discourse/app/assets/stylesheets/common/base/tooltip.scss

$discourse-tooltip-background: $secondary;
$discourse-tooltip-border: $primary-medium;

#discourse-tooltip {
  background-color: $discourse-tooltip-background;
  position: absolute;
  z-index: 1000;
  border: 1px solid $discourse-tooltip-border;
  max-width: 400px;
  margin-top: 25px;
  overflow-wrap: break-word;
  display: none;
  font-size: $font-0;
  font-weight: 500;

  &.retina {
    border: 0.5px solid $discourse-tooltip-border;
  }

  .tooltip-pointer {
    position: relative;
    background: $discourse-tooltip-background;
  }

  .tooltip-pointer:before, .tooltip-pointer:after {
    position: absolute;
    pointer-events: none;
    border: solid transparent;
    bottom: 100%;
    content: "";
    height: 0;
    width: 0;
  }

  .tooltip-pointer:after
  {
    border-bottom-color: $discourse-tooltip-background;
    border-width: 8px;
    left: 50%;
    margin-left: -8px;
    margin-bottom: -0.5px;
  }

  .tooltip-pointer:before {
    border-bottom-color: $discourse-tooltip-border;
    border-width: 9px;
    left: 50%;
    margin-left: -9px;
    margin-bottom: -0.5px;
  }

  .tooltip-content {
    padding: 1em;
    max-width: 250px;
    font-size: $font-down-1;
    color: $primary;
    box-shadow: shadow("dropdown");
    line-height: 1.4em;
  }
}