/**
 * CLASS 12 STUDY MATERIAL - PREMIUM OREO DESIGN SYSTEM
 * Color Palette:
 * Black: #111111
 * Deep Black: #080808
 * White: #FFFFFF
 * Soft Gray: #F5F5F5
 * Light Border: #E5E7EB
 * Muted Text: #6B7280
 */

:root {
  --black: #111111;
  --deep-black: #080808;
  --white: #ffffff;
  --soft-gray: #f5f5f5;
  --soft-gray-alt: #fafafa;
  --light-border: #e5e7eb;
  --dark-border: #111111;
  --muted-text: #6b7280;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-pill: 9999px;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.07);
}

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

html {
  font-family: var(--font-sans);
  background-color: var(--white);
  color: var(--black);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  color: var(--deep-black);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.02em;
}

h1 { font-size: clamp(2rem, 4vw, 3rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2.2rem); }
h3 { font-size: clamp(1.2rem, 2.2vw, 1.5rem); }
p { color: var(--black); font-size: 1rem; }
.text-muted { color: var(--muted-text); }
.text-center { text-align: center; }

a {
  color: inherit;
  text-decoration: none;
  transition: color 0.15s ease;
}

/* Container */
.container {
  width: 100%;
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 20px;
  padding-right: 20px;
}

.container-narrow {
  max-width: 800px;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--light-border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.25rem;
  letter-spacing: -0.03em;
  color: var(--deep-black);
}

.logo-badge {
  background-color: var(--black);
  color: var(--white);
  padding: 4px 8px;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  letter-spacing: 0.05em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
  list-style: none;
}

.nav-link {
  font-size: 0.95rem;
  font-weight: 500;
  color: #4b5563;
  padding: 8px 0;
  position: relative;
}

.nav-link:hover, .nav-link.active {
  color: var(--black);
}

.nav-link.active::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 2px;
  background-color: var(--black);
}

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

.menu-toggle {
  display: none;
  background: none;
  border: 1px solid var(--light-border);
  border-radius: var(--radius-sm);
  padding: 8px;
  cursor: pointer;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 22px;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.15s ease;
  min-height: 44px;
}

.btn-primary {
  background-color: var(--black);
  color: var(--white);
  border-color: var(--black);
}

.btn-primary:hover {
  background-color: var(--deep-black);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.btn-secondary {
  background-color: var(--white);
  color: var(--black);
  border-color: var(--light-border);
}

.btn-secondary:hover {
  background-color: var(--soft-gray);
  border-color: #d1d5db;
}

.btn-outline {
  background-color: transparent;
  color: var(--black);
  border-color: var(--black);
}

.btn-outline:hover {
  background-color: var(--black);
  color: var(--white);
}

.btn-sm {
  padding: 7px 14px;
  font-size: 0.85rem;
  min-height: 36px;
  border-radius: var(--radius-sm);
}

.btn-lg {
  padding: 14px 28px;
  font-size: 1.05rem;
  min-height: 52px;
  border-radius: var(--radius-md);
}

.btn-full {
  width: 100%;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

/* Pills & Badges */
.pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 12px;
  border-radius: var(--radius-pill);
  font-size: 0.8rem;
  font-weight: 600;
  white-space: nowrap;
}

.pill-gray {
  background-color: var(--soft-gray);
  color: var(--black);
  border: 1px solid var(--light-border);
}

.pill-dark {
  background-color: var(--black);
  color: var(--white);
}

.pill-success {
  background-color: #ecfdf5;
  color: #065f46;
  border: 1px solid #a7f3d0;
}

.pill-warning {
  background-color: #fffbeb;
  color: #92400e;
  border: 1px solid #fde68a;
}

/* Cards */
.card {
  background-color: var(--white);
  border: 1px solid var(--light-border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

.card:hover {
  border-color: #cbd5e1;
  box-shadow: var(--shadow-md);
}

.card-gray {
  background-color: var(--soft-gray);
  border-color: var(--light-border);
}

/* Section */
.section {
  padding: 64px 0;
}

.section-gray {
  background-color: var(--soft-gray);
  border-top: 1px solid var(--light-border);
  border-bottom: 1px solid var(--light-border);
}

.section-header {
  margin-bottom: 40px;
}

.section-title {
  margin-bottom: 12px;
}

.section-subtitle {
  color: var(--muted-text);
  font-size: 1.1rem;
  max-width: 680px;
}

/* Grids */
.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

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

.grid-4 {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

/* Hero Section */
.hero {
  padding: 72px 0 64px;
  text-align: center;
}

.hero-pill {
  margin-bottom: 20px;
}

.hero-title {
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  font-weight: 800;
  max-width: 860px;
  margin: 0 auto 20px;
  letter-spacing: -0.03em;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--muted-text);
  max-width: 680px;
  margin: 0 auto 36px;
  line-height: 1.6;
}

.hero-ctas {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 48px;
}

.feature-strip {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 32px;
  flex-wrap: wrap;
  padding: 24px;
  background-color: var(--soft-gray);
  border: 1px solid var(--light-border);
  border-radius: var(--radius-lg);
  max-width: 960px;
  margin: 0 auto;
}

.feature-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--deep-black);
}

/* Forms */
.form-group {
  margin-bottom: 20px;
}

.form-label {
  display: block;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--black);
  margin-bottom: 6px;
}

.form-input, .form-select, .form-textarea {
  width: 100%;
  padding: 11px 14px;
  font-size: 0.95rem;
  font-family: inherit;
  color: var(--black);
  background-color: var(--white);
  border: 1px solid var(--light-border);
  border-radius: var(--radius-md);
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
  min-height: 44px;
}

.form-textarea {
  min-height: 120px;
  resize: vertical;
}

.form-input:focus, .form-select:focus, .form-textarea:focus {
  border-color: var(--black);
  box-shadow: 0 0 0 3px rgba(17, 17, 17, 0.08);
}

.form-hint {
  font-size: 0.8rem;
  color: var(--muted-text);
  margin-top: 4px;
}

/* Tables */
.table-responsive {
  width: 100%;
  overflow-x: auto;
}

.oreo-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
}

.oreo-table th {
  padding: 12px 16px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--muted-text);
  text-transform: uppercase;
  letter-spacing: 0.03em;
  border-bottom: 1px solid var(--light-border);
  background-color: var(--soft-gray);
}

.oreo-table td {
  padding: 16px;
  font-size: 0.95rem;
  border-bottom: 1px solid var(--light-border);
  vertical-align: middle;
}

.oreo-table tr:hover td {
  background-color: var(--soft-gray-alt);
}

/* Price Box */
.price-display {
  display: flex;
  align-items: baseline;
  gap: 6px;
  margin: 16px 0;
}

.price-currency {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--deep-black);
}

.price-number {
  font-size: 3rem;
  font-weight: 800;
  line-height: 1;
  color: var(--deep-black);
}

.price-period {
  font-size: 0.9rem;
  color: var(--muted-text);
}

/* Check list */
.checklist {
  list-style: none;
  margin: 20px 0;
}

.checklist-item {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  margin-bottom: 12px;
  font-size: 0.95rem;
}

.check-icon {
  width: 18px;
  height: 18px;
  background-color: var(--black);
  color: var(--white);
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 11px;
  font-weight: bold;
  flex-shrink: 0;
  margin-top: 2px;
}

/* Footer */
.site-footer {
  background-color: var(--soft-gray);
  border-top: 1px solid var(--light-border);
  padding: 60px 0 28px;
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 48px;
}

.footer-col h4 {
  font-size: 0.95rem;
  margin-bottom: 18px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: 10px;
}

.footer-links a {
  color: var(--muted-text);
  font-size: 0.9rem;
}

.footer-links a:hover {
  color: var(--black);
}

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid var(--light-border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.85rem;
  color: var(--muted-text);
}

/* Toast Notifications */
.toast-container {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 100;
  display: flex;
  flex-direction: column;
  gap: 10px;
  max-width: 380px;
}

.toast {
  background-color: var(--deep-black);
  color: var(--white);
  padding: 14px 18px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  gap: 12px;
  animation: toastIn 0.2s ease-out;
}

.toast-error {
  background-color: #991b1b;
}

.toast-success {
  background-color: #065f46;
}

@keyframes toastIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Maintenance Banner */
.maintenance-banner {
  background-color: var(--black);
  color: var(--white);
  text-align: center;
  padding: 10px 20px;
  font-size: 0.9rem;
  font-weight: 500;
}

/* Mobile Responsive */
@media (max-width: 900px) {
  .grid-3 { grid-template-columns: 1fr; }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .nav-links { display: none; }
  .menu-toggle { display: block; }
  .feature-strip { gap: 16px; }
}

@media (max-width: 640px) {
  .grid-2 { grid-template-columns: 1fr; }
  .grid-4 { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .footer-bottom { flex-direction: column; gap: 12px; text-align: center; }
  .hero-ctas { flex-direction: column; width: 100%; }
  .hero-ctas .btn { width: 100%; }
}