#overlay {
    position: fixed;
    top: 0; left: 0;
    width: 100vw; height: 100vh;
    background: rgba(0,0,0,0.9);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
    color: white;
    font-family: Arial, sans-serif;
    font-size: 24px;
    user-select: none;
    cursor: pointer;
  }
  #mainContent {
    display: none;
  }