Sass mixin for visible baseline grid

baseline-grid.scss

@mixin baseline-grid(
  $line-height: false,
  $offset: false, 
  $element: html,
  $colour: rgba(0,0,0,.2)
) {
  #{$element} {
    &:after {
      content: "";
      position: absolute;
      top: $offset;
      height: 100%;
      width: 100%;
      background-image: 
        linear-gradient(
          180deg,
          $colour,
          $colour 1px,
          transparent 1px,
          transparent
        );
      background-size: $line-height $line-height;
    }
  }
}

Usage:

@include baseline-grid(20px, 30px, .grid, #f0f);

or without all the options:

@include baseline-grid(20px);