message: Change button active feedback
diff: @@ -8,6 +8,10 @@ button {
  @include size($padding-y, $padding-x, $font-size, $line-height, $border-radius);
  cursor: pointer;
  display: inline-block;
  + &:active{
  + opacity: 0.80;
  + transition: opacity 300ms;
  + }
  &.primary {
  @include primary;
  }
  @@ -59,3 +63,4 @@ button {
  }
  }
  +
  