@media (min-width: 640px) {
  body {
    width: 100%;
    height: 100%;
    background-image: url("../img/background/accueil.jpg");
    background-attachment: fixed;
    background-position: top;
    background-repeat: no-repeat;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    overflow: hidden;
  }
}

@media (max-width: 640px) {
  body {
    width: 100%;
    height: 100%;
    background-color: rgba(21, 13, 24, 0.2);
    background-image: url("../img/background/accueil.jpg");
    background-attachment: fixed;
    background-position: top;
    background-repeat: no-repeat;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    overflow-x: hidden;
  }
}