brk/website_next/learn/style.css

main.learn {
  --offset: 4rem;
  --content-width: 52rem;
  --heading-padding-bottom: 0.5rem;
  --topic-font-size: 2rem;
  --topic-padding-top: 4.5rem;
  --topic-sticky-size: calc(
    var(--topic-padding-top) + var(--topic-font-size) +
      var(--heading-padding-bottom) + 1px
  );
  --detail-font-size: 1.5rem;
  --detail-padding-top: calc(var(--topic-sticky-size) + 0.75rem);
  --detail-padding-bottom: 0.375rem;

  display: grid;
  grid-template-columns: 14rem minmax(0, 1fr);
  gap: 4rem;
  padding: 0 var(--page-x);

  article {
    counter-reset: theme;
    padding-block: var(--offset);

    &::before {
      content: "";
      position: sticky;
      top: 0;
      z-index: 4;
      display: block;
      height: var(--offset);
      margin-top: calc(-1 * var(--offset));
      margin-inline: auto;
      margin-bottom: calc(-1 * var(--offset));
      background: var(--black);
      pointer-events: none;
    }

    > section {
      counter-increment: theme;
      counter-reset: topic;
      width: min(100%, var(--content-width));
      margin-inline: auto;
      scroll-margin-top: var(--offset);
    }

    > section:first-of-type {
      margin-top: calc(-1 * var(--offset));
      padding-top: var(--offset);
    }

    > section + section {
      margin-top: 8rem;
    }

    > section > section {
      counter-increment: topic;
      counter-reset: detail;
      scroll-margin-top: var(--offset);
    }

    > section > section > section {
      counter-increment: detail;
      scroll-margin-top: var(--offset);
    }
  }

  h1,
  h2,
  h3 {
    line-height: 1;

    a {
      position: relative;
      display: inline-block;
      color: var(--white);
      text-decoration: none;

      &::before {
        position: absolute;
        top: 50%;
        right: 100%;
        translate: 0 -50%;
        opacity: 0;
        user-select: none;
        text-decoration: none;
      }

      &:hover::before {
        opacity: 0.5;
      }

      &:hover {
        text-decoration: underline;
        text-decoration-thickness: 1px;
        text-underline-offset: 0.125em;
      }

      &:active {
        color: var(--orange);
      }
    }
  }

  h1,
  h2,
  h3 {
    position: sticky;
    top: var(--offset);
    background: var(--black);
  }

  h1 {
    z-index: 3;
    padding-bottom: var(--heading-padding-bottom);
    border-bottom: 1px solid var(--dark-gray);
    font-size: 3rem;

    a::before {
      content: counter(theme, upper-roman) ". ";
    }
  }

  h2 {
    z-index: 2;
    padding-top: var(--topic-padding-top);
    padding-bottom: var(--heading-padding-bottom);
    border-bottom: 1px dashed var(--dark-gray);
    font-size: var(--topic-font-size);

    a::before {
      content: counter(topic) ". ";
    }
  }

  h3 {
    z-index: 1;
    padding-top: var(--detail-padding-top);
    padding-bottom: var(--detail-padding-bottom);
    border-bottom: 1px dotted var(--dark-gray);
    font-size: var(--detail-font-size);

    a::before {
      content: counter(detail, lower-alpha) ". ";
    }
  }

  p {
    margin-top: 1rem;
    color: var(--dark-white);
    font-size: var(--font-size-sm);
    line-height: var(--line-height-sm);
  }

  figure {
    margin-top: 2rem;
    color: var(--gray);
    font-size: var(--font-size-xs);

    &:not([data-chart]) {
      text-transform: uppercase;
    }

    > div {
      height: 18rem;
      display: grid;
      place-items: center;
      border: 1px solid var(--dark-gray);
      font-size: var(--font-size-sm);
    }

    figcaption {
      margin-top: 0.75rem;
    }
  }
}