* {
      box-sizing: border-box;
      padding: 0;
      margin: 0;
    }

    body {
      background-color: #1f2937;
      color: white;
      font-family: 'Segoe UI', sans-serif;
      padding: 20px;
    }

    .container {
      display: flex;
      justify-content: center;
      flex-wrap: wrap;
      gap: 20px;
    }

    .bill-box {
      background-color: #111827;
      padding: 20px;
      border-radius: 10px;
      box-shadow: 0 8px 16px rgba(0,0,0,0.6);
      width: 100%;
      max-width: 400px;
    }

    .bill-box h2 {
      text-align: center;
      color: #ffd369;
      font-style: italic;
      margin-bottom: 20px;
    }

    label {
      margin-top: 5px;
      font-size: 1.1rem;
      display: block;
      font-weight: 500;
    }

    input {
      width: 100%;
      padding: 6px;
      margin-top: 2px;
      margin-bottom: 8px;
      border-radius: 4px;
      border: none;
      box-shadow: inset 1px 1px 3px rgba(0,0,0,0.4);
    }

    button {
      margin: 10px 5px 20px 0;
      padding: 8px 16px;
      border: none;
      border-radius: 5px;
      font-weight: bold;
    }

    table {
      width: 100%;
    }

    table th, table td {
      padding: 5px;
      text-align: center;
    }

    table thead {
      background-color: #000;
    }

    #grandTotal {
      margin-top: 15px;
      font-size: 1.2rem;
      color: #bb86fc;
      text-align: center;
    }

    @media (max-width: 600px) {
      .bill-box {
        width: 90%;
      }
    }