#fullscreen-viewer {
    position: fixed;
    top: 0; left: 0;
    width: 100vw; height: 100vh;
    background-color: rgba(0, 0, 0, 0.9);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9999;
    flex-direction: row;
  }

  #fullscreen-viewer img {
    max-width: 90vw;
    max-height: 90vh;
    border-radius: 8px;
    box-shadow: 0 0 20px #000;
    transition: all 0.3s ease;
  }

  .close-btn {
    position: absolute;
    top: 20px;
    right: 30px;
    color: #fff;
    font-size: 40px;
    font-weight: bold;
    cursor: pointer;
    z-index: 10000;
  }

  .nav-btn {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    color: white;
    font-size: 50px;
    font-weight: bold;
    padding: 10px;
    cursor: pointer;
    user-select: none;
    z-index: 10000;
  }

  .prev-btn {
    left: 20px;
  }

  .next-btn {
    right: 20px;
  }

  @media (max-width: 768px) {
    .close-btn { font-size: 30px; top: 10px; right: 15px; }
    .nav-btn { font-size: 36px; padding: 5px; }
  }