:root {
  --primary: #00BA83;
  --primary-hover: #009E6F;
  --primary-subtle: #E8F8F3;
  --accent: #0586FE;
  --bg-page: #FBFDFD;
  --card-bg: #FFFFFF;
  --border-color: #E2E8F0;
  --border-hover: #CBD5E1;
  --text-main: #0F172A;
  --text-muted: #64748B;
  --text-subtle: #94A3B8;
  --header-height: 56px;
  --mobile-header-height: 44px;
  --mobile-bottom-nav: 54px;
  --radius-lg: 16px;
  --radius-md: 12px;
  --radius-sm: 8px;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.08);
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-page);
  color: var(--text-main);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  padding-bottom: 40px;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-link {
  display: flex;
  align-items: center;
  text-decoration: none;
  height: 28px;
}

.logo-img {
  height: 26px;
  width: auto;
  display: block;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.header-badge {
  font-size: 12px;
  font-weight: 600;
  color: var(--primary);
  background: var(--primary-subtle);
  padding: 4px 10px;
  border-radius: 999px;
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.search-input-wrap {
  position: relative;
  display: flex;
  align-items: center;
}

.search-input {
  background: #F1F5F9;
  border: 1px solid transparent;
  padding: 7px 12px 7px 32px;
  border-radius: 20px;
  font-size: 13px;
  width: 180px;
  transition: all 0.2s ease;
  color: var(--text-main);
}

.search-input:focus {
  outline: none;
  background: #FFFFFF;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(0, 186, 131, 0.15);
  width: 240px;
}

.search-icon {
  position: absolute;
  left: 10px;
  width: 14px;
  height: 14px;
  fill: var(--text-muted);
  pointer-events: none;
}

/* Background Atmosphere */
.hero-glow {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 100%;
  max-width: 1200px;
  height: 380px;
  background: radial-gradient(ellipse 65% 55% at 50% 0%, rgba(0, 186, 131, 0.12), rgba(5, 134, 254, 0.06), transparent 70%);
  pointer-events: none;
  z-index: 0;
}

/* Hero Section */
.hero-section {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: 36px 16px 24px;
  max-width: 800px;
  margin: 0 auto;
}

.hero-tag {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: #0E7490;
  background: #E0F2FE;
  padding: 4px 12px;
  border-radius: 999px;
  margin-bottom: 12px;
}

.hero-title {
  font-size: 28px;
  font-weight: 800;
  line-height: 1.25;
  color: var(--text-main);
  letter-spacing: -0.02em;
  margin-bottom: 8px;
}

.hero-subtitle {
  font-size: 14px;
  color: var(--text-muted);
  line-height: 1.5;
}

/* Course Grid */
.container {
  max-width: 1140px;
  margin: 0 auto;
  padding: 0 16px;
  position: relative;
  z-index: 1;
}

.courses-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
  margin-top: 16px;
}

/* Course Card */
.course-card {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  position: relative;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow-sm);
}

.course-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--border-hover);
}

.card-badge {
  position: absolute;
  top: 10px;
  right: 10px;
  background: linear-gradient(135deg, #6366F1, #8B5CF6);
  color: #FFFFFF;
  font-size: 11px;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 999px;
  z-index: 2;
  box-shadow: 0 2px 6px rgba(99, 102, 241, 0.4);
}

.card-image-wrap {
  width: 100%;
  aspect-ratio: 260 / 175;
  background: #F8FAFC;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  border-bottom: 1px solid #F1F5F9;
}

.card-image {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
  transition: transform 0.3s ease;
}

.course-card:hover .card-image {
  transform: scale(1.02);
}

.card-body {
  padding: 14px;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
  justify-content: space-between;
}

.card-title {
  font-size: 14px;
  font-weight: 700;
  line-height: 1.35;
  color: var(--text-main);
  margin-bottom: 8px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid #F1F5F9;
  font-size: 12px;
  color: var(--text-muted);
}

.card-chapters {
  font-size: 12px;
  font-weight: 600;
  color: var(--text-muted);
}

.card-arrow {
  color: var(--primary);
  font-size: 14px;
  font-weight: 700;
  transition: transform 0.2s ease;
}

.course-card:hover .card-arrow {
  transform: translateX(4px);
}

/* Feature Row */
.features-strip {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 28px;
  margin-top: 36px;
  padding: 14px 20px;
  background: #FFFFFF;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  max-width: 640px;
  margin-left: auto;
  margin-right: auto;
}

.feature-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-muted);
}

.feature-icon {
  width: 18px;
  height: 18px;
  color: var(--primary);
}

/* Mobile Bottom Navigation */
.mobile-bottom-nav {
  display: none;
}

/* Mobile Ergonomics <= 600px */
@media (max-width: 600px) {
  :root {
    --header-height: var(--mobile-header-height);
  }

  body {
    padding-bottom: calc(var(--mobile-bottom-nav) + 20px);
  }

  .site-header {
    height: var(--mobile-header-height);
    padding: 0 12px;
  }

  .logo-img {
    height: 22px;
  }

  .search-input {
    width: 130px;
    font-size: 12px;
    padding: 5px 10px 5px 28px;
  }

  .search-input:focus {
    width: 160px;
  }

  .hero-section {
    padding: 20px 12px 14px;
  }

  .hero-title {
    font-size: 20px;
  }

  .hero-subtitle {
    font-size: 13px;
  }

  /* Exact 2-Column Grid as in User's Mobile Screenshot */
  .courses-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
    margin-top: 10px;
  }

  .card-body {
    padding: 10px;
  }

  .card-title {
    font-size: 13px;
    margin-bottom: 4px;
  }

  .card-meta {
    margin-top: 6px;
    padding-top: 6px;
    font-size: 11px;
  }

  .btn-read {
    padding: 4px 8px;
    font-size: 11px;
  }

  .features-strip {
    flex-direction: column;
    gap: 8px;
    align-items: flex-start;
    padding: 12px 14px;
    margin-top: 20px;
  }

  /* Native Mobile Bottom Navigation */
  .mobile-bottom-nav {
    display: flex;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    height: var(--mobile-bottom-nav);
    background: rgba(255, 255, 255, 0.96);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-top: 1px solid var(--border-color);
    z-index: 100;
    align-items: center;
    justify-content: space-around;
  }

  .nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-width: 48px;
    min-height: 48px;
    text-decoration: none;
    color: var(--text-muted);
    font-size: 10px;
    font-weight: 600;
    gap: 3px;
  }

  .nav-item.active {
    color: var(--primary);
  }

  .nav-item svg {
    width: 20px;
    height: 20px;
  }
}

/* Tablet 601px - 1024px */
@media (min-width: 601px) and (max-width: 1024px) {
  .courses-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
  }
}