body {
  background-color: #ffffff;
  color: #000000;
  font-family: Arial, Helvetica, sans-serif;
  margin: 10px;
}

h1 {
  text-align: center;
}

nav {
  text-align: center;
  margin-bottom: 15px;
  padding-bottom: 10px;
  border-bottom: 1px solid #cccccc;
}

main {
  max-width: 900px;
  margin: 0 auto;
  padding-bottom: 10px;
}

footer {
  text-align: center;
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid #cccccc;
}

figure {
  margin: 20px auto;
  max-width: 600px;
}

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

figcaption {
  text-align: center;
}

iframe {
  display: block;
  margin: 20px auto;
}