/* ================================================================
   AIAS Modern Design System
   ================================================================ */

/* --- CSS Variables --- */
:root {
  /* Brand */
  --color-primary: #D3487B;
  --color-primary-dark: #b83a68;
  --color-primary-light: #F06292;
  --color-primary-gradient: linear-gradient(135deg, #D3487B 0%, #F06292 100%);

  /* Neutrals */
  --color-bg: #ffffff;
  --color-bg-secondary: #f8fafc;
  --color-bg-tertiary: #f1f5f9;
  --color-text: #1a1a2e;
  --color-text-secondary: #64748b;
  --color-text-muted: #94a3b8;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 25px -5px rgba(0, 0, 0, 0.08), 0 4px 10px -6px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 50px -12px rgba(0, 0, 0, 0.12);

  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  --space-4xl: 96px;

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Layout */
  --max-width: 1200px;
  --header-height: 64px;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", sans-serif;
  --font-mono: "SF Mono", "Fira Code", "Fira Mono", "Roboto Mono", monospace;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* --- Reset & Base --- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-family);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
}

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

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

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

ul, ol {
  list-style: none;
}

/* --- Container --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* --- Header --- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.82);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--color-border-light);
  transition: box-shadow var(--transition-base);
}

.site-header.scrolled {
  box-shadow: var(--shadow-md);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

/* Logo */
.site-logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 20px;
  font-weight: 700;
  color: var(--color-text);
  flex-shrink: 0;
}

.site-logo img {
  height: 40px;
  width: auto;
}

/* --- Navigation --- */
.site-nav {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  height: 100%;
}

.site-nav > li {
  position: relative;
  height: 100%;
  display: flex;
  align-items: center;
}

.site-nav > li > a {
  display: flex;
  align-items: center;
  gap: 4px;
  padding: var(--space-sm) var(--space-md);
  font-size: 15px;
  font-weight: 500;
  color: var(--color-text-secondary);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  position: relative;
  white-space: nowrap;
}

.site-nav > li > a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%) scaleX(0);
  width: calc(100% - 2 * var(--space-md));
  height: 2px;
  background: var(--color-primary);
  border-radius: 2px;
  transition: transform var(--transition-base);
}

.site-nav > li > a:hover,
.site-nav > li > a.active {
  color: var(--color-primary);
}

.site-nav > li > a:hover::after,
.site-nav > li > a.active::after {
  transform: translateX(-50%) scaleX(1);
}

.site-nav > li > a .arrow {
  font-size: 10px;
  transition: transform var(--transition-fast);
}

.site-nav > li:hover > a .arrow {
  transform: rotate(180deg);
}

/* Dropdown */
.site-nav .dropdown {
  position: absolute;
  top: 100%;
  left: 0;
  min-width: 180px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  padding: var(--space-sm);
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: all var(--transition-fast);
}

.site-nav > li:last-child .dropdown {
  left: auto;
  right: 0;
}

.site-nav > li:hover .dropdown {
  opacity: 1;
  visibility: visible;
  transform: translateY(4px);
}

.site-nav .dropdown li a {
  display: block;
  padding: var(--space-sm) var(--space-md);
  font-size: 14px;
  color: var(--color-text-secondary);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.site-nav .dropdown li a:hover {
  background: var(--color-bg-tertiary);
  color: var(--color-primary);
}

/* Mobile menu toggle */
.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 8px;
  background: none;
  border: none;
  cursor: pointer;
}

.menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: all var(--transition-fast);
}

/* --- Hero Section --- */
.hero {
  padding: calc(var(--header-height) + var(--space-4xl)) 0 var(--space-4xl);
  background: linear-gradient(160deg, #fdf2f8 0%, #f8fafc 40%, #ffffff 100%);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(ellipse at 30% 20%, rgba(211, 72, 123, 0.06) 0%, transparent 50%),
              radial-gradient(ellipse at 70% 80%, rgba(211, 72, 123, 0.04) 0%, transparent 50%);
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
  margin: 0 auto;
}

.hero-tag {
  display: inline-block;
  padding: var(--space-xs) var(--space-md);
  background: rgba(211, 72, 123, 0.08);
  color: var(--color-primary);
  border-radius: var(--radius-full);
  font-size: 13px;
  font-weight: 600;
  margin-bottom: var(--space-lg);
  letter-spacing: 0.02em;
}

.hero h1 {
  font-size: 52px;
  font-weight: 800;
  line-height: 1.15;
  color: var(--color-text);
  margin-bottom: var(--space-lg);
  letter-spacing: -0.02em;
}

.hero h1 .highlight {
  background: var(--color-primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 18px;
  color: var(--color-text-secondary);
  line-height: 1.8;
  max-width: 600px;
  margin: 0 auto var(--space-xl);
}

.hero-actions {
  display: flex;
  gap: var(--space-md);
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 12px 28px;
  font-size: 15px;
  font-weight: 600;
  border-radius: var(--radius-full);
  border: none;
  cursor: pointer;
  transition: all var(--transition-base);
  line-height: 1.5;
}

.btn-primary {
  background: var(--color-primary-gradient);
  color: #fff;
  box-shadow: 0 4px 15px rgba(211, 72, 123, 0.35);
}

.btn-primary:hover {
  box-shadow: 0 6px 20px rgba(211, 72, 123, 0.45);
  transform: translateY(-1px);
  color: #fff;
}

.btn-outline {
  background: transparent;
  color: var(--color-text);
  border: 2px solid var(--color-border);
}

.btn-outline:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  transform: translateY(-1px);
}

/* Hero visual (replaces old slider image) */
.hero-visual {
  position: relative;
  z-index: 1;
  max-width: 900px;
  margin: var(--space-3xl) auto 0;
}

.hero-visual img {
  width: 100%;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
}

/* --- Section --- */
.section {
  padding: var(--space-4xl) 0;
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.section-label {
  display: inline-block;
  font-size: 13px;
  font-weight: 600;
  color: var(--color-primary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-sm);
}

.section-title {
  font-size: 36px;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.section-subtitle {
  font-size: 16px;
  color: var(--color-text-secondary);
  margin-top: var(--space-sm);
}

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

.card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition-slow);
  display: flex;
  flex-direction: column;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-xl);
  border-color: transparent;
}

.card-image {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 10;
  background: var(--color-bg-tertiary);
}

.card-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-slow);
}

.card:hover .card-image img {
  transform: scale(1.06);
}

.card-image .card-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(to top, rgba(211, 72, 123, 0.15), transparent);
  opacity: 0;
  transition: opacity var(--transition-slow);
}

.card:hover .card-overlay {
  opacity: 1;
}

.card-body {
  padding: var(--space-lg);
  flex: 1;
  display: flex;
  flex-direction: column;
}

.card-title {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-xs);
}

.card-desc {
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* --- Page Header (for sub-pages) --- */
.page-header {
  padding: calc(var(--header-height) + var(--space-3xl)) 0 var(--space-3xl);
  background: var(--color-bg-secondary);
  text-align: center;
}

.page-header .section-title {
  font-size: 32px;
}

/* Breadcrumb */
.breadcrumb {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  font-size: 14px;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

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

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

.breadcrumb .sep {
  color: var(--color-border);
}

.breadcrumb .current {
  color: var(--color-primary);
}

/* --- Category Tabs --- */
.category-tabs {
  display: flex;
  justify-content: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-2xl);
  flex-wrap: wrap;
}

.category-tabs a {
  padding: 8px 20px;
  font-size: 14px;
  font-weight: 500;
  color: var(--color-text-secondary);
  border-radius: var(--radius-full);
  transition: all var(--transition-fast);
  border: 1px solid transparent;
}

.category-tabs a:hover {
  color: var(--color-primary);
  background: rgba(211, 72, 123, 0.06);
}

.category-tabs a.active {
  color: #fff;
  background: var(--color-primary-gradient);
  box-shadow: 0 2px 8px rgba(211, 72, 123, 0.3);
}

/* --- Footer --- */
.site-footer {
  background: var(--color-bg-secondary);
  border-top: 1px solid var(--color-border);
  padding: var(--space-lg) 0;
  text-align: center;
  font-size: 13px;
  color: var(--color-text-muted);
}

.site-footer a {
  color: var(--color-text-secondary);
}

.site-footer a:hover {
  color: var(--color-primary);
}

/* --- Animations --- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.animate {
  opacity: 0;
}

.animate.visible {
  animation: fadeInUp 0.6s ease forwards;
}

/* Animation delays for staggered effects */
.animate-delay-1 { animation-delay: 0.1s; }
.animate-delay-2 { animation-delay: 0.2s; }
.animate-delay-3 { animation-delay: 0.3s; }
.animate-delay-4 { animation-delay: 0.4s; }
.animate-delay-5 { animation-delay: 0.5s; }
.animate-delay-6 { animation-delay: 0.6s; }

/* --- Two Column Layout --- */
.two-col {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: var(--space-2xl);
}

/* Sidebar */
.sidebar {
  position: sticky;
  top: calc(var(--header-height) + var(--space-lg));
  align-self: start;
}

.sidebar-title {
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.sidebar-nav {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.sidebar-nav a {
  padding: var(--space-sm) var(--space-md);
  font-size: 14px;
  color: var(--color-text-secondary);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.sidebar-nav a:hover,
.sidebar-nav a.active {
  background: var(--color-bg-tertiary);
  color: var(--color-primary);
}

/* --- Responsive --- */
@media (max-width: 1024px) {
  .card-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero h1 {
    font-size: 42px;
  }

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

  .sidebar {
    position: static;
  }
}

/* --- SPA Page Transitions --- */
#view {
  min-height: calc(100vh - var(--header-height) - 200px);
}

#view.transitioning {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 150ms ease, transform 150ms ease;
}

#view.entered {
  opacity: 1;
  transform: translateY(0);
  transition: opacity 300ms ease, transform 350ms cubic-bezier(0.22, 0.61, 0.36, 1);
}

/* --- Skeleton Loading --- */
.skeleton {
  padding: var(--space-4xl) 0;
}

.skeleton-block {
  background: linear-gradient(90deg, var(--color-bg-tertiary) 25%, #e8ecf1 50%, var(--color-bg-tertiary) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s ease-in-out infinite;
  border-radius: var(--radius-sm);
  margin-bottom: var(--space-md);
}

.skeleton-block.title {
  height: 32px;
  width: 40%;
  margin-left: auto;
  margin-right: auto;
}

.skeleton-block.line {
  height: 16px;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.skeleton-block.line:last-child {
  width: 70%;
}

@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}

/* --- Detail Content Wrapper (for fetched Typora/VNote pages) --- */
.detail-content {
  color: #333;
  font-size: 15px;
  line-height: 1.8;
  max-width: 900px;
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-lg);
}

.detail-content h1,
.detail-content h2,
.detail-content h3,
.detail-content h4 {
  color: var(--color-text);
  margin-top: 1.5em;
  margin-bottom: 0.6em;
  font-weight: 600;
  line-height: 1.3;
}

.detail-content h1 { font-size: 2rem; }
.detail-content h2 { font-size: 1.6rem; }
.detail-content h3 { font-size: 1.3rem; }

.detail-content p {
  margin: 0.8em 0;
}

.detail-content img {
  max-width: 100%;
  border-radius: var(--radius-md);
  margin: var(--space-md) auto;
}

.detail-content pre {
  background: #1e293b;
  color: #e2e8f0;
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  overflow-x: auto;
  font-size: 13px;
  line-height: 1.6;
  margin: var(--space-md) 0;
}

.detail-content code {
  font-family: var(--font-mono);
  font-size: 0.9em;
}

.detail-content :not(pre) > code {
  background: var(--color-bg-tertiary);
  color: var(--color-primary-dark);
  padding: 2px 6px;
  border-radius: 4px;
}

.detail-content table {
  border-collapse: collapse;
  width: 100%;
  margin: var(--space-md) 0;
  font-size: 14px;
}

.detail-content th,
.detail-content td {
  border: 1px solid var(--color-border);
  padding: var(--space-sm) var(--space-md);
  text-align: left;
}

.detail-content th {
  background: var(--color-bg-secondary);
  font-weight: 600;
}

.detail-content blockquote {
  border-left: 3px solid var(--color-primary);
  padding: var(--space-sm) var(--space-md);
  margin: var(--space-md) 0;
  color: var(--color-text-secondary);
  background: var(--color-bg-secondary);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

.detail-content a {
  color: var(--color-primary);
}

.detail-content ul,
.detail-content ol {
  padding-left: 1.5em;
  margin: 0.5em 0;
}

.detail-content li {
  margin: 0.3em 0;
}

/* Back button for detail pages */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  color: var(--color-text-muted);
  margin-bottom: var(--space-lg);
  transition: color var(--transition-fast);
  cursor: pointer;
}

.back-link:hover {
  color: var(--color-primary);
}

@media (max-width: 768px) {
  :root {
    --header-height: 56px;
    --space-4xl: 64px;
  }

  .menu-toggle {
    display: flex;
  }

  .site-nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: var(--space-md);
    gap: 0;
    height: auto;
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-lg);
  }

  .site-nav.open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .site-nav > li {
    height: auto;
    width: 100%;
  }

  .site-nav > li > a {
    padding: var(--space-md);
    width: 100%;
    justify-content: space-between;
  }

  .site-nav > li > a::after {
    display: none;
  }

  .site-nav .dropdown {
    position: static;
    box-shadow: none;
    border: none;
    padding-left: var(--space-lg);
    opacity: 1;
    visibility: visible;
    transform: none;
    display: none;
  }

  .site-nav > li:hover .dropdown {
    display: block;
    transform: none;
  }

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

  .hero {
    padding-top: calc(var(--header-height) + var(--space-3xl));
    padding-bottom: var(--space-3xl);
  }

  .hero h1 {
    font-size: 32px;
  }

  .hero p {
    font-size: 16px;
  }

  .section-title {
    font-size: 28px;
  }
}