aside.toc {
    position: sticky;
    top: 0;
    max-width: 30%;

    // We want the table of contents to be on the left (horizontally), to be
    // positioned at a specific point (vertically), stick to the top on scroll
    // and it should not affect the layout of other elements.
    // "float: left" accomplishes the horizontal positioning, position in the
    // element tree the vertical positioning and "position: sticky" does the
    // stickiness. "height: 0" makes sure that the flow of other elements is not
    // affected.
    //
    // There does not seem to be a better way to do this unless one is willing
    // to implement scrolling in JS: "position" must be set to sticky so neither
    // fixed, nor absolute, nor relative positioning can be used.
    float: left;
    height: 0;
    overflow: display;

    // This is apparenty necessary so that the table of contents covers elements
    // with the "filter:" property set.
    z-index: 1;
}

#tocTitle {
    // This is so that we can measure it in JS
    width: fit-content;
}

#tocContainer:hover {
    width: calc(2rem + var(--measured-expanded-width));
}

#tocContainer:hover div#tocCollapsible {
    height: var(--measured-height);
    width: var(--measured-expanded-width);
}

#tocContainer {
    background-color: var(--grey-3);
    border-radius: 1rem;
    margin: 2rem;
    padding: 1rem;

    // This makes the gap between the two contained divs vanish. Why that gap
    // exists, no clue.
    display: flex;
    flex-direction: column;

    // We want to hide the table of contents before revealing it on hover
    overflow: hidden;

    // In addition to the measured width of the title, we need to add the two
    // rems for the border (we are using box-sizing: border-box). Also add a
    // reasonable default value to minimize visual changes while the page is
    // loading.
    width: calc(2rem + var(--measured-title-width));
    --measured-title-width: 2.4rem;

@include transition(
	$color-transition,
	width .1s ease-out,
	height .1s ease-out);
}

#tocContainer > div {
    border-left: 0.4rem solid var(--default-shade);
    padding-left: 1rem;
}

#tocContainer div#tocCollapsible {
    // Collapsed by default
    height: 0;

    // If we did not force this element to a given width, it would keep
    // re-wrapping during the opening/closing transition.
    width: var(--measured-expanded-width);

    // No transition on width so that there is no re-wrapping during the
    // opening/closing transition
    @include transition($color-transition, height .1s ease-out);
}

nav#TableOfContents ul {
    list-style-type: none;
    padding-inline-start: 1rem;
}

nav#TableOfContents > ul {
    padding-inline-start: 0;
}

nav#TableOfContents li {
    margin-top: 0.4rem;
}