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

<div align="center">

.adm-collapse-panel-header .adm-list-item-content-main {
  padding: 12px 0;
}
.adm-collapse-arrow {
  transform: rotate(0deg);
  transition: all ease 0.3s;
}
.adm-collapse-arrow-active {
  transform: rotate(-180deg);
}
.adm-collapse-panel-content {
  font-size: var(--adm-font-size-main);
  color: var(--adm-color-weak);
  overflow: hidden;
}