body {
  padding: 0;
  margin: 0;
  background-image: url("../images/bg.jpg");
  background-size: cover;
  background-repeat: no-repeat;
}
* {
  box-sizing: border-box;
}

img,
picture {
  max-width: 100%; /* 宽度不超过容器 */
  height: auto;    /* 高度按比例调整 */
}
html,
body {
  /* 禁止移动端页面缩放 */
  touch-action: pan-x pan-y;
  -webkit-user-drag: none;
}