discourse/app/assets/stylesheets/common/base/d-popover.scss

$d-popover-background: $secondary;
$d-popover-border: $primary-medium;

@-webkit-keyframes popoverFadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes popoverFadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

#d-popover {
  background-color: $d-popover-background;
  position: absolute;
  z-index: z("modal", "tooltip");
  border-color: $d-popover-border;
  border-style: solid;
  border-width: 1px;
  max-width: 300px;
  -webkit-animation: popoverFadeIn 0.5s;
  animation: popoverFadeIn 0.5s;
  background-clip: padding-box;
  display: block;
  box-shadow: shadow("dropdown");
  border-radius: 2px;

  &.is-under {
    margin-top: 0px;

    .d-popover-top-arrow {
      display: block;
    }

    .d-popover-bottom-arrow {
      display: none;
    }
  }

  &.is-above {
    margin-top: 0px;

    .d-popover-bottom-arrow {
      display: block;
    }

    .d-popover-top-arrow {
      display: none;
    }
  }

  &.retina {
    border-width: 0.5px;
  }

  .d-popover-content {
    padding: 0.5em;
    font-size: $font-down-1;
    overflow-wrap: break-word;
    -webkit-animation: popoverFadeIn 0.5s;
    animation: popoverFadeIn 0.5s;
  }

  .d-popover-arrow {
    border-style: solid;
    color: transparent;
    content: "";
    position: absolute;
    z-index: calc(z("tooltip") - 100);
  }

  .d-popover-top-arrow {
    border-color: transparent transparent $d-popover-border;
    top: 8px;
    transform: translate(0, -15px);
    border-width: 0 8px 8px;

    &:after {
      border-color: transparent transparent $d-popover-background;
      border-style: solid;
      border-width: 0 7px 7px;
      bottom: -8px;
      margin-left: -7px;
      position: absolute;
      content: "";
    }
  }

  .d-popover-bottom-arrow {
    border-color: $d-popover-border transparent transparent;
    top: calc(100% + 16px);
    transform: translate(0, -16px);
    border-width: 8px 8px 0;

    &:after {
      position: absolute;
      content: "";
      border-color: $d-popover-background transparent transparent;
      border-style: solid;
      border-width: 7px 7px 0;
      bottom: 2px;
      transform: translate(-7px, 0);
    }
  }
}