.calculator {
    width: 300px;
    margin: 50px auto;
    text-align: center;
  }
  
  #display {
    width: 100%;
    height: 50px;
    margin-bottom: 20px;
    font-size: 24px;
    text-align: right;
    padding: 5px;
  }
  
  button {
    width: 50px;
    height: 50px;
    font-size: 24px;
    margin: 5px;
    border: none;
    border-radius: 5px;
    background-color: #eee;
    cursor: pointer;
  }
  
  button:hover {
    background-color: #ddd;
  }
  
  button.operator {
    background-color: #f88;
    color: #fff;
  }