(--transition-fast);
}

#main-nav a::after {
  content: "";
  position: absolute;
  left: 50%;
  bottom: 4px;
  width: 0;
  height: 2px;
  border-radius: var(--radius-pill);
  background: var(--brand-accent);
  transform: translateX(-50%);
  transition: width var(--transition-smooth);
}

#main-nav a:hover,
#main-nav a:focus-visible {
  color: var(--brand-primary);
  background: var(--brand-accent-soft);
  transform: translateY(-2px);
}

#main-nav a:hover::after {
  width: 42%;
}

.header-actions {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 10px;
}

#site-search {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-soft);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-pill);
  padding: 4px 4px 4px 16px;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast);
}

#site-search:focus-within {
  border-color: var(--brand-accent);
  box-shadow: 0 0 0 4px var(--brand-accent-soft);
  background: var(--bg-elevated);
}

#search-input {
  border: none;
  background: transparent;
  outline: none;
  font-family: inherit;
  font-size: 0.92rem;
  color: var(--text-primary);
  width: 190px;
  padding: 8px 0;
}

#search-input::placeholder {
  color: var(--text-muted);
}

#site-search button {
  border: none;
  cursor: pointer;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--brand-primary);
  background: linear-gradient(135deg, var(--brand-accent), #f5d061);
  padding: 9px 18px;
  border-radius: var(--radius-pill);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), filter var(--transition-fast);
}

#site-search button:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
  filter: brightness(1.06);
}

#site-search button:active {
  transform: translateY(0);
}

#dark-toggle,
#mobile-menu-btn {
  border: 1px solid var(--border-medium);
  background: var(--bg-elevated);
  color: var(--text-primary);
  width: 42px;
  height: 42px;
  border-radius: 50%;
  font-size: 1.1rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast), border-color var(--transition-fast);
}

#dark-toggle:hover,
#mobile-menu-btn:hover {
  transform: translateY(-2px) rotate(8deg);
  box-shadow: var(--shadow-md);
  border-color: var(--brand-accent);
  background: var(--brand-accent-soft);
}

#mobile-menu-btn {
  display: none;
}

/* ============ HERO ============ */
#hero {
  position: relative;
  overflow: hidden;
  background:
    linear-gradient(135deg, var(--brand-gradient-start) 0%, var(--brand-gradient-mid) 48%, var(--brand-gradient-end) 100%);
  color: var(--text-invert);
  padding: clamp(56px, 9vw, 110px) 20px clamp(48px, 7vw, 88px);
  border-bottom-left-radius: var(--radius-xl);
  border-bottom-right-radius: var(--radius-xl);
  isolation: isolate;
}

#hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(720px 420px at 82% 12%, rgba(230, 180, 34, 0.24), transparent 62%),
    radial-gradient(620px 380px at 8% 88%, rgba(255, 255, 255, 0.1), transparent 60%);
  z-index: -1;
}

#hero::after {
  content: "";
  position: absolute;
  top: -140px;
  right: -120px;
  width: 420px;
  height: 420px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(230, 180, 34, 0.28), transparent 68%);
  filter: blur(6px);
  animation: heroFloat 12s ease-in-out infinite;
  z-index: -1;
}

@keyframes heroFloat {
  0%, 100% { transform: translate3d(0, 0, 0) scale(1); }
  50% { transform: translate3d(-26px, 28px, 0) scale(1.08); }
}

.hero-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  text-align: center;
  animation: fadeUp 0.9s var(--transition-smooth) both;
}

#hero h1 {
  color: #ffffff;
  text-shadow: 0 4px 24px rgba(0, 0, 0, 0.35);
  margin-bottom: 0.5em;
}

.hero-lead {
  max-width: 820px;
  margin: 0 auto 2.2em;
  font-size: clamp(1rem, 1.6vw, 1.14rem);
  line-height: 1.9;
  color: rgba(255, 255, 255, 0.86);
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 16px;
  max-width: 900px;
  margin: 0 auto;
}

.stat-item {
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(14px) saturate(160%);
  -webkit-backdrop-filter: blur(14px) saturate(160%);
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-radius: var(--radius-lg);
  padding: 20px 12px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  transition: transform var(--transition-smooth), box-shadow var(--transition-smooth), background var(--transition-smooth);
}

.stat-item:hover {
  transform: translateY(-6px);
  background: rgba(255, 255, 255, 0.16);
  box-shadow: 0 18px 40px rgba(0, 0, 0, 0.28);
}

.stat-num {
  font-size: clamp(1.5rem, 3.4vw, 2.3rem);
  font-weight: 900;
  line-height: 1.1;
  color: var(--brand-accent);
  text-shadow: 0 2px 16px rgba(230, 180, 34, 0.4);
}

.stat-label {
  font-size: 0.88rem;
  letter-spacing: 0.06em;
  color: rgba(255, 255, 255, 0.8);
}

/* ============ MAIN SECTIONS ============ */
#main-content {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px 40px;
}

#main-content > section {
  margin-top: clamp(48px, 7vw, 88px);
  scroll-margin-top: calc(var(--header-height) + 16px);
}

.content-block {
  background: var(--bg-glass-strong);
  backdrop-filter: blur(16px) saturate(160%);
  -webkit-backdrop-filter: blur(16px) saturate(160%);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-lg);
  padding: clamp(22px, 3.4vw, 40px);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-smooth), transform var(--transition-smooth), border-color var(--transition-smooth);
}

.content-block:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--border-medium);
}

.content-block h3 {
  margin-top: 1.6em;
  padding-left: 14px;
  position: relative;
}

.content-block h3:first-of-type {
  margin-top: 0;
}

.content-block h3::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.28em;
  bottom: 0.28em;
  width: 4px;
  border-radius: var(--radius-pill);
  background: linear-gradient(180deg, var(--brand-accent), var(--brand-gradient-end));
}

.section-intro {
  font-size: 1.02rem;
  color: var(--text-secondary);
  margin-bottom: 1.6em;
}

/* ============ ARTICLE CARDS ============ */
#articles {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 22px;
}

#articles h2,
#articles .section-intro {
  grid-column: 1 / -1;
}

.article-card {
  position: relative;
  background: var(--bg-elevated);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-lg);
  padding: 24px 22px 20px;
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-smooth), box-shadow var(--transition-smooth), border-color var(--transition-smooth);
}

.article-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--brand-accent), var(--brand-gradient-end));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition-smooth);
}

.article-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-lg);
  border-color: var(--brand-accent);
}

.article-card:hover::before {
  transform: scaleX(1);
}

.article-card h3 {
  font-size: 1.1rem;
  margin-bottom: 0.5em;
  transition: color var(--transition-fast);
}

.article-card:hover h3 {
  color: var(--brand-accent);
}

.article-meta {
  font-size: 0.82rem;
  color: var(--text-muted);
  letter-spacing: 0.02em;
  margin-bottom: 0.9em;
}

.article-summary {
  font-size: 0.94rem;
  line-height: 1.8;
  color: var(--text-secondary);
  flex: 1 1 auto;
  margin-bottom: 1.2em;
}

.read-more {
  align-self: flex-start;
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--brand-accent);
  padding: 6px 0;
  position: relative;
  transition: transform var(--transition-fast), letter-spacing var(--transition-fast);
}

.read-more:hover {
  transform: translateX(6px);
  letter-spacing: 0.03em;
  color: var(--brand-primary);
}

/* ============ FAQ ============ */
.faq-list {
  display: grid;
  gap: 14px;
}

.faq-list details {
  background: var(--bg-glass-strong);
  backdrop-filter: blur(14px) saturate(160%);
  -webkit-backdrop-filter: blur(14px) saturate(160%);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-md);
  padding: 4px 6px;
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast);
}

.faq-list details:hover {
  border-color: var(--border-medium);
  box-shadow: var(--shadow-md);
}

.faq-list details[open] {
  border-color: var(--brand-accent);
  box-shadow: 0 12px 34px var(--brand-accent-soft);
}

.faq-list summary {
  cursor: pointer;
  list-style: none;
  padding: 16px 18px;
  font-weight: 700;
  font-size: 1rem;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 12px;
  border-radius: var(--radius-md);
  transition: background var(--transition-fast), color var(--transition-fast);
}

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

.faq-list summary::before {
  content: "+";
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--brand-primary);
  background: var(--brand-accent-soft);
  border: 1px solid var(--brand-accent);
  transition: transform var(--transition-smooth), background var(--transition-fast), color var(--transition-fast);
}

.faq-list details[open] summary::before {
  content: "−";
  transform: rotate(180deg);
  background: var(--brand-accent);
  color: var(--brand-primary);
}

.faq-list summary:hover {
  background: var(--brand-accent-soft);
}

.faq-answer {
  padding: 0 18px 18px 56px;
  animation: fadeUp 0.4s var(--transition-smooth) both;
}

.faq-answer p {
  margin: 0;
  font-size: 0.95rem;
  line-height: 1.85;
}

/* ============ CONTACT ============ */
.contact-info p {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 10px;
  padding: 8px 0;
  border-bottom: 1px dashed var(--border-soft);
  margin: 0;
}

.contact-info p:last-child {
  border-bottom: none;
}

.contact-info strong {
  flex: 0 0 auto;
  min-width: 96px;
  color: var(--brand-accent);
}

/* ============ SITEMAP & FRIEND LINKS ============ */
#sitemap,
#friend-links {
  background: var(--bg-glass-strong);
  backdrop-filter: blur(16px) saturate(160%);
  -webkit-backdrop-filter: blur(16px) saturate(160%);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-lg);
  padding: clamp(22px, 3.2vw, 36px);
  box-shadow: var(--shadow-sm);
}

#sitemap ul,
.links-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 10px;
}

#sitemap a,
.links-list a {
  display: inline-block;
  padding: 10px 16px;
  background: var(--bg-soft);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-pill);
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-align: center;
  transition: transform var(--transition-fast), background var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
}

#sitemap a:hover,
.links-list a:hover {
  transform: translateY(-3px);
  background: linear-gradient(135deg, var(--brand-accent), #f5d061);
  color: var(--brand-primary);
  border-color: transparent;
  box-shadow: var(--shadow-glow);
}

/* ============ FOOTER ============ */
#site-footer {
  margin-top: clamp(56px, 8vw, 96px);
  background: linear-gradient(160deg, var(--brand-gradient-start), var(--brand-gradient-mid) 70%, var(--brand-gradient-end));
  color: rgba(255, 255, 255, 0.82);
  border-top-left-radius: var(--radius-xl);
  border-top-right-radius: var(--radius-xl);
  padding: clamp(40px, 6vw, 68px) 20px 0;
  position: relative;
  overflow: hidden;
}

#site-footer::before {
  content: "";
  position: absolute;
  top: -180px;
  left: -120px;
  width: 420px;
  height: 420px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(230, 180, 34, 0.2), transparent 68%);
  pointer-events: none;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 30px;
  position: relative;
  z-index: 1;
}

.footer-col h3 {
  color: #ffffff;
  font-size: 1.05rem;
  margin-bottom: 1em;
  position: relative;
  padding-bottom: 0.5em;
}

.footer-col h3::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 42px;
  height: 3px;
  border-radius: var(--radius-pill);
  background: var(--brand-accent);
}

.footer-col p {
  color: rgba(255, 255, 255, 0.72);
  font-size: 0.92rem;
  line-height: 1.8;
  margin: 0 0 0.7em;
}

.footer-col ul {
  display: grid;
  gap: 8px;
}

.footer-col ul a {
  color: rgba(255, 255, 255, 0.74);
  font-size: 0.92rem;
  display: inline-block;
  transition: color var(--transition-fast), transform var(--transition-fast);
}

.footer-col ul a:hover {
  color: var(--brand-accent);
  transform: translateX(5px);
}

.footer-bottom {
  max-width: var(--max-width);
  margin: 40px auto 0;
  padding: 24px 0 32px;
  border-top: 1px solid rgba(255, 255, 255, 0.14);
  display: grid;
  gap: 10px;
  position: relative;
  z-index: 1;
}

.footer-bottom p {
  margin: 0;
  font-size: 0.82rem;
  line-height: 1.8;
  color: rgba(255, 255, 255, 0.6);
}

/* ============ BACK TO TOP ============ */
#back-to-top {
  position: fixed;
  right: 22px;
  bottom: 26px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: 1px solid var(--border-medium);
  background: var(--bg-glass-strong);
  backdrop-filter: blur(12px) saturate(160%);
  -webkit-backdrop-filter: blur(12px) saturate(160%);
  color: var(--text-primary);
  font-size: 1.25rem;
  font-weight: 800;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  opacity: 0;
  visibility: hidden;
  transform: translateY(16px) scale(0.9);
  transition: opacity var(--transition-smooth), transform var(--transition-smooth), visibility var(--transition-smooth), background var(--transition-fast), box-shadow var(--transition-fast);
  z-index: 900;
}

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

#back-to-top:hover {
  background: linear-gradient(135deg, var(--brand-accent), #f5d061);
  color: var(--brand-primary);
  box-shadow: var(--shadow-glow);
  transform: translateY(-4px) scale(1.06);
}

/* ============ SCROLL ANIMATION ============ */
.reveal {
  opacity: 0;
  transform: translateY(34px);
  transition: opacity 0.75s cubic-bezier(0.22, 1, 0.36, 1), transform 0.75s cubic-bezier(0.22, 1, 0.36, 1);
  will-change: opacity, transform;
}

.reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(26px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ============ RESPONSIVE ============ */
@media (max-width: 1080px) {
  #main-nav {
    order: 3;
    flex-basis: 100%;
    justify-content: flex-start;
    padding-bottom: 10px;
  }

  #main-nav ul {
    gap: 2px;
  }

  #main-nav a {
    padding: 7px 11px;
    font-size: 0.88rem;
  }
}

@media (max-width: 860px) {
  .hero-stats {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  #articles {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
  :root {
    --header-height: 64px;
  }

  .header-inner {
    gap: 10px;
    padding: 10px 16px;
  }

  .brand-name {
    font-size: 1.1rem;
  }

  .logo-area svg {
    width: 36px;
    height: 36px;
  }

  #main-nav {
    display: none;
    flex-basis: 100%;
    order: 4;
  }

  #main-nav.is-open {
    display: block;
    animation: fadeUp 0.35s var(--transition-smooth) both;
  }

  #main-nav.is-open ul {
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
    padding: 8px 0 4px;
  }

  #main-nav.is-open a {
    display: block;
    padding: 11px 14px;
    background: var(--bg-soft);
    border-radius: var(--radius-md);
  }

  #main-nav.is-open a::after {
    display: none;
  }

  .header-actions {
    margin-left: auto;
  }

  #mobile-menu-btn {
    display: inline-flex;
  }

  #site-search {
    flex: 1 1 auto;
    min-width: 0;
    padding-left: 12px;
  }

  #search-input {
    width: 100%;
    min-width: 0;
    font-size: 0.86rem;
  }

  #site-search button {
    padding: 8px 14px;
    font-size: 0.84rem;
  }

  #hero {
    border-bottom-left-radius: var(--radius-lg);
    border-bottom-right-radius: var(--radius-lg);
  }

  .hero-stats {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 10px;
  }

  .stat-item {
    padding: 16px 8px;
    border-radius: var(--radius-md);
  }

  .content-block {
    border-radius: var(--radius-md);
  }

  .article-card {
    border-radius: var(--radius-md);
    padding: 20px 18px 16px;
  }

  .faq-answer {
    padding-left: 18px;
  }

  #sitemap ul,
  .links-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  #back-to-top {
    right: 14px;
    bottom: 18px;
    width: 44px;
    height: 44px;
  }
}

@media (max-width: 420px) {
  body {
    font-size: 15px;
  }

  .header-inner {
    padding: 10px 12px;
  }

  .brand-name {
    font-size: 1rem;
  }

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

  .stat-num {
    font-size: 1.4rem;
  }

  .stat-label {
    font-size: 0.78rem;
  }

  #sitemap ul,
  .links-list {
    grid-template-columns: 1fr;
  }

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

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }

  .reveal {
    opacity: 1;
    transform: none;
  }
}

@media print {
  #site-header,
  #back-to-top,
  #site-footer,
  #friend-links {
    display: none;
  }

  body {
    background: #ffffff;
    color: #000000;
  }
}