erynwells.me/assets/styles/root/002_columns.css

:root {
  --body-item-spacing: 4rem;
  --content-width: 80rem;
  --list-item-block-gap: var(--body-item-spacing);
  --margin-min-width: var(--body-item-spacing);
  --margin-max-width: 1fr;
  --nav-bulleted-spacing: 0.75rem;
}

@layer root {
    main {
        --content-columns: 5;
        --gutter-width: 3rem;

        display: grid;
        grid-template-columns:
            [margin-left]
            minmax(var(--margin-min-width), var(--margin-max-width))
            [wide-content-start wide-content-left-start]
            1fr
            [wide-content-left-end gutter-start gutter-left-start]
            var(--gutter-width)
            [gutter-left-end content-start]
            repeat(var(--content-columns),
                min(
                    calc((100% - 2 * var(--gutter-width)) / var(--content-columns)),
                    calc(var(--content-width) / var(--content-columns))
                )
            )
            [content-end gutter-right-start]
            var(--gutter-width)
            [gutter-right-end gutter-end wide-content-right-start]
            1fr
            [wide-content-right-end wide-content-end]
            minmax(var(--margin-min-width), var(--margin-max-width))
            [margin-right];
    }

    @media (max-width: 960px) {
        main {
            --margin-min-width: 0;
            --margin-max-width: 0;
        }
    }

    @media (max-width: 519px) {
        /* Collapse the margin and wide content tracks */
        main {
            --content-columns: 3;

            grid-template-columns:
                [margin-left wide-content-start wide-content-left-start wide-content-left-end gutter-start gutter-left-start]
                var(--gutter-width)
                [gutter-left-end content-start]
                repeat(var(--content-columns), min(calc((100% - 2 * var(--gutter-width)) / var(--content-columns)), calc(var(--content-width) / var(--content-columns))))
                [content-end gutter-right-start]
                var(--gutter-width)
                [gutter-right-end gutter-end wide-content-right-start wide-content-right-end wide-content-end margin-right];
        }
    }

    @media (max-width: 415px) {
        main {
            --content-columns: 1;

            display: grid;
            grid-template-columns:
                [margin-left wide-content-start wide-content-left-start wide-content-left-end gutter-start gutter-left-start]
                var(--gutter-width)
                [gutter-left-end content-start]
                calc(100% - 2 * var(--gutter-width))
                [content-end gutter-right-start]
                var(--gutter-width)
                [gutter-right-end gutter-end wide-content-right-start wide-content-right-end wide-content-end margin-right];
        }
    }

    main > * {
        grid-column: content-start / content-end;
    }

    main > figure,
    main > a.to-photo-post {
        grid-column: wide-content-start / wide-content-end;
    }

    p, ul {
        grid-column: content-start / content-end;
    }
}

@layer layout {
  blockquote {
    --line-width: 4px;

    border-inline-start: var(--line-width) solid var(--separator-color);
    padding-inline-start: calc(3rem - var(--line-width));

    margin: 0;
  }

  code.nobg {
    display: inline-block;
    margin: 0;
    padding: 0;
  }

  details {
    width: 100%;
  }

  details:has(#TableOfContents) {
    box-sizing: border-box;
    padding: var(--body-item-spacing);
  }

  fieldset {
    box-sizing: border-box;
    padding: var(--body-item-spacing);
    padding-top: calc(var(--body-item-spacing) / 10);
  }

  header>span.series {
    margin-inline-start: 0.5em;
  }

  header > span.series::before {
    margin-inline-end: 0.25em;
  }

  img {
    height: auto;
    max-width: 100%;
    width: 100%;
  }

  main {
    box-sizing: border-box;
    margin-block-start: var(--body-item-spacing);
    width: 100%;
  }

  nav.bulleted>li:first-child::before {
    margin-inline: 0;
  }

  nav.bulleted>li::before {
    margin-inline: var(--nav-bulleted-spacing);
  }

  ul,
  ol,
  dl,
  :is(ul, ol) > li,
  dl > dt {
    margin-inline-start: calc(var(--body-item-spacing) + 2px);
  }

  :is(ul, ol) > li {
      margin-block-start: 1rem;
  }

  :is(ul, ol) > li > :is(ul, ol) {
    margin-inline-start: 0;
  }

  table {
    border-collapse: collapse;
    margin-inline: auto;
    width: 50%;
  }

  td,
  th {
    padding-inline: 1rem;
  }

  .page {
    gap: var(--body-item-spacing) 0;
  }

  .page > header {
    align-items: first baseline;
    column-gap: 4rem;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
  }

  @media (max-width: 539px) {
    .page > header {
      grid-template-columns: auto;
    }
  }

  .page > header,
  .page > footer {
    grid-column: content-start / content-end;
  }

  .page > header > :is(h1, h2, h3, h4, h5, h6) {
    grid-column: 1;
  }

  .page > header > time {
    grid-column: 2;
  }

  .page > article > * {
    grid-column: gutter-start / gutter-end;
  }

  .page > :not(blockquote, figure.code, :has(> img)) {
    grid-column: content-start / content-end;
  }

  .page > article > :not(:last-child) {
    margin-block-end: var(--body-item-spacing);
  }

  .post {
    grid-column: gutter-start / gutter-end;
  }

  .post p,
  .post .tags,
  .post .title {
    grid-column: content-start / content-end;
  }
}