* {
    padding: 0;
    margin: 5px;
    text-align: center;
  }
  body {
    background-color:white;
  }
  .calculator {
    width: 350px;
    height: 420px;
    background-color: #c0c0c0;
    border: 4px solid black;
    border-radius: 7px;
  }
  #display {
    width: 400px;
    height: 60px;
    text-align: right;
    background-color: black;
    border: 3px solid white;
    font-size: 30px;
    left: 2px;
    top: 2px;
    color: white;
  }
  .btnTop{
    color: white;
    background-color: grey;
    font-size: 14px;
    margin: auto;
    width: 50px;
    height: 25px;
  }
  .btnNum {
    color: white;
    background-color: black;
    font-size: 16px;
    margin: auto;
    width: 55px;
    height: 25px;
  }
  .btnMath {
    color: white;
    background-color: green;
    font-size: 16px;
    margin: auto;
    width: 55px;
    height: 25px;
  }
  .btnOpps {
    color: white;
    background-color: navy;
    font-size: 16px;
    margin: auto;
    width: 55px;
    height: 25px;
  }
  footer {
    text-align: center;
    padding: 3px;
    background-color: DarkSalmon;
    color: white;
  }