<style>
  html, body, #video-container {
    margin: 0; padding: 0;
    width: 100vw; height: 100vh;
    overflow: hidden;
  }
  #video-container iframe {
    width: 100%; height: 100%;
    border: none;
  }
</style>

<div id="video-container">
  <iframe src="https://www.youtube.com/embed/hOd7vsGXMjE" allowfullscreen></iframe>
</div>