body {
  width: 100%;
  display: flex;
  flex-direction: column;
  margin: auto;
  background-color: #65C6D6;
  color: white;
  font-family: sans-serif;
}
.header{
  background-repeat: no-repeat;
  background-position: center top;
  background-size: cover;
}
@media (max-width:400px) {
  .header{
    width: 100%;
    background-image: url(assets/400x225.jpg);
    height: 225px;
  }
}
@media (min-width:401px) {
  .header{
    width: 400px;
    background-image: url(assets/400x225.jpg);
    height: 225px;
  }
  body {
     width: 400px;
  }
}
@media (min-width:701px){
  .header{
    background-image: url(assets/700x393.jpg);
    height: 393px;
    width: 700px;
  }
  body {
    width: 700px;
  }    
}
@media (min-width:1101px){
  .header{
    background-image: url(assets/1100x618.jpg);
    width: 1100px;
    height: 618px;
  }
  body {
    width: 1100px;
  }
}

.content  {
  flex-grow: 1;
}
a, a:visited, a:hover, a:active {
  color:white;
  font-weight: bold;
  text-decoration: underline;
}
.toc {
 white-space:pre-wrap;
}