/* ============================================
   FreeCourseHub Design System v1.0
   Built on Bootstrap 5 with CSS Custom Properties
   ============================================ */

/* ============================================
   COLORS
   ============================================ */
:root {
  /* Primary Palette - Trustworthy Blue/Teal */
  --color-primary: #0d6efd;
  --color-primary-dark: #0a58ca;
  --color-primary-light: #cfe2ff;
  --color-secondary: #6c757d;
  --color-secondary-light: #e9ecef;
  
  /* Semantic Colors */
  --color-success: #198754;
  --color-warning: #ffc107;
  --color-danger: #dc3545;
  --color-info: #0dcaf0;
  
  /* Neutral Colors */
  --color-bg: #f8f9fa;
  --color-surface: #ffffff;
  --color-border: #dee2e6;
  --color-text: #212529;
  --color-text-muted: #6c757d;
  --color-text-light: #f8f9fa;
  
  /* Course Level Colors */
  --color-level-beginner: #198754;
  --color-level-intermediate: #ffc107;
  --color-level-advanced: #dc3545;
}

/* ============================================
   TYPOGRAPHY
   ============================================ */
:root {
  /* Google Fonts: Inter for clean modern UI, with fallbacks */
  --font-family-base: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  
  /* Font Sizes */
  --font-size-xs: 0.75rem;    /* 12px */
  --font-size-sm: 0.875rem;   /* 14px */
  --font-size-base: 1rem;     /* 16px */
  --font-size-lg: 1.125rem;   /* 18px */
  --font-size-xl: 1.25rem;    /* 20px */
  --font-size-2xl: 1.5rem;    /* 24px */
  --font-size-3xl: 2rem;      /* 32px */
  --font-size-4xl: 2.5rem;    /* 40px */
  
  /* Font Weights */
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  
  /* Line Heights */
  --line-height-tight: 1.25;
  --line-height-normal: 1.5;
  --line-height-loose: 1.75;
}

/* Heading Scale */
h1, .h1 { font-size: var(--font-size-4xl); font-weight: var(--font-weight-bold); line-height: var(--line-height-tight); }
h2, .h2 { font-size: var(--font-size-3xl); font-weight: var(--font-weight-bold); line-height: var(--line-height-tight); }
h3, .h3 { font-size: var(--font-size-2xl); font-weight: var(--font-weight-semibold); line-height: var(--line-height-normal); }
h4, .h4 { font-size: var(--font-size-xl); font-weight: var(--font-weight-semibold); line-height: var(--line-height-normal); }
h5, .h5 { font-size: var(--font-size-lg); font-weight: var(--font-weight-semibold); line-height: var(--line-height-normal); }
h6, .h6 { font-size: var(--font-size-base); font-weight: var(--font-weight-semibold); line-height: var(--line-height-normal); }

/* ============================================
   SPACING SCALE (4px base unit)
   ============================================ */
:root {
  --space-1: 0.25rem;   /* 4px */
  --space-2: 0.5rem;    /* 8px */
  --space-3: 0.75rem;   /* 12px */
  --space-4: 1rem;      /* 16px */
  --space-5: 1.5rem;    /* 24px */
  --space-6: 2rem;      /* 32px */
  --space-7: 3rem;      /* 48px */
  --space-8: 4rem;      /* 64px */
}

/* ============================================
   RADIUS & SHADOW TOKENS
   ============================================ */
:root {
  --radius-sm: 0.25rem;
  --radius-md: 0.375rem;
  --radius-lg: 0.5rem;
  --radius-pill: 50rem;
  
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -1px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -2px rgba(0,0,0,0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1), 0 10px 10px -5px rgba(0,0,0,0.04);
}

/* ============================================
   REUSABLE COMPONENT CLASSES
   ============================================ */

/* Course Cards */
.card-course {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  box-shadow: var(--shadow-sm);
  height: 100%;
}
.card-course:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}
.card-course .card-img-top {
  width: 100%;
  height: 200px;
  object-fit: cover;
}
.card-course .card-body {
  padding: var(--space-4);
}
.card-course .card-title {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-2);
  color: var(--color-text);
}
.card-course .card-text {
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  margin-bottom: var(--space-3);
}
.card-course .course-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
}

/* Level Badges */
.badge-level {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-pill);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.badge-level-beginner {
  background-color: rgba(25, 135, 84, 0.15);
  color: var(--color-level-beginner);
}
.badge-level-intermediate {
  background-color: rgba(255, 193, 7, 0.15);
  color: var(--color-level-intermediate);
}
.badge-level-advanced {
  background-color: rgba(220, 53, 69, 0.15);
  color: var(--color-level-advanced);
}

/* Enroll Button */
.btn-enroll {
  display: inline-block;
  padding: 0.75rem 2rem;
  background: var(--color-primary);
  color: white;
  border: none;
  border-radius: var(--radius-pill);
  font-weight: var(--font-weight-semibold);
  font-size: var(--font-size-lg);
  text-decoration: none;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-md);
}
.btn-enroll:hover {
  background: var(--color-primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  color: white;
  text-decoration: none;
}
.btn-enroll:active {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

/* Stat Badge */
.stat-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.25rem 0.75rem;
  background: var(--color-bg);
  border-radius: var(--radius-pill);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}
.stat-badge i,
.stat-badge svg {
  font-size: 0.875rem;
}

/* Section Heading */
.section-heading {
  margin-bottom: var(--space-5);
}
.section-heading h2 {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-text);
  margin-bottom: var(--space-1);
}
.section-heading .subtitle {
  font-size: var(--font-size-base);
  color: var(--color-text-muted);
}

/* ============================================
   DARK MODE SUPPORT
   ============================================ */
[data-theme="dark"] {
  --color-bg: #1a1a2e;
  --color-surface: #16213e;
  --color-border: #2a2a4a;
  --color-text: #e2e8f0;
  --color-text-muted: #94a3b8;
  --color-text-light: #f8f9fa;
  --color-secondary-light: #2d3748;
  
  /* Adjust component colors for dark mode */
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.4);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.4);
}

/* ============================================
   RESPONSIVE ADJUSTMENTS
   ============================================ */
@media (max-width: 576px) {
  :root {
    --font-size-base: 0.9375rem;
    --font-size-lg: 1rem;
    --font-size-xl: 1.125rem;
    --font-size-2xl: 1.25rem;
    --font-size-3xl: 1.5rem;
    --font-size-4xl: 2rem;
    
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-7: 2rem;
    --space-8: 3rem;
  }
  
  .card-course .card-img-top {
    height: 150px;
  }
  
  .btn-enroll {
    padding: 0.5rem 1.5rem;
    font-size: var(--font-size-base);
  }
}

/* ============================================
   UTILITY HELPERS
   ============================================ */
.text-truncate-2 {
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.text-truncate-3 {
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.gap-1 { gap: var(--space-1); }
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }
.gap-5 { gap: var(--space-5); }