:root {
  --color-primary: #0A1F44;
  --color-accent: #D4AF37;
  --color-functional: #00FF88;
  --color-dot: #00BFFF;
  --color-card-bg: #F0F0F0;
  --color-dark-alt: #1A1A1A;
  --color-text-light: #FFFFFF;
  --color-text-muted: #B0B0B0;
  --color-text-dark: #1A1A1A;
  --font-heading: 'Exo 2', 'Exo 2 Bold', 'Arial Black', sans-serif;
  --font-body: 'Source Han Sans SC', 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --nav-width: 20%;
  --nav-width-tablet: 28%;
  --content-max: 1200px;
  --gap: 1.5rem;
  --radius: 6px;
  --shadow-card: 0 4px 20px rgba(0,0,0,0.06);
  --glow-gold: 0 0 12px rgba(212,175,55,0.35);
  --glow-green: 0 0 12px rgba(0,255,136,0.35);
  --transition: 0.25s ease;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-body);
  background: #F7F7F9;
  color: var(--color-text-dark);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: 0.01em;
}

h1 { font-size: 3rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p, li, a, span, div {
  font-family: var(--font-body);
}

a {
  color: var(--color-functional);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--color-accent);
}

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

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

ul, ol {
  list-style: none;
}

button {
  font-family: var(--font-body);
  cursor: pointer;
  border: none;
  background: none;
}

input, textarea, select {
  font-family: var(--font-body);
}

table {
  border-collapse: collapse;
  width: 100%;
}

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

.skip-link {
  position: absolute;
  top: -100px;
  left: 0;
  z-index: 9999;
  padding: 0.75rem 1.5rem;
  background: var(--color-primary);
  color: var(--color-text-light);
  font-size: 0.9rem;
  border-radius: 0 0 var(--radius) 0;
  transition: top 0.25s ease;
}

.skip-link:focus {
  top: 0;
  color: var(--color-text-light);
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0%;
  background: linear-gradient(90deg, var(--color-accent), var(--color-functional));
  z-index: 2000;
  pointer-events: none;
  transition: width 0.1s linear;
}

@media (prefers-reduced-motion: reduce) {
  .scroll-progress {
    transition: none;
  }
  html {
    scroll-behavior: auto;
  }
}

/* ===== HEADER ===== */
.site-header {
  position: fixed;
  left: 0;
  top: 0;
  width: var(--nav-width);
  height: 100vh;
  background: var(--color-primary);
  color: var(--color-text-light);
  z-index: 500;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  border-right: 2px solid transparent;
  background-clip: padding-box;
}

.site-header::after {
  content: '';
  position: absolute;
  right: 0;
  top: 0;
  width: 2px;
  height: 100%;
  background: linear-gradient(180deg, transparent 5%, var(--color-accent) 30%, var(--color-functional) 70%, transparent 95%);
  opacity: 0.7;
  pointer-events: none;
}

.header-inner {
  display: flex;
  flex-direction: column;
  padding: 2rem 1.25rem;
  height: 100%;
}

.header-brand {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.brand-link {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-accent);
  letter-spacing: 0.02em;
  text-shadow: 0 0 12px rgba(212,175,55,0.2);
  transition: text-shadow var(--transition);
}

.brand-link:hover {
  color: var(--color-accent);
  text-shadow: 0 0 20px rgba(212,175,55,0.5);
}

.brand-slogan {
  font-size: 0.7rem;
  color: var(--color-text-muted);
  letter-spacing: 0.03em;
  line-height: 1.4;
}

.header-divider {
  width: 60%;
  height: 2px;
  background: linear-gradient(90deg, var(--color-accent), transparent);
  margin: 1.25rem 0;
  opacity: 0.5;
  transform: skewX(-15deg);
}

.nav-toggle {
  display: none;
  position: absolute;
  right: 1rem;
  top: 1.25rem;
  width: 32px;
  height: 28px;
  flex-direction: column;
  justify-content: space-between;
  align-items: stretch;
  padding: 4px 0;
  z-index: 10;
}

.nav-toggle-line {
  display: block;
  height: 2px;
  background: var(--color-accent);
  border-radius: 2px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(1) {
  transform: translateY(9px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(2) {
  opacity: 0;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(3) {
  transform: translateY(-9px) rotate(-45deg);
}

.header-nav {
  flex: 1;
  display: flex;
  flex-direction: column;
}

.nav-list {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.nav-list a {
  display: block;
  padding: 0.6rem 0.75rem;
  font-size: 0.95rem;
  color: var(--color-text-light);
  border-radius: var(--radius);
  transition: background var(--transition), color var(--transition), box-shadow var(--transition);
  position: relative;
}

.nav-list a:hover {
  background: rgba(212,175,55,0.12);
  color: var(--color-accent);
  box-shadow: inset 3px 0 0 var(--color-accent);
}

.nav-list a[aria-current="page"] {
  color: var(--color-functional);
  background: rgba(0,255,136,0.08);
  box-shadow: inset 3px 0 0 var(--color-functional);
  font-weight: 600;
}

.nav-list a:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  background: rgba(212,175,55,0.08);
}

.header-cta {
  display: inline-block;
  margin-top: auto;
  padding: 0.75rem 1rem;
  background: var(--color-functional);
  color: var(--color-text-dark);
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.9rem;
  text-align: center;
  border-radius: var(--radius);
  letter-spacing: 0.04em;
  transition: background var(--transition), box-shadow var(--transition), transform var(--transition);
  box-shadow: 0 0 8px rgba(0,255,136,0.2);
}

.header-cta:hover {
  background: #00E67A;
  color: var(--color-text-dark);
  box-shadow: 0 0 20px rgba(0,255,136,0.4);
  transform: translateY(-1px);
}

.header-cta:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

/* ===== MAIN CONTENT ===== */
.main-content {
  margin-left: var(--nav-width);
  min-height: 100vh;
  padding: 2rem 2.5rem;
  background: #F7F7F9;
  background-image:
    linear-gradient(rgba(10,31,68,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(10,31,68,0.03) 1px, transparent 1px);
  background-size: 40px 40px;
  position: relative;
}

.container {
  max-width: var(--content-max);
  margin: 0 auto;
  width: 100%;
}

/* ===== FOOTER ===== */
.site-footer {
  margin-left: var(--nav-width);
  background: var(--color-primary);
  color: var(--color-text-light);
  padding: 2.5rem 2.5rem 1.5rem;
  border-top: 2px solid rgba(212,175,55,0.15);
  position: relative;
}

.site-footer::before {
  content: '';
  position: absolute;
  top: -2px;
  left: 0;
  width: 100%;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--color-accent), var(--color-functional), transparent);
  opacity: 0.4;
}

.footer-inner {
  max-width: var(--content-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 2rem;
  align-items: start;
}

.footer-brand {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.footer-brand-name {
  font-family: var(--font-heading);
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--color-accent);
}

.footer-brand-desc {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.footer-contact {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.contact-item {
  display: block;
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  align-items: flex-end;
}

.footer-links a {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  transition: color var(--transition);
}

.footer-links a:hover {
  color: var(--color-accent);
}

.footer-links a:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: 2px;
}

.footer-icp {
  grid-column: 1 / -1;
  font-size: 0.75rem;
  color: var(--color-text-muted);
  text-align: center;
  padding-top: 1.5rem;
  border-top: 1px solid rgba(255,255,255,0.06);
  margin-top: 0.5rem;
}

.footer-note {
  grid-column: 1 / -1;
  font-size: 0.75rem;
  color: var(--color-text-muted);
  text-align: center;
  line-height: 1.5;
}

.footer-copy {
  grid-column: 1 / -1;
  font-size: 0.75rem;
  color: var(--color-text-muted);
  text-align: center;
  padding-top: 0.5rem;
}

/* ===== COMMON COMPONENTS ===== */
.section {
  padding: 2rem 0;
}

.card {
  background: var(--color-card-bg);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition), transform var(--transition);
}

.card:hover {
  box-shadow: 0 8px 30px rgba(0,0,0,0.08);
  transform: translateY(-2px);
}

.btn {
  display: inline-block;
  padding: 0.65rem 1.5rem;
  background: var(--color-functional);
  color: var(--color-text-dark);
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 0.9rem;
  border-radius: var(--radius);
  text-align: center;
  transition: background var(--transition), box-shadow var(--transition), transform var(--transition);
  box-shadow: 0 0 6px rgba(0,255,136,0.15);
}

.btn:hover {
  background: #00E67A;
  color: var(--color-text-dark);
  box-shadow: 0 0 18px rgba(0,255,136,0.3);
  transform: translateY(-1px);
}

.btn:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

.btn-outline {
  background: transparent;
  border: 2px solid var(--color-accent);
  color: var(--color-accent);
  box-shadow: none;
}

.btn-outline:hover {
  background: var(--color-accent);
  color: var(--color-primary);
}

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 0.8rem;
  font-size: 0.85rem;
  color: var(--color-text-muted);
  padding: 0.75rem 0;
  margin-bottom: 1rem;
}

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

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

.breadcrumb span {
  color: var(--color-text-dark);
  font-weight: 500;
}

.breadcrumb-item + .breadcrumb-item::before {
  content: '/';
  margin-right: 0.6rem;
  color: var(--color-text-muted);
}

.chapter-preview {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin: 2rem 0;
}

.glow-border {
  position: relative;
}

.glow-border::after {
  content: '';
  position: absolute;
  inset: -1px;
  border-radius: inherit;
  background: linear-gradient(135deg, var(--color-accent), var(--color-functional));
  z-index: -1;
  opacity: 0.3;
  transition: opacity var(--transition);
}

.glow-border:hover::after {
  opacity: 0.6;
}

/* ===== TABLET ===== */
@media (max-width: 1199px) {
  .site-header {
    width: var(--nav-width-tablet);
  }
  .main-content {
    margin-left: var(--nav-width-tablet);
  }
  .site-footer {
    margin-left: var(--nav-width-tablet);
  }
  .header-inner {
    padding: 1.5rem 1rem;
  }
  .brand-link {
    font-size: 1.4rem;
  }
  .nav-list a {
    font-size: 0.85rem;
    padding: 0.5rem 0.6rem;
  }
  .footer-inner {
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
  }
  .footer-links {
    align-items: flex-start;
  }
}

/* ===== MOBILE ===== */
@media (max-width: 767px) {
  .site-header {
    position: relative;
    width: 100%;
    height: auto;
    flex-direction: row;
    align-items: center;
    padding: 0.75rem 1rem;
    border-right: none;
    border-bottom: 2px solid rgba(212,175,55,0.15);
  }
  .site-header::after {
    display: none;
  }
  .header-inner {
    flex-direction: row;
    flex-wrap: wrap;
    padding: 0;
    width: 100%;
    align-items: center;
  }
  .header-brand {
    flex: 1;
    flex-direction: row;
    align-items: center;
    gap: 0.75rem;
  }
  .brand-link {
    font-size: 1.2rem;
  }
  .brand-slogan {
    display: none;
  }
  .header-divider {
    display: none;
  }
  .nav-toggle {
    display: flex;
    position: relative;
    right: auto;
    top: auto;
  }
  .header-nav {
    display: none;
    width: 100%;
    padding: 1rem 0 0.5rem;
    flex: 0 0 100%;
    order: 3;
  }
  .header-nav[data-open] {
    display: block;
  }
  .nav-list {
    flex-direction: column;
    gap: 0;
  }
  .nav-list a {
    padding: 0.75rem 0.5rem;
    border-bottom: 1px solid rgba(255,255,255,0.05);
  }
  .header-cta {
    margin-top: 0.75rem;
    width: 100%;
    text-align: center;
  }
  .main-content {
    margin-left: 0;
    padding: 1.25rem 1rem;
    background-size: 30px 30px;
  }
  .site-footer {
    margin-left: 0;
    padding: 1.5rem 1rem 1rem;
  }
  .footer-inner {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  .footer-links {
    align-items: flex-start;
    flex-direction: row;
    gap: 1.25rem;
    flex-wrap: wrap;
  }
  .footer-icp,
  .footer-note,
  .footer-copy {
    text-align: left;
  }
  .chapter-preview {
    grid-template-columns: 1fr;
  }
  h1 { font-size: 2rem; }
  h2 { font-size: 1.5rem; }
  h3 { font-size: 1.2rem; }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
  .card:hover {
    transform: none;
  }
  .header-cta:hover {
    transform: none;
  }
}