* {
  box-sizing: border-box;
}

body {
  font-family: Arial, Helvetica, sans-serif;
  background-color: #0A0945;
}

header {
  background-color: #0A0945;
  padding: 30px;
  text-align: center;
  font-size: 35px;
  color: white;
}

section {
  display: -webkit-flex;
  display: flex;
}

nav {
  -webkit-flex: 1;
  -ms-flex: 1;
  flex: 1;
  background: #ccc;
  padding: 20px;
}

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

nav ul ul {
  margin-left: .5em;
}

nav li {
  margin: .5em 0;
}

nav li a {
  display: block;
}

article {
  -webkit-flex: 3;
  -ms-flex: 3;
  flex: 3;
  background-color: #f1f1f1;
  padding: 10px;
}

footer {
  background-color: #0A0945;
  padding: 10px;
  text-align: center;
  color: white;
}

@media (max-width: 600px) {
  section {
    -webkit-flex-direction: column;
    flex-direction: column;
  }
}