@media screen and (max-width: 768px) {
    .object-fit-sm-cover {
      object-fit: cover;
    }
  }
body {
  background-image: url(images/DeepSpace2.gif);
  /* background-color: gray; */
  background-repeat: repeat;
  background-attachment: fixed;
}
.laterale {
  height: 300px;
}
.video-responsive {
  overflow: hidden;
  padding-bottom: 56.25%;
  position: relative;
  height: 0;
}

.video-responsive iframe {
  left: 0;
  top: 0;
  height: 100%;
  width: 100%;
  position: absolute;
}
nav {
  position: sticky;
}


/* uniquement sur un ecran de taille inférieur a 768px media query */