sass-site/source/assets/css/layout/_holy-grail.scss

.sl-l-holy-grail {
  margin: {
    right: -2rem;
    left:  -2rem;
  };
  display: grid;
  grid-template-rows: auto
                      1fr
                      auto;
  //min-height: 100vh;

  &--has {
    &-navigation {
      grid-template: {
        areas: 'header header'
               'navigation main'
               'footer footer';
        columns: 20rem 1fr;
      };
    }

    &-complementary {
      grid-template: {
        areas: 'header header'
               'main complementary'
               'footer footer';
        columns: 1fr 30rem;
      };
    }

    &-both-sidebars {
      grid-template: {
        areas: 'header header header'
               'navigation main complementary'
               'footer footer footer';
        columns: 20rem 1fr 30rem;
      };
    }

    &-no-sidebars {
      grid-template: {
        areas: 'header'
               'main'
               'footer';
        columns: 1fr;
      };
    }
  }

  &__header,
  &__main,
  &__navigation,
  &__complementary,
  &__footer {
    padding: {
      right: 2rem;
      left:  2rem;
    };
  }

  &__header        { grid-area: header;        }
  &__main          { grid-area: main;          }
  &__navigation    { grid-area: navigation;    }
  &__complementary { grid-area: complementary; }
  &__footer        { grid-area: footer;        }

  @media screen and (max-width: 40em) {
    grid-template: {
      areas: 'header'
             'navigation'
             'main'
             'complementary'
             'footer';
      columns: 100%;
      rows: auto
            auto
            auto
            auto
            auto;
    };
  }
}