*,
*:before,
*:after {
  list-style: none;
}
nav {
  font-size: 20px;
  background-color: #808080;
}
header {
  margin-top: 10vh;
  text-align: center;
  border: #000 1px solid;
}
a {
  color: #fff;
  text-decoration: none;
}
section {
  padding-top: 10vh;
}
section .container {
  height: 70vh;
  border: #000 1px solid;
  border-radius: 10px;
}