BODY {
  background-image: url(back.jpg);
  background-size: cover;        /* 画面いっぱいに拡大 */
  background-position: center;   /* 中央基準 */
  background-repeat: no-repeat;  /* 繰り返さない */
  text-align: center;
}
TABLE, TD, TH { 
  border: 1px #808080 solid;
}
body::after {
  content: "";
  position: fixed;
  inset: 0;

  background: rgba(255,255,255,0.5);
  backdrop-filter: blur(6px);
  z-index: -1;
}