* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Poppins", sans-serif;
}

body {
  background-color: #f5f9fc;
  color: #333;
  line-height: 1.6;
}

header {
  background: #0077b6;
  color: white;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 15px 40px;
  position: sticky;
  top: 0;
  z-index: 100;
}

header h1 {
  font-size: 1.5em;
}

nav a {
  color: white;
  text-decoration: none;
  margin-left: 20px;
  font-weight: 500;
}

nav a:hover {
  text-decoration: underline;
}

.hero {
  background: url('https://upload.wikimedia.org/wikipedia/commons/9/97/The_Earth_seen_from_Apollo_17.jpg') center/cover no-repeat;
  color: white;
  text-align: center;
  padding: 120px 20px;
}

.hero-text {
  background: rgba(0, 0, 0, 0.5);
  display: inline-block;
  padding: 20px 30px;
  border-radius: 10px;
}

.btn {
  display: inline-block;
  margin-top: 15px;
  background: #00b4d8;
  color: white;
  padding: 10px 20px;
  border-radius: 6px;
  text-decoration: none;
  font-weight: 600;
}

.btn:hover {
  background: #0096c7;
}

.content {
  padding: 60px 40px;
  text-align: center;
}

.content.alt {
  background: #caf0f8;
}

.cards {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 20px;
  margin-top: 30px;
}

.card {
  background: white;
  border-radius: 10px;
  box-shadow: 0 3px 8px rgba(0,0,0,0.1);
  padding: 20px;
  width: 250px;
  transition: transform 0.2s;
}

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

footer {
  background: #0077b6;
  color: white;
  text-align: center;
  padding: 20px;
  margin-top: 40px;
}