.calculator {
    width: 50%;
    margin: 0 auto;
    margin-top: 30px;
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-auto-rows: minmax(50px, auto);
    height: 90%;

  }

  #screen {
    grid-column: 1/5;
    background-color: #333;
    color: white;
    border: 1px solid green;
    font-size: larger;
    text-align: right;
    padding: 10px;
  }

  .zero {
    grid-column: 1/3;
  }

  .btn {
    background: #eeeeee;
    border: 1px solid black;
    cursor: pointer;
    text-align: center;
    font-size: large;

  }

  .btn:hover{background-color: white;}

  #operator {
    background-color: lightblue;
    color: white;

  }

  #ac {
    background-color: rgb(240, 192, 192);
  }

  #ac:hover {
    background-color: rgb(230, 195, 195);
  }

  footer {
    text-align: center;
    color: lightblue;
    margin: 20px;
  }

  @media screen and (max-width: 1024px) {
    .calculator{width: 75%;}
  }