body{
    font-family: Atial, sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
}
header{
    background: #333;
    color: #fff;
    padding: 10px 0;
    text-align: center;
}
nav ul{
    list-style: none;
    padding: 0;
}
nav ul li{
    display: inline;
    margin: 0 15px;
}
nav ul li a{
    color: #fff;
    text-decoration: none;
}
main{
    padding: 20px;
}
section{
    margin-bottom: 20px;
}
footer{
    text-align: center;
    padding: 10px 0;
    background: #333;
    color: #fff;
}
@media (max-width: 600px){
  nav ul li {
    display: block;
    margin: 10px 0;
  }
}