.balloon(
  @direction: top, 
  @bg: rgba(0, 0, 0, 0.7), 
  @trangle-height: 6px, 
  @color: #fff, 
  @font: 14px
) {
  position: relative;
  &:before,
  &:after {
    position: absolute;
    z-index: 10;
    opacity: 0;
    pointer-events: none;
    transition: all 0.18s ease-out 0.18s;
    & when (@direction = top) {
      left: 50%;
      bottom: 100%;
      transform: translate(-50%, 3px);
    }
    & when (@direction = bottom) {
      left: 50%;
      top: 100%;
      transform: translate(-50%, 3px);
    }
    & when (@direction = left) {
      top: 50%;
      right: 100%;
      transform: translate(3px, -50%);
    }
    & when (@direction = right) {
      top: 50%;
      left: 100%;
      transform: translate(-3px, -50%);
    }
  }
  &:before {
    content: "";
    & when (@direction = top) {
      margin-bottom: 5px;
      border-left: @trangle-height solid transparent;
      border-right: @trangle-height solid transparent;
      border-@{direction}: @trangle-height solid @bg;
    }
    & when (@direction = bottom) {
      margin-top: 5px;
      border-left: @trangle-height solid transparent;
      border-right: @trangle-height solid transparent;
      border-@{direction}: @trangle-height solid @bg;
    }
    & when (@direction = left) {
      margin-right: 5px;
      border-top: @trangle-height solid transparent;
      border-bottom: @trangle-height solid transparent;
      border-@{direction}: @trangle-height solid @bg;
    }
    & when (@direction = right) {
      margin-left: 5px;
      border-top: @trangle-height solid transparent;
      border-bottom: @trangle-height solid transparent;
      border-@{direction}: @trangle-height solid @bg;
    }
  }

  &:after {
    content: attr(data-balloon);
    background: @bg;
    border-radius: 4px;
    color: @color;
    font-size: @font;
    padding: 0.6em 0.8em;
    white-space: nowrap;
    & when (@direction = top) {
      margin-bottom: @trangle-height + 5px;
    }
    & when (@direction = bottom) {
      margin-top: @trangle-height + 5px;
    }
    & when (@direction = left) {
      margin-right: @trangle-height + 5px;
    }
    & when (@direction = right) {
      margin-left: @trangle-height + 5px;
    }
  }
  &:hover {
    &:after,
    &:before {
      opacity: 1;
      pointer-events: auto;
      & when (@direction = top), (@direction = bottom) {
        transform: translate(-50%, 0);
      }
      & when (@direction = left), (@direction = right) {
        transform: translate(0, -50%);
      }
    }
  }
}