gradient underline

underline-4.scss

a{
  background-image: linear-gradient(rgba(0, 0, 0, 0) 82%,
                                    red 82%,
                                    red 90%, 
                                    rgba(0, 0, 0, 0) 90%);

  // with compass
  // @include background-image(linear-gradient(hsla(0,0,0,0) 82%, $color 82%, $color 90%, hsla(0,0,0,0) 90%));
}