#universe{
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100vh;
  pointer-events: none;
  z-index: 0;            /* 不要用 -1 */
}
#web_bg, .full_page, .main, #content-inner{
  position: relative;
  z-index: 1;            /* 正文在画布上面 */
}