:root {
  --color-bg: #f4f7fb;
  --color-surface: #ffffff;
  --color-surface-alt: #eef2f9;
  --color-text-primary: #17202A;
  --color-text-secondary: #334155;
  --color-text-muted: #475569;
  --color-heading: #0f172a;
  --color-link: #1e40af;
  --color-link-hover: #1e3a8a;
  --color-border: #cbd5e1;
  --color-brand: #2563eb;
  --color-brand-dark: #1d4ed8;
  --color-brand-text: #ffffff;
  --color-nav-bg: rgba(255, 255, 255, 0.72);
  --color-nav-text: #1e293b;
  --color-footer-bg: #1e293b;
  --color-footer-text: #e2e8f0;
  --color-footer-muted: #94a3b8;
  --color-card-bg: rgba(255, 255, 255, 0.82);
  --color-card-text: #1e293b;
  --color-faq-bg: rgba(255, 255, 255, 0.82);
  --color-faq-question: #0f172a;
  --color-faq-answer: #334155;
  --color-btn-bg: #2563eb;
  --color-btn-text: #ffffff;
  --color-input-bg: rgba(255, 255, 255, 0.7);
  --color-input-text: #17202A;
  --color-input-border: #94a3b8;
  --color-tag-bg: rgba(226, 232, 240, 0.85);
  --color-tag-text: #1e293b;
  --color-table-head-bg: #1e293b;
  --color-table-head-text: #f1f5f9;
  --color-table-row-alt: #f1f5f9;
  --color-shadow: rgba(15, 23, 42, 0.08);
  --color-shadow-strong: rgba(15, 23, 42, 0.16);
  --color-overlay: rgba(0, 0, 0, 0.5);
  --color-banner-text: #ffffff;
  --color-banner-sub: #e2e8f0;
  --glass-blur: blur(14px);
  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 22px;
  --gradient-1: linear-gradient(135deg, #1e3a8a 0%, #2563eb 55%, #38bdf8 100%);
  --gradient-2: linear-gradient(135deg, #6d28d9 0%, #a855f7 55%, #ec4899 100%);
  --gradient-3: linear-gradient(135deg, #0f766e 0%, #14b8a6 55%, #22d3ee 100%);
}

html.dark-mode {
  --color-bg: #0b1220;
  --color-surface: #1e293b;
  --color-surface-alt: #1e293b;
  --color-text-primary: #E5E7EB;
  --color-text-secondary: #E2E8F0;
  --color-text-muted: #cbd5e1;
  --color-heading: #FFFFFF;
  --color-link: #93c5fd;
  --color-link-hover: #bfdbfe;
  --color-border: #334155;
  --color-brand: #3b82f6;
  --color-brand-dark: #60a5fa;
  --color-brand-text: #ffffff;
  --color-nav-bg: rgba(15, 23, 42, 0.72);
  --color-nav-text: #F1F5F9;
  --color-footer-bg: #020617;
  --color-footer-text: #E2E8F0;
  --color-footer-muted: #94a3b8;
  --color-card-bg: rgba(30, 41, 59, 0.78);
  --color-card-text: #E2E8F0;
  --color-faq-bg: rgba(30, 41, 59, 0.78);
  --color-faq-question: #FFFFFF;
  --color-faq-answer: #E2E8F0;
  --color-btn-bg: #3b82f6;
  --color-btn-text: #ffffff;
  --color-input-bg: rgba(30, 41, 59, 0.7);
  --color-input-text: #F1F5F9;
  --color-input-border: #475569;
  --color-tag-bg: rgba(51, 65, 85, 0.85);
  --color-tag-text: #F1F5F9;
  --color-table-head-bg: #334155;
  --color-table-head-text: #F1F5F9;
  --color-table-row-alt: #1e293b;
  --color-shadow: rgba(0, 0, 0, 0.4);
  --color-shadow-strong: rgba(0, 0, 0, 0.6);
  --color-overlay: rgba(0, 0, 0, 0.7);
  --color-banner-text: #FFFFFF;
  --color-banner-sub: #E2E8F0;
  --gradient-1: linear-gradient(135deg, #1e3a8a 0%, #1d4ed8 55%, #0ea5e9 100%);
  --gradient-2: linear-gradient(135deg, #5b21b6 0%, #7c3aed 55%, #db2777 100%);
  --gradient-3: linear-gradient(135deg, #115e59 0%, #0d9488 55%, #0891b2 100%);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  background-color: var(--color-bg);
  background-image:
    radial-gradient(circle at 12% 8%, rgba(37, 99, 235, 0.10), transparent 42%),
    radial-gradient(circle at 88% 4%, rgba(168, 85, 247, 0.10), transparent 40%),
    radial-gradient(circle at 50% 100%, rgba(20, 184, 166, 0.08), transparent 46%);
  background-attachment: fixed;
  color: var(--color-text-primary);
  line-height: 1.75;
  transition: background-color 0.35s ease, color 0.35s ease;
  overflow-x: hidden;
}

h1, h2, h3, h4 {
  color: var(--color-heading);
  line-height: 1.3;
  font-weight: 700;
  transition: color 0.3s ease;
}

h1 {
  font-size: 2.2rem;
  margin-bottom: 1rem;
  letter-spacing: -0.02em;
  background: linear-gradient(120deg, var(--color-heading) 30%, var(--color-brand) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

html.dark-mode h1 {
  background: linear-gradient(120deg, #ffffff 30%, #93c5fd 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

h2 {
  font-size: 1.75rem;
  margin-bottom: 0.9rem;
  border-left: 5px solid var(--color-brand);
  padding-left: 0.75rem;
  position: relative;
}

h2::after {
  content: "";
  position: absolute;
  left: -5px;
  bottom: -2px;
  width: 5px;
  height: 0;
  background: var(--color-brand-dark);
  transition: height 0.4s ease;
}

h2:hover::after {
  height: 100%;
}

h3 { font-size: 1.35rem; margin-bottom: 0.7rem; }
h4 { font-size: 1.1rem; margin-bottom: 0.5rem; }

p, li, td, th, dd, dt, blockquote, figcaption, label, span {
  color: var(--color-text-primary);
  transition: color 0.3s ease;
}

a {
  color: var(--color-link);
  text-decoration: none;
  transition: color 0.2s ease, opacity 0.2s ease;
}

a:hover, a:focus {
  color: var(--color-link-hover);
  text-decoration: underline;
}

a:focus-visible,
button:focus-visible,
input:focus-visible {
  outline: 2px solid var(--color-brand);
  outline-offset: 2px;
  border-radius: 4px;
}

::selection {
  background: var(--color-brand);
  color: #ffffff;
}

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--color-surface-alt); }
::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: 999px;
}
::-webkit-scrollbar-thumb:hover { background: var(--color-brand); }

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

.navbar {
  position: sticky;
  top: 0;
  z-index: 1000;
  background-color: var(--color-nav-bg);
  -webkit-backdrop-filter: var(--glass-blur) saturate(180%);
  backdrop-filter: var(--glass-blur) saturate(180%);
  color: var(--color-nav-text);
  box-shadow: 0 2px 20px var(--color-shadow);
  border-bottom: 1px solid var(--color-border);
  transition: background-color 0.35s ease, color 0.35s ease, border-color 0.35s ease, box-shadow 0.35s ease;
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  padding: 0.75rem 0;
  gap: 0.5rem;
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--color-heading);
  letter-spacing: -0.5px;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: transform 0.3s ease;
}

.logo:hover {
  transform: translateY(-2px);
  text-decoration: none;
}

.logo svg {
  width: 36px;
  height: 36px;
  transition: transform 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
  filter: drop-shadow(0 4px 8px rgba(37, 99, 235, 0.35));
}

.logo:hover svg {
  transform: rotate(-12deg) scale(1.08);
}

.nav-links {
  display: flex;
  gap: 1.5rem;
  list-style: none;
  flex-wrap: wrap;
}

.nav-links a {
  color: var(--color-nav-text);
  font-weight: 500;
  padding: 0.25rem 0;
  border-bottom: 2px solid transparent;
  position: relative;
  transition: border-color 0.25s, color 0.25s;
}

.nav-links a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 0;
  height: 2px;
  background: var(--color-brand);
  transition: width 0.3s ease;
}

.nav-links a:hover::after,
.nav-links a:focus::after {
  width: 100%;
}

.nav-links a:hover, .nav-links a:focus {
  color: var(--color-brand);
  border-bottom-color: transparent;
  text-decoration: none;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.search-box {
  display: flex;
  align-items: center;
  background: var(--color-input-bg);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  border: 1px solid var(--color-input-border);
  border-radius: 999px;
  padding: 0.2rem 0.2rem 0.2rem 0.9rem;
  transition: border-color 0.25s, box-shadow 0.25s, background 0.25s;
}

.search-box:focus-within {
  border-color: var(--color-brand);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.18);
}

.search-box input {
  border: none;
  background: transparent;
  color: var(--color-input-text);
  font-size: 0.9rem;
  outline: none;
  width: 130px;
  padding: 0.3rem 0;
  font-family: inherit;
}

.search-box input::placeholder {
  color: var(--color-text-muted);
  opacity: 1;
}

.search-box button {
  background: var(--color-btn-bg);
  color: var(--color-btn-text);
  border: none;
  border-radius: 999px;
  padding: 0.35rem 0.9rem;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
  transition: background 0.25s, transform 0.2s;
}

.search-box button:hover {
  background: var(--color-brand-dark);
  transform: scale(1.04);
}

.search-box button:active {
  transform: scale(0.97);
}

.theme-toggle {
  background: var(--color-input-bg);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  border: 1px solid var(--color-border);
  border-radius: 999px;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1.2rem;
  color: var(--color-text-primary);
  transition: background 0.25s, border-color 0.25s, color 0.25s, transform 0.3s;
}

.theme-toggle:hover {
  background: var(--color-border);
  transform: rotate(18deg) scale(1.06);
}

.mobile-menu-btn {
  display: none;
  background: var(--color-input-bg);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  font-size: 1.5rem;
  padding: 0.2rem 0.6rem;
  color: var(--color-text-primary);
  cursor: pointer;
  transition: background 0.25s;
}

.mobile-menu-btn:hover {
  background: var(--color-border);
}

.banner {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-lg);
  margin: 1.5rem 0;
  background: var(--gradient-1);
  min-height: 280px;
  display: flex;
  align-items: center;
  color: var(--color-banner-text);
  box-shadow: 0 18px 44px -12px var(--color-shadow-strong);
  isolation: isolate;
}

.banner::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 18% 22%, rgba(255, 255, 255, 0.22), transparent 34%),
    radial-gradient(circle at 82% 78%, rgba(255, 255, 255, 0.14), transparent 38%);
  z-index: 1;
  pointer-events: none;
}

.banner-slide {
  position: absolute;
  inset: 0;
  opacity: 0;
  transition: opacity 0.8s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem 1.5rem;
  text-align: center;
  background: var(--gradient-1);
}

.banner-slide.active {
  opacity: 1;
  position: relative;
}

.banner-slide:nth-child(2) {
  background: var(--gradient-2);
}

.banner-slide:nth-child(3) {
  background: var(--gradient-3);
}

.banner-content {
  max-width: 700px;
  position: relative;
  z-index: 2;
  animation: bannerFadeUp 0.8s ease both;
}

@keyframes bannerFadeUp {
  from { opacity: 0; transform: translateY(18px); }
  to { opacity: 1; transform: translateY(0); }
}

.banner-content h2 {
  color: #ffffff;
  border-left: none;
  padding-left: 0;
  font-size: 2rem;
  margin-bottom: 0.75rem;
  text-shadow: 0 2px 12px rgba(0, 0, 0, 0.45);
  -webkit-text-fill-color: #ffffff;
}

.banner-content p {
  color: #f1f5f9;
  font-size: 1.05rem;
  text-shadow: 0 1px 8px rgba(0, 0, 0, 0.45);
}

.banner-dots {
  position: absolute;
  bottom: 18px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  gap: 10px;
  z-index: 5;
}

.banner-dots span {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.5);
  cursor: pointer;
  transition: background 0.3s, transform 0.3s, width 0.3s;
}

.banner-dots span:hover {
  background: rgba(255, 255, 255, 0.8);
  transform: scale(1.15);
}

.banner-dots span.active {
  background: #ffffff;
  width: 28px;
  border-radius: 999px;
}

.card {
  background: var(--color-card-bg);
  -webkit-backdrop-filter: var(--glass-blur) saturate(160%);
  backdrop-filter: var(--glass-blur) saturate(160%);
  color: var(--color-card-text);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  box-shadow: 0 6px 22px -6px var(--color-shadow);
  border: 1px solid var(--color-border);
  position: relative;
  overflow: hidden;
  transition: background 0.35s, color 0.35s, border-color 0.35s, box-shadow 0.35s, transform 0.35s;
}

.card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--color-brand), #a855f7, #14b8a6);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.45s ease;
}

.card:hover {
  box-shadow: 0 16px 38px -10px var(--color-shadow-strong);
  transform: translateY(-6px);
}

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

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 1.25rem;
  margin: 2rem 0;
}

.stat-item {
  text-align: center;
  padding: 1.5rem 1rem;
  background: var(--color-card-bg);
  -webkit-backdrop-filter: var(--glass-blur);
  backdrop-filter: var(--glass-blur);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  position: relative;
  overflow: hidden;
  transition: background 0.35s, border-color 0.35s, transform 0.35s, box-shadow 0.35s;
}

.stat-item::after {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at 50% 0%, rgba(37, 99, 235, 0.12), transparent 70%);
  opacity: 0;
  transition: opacity 0.35s;
}

.stat-item:hover {
  transform: translateY(-5px);
  box-shadow: 0 14px 30px -10px var(--color-shadow-strong);
}

.stat-item:hover::after {
  opacity: 1;
}

.stat-number {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--color-brand);
  display: block;
  line-height: 1.2;
  font-variant-numeric: tabular-nums;
  position: relative;
  z-index: 1;
}

.stat-label {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  position: relative;
  z-index: 1;
}

.article-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin: 1.5rem 0;
}

.article-card {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.article-card h3 {
  font-size: 1.15rem;
  margin-bottom: 0.2rem;
  transition: color 0.25s;
}

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

.article-meta {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.article-summary {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  flex: 1;
}

.read-more {
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--color-link);
  align-self: flex-start;
  position: relative;
  transition: color 0.25s, transform 0.25s;
}

.read-more:hover {
  text-decoration: none;
  transform: translateX(4px);
}

.faq-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  margin: 1.5rem 0;
}

.faq-item {
  background: var(--color-faq-bg);
  -webkit-backdrop-filter: var(--glass-blur);
  backdrop-filter: var(--glass-blur);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  overflow: hidden;
  transition: background 0.35s, border-color 0.35s, box-shadow 0.35s;
}

.faq-item:hover {
  box-shadow: 0 8px 22px -8px var(--color-shadow-strong);
}

.faq-item.open {
  border-color: var(--color-brand);
  box-shadow: 0 8px 24px -8px rgba(37, 99, 235, 0.35);
}

.faq-question {
  width: 100%;
  text-align: left;
  padding: 1rem 1.25rem;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-faq-question);
  background: transparent;
  border: none;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  font-family: inherit;
  transition: background 0.25s, color 0.25s;
}

.faq-question:hover {
  background: var(--color-surface-alt);
}

.faq-question .icon {
  font-size: 1.4rem;
  font-weight: 400;
  color: var(--color-brand);
  transition: transform 0.35s cubic-bezier(0.34, 1.56, 0.64, 1);
  flex-shrink: 0;
}

.faq-item.open .faq-question .icon {
  transform: rotate(45deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.45s ease, padding 0.3s ease;
  padding: 0 1.25rem;
  color: var(--color-faq-answer);
  font-size: 0.98rem;
  line-height: 1.8;
}

.faq-item.open .faq-answer {
  max-height: 700px;
  padding: 0 1.25rem 1.25rem;
}

.howto-steps {
  counter-reset: step;
  list-style: none;
  margin: 1.5rem 0;
}

.howto-steps li {
  counter-increment: step;
  position: relative;
  padding-left: 3.5rem;
  margin-bottom: 1.5rem;
  color: var(--color-text-primary);
  transition: transform 0.3s ease;
}

.howto-steps li:hover {
  transform: translateX(6px);
}

.howto-steps li::before {
  content: counter(step);
  position: absolute;
  left: 0;
  top: 0;
  width: 2.4rem;
  height: 2.4rem;
  background: var(--gradient-1);
  color: #ffffff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1.1rem;
  box-shadow: 0 6px 16px -4px rgba(37, 99, 235, 0.55);
  transition: transform 0.35s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.howto-steps li:hover::before {
  transform: scale(1.12) rotate(-8deg);
}

.howto-steps h4 {
  margin-bottom: 0.3rem;
  color: var(--color-heading);
}

.howto-steps p {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
}

.table-wrap {
  overflow-x: auto;
  margin: 1.5rem 0;
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-border);
  box-shadow: 0 6px 20px -8px var(--color-shadow);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}

thead th {
  background: var(--color-table-head-bg);
  color: var(--color-table-head-text);
  padding: 0.9rem 1rem;
  text-align: left;
  font-weight: 700;
  white-space: nowrap;
}

tbody td {
  padding: 0.8rem 1rem;
  color: var(--color-text-primary);
  border-top: 1px solid var(--color-border);
  transition: background 0.25s;
}

tbody tr:nth-child(even) {
  background: var(--color-table-row-alt);
}

tbody tr:hover {
  background: rgba(37, 99, 235, 0.08);
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 1rem 0;
}

.tag {
  background: var(--color-tag-bg);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  color: var(--color-tag-text);
  padding: 0.3rem 0.9rem;
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 500;
  border: 1px solid transparent;
  transition: background 0.25s, color 0.25s, transform 0.25s, border-color 0.25s, box-shadow 0.25s;
}

.tag:hover {
  background: var(--color-brand);
  color: #ffffff;
  border-color: var(--color-brand);
  transform: translateY(-3px);
  box-shadow: 0 8px 18px -6px rgba(37, 99, 235, 0.6);
  text-decoration: none;
}

footer {
  background: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: 2.5rem 0 1.5rem;
  margin-top: 3rem;
  position: relative;
  transition: background 0.35s, color 0.35s;
}

footer::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, #2563eb, #a855f7, #14b8a6, #2563eb);
  background-size: 300% 100%;
  animation: footerGradient 8s linear infinite;
}

@keyframes footerGradient {
  0% { background-position: 0% 50%; }
  100% { background-position: 300% 50%; }
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
  margin-bottom: 2rem;
}

.footer-col h4 {
  color: var(--color-footer-text);
  font-size: 1.05rem;
  margin-bottom: 0.9rem;
  font-weight: 700;
}

.footer-col ul {
  list-style: none;
}

.footer-col li {
  margin-bottom: 0.5rem;
}

.footer-col a {
  color: var(--color-footer-muted);
  font-size: 0.92rem;
  transition: color 0.25s, padding-left 0.25s;
  position: relative;
}

.footer-col a:hover {
  color: var(--color-footer-text);
  text-decoration: underline;
  padding-left: 6px;
}

.footer-col p {
  color: var(--color-footer-muted);
  font-size: 0.92rem;
  margin-bottom: 0.4rem;
}

.footer-bottom {
  border-top: 1px solid var(--color-border);
  padding-top: 1.5rem;
  text-align: center;
  color: var(--color-footer-muted);
  font-size: 0.88rem;
}

.footer-bottom a {
  color: var(--color-footer-muted);
  margin: 0 0.4rem;
  transition: color 0.25s;
}

.footer-bottom a:hover {
  color: var(--color-footer-text);
}

.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--color-btn-bg);
  color: var(--color-btn-text);
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  box-shadow: 0 8px 24px -6px rgba(37, 99, 235, 0.65);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 999;
  transition: background 0.25s, opacity 0.35s, transform 0.35s;
}

.back-to-top.show {
  display: flex;
  animation: popIn 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes popIn {
  from { opacity: 0; transform: scale(0.6); }
  to { opacity: 1; transform: scale(1); }
}

.back-to-top:hover {
  background: var(--color-brand-dark);
  transform: translateY(-4px) scale(1.08);
}

.fade-in {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.75s cubic-bezier(0.22, 1, 0.36, 1), transform 0.75s cubic-bezier(0.22, 1, 0.36, 1);
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

.text-muted { color: var(--color-text-muted); }
.text-secondary { color: var(--color-text-secondary); }

.section { margin: 2.5rem 0; }
.section-title { margin-bottom: 1.25rem; }

.breadcrumb {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin: 1rem 0;
}

.breadcrumb a { color: var(--color-link); }
.breadcrumb span { color: var(--color-text-muted); }

.divider {
  height: 1px;
  background: var(--color-border);
  margin: 2rem 0;
}

.highlight-box {
  background: var(--color-card-bg);
  -webkit-backdrop-filter: var(--glass-blur);
  backdrop-filter: var(--glass-blur);
  border-left: 4px solid var(--color-brand);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--color-text-primary);
  margin: 1.25rem 0;
  box-shadow: 0 6px 20px -10px var(--color-shadow);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.highlight-box:hover {
  transform: translateX(4px);
  box-shadow: 0 10px 26px -10px var(--color-shadow-strong);
}

.highlight-box p {
  color: var(--color-text-primary);
}

@keyframes floatSoft {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
  .fade-in { opacity: 1; transform: none; }
}

@media (max-width: 992px) {
  .search-box input { width: 110px; }
  .nav-links { gap: 1rem; }
}

@media (max-width: 768px) {
  html { font-size: 15px; }
  h1 { font-size: 1.7rem; }
  h2 { font-size: 1.4rem; }
  h3 { font-size: 1.2rem; }

  .nav-inner {
    flex-wrap: wrap;
  }

  .nav-links {
    display: none;
    flex-direction: column;
    width: 100%;
    gap: 0.5rem;
    padding: 0.75rem 0;
    border-top: 1px solid var(--color-border);
    animation: menuSlide 0.35s ease;
  }

  @keyframes menuSlide {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links a {
    display: block;
    padding: 0.5rem 0.25rem;
  }

  .mobile-menu-btn {
    display: block;
  }

  .search-box input {
    width: 100px;
  }

  .banner {
    min-height: 240px;
    border-radius: var(--radius-md);
  }

  .banner-content h2 {
    font-size: 1.5rem;
  }

  .banner-content p {
    font-size: 0.95rem;
  }

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

  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 0.9rem;
  }

  .stat-number { font-size: 1.75rem; }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .back-to-top {
    bottom: 1rem;
    right: 1rem;
    width: 42px;
    height: 42px;
    font-size: 1.2rem;
  }

  .howto-steps li {
    padding-left: 3rem;
  }

  .howto-steps li::before {
    width: 2.1rem;
    height: 2.1rem;
    font-size: 1rem;
  }
}

@media (max-width: 480px) {
  .container { padding: 0 14px; }
  h1 { font-size: 1.5rem; }
  .banner-content h2 { font-size: 1.3rem; }
  .search-box input { width: 80px; }
  .stats-grid { grid-template-columns: 1fr 1fr; }
  .stat-item { padding: 1.1rem 0.6rem; }
  .stat-number { font-size: 1.5rem; }
  .card { padding: 1.1rem; }
}

@media print {
  .navbar,
  .back-to-top,
  .theme-toggle,
  .mobile-menu-btn,
  .search-box,
  .banner { display: none !important; }
  body { background: #fff; color: #000; }
  .card, .faq-item, .stat-item { box-shadow: none; border: 1px solid #ccc; }
}