/****************************************/

@media screen and (min-width: 481px) and (max-width: 768px) {
  nav {
    width: 100%;
  }

  nav a {
    background-color: blue;
  }
}

/****************************************/

@media screen and (max-width: 480px) {
  nav {
    width: 100%;
  }

  nav a {
    font-size: small;
    background-color: blue;
  }
}