body {
  background-color: black;
  color: white;
}

header {
  background-color: #333;
  color: white;
  padding: 20px;
  text-align: center;
}

nav {
  display: flex;
  justify-content: center;
}

nav a {
  text-decoration: none;
  color: white;
  margin: 0 20px;
  font-weight: bold;
}

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

@media screen and (max-width: 768px) {
  header {
    max-width: 100%;
  }

  nav a {
    margin: 10px;
  }

  h1 {
    font-size: 200%;
  }
  img {
    max-width: 100%;
    height: auto;
  }
  p {
    width: 100%;
  }
  table {
    width: 100%;
  }
  iframe {
    max-width: 100%;
    height: auto;
  }
}

@media screen and (min-width: 769px) {
  img {
    max-width: 500px;
  }
  p {
    width: 500px;
  }
  table {
    width: 500px;
  }
}