* {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    body {
      position: relative;
      font-family: 'Be Vietnam Pro', sans-serif;
      min-height: 100vh;
      background: url('background.jpeg') no-repeat center/cover fixed;
      display: flex;
      align-items: center;
      justify-content: center;
      padding: 2rem;
    }

    /* Nút quay về Trang Chủ */
    .back-button {
      position: absolute;
      top: 20px;
      left: 20px;
      display: flex;
      align-items: center;
      gap: 0.3em;
      padding: 0.6em 1em;
      background-color: rgba(255, 255, 255, 0.3);
      backdrop-filter: blur(20px);
      -webkit-backdrop-filter: blur(20px);
      border-radius: 25px;
      text-decoration: none;
      color: #000;
      font-weight: 500;
      transition: background-color 0.2s ease;
    }
    .back-button:hover {
      background-color: rgba(255, 255, 255, 0.35);
    }
    .back-button svg {
      width: 1em;
      height: 1em;
      stroke: currentColor;
      stroke-width: 2;
      fill: none;
      stroke-linecap: round;
      stroke-linejoin: round;
    }

    /* Khung chính */
    .container {
      width: 100%;
      max-width: 600px;
      background-color: rgba(255, 255, 255, 0.3);
      backdrop-filter: blur(20px);
      -webkit-backdrop-filter: blur(20px);
      border-radius: 25px;
      padding: 2rem;
      text-align: center;
      color: #000;
    }
    .container h1 {
      font-size: 2.2rem;
      margin-bottom: 0.5em;
    }
    .container p.subtitle {
      font-size: 1.1rem;
      margin-bottom: 1.5em;
      color: #333;
    }

    /* Danh sách liên kết xã hội */
    .social-list {
      list-style: none;
    }
    .social-list li + li {
      margin-top: 1rem;
    }
    .social-list a {
      display: inline-block;
      padding: 0.6em 1.2em;
      background-color: rgba(255, 255, 255, 0.2);
      backdrop-filter: blur(15px);
      -webkit-backdrop-filter: blur(15px);
      border-radius: 25px;
      color: #000;
      text-decoration: none;
      font-weight: 500;
      transition: background-color 0.3s ease;
    }
    .social-list a:hover {
      background-color: rgba(255, 255, 255, 0.3);
    }

    @media (max-width: 600px) {
      .back-button {
        top: 10px;
        left: 10px;
        padding: 0.4em 0.8em;
      }
      .container {
        padding: 1.5rem;
      }
      .container h1 {
        font-size: 1.8rem;
      }
      .container p.subtitle {
        font-size: 1rem;
      }
      .social-list a {
        padding: 0.5em 1em;
        font-size: 0.9rem;
      }
    }