:root {
  --primary: #1a365d;
  --primary-light: #2a4a7f;
  --accent: #38b2ac;
  --accent-light: #4fd1c5;
  --dark: #1a202c;
  --gray-100: #f7fafc;
  --gray-200: #edf2f7;
  --gray-300: #e2e8f0;
  --gray-600: #718096;
  --gray-800: #2d3748;
  --white: #ffffff;
  --danger: #e53e3e;
  --warning: #dd6b20;
  --success: #38a169;
}

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

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  color: var(--gray-800);
  line-height: 1.6;
  background: var(--white);
}

/* Navigation */
nav {
  background: var(--gray-100);
  padding: 0 2rem;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 4px rgba(0,0,0,0.06);
  border-bottom: 1px solid var(--gray-200);
}

nav .nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

nav .logo {
  color: var(--white);
  font-size: 1.4rem;
  font-weight: 700;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

nav .logo span.accent {
  color: var(--accent-light);
}

nav ul {
  list-style: none;
  display: flex;
  gap: 0.25rem;
}

nav ul li a {
  color: var(--primary);
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: 6px;
  font-size: 0.95rem;
  font-weight: 500;
  transition: all 0.2s;
}

nav ul li a:hover,
nav ul li a.active {
  color: var(--primary);
  background: rgba(26,54,93,0.08);
}

/* Mobile nav */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--primary);
  font-size: 1.5rem;
  cursor: pointer;
}

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 50%, var(--accent) 100%);
  color: var(--white);
  padding: 5rem 2rem;
  text-align: center;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 800;
  margin-bottom: 1rem;
  letter-spacing: -0.02em;
}

.hero p {
  font-size: 1.25rem;
  max-width: 700px;
  margin: 0 auto 2rem;
  opacity: 0.9;
}

.hero .badge {
  display: inline-block;
  background: rgba(255,255,255,0.15);
  border: 1px solid rgba(255,255,255,0.3);
  padding: 0.35rem 1rem;
  border-radius: 50px;
  font-size: 0.85rem;
  margin-bottom: 1.5rem;
}

/* Page hero (smaller, for subpages) */
.page-hero {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
  color: var(--white);
  padding: 3.5rem 2rem;
  text-align: center;
}

.page-hero h1 {
  font-size: 2.4rem;
  font-weight: 800;
  margin-bottom: 0.75rem;
}

.page-hero p {
  font-size: 1.1rem;
  max-width: 650px;
  margin: 0 auto;
  opacity: 0.9;
}

/* Sections */
.section {
  padding: 5rem 2rem;
}

.section.alt {
  background: var(--gray-100);
}

.container {
  max-width: 1200px;
  margin: 0 auto;
}

.section-title {
  text-align: center;
  margin-bottom: 3rem;
}

.section-title h2 {
  font-size: 2rem;
  color: var(--primary);
  margin-bottom: 0.5rem;
}

.section-title p {
  color: var(--gray-600);
  font-size: 1.1rem;
  max-width: 600px;
  margin: 0 auto;
}

/* Cards grid */
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.card {
  background: var(--white);
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 1px 3px rgba(0,0,0,0.08), 0 4px 12px rgba(0,0,0,0.04);
  border: 1px solid var(--gray-200);
  transition: transform 0.2s, box-shadow 0.2s;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.1), 0 8px 24px rgba(0,0,0,0.06);
}

.card .icon {
  width: 48px;
  height: 48px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  margin-bottom: 1rem;
}

.card .icon.blue { background: #ebf4ff; color: var(--primary); }
.card .icon.teal { background: #e6fffa; color: var(--accent); }
.card .icon.orange { background: #fffaf0; color: var(--warning); }
.card .icon.red { background: #fff5f5; color: var(--danger); }
.card .icon.green { background: #f0fff4; color: var(--success); }
.card .icon.purple { background: #faf5ff; color: #805ad5; }

.card h3 {
  font-size: 1.15rem;
  color: var(--dark);
  margin-bottom: 0.5rem;
}

.card p {
  color: var(--gray-600);
  font-size: 0.95rem;
  line-height: 1.6;
}

/* Feature rows (alternating left/right) */
.feature-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: center;
  margin-bottom: 4rem;
}

.feature-row:last-child {
  margin-bottom: 0;
}

.feature-row.reverse .feature-text {
  order: 2;
}

.feature-row.reverse .feature-visual {
  order: 1;
}

.feature-text h3 {
  font-size: 1.6rem;
  color: var(--primary);
  margin-bottom: 0.75rem;
}

.feature-text p {
  color: var(--gray-600);
  margin-bottom: 1rem;
}

.feature-text ul {
  list-style: none;
  padding: 0;
}

.feature-text ul li {
  padding: 0.35rem 0;
  padding-left: 1.5rem;
  position: relative;
  color: var(--gray-600);
}

.feature-text ul li::before {
  content: "\2713";
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: 700;
}

/* Visual panels */
.feature-visual {
  background: var(--gray-100);
  border-radius: 12px;
  padding: 2rem;
  border: 1px solid var(--gray-200);
}

.visual-metric {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.75rem 0;
  border-bottom: 1px solid var(--gray-200);
}

.visual-metric:last-child { border-bottom: none; }

.visual-metric .dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex-shrink: 0;
}

.visual-metric .dot.green { background: var(--success); }
.visual-metric .dot.yellow { background: var(--warning); }
.visual-metric .dot.red { background: var(--danger); }
.visual-metric .dot.blue { background: var(--primary); }

.visual-metric .label {
  flex: 1;
  font-size: 0.9rem;
  color: var(--gray-600);
}

.visual-metric .value {
  font-weight: 700;
  font-size: 0.9rem;
  color: var(--dark);
}

/* Formula block */
.formula-block {
  background: var(--dark);
  color: var(--accent-light);
  padding: 1.5rem;
  border-radius: 8px;
  font-family: 'Courier New', monospace;
  font-size: 0.95rem;
  line-height: 2;
  margin: 1rem 0;
}

.formula-block .comment {
  color: var(--gray-600);
}

/* Stats bar */
.stats-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
  padding: 3rem 2rem;
  background: var(--dark);
  color: var(--white);
}

.stat-item {
  text-align: center;
}

.stat-item .number {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--accent-light);
}

.stat-item .label {
  font-size: 0.9rem;
  opacity: 0.7;
  margin-top: 0.25rem;
}

/* Table styling */
.data-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0;
  font-size: 0.9rem;
}

.data-table th {
  background: var(--primary);
  color: var(--white);
  padding: 0.75rem 1rem;
  text-align: left;
  font-weight: 600;
}

.data-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--gray-200);
}

.data-table tr:nth-child(even) {
  background: var(--gray-100);
}

.data-table .badge-cell {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: 4px;
  font-size: 0.8rem;
  font-weight: 600;
}

.badge-green { background: #c6f6d5; color: #22543d; }
.badge-yellow { background: #fefcbf; color: #744210; }
.badge-red { background: #fed7d7; color: #822727; }
.badge-blue { background: #bee3f8; color: #2a4365; }

/* CTA section */
.cta {
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  color: var(--white);
  text-align: center;
  padding: 4rem 2rem;
}

.cta h2 {
  font-size: 2rem;
  margin-bottom: 1rem;
}

.cta p {
  font-size: 1.1rem;
  opacity: 0.9;
  max-width: 600px;
  margin: 0 auto 2rem;
}

.btn {
  display: inline-block;
  padding: 0.75rem 2rem;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  text-decoration: none;
  transition: all 0.2s;
}

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

.btn-white:hover {
  background: var(--gray-100);
  transform: translateY(-1px);
}

.btn-accent {
  background: var(--accent);
  color: var(--white);
}

.btn-accent:hover {
  background: var(--accent-light);
  transform: translateY(-1px);
}

.btn-outline {
  background: transparent;
  color: var(--white);
  border: 2px solid rgba(255,255,255,0.4);
}

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

.hero-buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* Footer */
footer {
  background: var(--dark);
  color: rgba(255,255,255,0.6);
  padding: 2.5rem 2rem;
  text-align: center;
  font-size: 0.9rem;
}

footer a {
  color: var(--accent-light);
  text-decoration: none;
}

footer .footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

footer .footer-links {
  display: flex;
  gap: 1.5rem;
}

/* Responsive */
@media (max-width: 768px) {
  .nav-toggle { display: block; }

  nav ul {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--gray-100);
    flex-direction: column;
    padding: 1rem;
    gap: 0;
  }

  nav ul.open { display: flex; }

  nav ul li a {
    display: block;
    padding: 0.75rem 1rem;
  }

  .hero h1 { font-size: 2rem; }
  .page-hero h1 { font-size: 1.8rem; }

  .feature-row {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .feature-row.reverse .feature-text,
  .feature-row.reverse .feature-visual {
    order: unset;
  }

  .stats-bar {
    grid-template-columns: repeat(2, 1fr);
    gap: 1.5rem;
  }

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

  footer .footer-inner {
    flex-direction: column;
    gap: 1rem;
  }
}