body {
  margin: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: #f4f7fa;
  color: #2c3e50;
}

/* HEADER CON IMAGEN DE FONDO */
header {
  position: relative;
  text-align: center;
  padding: 2rem 1rem;
  color: white;
  overflow: hidden;
  background-color: #00357a;
}

header::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background-image: url('https://infraterra.com.ar/images/liex.JPG');
  background-size: cover;
  background-position: center;
  opacity: 0.25;
  z-index: 0;
}

header > * {
  position: relative;
  z-index: 1;
}

.logo {
  width: 50px;
  margin-bottom: 1rem;
}

.subtitle {
  font-weight: 300;
  font-size: 1.1rem;
}

nav {
  background: #fff;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

nav ul {
  list-style: none;
  display: flex;
  justify-content: center;
  padding: 0;
  margin: 0;
  flex-wrap: wrap;
}

nav li {
  margin: 0.5rem 1rem;
}

nav a {
  text-decoration: none;
  color: #003366;
  font-weight: 500;
  transition: color 0.3s ease;
}

nav a:hover {
  color: #ff9900;
}

main {
  max-width: 1100px;
  margin: 2rem auto;
  padding: 0 1rem;
}

section {
  margin-bottom: 3rem;
}

.grid {
  display: grid;
  gap: 2rem;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

article {
  background: white;
  border-radius: 10px;
  padding: 1.5rem;
  box-shadow: 0 4px 12px rgba(0,0,0,0.05);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

article:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 20px rgba(0,0,0,0.1);
}

h2 {
  color: #003366;
}

h3 {
  color: #00509e;
  margin-bottom: 0.5rem;
}

footer {
  background: #003366;
  color: white;
  text-align: center;
  padding: 1.5rem;
  font-size: 0.95rem;
}

footer a {
  color: white;
  text-decoration: none;
  font-weight: 500;
}