KNACSS/sass/components/_badges.scss

/* ----------------------------- */
/* ==Badges                      */
/* ----------------------------- */
/* use .badge-- classes for variants */

.badge {
  display: inline-block;
  padding: $spacer-tiny;
  border-radius: 50%;
  color: $color-base;
  background-color: $color-muted;
  line-height: 1;

  &::before {
    content: "";
    display: inline-block;
    vertical-align: middle;
    padding-top: 100%;
  }
}

.badge {
  @each $name, $background-color, $color, $border in $variants-list {
    &--#{$name} {
      @extend .badge;
      background-color: $background-color;
      color: $color;
    }
  }
}

// badge state variants
.badge {
  &--small {
    font-size: $font-size-base - 0.4rem;
  }

  &--big {
    font-size: $font-size-base + 0.4rem;
  }

  &.disabled,
  &--disabled {
    opacity: 0.5;
    cursor: not-allowed;
  }

  &:empty {
    display: none;
  }
}