.btn_turn{
  background : url(/img/icon/down-button.png);
  background-repeat: no-repeat;
  background-position: center;
  background-size: contain;
  width: 40px;
  height: 40px;
  filter: invert(100%);
  transition: transform .5s;
}
.up_btn{
  transform:rotateX(180deg);
}
.height0{
  height: 0 !important;
  overflow: hidden;
}