antd-mobile/es/components/popup/popup.css

<div align="center">

.adm-popup {
  --z-index: var(--adm-popup-z-index, 1000);
  position: fixed;
  z-index: var(--z-index);
}
.adm-popup-body {
  position: fixed;
  background-color: var(--adm-color-background);
  z-index: calc(var(--z-index) + 10);
}
.adm-popup-body .adm-popup-close-icon {
  position: absolute;
  z-index: 100;
}
.adm-popup-body-position-bottom {
  width: 100%;
  bottom: 0;
  left: 0;
}
.adm-popup-body-position-bottom .adm-popup-close-icon {
  right: 8px;
  top: 8px;
}
.adm-popup-body-position-top {
  width: 100%;
  top: 0;
  left: 0;
}
.adm-popup-body-position-top .adm-popup-close-icon {
  right: 8px;
  bottom: 8px;
}
.adm-popup-body-position-left {
  height: 100%;
  top: 0;
  left: 0;
}
.adm-popup-body-position-left .adm-popup-close-icon {
  right: 8px;
  top: 8px;
}
.adm-popup-body-position-right {
  height: 100%;
  top: 0;
  right: 0;
}
.adm-popup-body-position-right .adm-popup-close-icon {
  left: 8px;
  top: 8px;
}
.adm-popup-close-icon {
  cursor: pointer;
  padding: 4px;
  font-size: 18px;
  line-height: 1;
  color: var(--adm-color-weak);
}