body {
    background: #47503e;
    color: #fff;
    font-family: Arial, sans-serif;
    display: flex;
    height: 100vh;
    justify-content: center;
    align-items: center;
  }
  
  .calculator {
    background: #333;
    padding: 20px;
    border-radius: 16px;
    box-shadow: 0 0 10px #000;
  }
  
  #display {
    background: white;
    width: 100%;
    font-size: 2rem;
    padding: 10px;
    margin-bottom: 10px;
    text-align: right;
    border: none;
    border-radius: 9px;
    outline: none;
  }
  
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 95px);
    gap: 10px;
  }
  
  button {
    font-size: 1.2rem;
    padding: 15px;
    border: none;
    border-radius: 8px;
    background: #555;
    color: #fff;
    cursor: pointer;
    transition: background 0.2s ease-in-out;
  }
  
  button:hover {
    background: #777;
  }
  
  .equal {
    grid-column: span 2;
    background: #00b894;
  }