body {
    font-family: Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f0f0f0;
    margin: 0;
  }
  
  .calculator {
    background-color: white;
    border-radius: 10px;
    box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.1);
    padding: 20px;
    width: 250px;
  }
  
  .display {
    background-color: #222;
    color: white;
    font-size: 2em;
    text-align: right;
    padding: 10px;
    border-radius: 5px;
    margin-bottom: 10px;
  }
  
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
  }
  
  button {
    padding: 20px;
    font-size: 1.5em;
    background-color: #eee;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s ease;
  }
  
  button:hover {
    background-color: #ddd;
  }
  
  button.operator {
    background-color: #ff9800;
    color: white;
  }
  
  button.operator:hover {
    background-color: #f57c00;
  }
  
  button:active {
    transform: scale(0.98);
  }