@media (min-width: 640px) {
  body, html {
    width: 100%;
    height: 100%;
    background-image: url("../img/background/biographie.jpg");
    background-attachment: fixed;
    background-position: center center;
    background-size: cover;
    background-repeat: no-repeat;
    overflow: hidden;
  }
}

@media (max-width: 640px) {
  body, html {
    width: 100%;
    height: 100%;
    background-image: url("../img/background/biographie.jpg");
    background-attachment: fixed;
    background-position: center center;
    background-size: cover;
    background-repeat: no-repeat;
    overflow-x: hidden;
  }
}

.back {
  background-color: rgba(0, 0, 0, 0.3);
}