/* ========================================
   OSLING - Institutional Knowledge Portal
   Design System & Global Styles
   ======================================== */

/* ========================================
   1. ROOT & CSS VARIABLES
   ======================================== */
:root {
  /* Primary Colors */
  --primary: #2F4F4F; /* Deep Slate Gray */
  --secondary: #36454F; /* Charcoal */
  
  /* Accent Colors */
  --accent-teal: #4CAF50; /* Muted Teal */
  --accent-beige: #E0CCA8; /* Warm Beige */
  --accent-gold: #C8AE71; /* Soft Gold */
  
  /* Neutrals */
  --bg-light: #F5F5DC; /* Creamy Beige */
  --neutral-grey: #D3D3D3; /* Light Grey */
  --text-dark: #1A1A1A; /* Near Black */
  --text-grey: #4A4A4A; /* Medium Grey */
  
  /* Typography */
  --font-sans: 'Open Sans', 'Lato', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-serif: 'Merriweather', 'Georgia', serif;
  
  /* Spacing Scale */
  --spacing-xs: 8px;
  --spacing-sm: 16px;
  --spacing-md: 24px;
  --spacing-lg: 48px;
  --spacing-xl: 80px;
  --spacing-2xl: 120px;
  
  /* Container */
  --container-width: 1200px;
  --container-lg: 1400px;
  
  /* Transitions */
  --transition: all 0.3s ease;
  --transition-slow: all 0.4s ease;
}

/* ========================================
   2. RESET & BASE STYLES
   ======================================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-serif);
  color: var(--text-dark);
  background-color: #FFFFFF;
  line-height: 1.6;
  font-size: 16px;
}

/* ========================================
   3. TYPOGRAPHY
   ======================================== */
h1 {
  font-family: var(--font-sans);
  font-size: 3.5rem;
  font-weight: 700;
  line-height: 1.2;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: -1px;
  margin-bottom: var(--spacing-md);
}

h2 {
  font-family: var(--font-sans);
  font-size: 2.5rem;
  font-weight: 700;
  line-height: 1.3;
  color: var(--primary);
  text-transform: uppercase;
  margin-bottom: var(--spacing-md);
  margin-top: var(--spacing-xl);
}

h3 {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--secondary);
  margin-bottom: var(--spacing-sm);
  margin-top: var(--spacing-lg);
}

p {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--text-dark);
  margin-bottom: var(--spacing-md);
  letter-spacing: 0.3px;
}

a {
  color: var(--accent-teal);
  text-decoration: none;
  border-bottom: 2px solid transparent;
  transition: var(--transition);
}

a:hover {
  border-bottom-color: var(--accent-teal);
  color: var(--secondary);
}

/* Lists */
ul, ol {
  margin-left: var(--spacing-lg);
  margin-bottom: var(--spacing-md);
}

li {
  margin-bottom: var(--spacing-sm);
  line-height: 1.8;
}

/* Code & Blockquotes */
blockquote {
  border-left: 4px solid var(--accent-beige);
  padding-left: var(--spacing-lg);
  margin: var(--spacing-lg) 0;
  font-style: italic;
  color: var(--text-grey);
}

/* ========================================
   4. HEADER & NAVIGATION
   ======================================== */
header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background-color: rgba(255, 255, 255, 0.98);
  backdrop-filter: blur(10px);
  z-index: 1000;
  border-bottom: 1px solid var(--neutral-grey);
  box-shadow: 0 2px 8px rgba(47, 79, 79, 0.05);
}

.header-content {
  max-width: var(--container-lg);
  margin: 0 auto;
  padding: var(--spacing-sm) var(--spacing-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-family: var(--font-sans);
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 2px;
  transition: var(--transition);
}

.logo:hover {
  color: var(--accent-teal);
}

nav ul {
  list-style: none;
  display: flex;
  gap: var(--spacing-lg);
  margin: 0;
}

nav a {
  font-family: var(--font-sans);
  font-size: 0.9rem;
  text-transform: uppercase;
  color: var(--text-dark);
  font-weight: 500;
  letter-spacing: 0.5px;
  position: relative;
  transition: var(--transition);
}

nav a::after {
  content: '';
  position: absolute;
  bottom: -5px;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--accent-teal);
  transition: width 0.3s ease;
}

nav a:hover::after {
  width: 100%;
}

nav a.active {
  color: var(--accent-teal);
  font-weight: 700;
}

/* ========================================
   5. FOOTER
   ======================================== */
footer {
  background-color: var(--primary);
  color: var(--bg-light);
  padding: var(--spacing-2xl) var(--spacing-lg);
  margin-top: var(--spacing-2xl);
}

.footer-content {
  max-width: var(--container-lg);
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.footer-section h3 {
  color: var(--accent-beige);
  margin-bottom: var(--spacing-md);
  font-size: 1.2rem;
}

.footer-section p {
  color: var(--bg-light);
  font-size: 0.95rem;
  line-height: 1.8;
}

.footer-section a {
  color: var(--accent-gold);
  border-bottom: 2px solid transparent;
  transition: var(--transition);
}

.footer-section a:hover {
  border-bottom-color: var(--accent-gold);
}

.footer-bottom {
  max-width: var(--container-lg);
  margin: 0 auto;
  padding-top: var(--spacing-lg);
  border-top: 1px solid rgba(224, 204, 168, 0.3);
  text-align: center;
  color: var(--bg-light);
  font-size: 0.9rem;
}

/* ========================================
   6. MAIN LAYOUT & CONTAINER
   ======================================== */
main {
  padding-top: 120px;
  min-height: 100vh;
}

.container {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

.container-lg {
  max-width: var(--container-lg);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

/* ========================================
   7. HERO SECTION
   ======================================== */
.hero {
  background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
  color: var(--bg-light);
  padding: var(--spacing-2xl) var(--spacing-lg);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-image: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.05'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 900px;
  margin: 0 auto;
}

.hero h1 {
  color: var(--bg-light);
  font-size: 3.5rem;
  margin-bottom: var(--spacing-md);
}

.hero p {
  color: var(--accent-beige);
  font-size: 1.3rem;
  line-height: 1.8;
}

/* ========================================
   8. SECTION STYLES
   ======================================== */
section {
  padding: var(--spacing-2xl) var(--spacing-lg);
  position: relative;
}

.section-title {
  text-align: center;
  margin-bottom: var(--spacing-xl);
}

.section-title h2 {
  margin-top: 0;
}

/* Alternating Sections */
.section-dark {
  background-color: var(--bg-light);
  border-top: 1px solid var(--neutral-grey);
  border-bottom: 1px solid var(--neutral-grey);
}

/* ========================================
   9. TWO-COLUMN LAYOUT
   ======================================== */
.two-column {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-xl);
  align-items: center;
  max-width: var(--container-lg);
  margin: 0 auto;
}

.two-column.reverse {
  direction: rtl;
}

.two-column.reverse > * {
  direction: ltr;
}

.two-column-text {
  padding: var(--spacing-lg);
}

.two-column-image {
  position: relative;
  overflow: hidden;
  border-radius: 2px;
  box-shadow: 0 8px 24px rgba(47, 79, 79, 0.15);
}

.two-column-image img {
  width: 100%;
  height: auto;
  display: block;
  transition: var(--transition-slow);
}

.two-column-image:hover img {
  transform: scale(1.02);
}

/* ========================================
   10. CARD GRID
   ======================================== */
.card-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-lg);
  max-width: var(--container-lg);
  margin: 0 auto;
}

.card {
  background-color: #FFFFFF;
  border: 1px solid var(--neutral-grey);
  padding: var(--spacing-lg);
  border-radius: 2px;
  box-shadow: 0 4px 12px rgba(47, 79, 79, 0.08);
  transition: var(--transition);
}

.card:hover {
  box-shadow: 0 8px 24px rgba(47, 79, 79, 0.15);
  border-color: var(--accent-teal);
  transform: translateY(-2px);
}

.card h3 {
  color: var(--secondary);
  margin-top: 0;
}

.card p {
  color: var(--text-grey);
}

/* ========================================
   11. BUTTONS
   ======================================== */
.btn {
  display: inline-block;
  padding: var(--spacing-sm) var(--spacing-lg);
  background-color: var(--primary);
  color: var(--bg-light);
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  border: 2px solid var(--primary);
  border-radius: 2px;
  cursor: pointer;
  transition: var(--transition-slow);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.btn:hover {
  background-color: var(--accent-teal);
  border-color: var(--accent-teal);
  transform: scale(1.02);
}

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

.btn-secondary:hover {
  background-color: var(--primary);
  color: var(--bg-light);
}

/* ========================================
   12. FORMS
   ======================================== */
.form-group {
  margin-bottom: var(--spacing-lg);
}

label {
  display: block;
  font-family: var(--font-sans);
  font-weight: 600;
  color: var(--text-dark);
  margin-bottom: var(--spacing-sm);
  text-transform: uppercase;
  font-size: 0.9rem;
  letter-spacing: 0.5px;
}

input[type="text"],
input[type="email"],
input[type="tel"],
input[type="date"],
textarea,
select {
  width: 100%;
  padding: var(--spacing-md);
  border: 1px solid var(--neutral-grey);
  border-radius: 2px;
  font-family: var(--font-serif);
  font-size: 1rem;
  background-color: #FFFFFF;
  color: var(--text-dark);
  transition: var(--transition);
}

input[type="text"]:focus,
input[type="email"]:focus,
input[type="tel"]:focus,
input[type="date"]:focus,
textarea:focus,
select:focus {
  outline: none;
  border-color: var(--accent-teal);
  box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.1);
}

textarea {
  resize: vertical;
  min-height: 150px;
}

/* ========================================
   13. ACCORDION
   ======================================== */
.accordion {
  border: 1px solid var(--neutral-grey);
  margin-bottom: var(--spacing-lg);
}

.accordion-item {
  border-bottom: 1px solid var(--neutral-grey);
}

.accordion-item:last-child {
  border-bottom: none;
}

.accordion-header {
  background-color: var(--bg-light);
  padding: var(--spacing-md) var(--spacing-lg);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-sans);
  font-weight: 600;
  color: var(--primary);
  transition: var(--transition);
  user-select: none;
}

.accordion-header:hover {
  background-color: #EFEFD0;
}

.accordion-header.active {
  background-color: var(--accent-beige);
  color: var(--secondary);
}

.accordion-toggle {
  width: 24px;
  height: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}

.accordion-header.active .accordion-toggle {
  transform: rotate(180deg);
}

.accordion-content {
  display: none;
  padding: var(--spacing-lg);
  background-color: #FFFFFF;
  color: var(--text-dark);
  line-height: 1.8;
}

.accordion-content.active {
  display: block;
}

/* ========================================
   14. IMAGES & MEDIA
   ======================================== */
img {
  max-width: 100%;
  height: auto;
  display: block;
}

/* Full-width Section Images */
.section-image {
  width: 100%;
  height: 500px;
  object-fit: cover;
  display: block;
  margin: var(--spacing-xl) 0;
  box-shadow: 0 8px 24px rgba(47, 79, 79, 0.15);
}

/* ========================================
   15. UTILITY CLASSES
   ======================================== */
.text-center {
  text-align: center;
}

.text-left {
  text-align: left;
}

.text-right {
  text-align: right;
}

.mt-lg {
  margin-top: var(--spacing-xl);
}

.mb-lg {
  margin-bottom: var(--spacing-xl);
}

.py-lg {
  padding-top: var(--spacing-xl);
  padding-bottom: var(--spacing-xl);
}

.highlight {
  background-color: var(--accent-beige);
  padding: 2px 6px;
  border-radius: 2px;
}

.icon-list li::before {
  content: '✓ ';
  color: var(--accent-teal);
  font-weight: bold;
  margin-right: 8px;
}

/* ========================================
   16. RESPONSIVE DESIGN
   ======================================== */
@media (max-width: 768px) {
  h1 {
    font-size: 2.5rem;
  }
  
  h2 {
    font-size: 1.8rem;
  }
  
  h3 {
    font-size: 1.3rem;
  }
  
  .header-content {
    flex-wrap: wrap;
    gap: var(--spacing-md);
  }
  
  nav ul {
    flex-direction: column;
    gap: var(--spacing-sm);
    width: 100%;
  }
  
  .two-column {
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }
  
  .two-column.reverse {
    direction: ltr;
  }
  
  .card-grid {
    grid-template-columns: 1fr;
  }
  
  .footer-content {
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }
  
  .section-image {
    height: 300px;
  }
  
  main {
    padding-top: 180px;
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 1.8rem;
  }
  
  h2 {
    font-size: 1.4rem;
  }
  
  p {
    font-size: 0.95rem;
  }
  
  .hero {
    padding: var(--spacing-lg);
  }
  
  .container,
  .container-lg {
    padding: 0 var(--spacing-md);
  }
  
  .btn {
    width: 100%;
    justify-content: center;
  }
}