body:has(main) main {
  background-image: url("../img/haikei.bmp");
  background-repeat: repeat-y;
  background-position: left;
  background-color: #00aaaa;
  color: #000000;
}

body:not(:has(main)) {
  background-image: url("../img/haikei.bmp");
  background-attachment: fixed;
  background-repeat: repeat-y;
  background-position: left;
  background-color: #00aaaa;
  color: #000000;
}