.overlay {
  position: fixed;
  top:0; left:0;
  width:100%; height:100%;
  background: rgba(255,255,255,0.95);
  z-index:9999;

  /* flexで縦横中央に配置 */
  display:flex;
  align-items:center;   /* 縦中央 */
  justify-content:center; /* 横中央 */
}

.overlay-content {
  background:#fff;
  padding:30px;height:100%;
  border-radius:12px;
  box-shadow:0 4px 16px rgba(0,0,0,0.3);

  /* 内部要素も縦に並べて中央寄せ */
  display:flex;
  flex-direction:column;
  align-items:center;
  justify-content:center;
  text-align:center;
}
.bhidden { display:none; }