body {
    font-family: Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #333;
    margin: 0;
  }
  
  .calculator {
    background: #e0e0e0;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
    width: 400px; /* Increase calculator width */
    padding: 20px;
  }
  
  .display {
    width: 95%;
    height: 80px; /* Increase height for better visibility */
    font-size: 2rem; /* Bigger font size */
    text-align: right;
    padding: 10px;
    border: none;
    margin-bottom: 20px;
    border-radius: 5px;
    background: #fff;
    box-shadow: inset 0 1px 5px rgba(10, 0, 0, 10.2);
  }
  
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr); /* 4 buttons per row */
    gap: 15px; /* Spacing between buttons */
  }
  
  .btn {
    background: #f1f1f1;
    border: none;
    height: 80px; /* Increase button height */
    font-size: 1.5rem; /* Bigger button text */
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
    cursor: pointer;
    transition: background 0.2s ease, transform 0.1s ease;
  }
  
  .btn:hover {
    background: #dcdcdc;
  }
  
  .operator {
    background: #4a4a4a;
    color: white;
  }
  
  .equals {
    background: #0078d7;
    color: white;
  }
  
  .clear {
    background: #d70000;
    color: white;
  }