@media screen {
  a {
    color: black;
    height: 8px;
  }
}
a {
  color: red;
}
@media screen {
  a {
    color: blue;
    height: 10px;
  }
}

a {
  color: beige;
}
a b {
  color: teal;
}
@media screen {
  a b {
    color: orange;
  }
  a b c {
    height: 12px;
  }
}