dots/usr/share/themes/Dracula/gtk-3.20/widgets/_app-notifications.scss

/*********************
 * App Notifications *
 *********************/
.app-notification,
.app-notification.frame {
  @extend %osd;

  padding: 10px;
  border-radius: 0 0 5px 5px;
  background-color: $osd_bg_color;
  background-image: linear-gradient(to bottom, transparentize(black, 0.8),
                                               transparent 2px);
  background-clip: padding-box;

  &:backdrop {
    background-image: none;
    transition: $backdrop_transition;
  }

  button { @extend %osd_button; }

  border { border: none; }
}