How to make a fake progressbar

I need to generate a progress bar like the one on this site: https://vturb.com.br. “Basically” it loads quickly in the first moments of the video and gradually slows down until the end of the video.

The closest I could come up with was this:

const myVideo = document.querySelector('video');
const progressBar = document.querySelector('.progress > div')

myVideo.ontimeupdate = ({
  target
}) => {
  const progress = Math.round(Math.atan(target.currentTime) / (Math.PI / 2) * 100 * 1000) / 1000;

  progressBar.style.width = progress + '%';

};
.video-wrapper {
  position: relative;
  width: fit-content;
}

.progress {
  position: absolute;
  width: 100%
}

.progress>div {
  background-color: red;
  height: 100%;
  transition: width ease-in-out .5s;
}
<div class="video-wrapper">
  <video autoplay muted src="https://edisciplinas.usp.br/pluginfile.php/5196097/mod_resource/content/1/Teste.mp4" type="video/mp4"></video>
  <div class="progress" style="height: 8px;">
    <div style="width: 0%"></div>
  </div>
</div>