:root {
  --primary-color: #0F2537; /* Deep scientific blue */
  --secondary-color: #F4C10F; /* Sunflower yellow */
  --text-main: #333333;
  --text-light: #666666;
  --bg-light: #F8F9FA;
  --white: #FFFFFF;
  --border-color: #E0E0E0;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

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

body {
  font-family: var(--font-family);
  color: var(--text-main);
  line-height: 1.6;
  background-color: var(--bg-light);
}

a {
  text-decoration: none;
  color: var(--primary-color);
  transition: color 0.3s ease;
}

a:hover {
  color: var(--secondary-color);
}

ul {
  list-style: none;
}

/* Header */
header {
  background-color: var(--white);
  box-shadow: 0 2px 10px rgba(0,0,0,0.05);
  position: sticky;
  top: 0;
  z-index: 1000;
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 80px;
}

.logo a {
  font-size: 24px;
  font-weight: 700;
  color: var(--primary-color);
  display: flex;
  align-items: center;
  gap: 10px;
}

.logo a span {
  color: var(--secondary-color);
}

.nav-links {
  display: flex;
  gap: 30px;
}

.nav-links a {
  font-weight: 500;
  color: var(--text-main);
}

.nav-links a:hover, .nav-links a.active {
  color: var(--secondary-color);
}

.mobile-menu-btn {
  display: none;
  font-size: 24px;
  cursor: pointer;
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, var(--primary-color) 0%, #1a3c59 100%);
  color: var(--white);
  padding: 100px 20px;
  text-align: center;
}

.hero h1 {
  font-size: 48px;
  margin-bottom: 20px;
}

.hero p {
  font-size: 20px;
  max-width: 800px;
  margin: 0 auto 30px;
  opacity: 0.9;
}

.btn {
  display: inline-block;
  padding: 12px 30px;
  border-radius: 4px;
  font-weight: 600;
  transition: all 0.3s ease;
}

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

.btn-primary:hover {
  background-color: #d9ab0d;
  color: var(--primary-color);
}

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

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

/* Main Content */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 60px 20px;
}

.section-title {
  text-align: center;
  font-size: 32px;
  color: var(--primary-color);
  margin-bottom: 40px;
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 3px;
  background-color: var(--secondary-color);
  margin: 15px auto 0;
}

/* Grid Layouts */
.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 30px;
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 40px;
}

.card {
  background: var(--white);
  padding: 30px;
  border-radius: 8px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.05);
  transition: transform 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
}

.card h3 {
  color: var(--primary-color);
  margin-bottom: 15px;
  font-size: 20px;
}

/* Footer */
footer {
  background-color: var(--primary-color);
  color: var(--white);
  padding: 60px 20px 20px;
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 40px;
  margin-bottom: 40px;
}

.footer-col h4 {
  color: var(--secondary-color);
  margin-bottom: 20px;
  font-size: 18px;
}

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

.footer-col ul li a {
  color: #ccc;
}

.footer-col ul li a:hover {
  color: var(--white);
}

.footer-bottom {
  text-align: center;
  padding-top: 20px;
  border-top: 1px solid rgba(255,255,255,0.1);
  color: #888;
  font-size: 14px;
}

/* Responsive */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 80px;
    left: 0;
    width: 100%;
    background: var(--white);
    flex-direction: column;
    padding: 20px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
  }
  
  .nav-links.active {
    display: flex;
  }
  
  .mobile-menu-btn {
    display: block;
  }
  
  .grid-3, .grid-2, .footer-content {
    grid-template-columns: 1fr;
  }
  
  .hero h1 {
    font-size: 32px;
  }
}