style.css
body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: #1e1e1e;
    font-family: Arial, sans-serif;
  }
  
  .calculator {
    background: #333;
    padding: 20px;
    border-radius: 10px;
  }
  
  #display {
    width: 100%;
    height: 50px;
    margin-bottom: 10px;
    font-size: 1.5em;
    text-align: right;
    padding: 10px;
    border: none;
    border-radius: 5px;
  }
  
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 60px);
    gap: 10px;
  }
  
  button {
    height: 60px;
    font-size: 1.2em;
    border: none;
    border-radius: 5px;
    background: #555;
    color: white;
    cursor: pointer;
  }
  
  button:hover {
    background: #777;
  }