/* A Codex-like outline in the unused left gutter, away from Tufte margin notes. */
.reading-nav {
    --toc-step: 24px;
    position: fixed;
    z-index: 20;
    left: clamp(0.75rem, 2.6vw, 3rem);
    top: 50%;
    transform: translateY(-50%);
    box-sizing: border-box;
    width: 44px;
    padding: 8px 5px;
    border: 1px solid transparent;
    border-radius: 12px;
    color: var(--theme-muted);
    font-family: var(--font-interface, sans-serif);
}

.reading-nav.is-open {
    width: min(320px, calc(100vw - 2rem));
    padding: 8px 5px;
    top: var(--toc-top, 50%);
    transform: none;
    background: var(--theme-bg);
    border-color: var(--theme-rule);
    box-shadow: 0 12px 40px #0000001a;
}

.reading-nav-toggle {
    display: flex;
    align-items: center;
    gap: 12px;
    box-sizing: border-box;
    width: 100%;
    min-height: 32px;
    padding: 4px 6px;
    margin: 0 0 6px;
    color: inherit;
    border: 0;
    background: none;
    cursor: pointer;
    font: inherit;
    font-size: 12px;
    text-align: left;
}

.reading-nav-icon {
    display: block;
    width: 16px;
    height: 12px;
    flex: 0 0 16px;
    background: linear-gradient(currentColor, currentColor) left top / 16px 1px no-repeat,
                linear-gradient(currentColor, currentColor) left center / 10px 1px no-repeat,
                linear-gradient(currentColor, currentColor) left bottom / 13px 1px no-repeat;
}

.reading-nav-label { display: none; }
.reading-nav.is-open .reading-nav-label { display: inline; }

.reading-nav-list {
    list-style: none;
    width: 100%;
    max-height: 60vh;
    overflow: auto;
    overscroll-behavior: contain;
    scrollbar-width: thin;
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

.reading-nav-list li { margin: 0; padding: 0; line-height: 1; }

.reading-nav a.reading-nav-link {
    display: flex;
    align-items: center;
    gap: 12px;
    box-sizing: border-box;
    min-height: var(--toc-step);
    padding: 4px 6px;
    font-size: 12px;
    line-height: 1.45;
    text-decoration: none !important;
    border-radius: 5px;
}

.reading-nav-tick {
    display: block;
    width: 18px;
    height: 2px;
    flex: 0 0 auto;
    background: var(--theme-rule);
    transition: width 140ms ease, background-color 140ms ease;
}

.reading-nav-link[data-depth="2"] .reading-nav-tick { width: 10px; }
.reading-nav-link.is-past .reading-nav-tick { background: var(--theme-muted); }
.reading-nav-link[aria-current="location"] .reading-nav-tick { width: 28px; background: var(--theme-text); }
.reading-nav-link[aria-current="location"] .reading-nav-text { color: var(--theme-text); }

/* Visually hidden labels remain the accessible names of the collapsed links. */
.reading-nav-text {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip-path: inset(50%);
    white-space: nowrap;
}

/* Keep each desktop target in place as labels appear on hover. */
.reading-nav.is-open .reading-nav-link { height: var(--toc-step); }
.reading-nav.is-open .reading-nav-list { max-height: min(60vh, calc(100vh - var(--toc-top, 0px) - 70px)); }
.reading-nav.is-open .reading-nav-tick { flex: 0 0 16px; width: 16px; }
.reading-nav.is-open .reading-nav-link[data-depth="2"] .reading-nav-tick { flex-basis: 8px; margin-left: 8px; }
.reading-nav.is-open .reading-nav-text {
    position: static;
    width: auto;
    height: auto;
    min-width: 0;
    overflow: hidden;
    clip-path: none;
    white-space: nowrap;
    text-overflow: ellipsis;
}

.reading-nav.is-open a.reading-nav-link:hover,
.reading-nav.is-open a.reading-nav-link[aria-current="location"] {
    background-color: var(--theme-surface) !important;
}

.reading-nav :focus-visible { outline-offset: -2px; }
.reading-page :is(h2, h3, h4, h5):focus { outline: none; }
.reading-page :is(h2, h3, h4, h5):focus-visible { outline: 1px solid var(--theme-rule); outline-offset: 6px; }

@media (max-width: 1050px) {
    .reading-nav {
        top: auto;
        bottom: max(1rem, env(safe-area-inset-bottom));
        left: auto;
        right: 1rem;
        transform: none;
        width: auto;
        padding: 4px 8px;
        background: var(--theme-bg);
        border-color: var(--theme-rule);
        box-shadow: 0 4px 18px #00000014;
    }
    .reading-nav-toggle { min-height: 36px; margin: 0; padding: 4px 8px; }
    .reading-nav-label { display: inline; }
    .reading-nav:not(.is-open) .reading-nav-list { display: none; }
    .reading-nav.is-open { width: min(320px, calc(100vw - 2rem)); top: auto; }
    .reading-nav.is-open .reading-nav-list { max-height: min(55vh, 440px); }
    .reading-nav.is-open .reading-nav-link { min-height: 44px; height: auto; padding: 8px 6px; }
    .reading-nav.is-open .reading-nav-text { white-space: normal; }
    body:has(.reading-page) > footer { padding-bottom: 5rem; }
}

@media (prefers-reduced-motion: reduce) {
    .reading-nav-tick { transition: none; }
}

@media print {
    .reading-nav { display: none; }
}