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

<div align="center">

.adm-dropdown {
  background-color: var(--adm-color-background);
}
.adm-dropdown .adm-dropdown-nav {
  display: flex;
  border-bottom: 1px solid transparent;
}
.adm-dropdown-open .adm-dropdown-nav {
  border-bottom-color: var(--adm-color-border);
}
.adm-dropdown-item {
  display: flex;
  flex: 1;
  justify-content: center;
  min-width: 0;
  cursor: pointer;
}
.adm-dropdown-item .adm-dropdown-item-title {
  display: flex;
  align-items: center;
  position: relative;
  max-width: 100%;
  font-size: var(--adm-font-size-main);
  padding: 12px;
}
.adm-dropdown-item .adm-dropdown-item-title-text {
  margin-right: 5px;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
}
.adm-dropdown-item .adm-dropdown-item-title-arrow {
  color: var(--adm-color-light);
  font-size: 9px;
  transform: rotate(0deg) translateY(1px);
  transition: all ease 0.2s;
}
.adm-dropdown-item .adm-dropdown-item-title-arrow-active {
  transform: rotate(-180deg) translateY(-1px);
}
.adm-dropdown-item .adm-dropdown-item-title:active {
  opacity: 0.7;
}
.adm-dropdown-item-highlight {
  color: var(--adm-color-primary);
}
.adm-dropdown-item-active .adm-dropdown-item-title:after {
  margin-top: -1px;
  transform: rotate(135deg);
}
.adm-dropdown-item-content {
  width: 100%;
  background: var(--adm-color-background);
}
.adm-dropdown-item-content-hidden {
  display: none;
}
.adm-dropdown-popup {
  position: fixed;
  overflow: hidden;
  width: 100%;
  right: 0;
  bottom: 0;
  left: 0;
}
.adm-dropdown-popup .adm-dropdown-popup-mask {
  position: absolute;
}
.adm-dropdown-popup .adm-dropdown-popup-body {
  position: absolute;
}