body {
    font-family: 'Arial', sans-serif;
    text-align: center;
    margin: 50px;
  }
  
  #calculator {
    width: 340px;
    margin: 0 auto;
    border: 2px solid #ccc;
    border-radius: 8px;
    overflow: hidden;
  }
  
  input {
    width: 100%;
    height: 60px;
    font-size: 24px;
    border: none;
    padding: 0 10px;
    box-sizing: border-box;
  }
  
  button {
    width: 80px;
    height: 60px;
    font-size: 18px;
    border: none;
    cursor: pointer;
    background-color: #f1f1f1;
  }
  
  button.operator {
    background-color: #ff8c00;
    color: #fff;
  }
  
  button.double {
    width: 80px;
  }
  
  button.equal {
    background-color: #4caf50;
    color: #fff;
  }