body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background: #f5f5f5;
  color: #333;
}
header {
  background: #009688;
  color: white;
  padding: 1em;
  text-align: center;
}
nav a {
  color: white;
  margin: 0 10px;
  text-decoration: underline;
}
main {
  padding: 20px;
}
img {
  max-width: 100%;
  height: auto;
}
section {
  margin-bottom: 30px;
}