update.html

<style>
  @keyframes rainbowbackground {
    0%{background-position:90% 0%}
    50%{background-position:0% 85%}
    100%{background-position:90% 0%}
}

  body {
    font-family: system, -apple-system, '.SFNSText-Regular', 'SF UI Text', 'Lucida Grande', 'Segoe UI', Ubuntu, Cantarell, sans-serif;
    color: #fff;
    text-align: center;
    font-size: 40px;
    background: linear-gradient(200deg, #00ff00, #7289DA, #000000, #000000);
    background-size: 2000% 2000%;

    animation: rainbowbackground 15s ease infinite;
    animation-fill-mode: forwards; 
    -webkit-app-region: drag;
  }
  
  #loading {
    padding: 0;
    margin: 0;
    position: fixed;
    bottom: 10%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 40;
  }

  #title {
    padding: 0;
    margin: 0;
    position: fixed;
    top: 55%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 40;
  }

  #dev {
    padding: 0;
    margin: 0;
    position: fixed;
    font-size: 20px;
    top: 63%;
    left: 50%;
    transform: translate(-50%, -50%);
  }

  img {
    position: fixed;
    top: 30%;
    left: 50%;
    transform: translate(-50%, -50%);
  }
  
</style>
  <img src="img/logo.png">
  <h2 id="title">update downloaded</h2>
  <h2 id="loading">restarting to install update...</h2>