body {
  font-family: Arial, sans-serif;
}

header {
  background-color: #8bc34a;
  color: #fff;
  padding: 20px;
}

nav {
  float: right;
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

nav li {
  display: inline-block;
  margin-left: 20px;
}

nav a {
  color: #fff;
  text-decoration: none;
}

main {
  max-width: 800px;
  margin: 0 auto 200px 0;
}

section img {
  max-width: 100%;
  height: auto;
}

footer {
  position: fixed;
  bottom: 0;
  width: 100%;
  height: auto;
  margin-top: 40px;
  background: #8bc34a;
  text-align: center;
}