:root {
    --paper: #f8f3e8;
    --paper-strong: #fffaf1;
    --ink: #201912;
    --muted: #63594c;
    --line: rgba(46, 38, 29, 0.14);
    --accent: #0f6a56;
    --accent-soft: rgba(15, 106, 86, 0.12);
    --accent-strong: #094739;
    --warm: #8e4b10;
    --warm-soft: rgba(142, 75, 16, 0.1);
    --shadow: 0 24px 60px rgba(31, 24, 18, 0.08);
    --sans: "Avenir Next", "Segoe UI", "Helvetica Neue", Helvetica, Arial, sans-serif;
    --serif: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Georgia, serif;
    --mono: "SFMono-Regular", "JetBrains Mono", Consolas, Menlo, monospace;
    --radius-lg: 24px;
    --radius-md: 16px;
    --radius-sm: 12px;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    color: var(--ink);
    background:
        radial-gradient(circle at top left, rgba(15, 106, 86, 0.1), transparent 30%),
        radial-gradient(circle at bottom right, rgba(142, 75, 16, 0.12), transparent 35%),
        linear-gradient(180deg, #faf6ed 0%, var(--paper) 100%);
    font-family: var(--sans);
    line-height: 1.7;
}

body::before {
    content: "";
    position: fixed;
    inset: 0;
    pointer-events: none;
    background-image:
        linear-gradient(rgba(53, 44, 35, 0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(53, 44, 35, 0.03) 1px, transparent 1px);
    background-size: 34px 34px;
    mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.3), transparent 88%);
}

.book-shell {
    position: relative;
    display: grid;
    grid-template-columns: 300px minmax(0, 1fr);
    gap: 28px;
    max-width: 1440px;
    margin: 0 auto;
    padding: 30px 28px 56px;
}

.sidebar {
    position: sticky;
    top: 24px;
    align-self: start;
    padding: 26px 22px;
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    background: rgba(255, 251, 242, 0.86);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow);
}

.eyebrow {
    margin: 0 0 10px;
    color: var(--accent);
    font-size: 0.76rem;
    font-weight: 800;
    letter-spacing: 0.12em;
    text-transform: uppercase;
}

.brand h1,
.content h2,
.content h3,
.hero h1 {
    font-family: var(--serif);
    letter-spacing: -0.02em;
}

.brand h1 {
    margin: 0;
    font-size: 2.2rem;
    line-height: 0.96;
}

.brand p {
    margin: 8px 0 0;
    color: var(--muted);
}

.sidebar-actions {
    display: grid;
    gap: 10px;
    margin: 22px 0 24px;
}

.button,
.button:visited {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 11px 14px;
    border: 1px solid rgba(15, 106, 86, 0.18);
    border-radius: 999px;
    background: var(--accent-soft);
    color: var(--accent-strong);
    font-weight: 700;
    text-decoration: none;
    cursor: pointer;
}

.button.secondary,
.button.secondary:visited {
    background: rgba(255, 255, 255, 0.8);
    color: var(--ink);
}

.toc {
    display: grid;
    gap: 8px;
}

.toc a {
    padding: 8px 10px;
    border-radius: 999px;
    color: var(--muted);
    text-decoration: none;
    transition: background-color 160ms ease, color 160ms ease, transform 160ms ease;
}

.toc a:hover {
    color: var(--ink);
    background: var(--accent-soft);
    transform: translateX(3px);
}

.sidebar-note {
    margin-top: 22px;
    padding-top: 18px;
    border-top: 1px solid var(--line);
    color: var(--muted);
    font-size: 0.94rem;
}

.content {
    min-width: 0;
}

.hero,
.chapter,
.appendix {
    margin-bottom: 24px;
    padding: 30px 34px;
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    background: rgba(255, 251, 242, 0.86);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow);
}

.badge {
    display: inline-block;
    padding: 7px 12px;
    border-radius: 999px;
    background: var(--accent-soft);
    color: var(--accent);
    font-size: 0.82rem;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.hero h1 {
    margin: 16px 0 10px;
    font-size: clamp(2.6rem, 4.7vw, 4.4rem);
    line-height: 0.94;
}

.hero .lead {
    max-width: 48rem;
    margin: 0;
    color: var(--muted);
    font-size: 1.08rem;
}

.hero-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 16px;
    margin-top: 24px;
}

.callout {
    padding: 18px 20px;
    border-radius: var(--radius-md);
    border: 1px solid rgba(31, 24, 18, 0.08);
    background: rgba(255, 255, 255, 0.66);
}

.callout.warm {
    background: var(--warm-soft);
    border-color: rgba(142, 75, 16, 0.18);
}

.chapter h2,
.appendix h2 {
    margin: 0 0 10px;
    font-size: 2rem;
}

.chapter h3,
.appendix h3 {
    margin: 26px 0 10px;
    font-size: 1.3rem;
}

p,
li,
td,
th {
    font-size: 1rem;
}

ul,
ol {
    padding-left: 22px;
}

li + li {
    margin-top: 7px;
}

code,
pre {
    font-family: var(--mono);
}

code {
    padding: 0.15rem 0.3rem;
    border-radius: 6px;
    background: rgba(28, 28, 26, 0.08);
}

pre {
    overflow-x: auto;
    padding: 18px 20px;
    border-radius: var(--radius-md);
    background: #1d1c19;
    color: #f9f5ea;
    line-height: 1.55;
}

.diagram-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
    margin: 20px 0;
}

.diagram-card {
    padding: 16px;
    border-radius: var(--radius-md);
    border: 1px solid rgba(15, 106, 86, 0.16);
    background: rgba(255, 255, 255, 0.75);
}

.diagram-card strong {
    display: block;
    margin-bottom: 8px;
    color: var(--accent-strong);
}

.diagram-flow {
    margin: 18px 0;
    padding: 18px;
    border-radius: var(--radius-md);
    background: linear-gradient(180deg, rgba(15, 106, 86, 0.08), rgba(15, 106, 86, 0.02));
    border: 1px solid rgba(15, 106, 86, 0.12);
}

.flow-line {
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 10px 0;
}

.flow-node {
    flex: 1;
    padding: 12px 14px;
    border-radius: 999px;
    border: 1px solid rgba(15, 106, 86, 0.14);
    background: rgba(255, 255, 255, 0.8);
    text-align: center;
    font-weight: 700;
}

.flow-arrow {
    color: var(--accent-strong);
    font-size: 1.1rem;
    font-weight: 800;
}

.code-map,
.worked-example,
.reading-card {
    margin: 18px 0;
    padding: 18px 20px;
    border-radius: var(--radius-md);
    border: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.72);
}

.worked-example {
    background: linear-gradient(180deg, rgba(142, 75, 16, 0.08), rgba(255, 255, 255, 0.75));
}

.code-map ul,
.worked-example ul,
.reading-card ul {
    margin: 0;
}

.chapter-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 18px;
}

.chapter-nav a {
    padding: 8px 12px;
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.8);
    border: 1px solid var(--line);
    color: var(--ink);
    text-decoration: none;
    font-weight: 700;
}

.small {
    color: var(--muted);
    font-size: 0.94rem;
}

@media (max-width: 980px) {
    .book-shell {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: static;
    }

    .hero-grid,
    .diagram-grid {
        grid-template-columns: 1fr;
    }

    .flow-line {
        flex-direction: column;
    }

    .flow-arrow {
        transform: rotate(90deg);
    }
}

@media print {
    @page {
        margin: 14mm;
    }

    body {
        background: #fff !important;
        color: #111 !important;
    }

    html,
    body,
    .book-shell,
    .content {
        display: block !important;
        position: static !important;
        width: auto !important;
        max-width: none !important;
        min-width: 0 !important;
        height: auto !important;
        min-height: 0 !important;
        margin: 0 !important;
        padding: 0 !important;
        overflow: visible !important;
        background: #fff !important;
        color: #111 !important;
    }

    body::before,
    .sidebar,
    .button,
    .sidebar-actions {
        display: none !important;
    }

    .hero,
    .chapter,
    .appendix,
    .callout,
    .diagram-flow,
    .diagram-card,
    .code-map,
    .worked-example,
    .reading-card,
    .chapter-nav {
        display: block !important;
        position: static !important;
        float: none !important;
        width: auto !important;
        max-width: none !important;
        height: auto !important;
        min-height: 0 !important;
        margin: 0 0 14pt !important;
        padding: 0 !important;
        overflow: visible !important;
        border: 0 !important;
        background: transparent !important;
        box-shadow: none !important;
        filter: none !important;
        backdrop-filter: none !important;
        transform: none !important;
        break-inside: auto !important;
        page-break-inside: auto !important;
    }

    .hero-grid,
    .diagram-grid,
    .flow-line {
        display: block !important;
    }

    .chapter h2,
    .appendix h2 {
        break-after: avoid;
    }

    .flow-arrow {
        display: block !important;
        margin: 4pt 0 !important;
        transform: none !important;
    }

    a {
        color: inherit;
        text-decoration: none;
    }

    pre {
        display: block !important;
        white-space: pre-wrap;
        word-break: break-word;
        color: #111;
        background: #f3f3f3 !important;
        border: 1px solid #ddd;
        padding: 10pt !important;
    }

    code {
        background: transparent !important;
    }
}