body {
      font-family: Arial, sans-serif;
      padding: 2rem;
      max-width: 600px;
      margin: auto;
    }
    label {
      font-weight: bold;
      display: block;
      margin-top: 1rem;
    }
    select, button {
      width: 100%;
      padding: 0.5rem;
      margin-top: 0.5rem;
    }
    .result {
      margin-top: 2rem;
      font-size: 1.2rem;
    }