/* ===== 全局重置与变量 ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg-primary: #0B1B3A;
  --bg-secondary: #6C3483;
  --accent-primary: #D4AF37;
  --accent-light: #F1C40F;
  --text-primary: #E5E7EB;
  --text-muted: #9CA3AF;
  --glass-bg: rgba(255, 255, 255, 0.08);
  --border-gold: rgba(212, 175, 55, 0.4);
  --success: #28B463;
  --warning: #F39C12;

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

  --fs-hero: clamp(3rem, 8vw, 6rem);
  --fs-h1: clamp(2.2rem, 5vw, 3.5rem);
  --fs-h2: clamp(1.8rem, 3vw, 2.4rem);
  --fs-h3: clamp(1.4rem, 2vw, 1.8rem);
  --fs-body: 1rem;
  --fs-small: 0.875rem;

  --radius-pill: 999px;
  --radius-lg: 24px;
  --radius-md: 16px;
  --radius-sm: 8px;

  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --nav-height: 72px;
  --container: 1280px;
  --shadow-lg: 0 20px 40px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 10px 30px rgba(0, 0, 0, 0.25);
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  padding-top: calc(var(--nav-height) + 32px);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img, svg, video { display: block; max-width: 100%; height: auto; }
a { color: var(--accent-light); text-decoration: none; transition: color var(--transition); }
ul, ol { list-style: none; }

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.3;
  color: var(--text-primary);
}

button { font-family: inherit; cursor: pointer; background: none; border: none; }
input, select, textarea { font-family: inherit; }

:focus-visible {
  outline: 3px solid var(--accent-primary);
  outline-offset: 4px;
  border-radius: var(--radius-sm);
}

/* ===== 通用容器与排版 ===== */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: 24px;
}

.skip-link {
  position: fixed;
  top: -100px;
  left: 16px;
  z-index: 2000;
  background: var(--accent-primary);
  color: var(--bg-primary);
  padding: 8px 20px;
  border-radius: var(--radius-pill);
  font-weight: 700;
  transition: top var(--transition);
}
.skip-link:focus-visible { top: 16px; }

/* ===== 顶部悬浮导航 ===== */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  padding: 16px 24px 0;
  pointer-events: none;
}

.site-header > * { pointer-events: auto; }

.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  z-index: 1500;
  background: transparent;
}
.reading-progress span {
  display: block;
  width: 0%;
  height: 100%;
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-light));
  box-shadow: 0 0 12px rgba(212, 175, 55, 0.6);
  transition: width 0.1s linear;
}

.nav-shell {
  max-width: 1280px;
  margin-inline: auto;
  background: rgba(11, 27, 58, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-gold);
  border-radius: var(--radius-pill);
  box-shadow: var(--shadow-lg);
  transition: border-color var(--transition), background var(--transition);
}
.nav-shell:hover {
  border-color: rgba(212, 175, 55, 0.7);
  background: rgba(11, 27, 58, 0.9);
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  height: calc(var(--nav-height) - 20px);
  padding-inline: 24px;
}

.brand {
  display: inline-flex;
  align-items: center;
  flex-shrink: 0;
}
.brand-mark {
  font-family: var(--font-heading);
  font-size: 1.8rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent-light), var(--accent-primary));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: 0.1em;
  line-height: 1.2;
}

.main-nav {
  flex: 1;
  display: flex;
  justify-content: center;
}
.nav-list {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}
.nav-link {
  display: inline-block;
  padding: 8px 16px;
  font-size: var(--fs-small);
  font-weight: 500;
  color: var(--text-primary);
  border-radius: var(--radius-pill);
  border: 1px solid transparent;
  transition: all var(--transition);
  white-space: nowrap;
}
.nav-link:hover {
  color: var(--accent-light);
  background: var(--glass-bg);
  border-color: var(--border-gold);
}
.nav-link[aria-current="page"] {
  background: rgba(212, 175, 55, 0.12);
  color: var(--accent-light);
  border-color: var(--border-gold);
  box-shadow: inset 0 0 12px rgba(212, 175, 55, 0.1);
  font-weight: 700;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-shrink: 0;
}

/* ===== 按钮系统 ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius-pill);
  font-size: var(--fs-body);
  font-weight: 600;
  letter-spacing: 0.02em;
  transition: all var(--transition);
  line-height: 1.2;
  white-space: nowrap;
}
.btn-sm { padding: 8px 20px; font-size: var(--fs-small); }
.btn-lg { padding: 16px 32px; font-size: 1.125rem; }

.btn-gold {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-light));
  color: var(--bg-primary);
  border: 1px solid rgba(255, 255, 255, 0.2);
  box-shadow: 0 4px 16px rgba(212, 175, 55, 0.3);
}
.btn-gold:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(212, 175, 55, 0.4);
  filter: brightness(1.1);
}

.btn-outline {
  border: 1px solid var(--border-gold);
  color: var(--accent-light);
  background: transparent;
}
.btn-outline:hover {
  background: var(--glass-bg);
  border-color: var(--accent-primary);
  transform: translateY(-2px);
}

/* ===== 移动端导航按钮 ===== */
.nav-toggle {
  display: none;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border-gold);
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
  background: var(--glass-bg);
}
.nav-toggle:hover { border-color: var(--accent-primary); }
.nav-toggle-box {
  position: relative;
  width: 20px;
  height: 14px;
}
.nav-toggle-inner,
.nav-toggle-inner::before,
.nav-toggle-inner::after {
  content: '';
  display: block;
  position: absolute;
  left: 0;
  width: 20px;
  height: 2px;
  background: var(--accent-light);
  border-radius: 2px;
  transition: all var(--transition);
}
.nav-toggle-inner { top: 6px; }
.nav-toggle-inner::before { top: -6px; }
.nav-toggle-inner::after { top: 6px; }

.nav-toggle[aria-expanded="true"] .nav-toggle-inner { background: transparent; }
.nav-toggle[aria-expanded="true"] .nav-toggle-inner::before { top: 0; transform: rotate(45deg); background: var(--accent-primary); }
.nav-toggle[aria-expanded="true"] .nav-toggle-inner::after { top: 0; transform: rotate(-45deg); background: var(--accent-primary); }

/* ===== 页脚 ===== */
.site-footer {
  position: relative;
  margin-top: 80px;
  background-color: #07122A;
  border-top: 1px solid var(--border-gold);
  overflow: hidden;
}

.footer-bg {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
}
.footer-glow {
  position: absolute;
  display: block;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.4;
}
.footer-glow--gold {
  width: 400px;
  height: 400px;
  background: var(--accent-primary);
  top: -150px;
  left: -80px;
}
.footer-glow--indigo {
  width: 500px;
  height: 500px;
  background: var(--bg-secondary);
  bottom: -200px;
  right: -100px;
  opacity: 0.6;
}

.footer-shell {
  position: relative;
  z-index: 1;
  padding-top: 64px;
  padding-bottom: 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  padding-bottom: 48px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.footer-brand .brand--footer {
  margin-bottom: 16px;
}
.brand--footer .brand-mark {
  font-size: 2.25rem;
}

.footer-tagline {
  font-family: var(--font-heading);
  color: var(--accent-light);
  font-size: 1.125rem;
  margin-bottom: 12px;
  letter-spacing: 0.05em;
}
.footer-trust {
  color: var(--text-muted);
  font-size: var(--fs-small);
  line-height: 1.8;
  max-width: 360px;
}

.footer-heading {
  color: var(--text-primary);
  font-size: 1.125rem;
  margin-bottom: 20px;
  position: relative;
  padding-bottom: 8px;
}
.footer-heading::after {
  content: '';
  display: block;
  width: 24px;
  height: 2px;
  background: linear-gradient(90deg, var(--accent-primary), transparent);
  border-radius: 2px;
  position: absolute;
  bottom: 0;
  left: 0;
}

.footer-links ul,
.footer-contact ul,
.footer-legal ul {
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.footer-links a,
.footer-contact a,
.footer-legal a {
  color: var(--text-muted);
  font-size: var(--fs-small);
  transition: all var(--transition);
}
.footer-links a:hover,
.footer-contact a:hover,
.footer-legal a:hover {
  color: var(--accent-light);
  padding-left: 4px;
}

.footer-contact li {
  color: var(--text-muted);
  font-size: var(--fs-small);
  line-height: 1.6;
  word-break: break-all;
}

.footer-bottom {
  padding-top: 24px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  color: var(--text-muted);
  font-size: 0.8125rem;
}
.footer-bottom p { margin: 0; }

/* ===== 通用章节 & 基础组件 ===== */
.section-header { margin-bottom: 48px; }
.section-tag {
  display: inline-block;
  background: var(--glass-bg);
  border: 1px solid var(--border-gold);
  color: var(--accent-light);
  padding: 4px 16px;
  border-radius: var(--radius-pill);
  font-size: var(--fs-small);
  letter-spacing: 0.1em;
  margin-bottom: 16px;
}
.section-title { font-size: var(--fs-h2); margin-bottom: 12px; }
.section-desc { color: var(--text-muted); max-width: 640px; }

.chapter { display: flex; gap: 32px; align-items: flex-start; }
.chapter-num {
  font-family: var(--font-heading);
  font-size: clamp(4rem, 8vw, 6rem);
  font-weight: 800;
  color: transparent;
  -webkit-text-stroke: 2px var(--border-gold);
  line-height: 1;
  flex-shrink: 0;
  min-width: 120px;
}
.chapter-content { flex: 1; }

.card-grid { display: grid; gap: 24px; grid-template-columns: repeat(3, 1fr); }
.card-grid .span-2 { grid-column: span 2; }
.card-grid .span-3 { grid-column: span 3; }
.card-grid .span-4 { grid-column: span 4; }

.card {
  background: var(--glass-bg);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-lg);
  padding: 32px;
  backdrop-filter: blur(8px);
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}
.card:hover {
  border-color: var(--border-gold);
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}
.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--accent-primary), transparent);
  opacity: 0;
  transition: opacity var(--transition);
}
.card:hover::before { opacity: 1; }
.card-body { }
.card-title { font-size: var(--fs-h3); margin-bottom: 12px; }
.card-text { color: var(--text-muted); }

.badge {
  display: inline-block;
  padding: 4px 12px;
  border-radius: var(--radius-pill);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.05em;
}
.badge-success { background: rgba(40, 180, 99, 0.15); color: var(--success); border: 1px solid rgba(40, 180, 99, 0.3); }
.badge-warning { background: rgba(243, 156, 18, 0.15); color: var(--warning); border: 1px solid rgba(243, 156, 18, 0.3); }

.figure-placeholder {
  position: relative;
  background: var(--glass-bg);
  border: 1px dashed var(--border-gold);
  border-radius: var(--radius-lg);
  overflow: hidden;
  aspect-ratio: 16 / 9;
}
.figure-placeholder img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* ===== 返回顶部 ===== */
.scroll-top {
  position: fixed;
  right: 24px;
  bottom: 24px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-light));
  color: var(--bg-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: all var(--transition);
  box-shadow: 0 8px 24px rgba(212, 175, 55, 0.4);
  z-index: 900;
}
.scroll-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.scroll-top:hover { filter: brightness(1.1); }
.scroll-top-icon { font-size: 1.5rem; }

/* ===== 滚动显现 ===== */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== 响应式 ===== */
@media (max-width: 1024px) {
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 32px; }
  .chapter { flex-direction: column; gap: 12px; }
  .chapter-num { min-width: auto; }
}

@media (max-width: 768px) {
  body { padding-top: calc(var(--nav-height) + 16px); }
  .site-header { padding: 12px 16px 0; }
  .nav-container { height: 60px; padding-inline: 16px; gap: 12px; }

  .main-nav {
    position: fixed;
    top: 88px;
    left: 16px;
    right: 16px;
    background: rgba(11, 27, 58, 0.97);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--border-gold);
    border-radius: var(--radius-lg);
    padding: 24px;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-12px);
    transition: all var(--transition);
    box-shadow: var(--shadow-lg);
  }
  .main-nav[data-open="true"] {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }
  .nav-list { flex-direction: column; gap: 8px; width: 100%; }
  .nav-link { display: block; text-align: center; padding: 12px; font-size: 1rem; }

  .header-actions .btn { display: none; }
  .nav-toggle { display: flex; }

  .footer-grid { grid-template-columns: 1fr; gap: 32px; }
  .footer-bottom { flex-direction: column; text-align: center; }
  .card-grid { grid-template-columns: 1fr; }
  .card-grid .span-2, .card-grid .span-3, .card-grid .span-4 { grid-column: span 1; }
}

@media (max-width: 480px) {
  .container { padding-inline: 16px; }
}

/* ===== 无障碍偏好：减弱动效 ===== */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  .reveal { opacity: 1; transform: none; }
  .scroll-top { transition: none; }
  .reading-progress span { transition: none; }
}