*, *::before, *::after {
            box-sizing: border-box;
        }

        :root {
            --background-light: #f8f6f1;
            --surface-light: #f2efe8;
            --text-dark: #1a1a1a;
            --border-light: #ddd9d0;
            --muted: #5f6672;
            --max-width: 48rem;
            --font-sans: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
            --font-serif: ui-serif, 'Iowan Old Style', 'Palatino Linotype', Palatino, Georgia, Cambria, 'Times New Roman', Times, serif;
        }

        @media (prefers-color-scheme: dark) {
            :root {
                --background-light: #171614;
                --surface-light: #211f1b;
                --text-dark: #f0ede6;
                --border-light: #3a3732;
                --muted: #aaa59c;
            }
        }

        html {
            scroll-behavior: auto;
        }

        body {
            font-family: var(--font-sans); 
            line-height: 1.6;
            -webkit-font-smoothing: antialiased;
            background-color: var(--background-light);
            color: var(--text-dark);
            display: flex;
            justify-content: center;
            min-height: 100dvh;
            margin: 0;
        }

        #progress-bar {
            position: fixed;
            top: 0;
            left: 0;
            height: 3px;
            background-color: var(--text-dark);
            width: 0%;
            z-index: 100;
            transition: width 100ms ease-out;
        }

        .container {
            width: 100%;
            max-width: var(--max-width);
            padding: 2rem 1rem;
        }

        header.reader-header {
            border: 1px solid var(--text-dark);
            min-width: 0;
            padding: 0.75rem 1rem; 
            position: sticky;
            top: 0;
            background-color: var(--background-light);
            z-index: 10;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 1rem;
        }

        .nav-back {
            display: inline-flex;
            align-items: center;
            min-height: 2.75rem;
            flex: 0 0 auto;
            font-size: 0.75rem;
            text-transform: uppercase;
            letter-spacing: 0.045em;
            font-weight: 700;
            border: 1px solid var(--text-dark);
            padding: 0.25rem 0.5rem;
            background: var(--text-dark);
            color: var(--background-light);
            text-decoration: none;
            white-space: nowrap;
            transition: color 150ms, background-color 150ms;
        }

        .nav-back:hover {
            background-color: var(--background-light);
            color: var(--text-dark);
        }

        .toc-select {
            min-width: 0;
            flex: 1 1 auto;
            width: auto;
            min-height: 2.75rem;
            font-family: var(--font-sans);
            font-size: 0.8125rem;
            background-color: var(--background-light);
            color: var(--text-dark);
            border: 1px solid var(--text-dark);
            padding: 0.25rem 0.5rem;
            max-width: 16rem;
            text-overflow: ellipsis;
            cursor: pointer;
        }

        main {
            border-inline: 1px solid var(--text-dark);
            border-block-end: 1px solid var(--text-dark);
            padding: 2rem 1.5rem;
        }

        .book-title-header {
            border-bottom: 1px solid var(--border-light);
            padding-bottom: 2rem;
            margin-bottom: 2.5rem;
            text-align: center;
        }

        h1.book-title { 
            margin: 0 0 0.5rem 0; 
            font-family: var(--font-serif);
            font-weight: 700; 
            font-size: 2.25rem; 
            letter-spacing: 0.025em;
            line-height: 1.05;
            text-transform: uppercase;
        }

        .book-author {
            color: var(--muted);
            font-size: 0.875rem;
            text-transform: uppercase;
            letter-spacing: 0.09em;
            line-height: 1.35;
        }

        article.reader-body {
            max-width: 39rem;
            margin: 0 auto;
            font-family: var(--font-serif);
            font-size: 1.125rem;
            line-height: 1.78;
            font-optical-sizing: auto;
            font-kerning: normal;
            font-variant-ligatures: common-ligatures contextual;
            font-variant-numeric: proportional-nums;
            font-synthesis: auto;
            text-rendering: optimizeLegibility;
        }

        article.reader-body section {
            scroll-margin-top: 5rem;
            margin-bottom: 3.5rem;
            padding-bottom: 2.5rem;
            border-bottom: 1px solid var(--border-light);
        }

        article.reader-body section:last-of-type {
            border-bottom: none;
        }

        h2.chapter-title {
            font-family: var(--font-serif);
            font-size: 1.55rem;
            line-height: 1.25;
            letter-spacing: -0.012em;
            margin: 0 0 1.5rem 0;
            font-weight: 700;
            color: var(--text-dark);
        }

        h3.section-subtitle {
            font-family: var(--font-serif);
            font-size: 1.2rem;
            line-height: 1.35;
            letter-spacing: -0.008em;
            margin: 2.25rem 0 1rem 0;
            font-weight: 700;
        }

        article.reader-body p {
            margin: 0 0 1.45rem;
            text-align: left;
            -webkit-hyphens: manual;
            hyphens: manual;
            overflow-wrap: break-word;
        }

        ul.bib-list {
            list-style: none;
            padding: 0;
            margin: 0;
            font-family: var(--font-sans);
            font-size: 0.9rem;
            line-height: 1.6;
        }

        ul.bib-list li {
            margin-bottom: 0.75rem;
            padding-left: 1.5rem;
            text-indent: -1.5rem;
        }

        footer.reader-footer {
            margin-top: 3rem;
            padding-top: 1.5rem;
            border-top: 1px solid var(--text-dark);
            text-align: center;
        }

        @media (min-width: 640px) {
            .container { padding-inline: 2rem; }
            h1.book-title { font-size: 2.75rem; }
            .toc-select { max-width: 22rem; }
        }

        @media (min-width: 768px) {
            .container { padding-block: 3rem; }
            main { padding: 3rem 2.5rem; }
        }

/* Reading experience: restrained enhancements built on the original visual system. */
html {
    scroll-behavior: auto;
    scrollbar-gutter: stable;
    text-size-adjust: 100%;
    -webkit-text-size-adjust: 100%;
}

body {
    text-rendering: optimizeLegibility;
    font-kerning: normal;
    overflow-x: clip;
}

#progress-bar {
    transform-origin: left center;
    pointer-events: none;
}

.reader-header {
    isolation: isolate;
}

.reader-tools {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    margin-left: auto;
}

.reader-tool-button {
    appearance: none;
    min-width: 2.25rem;
    min-height: 2.25rem;
    padding: 0.25rem 0.45rem;
    border: 1px solid var(--border-light);
    background: transparent;
    color: var(--text-dark);
    font: inherit;
    font-size: 0.75rem;
    line-height: 1;
    cursor: pointer;
    transition: background-color 150ms ease, color 150ms ease, border-color 150ms ease;
}

.reader-tool-button:hover,
.reader-tool-button[aria-pressed="true"] {
    border-color: var(--text-dark);
    background: var(--text-dark);
    color: var(--background-light);
}

.reader-settings {
    position: absolute;
    top: calc(100% + 0.5rem);
    right: 0;
    z-index: 20;
    width: min(18rem, calc(100vw - 2rem));
    padding: 1rem;
    border: 1px solid var(--text-dark);
    background: var(--background-light);
    color: var(--text-dark);
}

.reader-settings[hidden] {
    display: none;
}

.reader-settings-title {
    margin: 0 0 0.75rem;
    font-family: var(--font-sans);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.reader-setting {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 0.75rem;
    align-items: center;
    margin-top: 0.75rem;
    font-family: var(--font-sans);
    font-size: 0.8125rem;
}

.reader-setting-control {
    display: inline-flex;
    align-items: center;
    gap: 0.25rem;
}

.reader-setting-control button {
    min-width: 2rem;
    min-height: 2rem;
    border: 1px solid var(--text-dark);
    background: var(--background-light);
    color: var(--text-dark);
    cursor: pointer;
}

.reader-setting-control button:hover {
    background: var(--text-dark);
    color: var(--background-light);
}

.reader-meta {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
    margin-top: 0.35rem;
    color: var(--muted);
    font-family: var(--font-sans);
    font-size: 0.75rem;
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

.reader-chapter-progress {
    min-width: 0;
}

article.reader-body {
    --reader-font-scale: 1;
    --reader-measure-scale: 1;
    max-width: calc(39rem * var(--reader-measure-scale));
    font-size: calc(1.125rem * var(--reader-font-scale));
    line-height: 1.78;
    text-wrap: pretty;
    text-rendering: optimizeLegibility;
}

article.reader-body p {
    text-wrap: pretty;
}

article.reader-body h2,
article.reader-body h3 {
    text-wrap: balance;
    font-optical-sizing: auto;
}

article.reader-body strong {
    font-weight: 700;
}

article.reader-body em {
    font-style: italic;
}

article.reader-body a {
    text-decoration-thickness: 0.06em;
    text-underline-offset: 0.16em;
}

.reader-chapter-nav {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    gap: 2rem;
    margin-top: 4rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-light);
}

.reader-chapter-link {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
    min-width: 0;
    padding-block: 0.5rem;
    color: var(--text-dark);
    text-decoration: none;
}

.reader-chapter-link--next {
    align-items: flex-end;
    text-align: right;
}

.reader-chapter-link-label {
    color: var(--muted);
    font-family: var(--font-sans);
    font-size: 0.6875rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    line-height: 1.2;
    text-transform: uppercase;
}

.reader-chapter-link-title {
    max-width: 100%;
    font-family: var(--font-serif);
    font-size: 1rem;
    font-weight: 700;
    line-height: 1.35;
    overflow-wrap: anywhere;
}

.reader-chapter-link:hover .reader-chapter-link-title {
    text-decoration: underline;
    text-decoration-thickness: 1px;
    text-underline-offset: 0.16em;
}

.reader-tool-button:focus-visible,
.reader-setting-control button:focus-visible,
.reader-chapter-link:focus-visible,
.toc-select:focus-visible,
.nav-back:focus-visible {
    outline: 2px solid currentColor;
    outline-offset: 3px;
}

@media (max-width: 639px) {
    .reader-header {
        padding-inline: 0.65rem;
    }

    .reader-tools {
        gap: 0.2rem;
    }

    .reader-tool-button {
        min-width: 2.75rem;
        min-height: 2.75rem;
        padding-inline: 0.45rem;
    }

    .reader-header .toc-select {
        width: auto;
        max-width: none;
    }

    .reader-settings {
        width: min(18rem, calc(100vw - 2rem));
    }

    article.reader-body {
        max-width: 100%;
    }

    .reader-chapter-nav {
        gap: 1rem;
    }

    .reader-chapter-link-title {
        font-size: 0.9375rem;
    }
}

@media (prefers-reduced-motion: reduce) {
    .reader-tool-button,
    .nav-back,
    .reader-chapter-link {
        transition: none;
    }
}

@media print {
    .reader-tools,
    .reader-settings,
    #progress-bar,
    .reader-chapter-nav {
        display: none !important;
    }
}