* {
    padding: 0;
    margin: 5px;
    text-align: center;
  }
  body {
    background-color:rgb(149, 149, 223);
  }
  .calculator {
    width: 850px;
    height: 520px;
    background-color: #c0c0c0;
    box-shadow: 0px 0px 0px 10px #666;
    border: 5px solid black;
    border-radius: 10px;
    position: fixed;


  }
  #display {
    width: 320px;
    height: 40px;
    text-align: right;
    background-color: black;
    border: 3px solid white;
    font-size: 18px;
    left: 52px;
    top: 12px;
    color: #7fff00;
  }
  .btnTop{
    color: white;
    background-color: #6f6f6f;
    font-size: 14px;
    margin: auto;
    width: 70px;
    height: 45px;
  }
  .btnNum {
    color: white;
    background-color: black;
    font-size: 14px;
    margin: auto;
    width: 70px;
    height: 45px;
  }
  .btnMath {
    color: white;
    background-color: #e60e2f;
    font-size: 14px;
    margin: auto;
    width: 70px;
    height: 45px;
  }
  .btnOpps {
    color: white;
    background-color: #0a4e69;
    font-size: 14px;
    margin: auto;
    width: 70px;
    height: 45px;
  }
  .copy_right_footer {
    position: fixed;
    color: #f5f5f5;
    bottom: 0;
    width: 100%;
    background-color: #6c757d;
    line-height: 2;
    text-align: center;
 }
 .heading_div
  {
    float: none ; 
    background: white ; 
    padding: 10px; 
    border-radius: 20px; 
    color: black;
    box-shadow:5px 5px 5px grey;
  }