CSS3:如何将内容放在手机背景中

body {
  background-image: url('background.jpg');
  background-size: cover;
}

body {
  background-image: url('background.jpg');
  background-size: contain;
  background-position: center;
}

body {
  background-image: url('background.jpg');
  background-size: cover;
  background-attachment: fixed;
}

@media (max-width: 768px) {
  body {
    background-image: url('background-mobile.jpg');
    background-size: cover;
  }
}

@media (min-width: 769px) {
  body {
    background-image: url('background-desktop.jpg');
    background-size: cover;
  }
}