:root {
            --font-body: 'DM Sans', sans-serif;
            --font-display: 'Fraunces', serif;
            --font-mono: 'JetBrains Mono', monospace;
            --radius: 12px;
            --radius-sm: 8px;
            --sidebar-width: 260px;
            --nav-height: 64px;
        }

        [data-theme="light"] {
            --bg: #FAFAF8;
            --bg-warm: #F5F3EF;
            --bg-card: #FFFFFF;
            --text: #1A1A1A;
            --text-secondary: #6B6B6B;
            --text-muted: #999999;
            --accent: #2C5F2D;
            --accent-light: #97BC62;
            --border: #E8E6E1;
            --border-light: #F0EDE8;
            --code-bg: #1E2028;
            --code-text: #E4E4E7;
            --code-accent: #97BC62;
            --code-comment: #6B7280;
            --code-string: #86EFAC;
            --code-keyword: #C4B5FD;
            --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
            --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.06);
            --nav-bg: rgba(250, 250, 248, 0.92);
            --sidebar-bg: #F5F3EF;
            --tag-bg: rgba(44, 95, 45, 0.06);
        }

        [data-theme="dark"] {
            --bg: #111114;
            --bg-warm: #18181C;
            --bg-card: #1E1E23;
            --text: #E8E6E1;
            --text-secondary: #9A9A9A;
            --text-muted: #666666;
            --accent: #97BC62;
            --accent-light: #B8D888;
            --border: #2A2A30;
            --border-light: #1F1F24;
            --code-bg: #0C0C0F;
            --code-text: #E4E4E7;
            --code-accent: #97BC62;
            --code-comment: #6B7280;
            --code-string: #86EFAC;
            --code-keyword: #C4B5FD;
            --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.2);
            --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.3);
            --nav-bg: rgba(17, 17, 20, 0.92);
            --sidebar-bg: #18181C;
            --tag-bg: rgba(151, 188, 98, 0.1);
        }

        *,
        *::before,
        *::after {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        html {
            scroll-behavior: smooth;
            font-size: 16px;
        }

        body {
            font-family: var(--font-body);
            color: var(--text);
            background: var(--bg);
            line-height: 1.7;
            -webkit-font-smoothing: antialiased;
            overflow-x: hidden;
            transition: background 0.3s, color 0.3s;
        }

        /* ── Navigation ── */
        nav {
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            z-index: 200;
            height: var(--nav-height);
            background: var(--nav-bg);
            backdrop-filter: blur(20px);
            -webkit-backdrop-filter: blur(20px);
            border-bottom: 1px solid var(--border-light);
            transition: background 0.3s;
        }

        nav .nav-inner {
            display: flex;
            align-items: center;
            justify-content: space-between;
            height: 100%;
            padding: 0 24px;
            max-width: 100%;
        }

        .nav-left {
            display: flex;
            align-items: center;
            gap: 24px;
        }

        .nav-logo {
            display: flex;
            align-items: center;
            gap: 10px;
            text-decoration: none;
            color: var(--text);
        }

        .nav-logo svg.tux-logo {
            width: 26px;
            height: 26px;
            flex-shrink: 0;
            color: var(--text);
        }

        .nav-logo span {
            font-family: var(--font-display);
            font-weight: 600;
            font-size: 1.1rem;
            letter-spacing: -0.02em;
        }

        .nav-badge {
            font-size: 0.7rem;
            font-family: var(--font-mono);
            color: var(--accent);
            background: var(--tag-bg);
            border: 1px solid rgba(44, 95, 45, 0.15);
            padding: 3px 10px;
            border-radius: 100px;
            letter-spacing: 0.04em;
        }

        [data-theme="dark"] .nav-badge {
            border-color: rgba(151, 188, 98, 0.2);
        }

        .nav-right {
            display: flex;
            align-items: center;
            gap: 12px;
        }

        .nav-link {
            font-size: 0.85rem;
            color: var(--text-secondary);
            text-decoration: none;
            transition: color 0.2s;
        }

        .nav-link:hover {
            color: var(--text);
        }

        .btn-nav-sm {
            display: inline-flex;
            align-items: center;
            gap: 6px;
            padding: 7px 16px;
            background: var(--text);
            color: var(--bg);
            border-radius: 100px;
            font-size: 0.8rem;
            font-weight: 500;
            text-decoration: none;
            transition: opacity 0.2s;
        }

        .btn-nav-sm:hover {
            opacity: 0.82;
        }

        .theme-toggle {
            background: none;
            border: 1px solid var(--border);
            border-radius: 100px;
            width: 34px;
            height: 34px;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--text-secondary);
            transition: all 0.2s;
            flex-shrink: 0;
        }

        .theme-toggle:hover {
            color: var(--text);
            border-color: var(--text-muted);
        }

        .theme-toggle svg {
            width: 15px;
            height: 15px;
        }

        .theme-toggle .icon-moon {
            display: block;
        }

        .theme-toggle .icon-sun {
            display: none;
        }

        [data-theme="dark"] .theme-toggle .icon-moon {
            display: none;
        }

        [data-theme="dark"] .theme-toggle .icon-sun {
            display: block;
        }

        /* ── Layout ── */
        .docs-layout {
            display: grid;
            grid-template-columns: var(--sidebar-width) 1fr;
            min-height: 100vh;
            padding-top: var(--nav-height);
        }

        /* ── Sidebar ── */
        .docs-sidebar {
            position: sticky;
            top: var(--nav-height);
            height: calc(100vh - var(--nav-height));
            overflow-y: auto;
            background: var(--sidebar-bg);
            border-right: 1px solid var(--border);
            padding: 28px 0 40px;
            transition: background 0.3s;
            scrollbar-width: thin;
            scrollbar-color: var(--border) transparent;
        }

        .docs-sidebar::-webkit-scrollbar {
            width: 4px;
        }

        .docs-sidebar::-webkit-scrollbar-thumb {
            background: var(--border);
            border-radius: 2px;
        }

        .sidebar-group {
            margin-bottom: 28px;
        }

        .sidebar-group-label {
            display: block;
            font-size: 0.65rem;
            text-transform: uppercase;
            letter-spacing: 0.12em;
            color: var(--text-muted);
            font-weight: 600;
            padding: 0 20px;
            margin-bottom: 6px;
        }

        .sidebar-link {
            display: block;
            padding: 6px 20px;
            font-size: 0.84rem;
            color: var(--text-secondary);
            text-decoration: none;
            border-left: 2px solid transparent;
            transition: all 0.15s;
            line-height: 1.4;
            text-transform: lowercase;
        }

        .sidebar-link:hover {
            color: var(--text);
            background: rgba(0, 0, 0, 0.03);
        }

        [data-theme="dark"] .sidebar-link:hover {
            background: rgba(255, 255, 255, 0.03);
        }

        .sidebar-link.active {
            color: var(--accent);
            border-left-color: var(--accent);
            background: var(--tag-bg);
            font-weight: 500;
        }

        .sidebar-link code {
            font-family: var(--font-mono);
            font-size: 0.75rem;
        }

        /* ── Content ── */
        .docs-content {
            padding: 56px 64px 100px;
            max-width: 860px;
            min-width: 0;
        }

        /* ── Doc sections ── */
        .doc-section {
            margin-bottom: 72px;
            scroll-margin-top: calc(var(--nav-height) + 24px);
        }

        .doc-section-label {
            display: block;
            font-size: 0.65rem;
            text-transform: uppercase;
            letter-spacing: 0.14em;
            color: var(--accent);
            font-weight: 600;
            margin-bottom: 12px;
        }

        .doc-section h2 {
            font-family: var(--font-display);
            font-size: clamp(1.5rem, 3vw, 2rem);
            font-weight: 600;
            letter-spacing: -0.02em;
            line-height: 1.2;
            margin-bottom: 20px;
        }

        .doc-section h3 {
            font-family: var(--font-display);
            font-size: 1.15rem;
            font-weight: 600;
            letter-spacing: -0.01em;
            margin-top: 40px;
            margin-bottom: 12px;
            padding-bottom: 8px;
            border-bottom: 1px solid var(--border-light);
        }

        .doc-section h4 {
            font-size: 0.9rem;
            font-weight: 500;
            margin-top: 28px;
            margin-bottom: 10px;
            color: var(--text);
        }

        .doc-section p {
            font-size: 0.95rem;
            color: var(--text-secondary);
            line-height: 1.8;
            margin-bottom: 16px;
        }

        .doc-section p:last-child {
            margin-bottom: 0;
        }

        .doc-section ul,
        .doc-section ol {
            padding-left: 20px;
            margin-bottom: 16px;
        }

        .doc-section li {
            font-size: 0.93rem;
            color: var(--text-secondary);
            line-height: 1.8;
            margin-bottom: 4px;
        }

        .doc-section li code,
        .doc-section p code {
            font-family: var(--font-mono);
            font-size: 0.8em;
            background: var(--bg-warm);
            border: 1px solid var(--border);
            color: var(--text);
            padding: 2px 6px;
            border-radius: 4px;
        }

        /* ── Doc content links ── */
        .doc-section a {
            color: var(--accent);
            text-decoration: none;
            border-bottom: 1px solid transparent;
            transition: color 0.2s, border-color 0.2s;
        }

        .doc-section a:hover {
            color: var(--accent-light);
            border-bottom-color: var(--accent-light);
        }

        .doc-section a:visited {
            color: var(--accent);
        }

        .doc-section a:visited:hover {
            color: var(--accent-light);
        }

        /* ── Code blocks ── */
        .code-block {
            background: var(--code-bg);
            border-radius: var(--radius);
            overflow: hidden;
            margin: 20px 0;
            position: relative;
        }

        .code-block-header {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: 10px 16px;
            border-bottom: 1px solid rgba(255, 255, 255, 0.06);
        }

        .code-block-lang {
            font-family: var(--font-mono);
            font-size: 0.65rem;
            text-transform: uppercase;
            letter-spacing: 0.08em;
            color: var(--code-comment);
        }

        .code-copy-btn {
            background: rgba(255, 255, 255, 0.06);
            border: 1px solid rgba(255, 255, 255, 0.08);
            border-radius: 5px;
            padding: 4px 10px;
            cursor: pointer;
            color: var(--code-comment);
            font-size: 0.7rem;
            font-family: var(--font-mono);
            transition: all 0.2s;
        }

        .code-copy-btn:hover {
            background: rgba(255, 255, 255, 0.12);
            color: var(--code-text);
        }

        .code-block pre {
            padding: 20px 20px;
            overflow-x: auto;
            font-family: var(--font-mono);
            font-size: 0.82rem;
            line-height: 1.7;
            color: var(--code-text);
            scrollbar-width: thin;
            scrollbar-color: rgba(255, 255, 255, 0.1) transparent;
        }

        .code-block pre::-webkit-scrollbar {
            height: 4px;
        }

        .code-block pre::-webkit-scrollbar-thumb {
            background: rgba(255, 255, 255, 0.1);
            border-radius: 2px;
        }

        .code-block .c {
            color: var(--code-comment);
            font-style: italic;
        }

        .code-block .s {
            color: var(--code-string);
        }

        .code-block .k {
            color: var(--code-keyword);
        }

        .code-block .p {
            color: var(--code-accent);
        }

        /* ── Callout / Alert ── */
        .callout {
            border-radius: var(--radius-sm);
            padding: 16px 20px;
            margin: 20px 0;
            font-size: 0.88rem;
            line-height: 1.7;
            display: flex;
            gap: 12px;
            align-items: flex-start;
        }

        .callout-icon {
            flex-shrink: 0;
            margin-top: 1px;
        }

        .callout.info {
            background: rgba(97, 175, 239, 0.08);
            border: 1px solid rgba(97, 175, 239, 0.2);
            color: var(--text-secondary);
        }

        .callout.warning {
            background: rgba(229, 192, 123, 0.08);
            border: 1px solid rgba(229, 192, 123, 0.2);
            color: var(--text-secondary);
        }

        .callout.success {
            background: rgba(151, 188, 98, 0.08);
            border: 1px solid rgba(151, 188, 98, 0.2);
            color: var(--text-secondary);
        }

        .callout strong {
            color: var(--text);
        }

        /* ── Command reference table ── */
        .cmd-table {
            width: 100%;
            border-collapse: collapse;
            margin: 16px 0;
            font-size: 0.85rem;
            border-radius: var(--radius-sm);
            overflow: hidden;
            border: 1px solid var(--border);
        }

        .cmd-table thead {
            background: var(--bg-warm);
        }

        .cmd-table th {
            padding: 10px 16px;
            text-align: left;
            font-size: 0.72rem;
            text-transform: uppercase;
            letter-spacing: 0.06em;
            color: var(--text-muted);
            font-weight: 500;
            border-bottom: 1px solid var(--border);
        }

        .cmd-table td {
            padding: 11px 16px;
            border-bottom: 1px solid var(--border-light);
            vertical-align: top;
        }

        .cmd-table tr:last-child td {
            border-bottom: none;
        }

        .cmd-table td:first-child {
            font-family: var(--font-mono);
            font-size: 0.78rem;
            color: var(--code-accent);
            white-space: nowrap;
        }

        .cmd-table td:last-child {
            color: var(--text-secondary);
            line-height: 1.6;
        }

        /* ── Options list ── */
        .options-list {
            margin: 12px 0 20px;
        }

        .option-item {
            display: grid;
            grid-template-columns: auto 1fr;
            gap: 16px;
            padding: 10px 0;
            border-bottom: 1px solid var(--border-light);
            align-items: baseline;
        }

        .option-item:last-child {
            border-bottom: none;
        }

        .option-item code {
            font-family: var(--font-mono);
            font-size: 0.78rem;
            color: var(--accent);
            background: var(--tag-bg);
            padding: 2px 8px;
            border-radius: 4px;
            white-space: nowrap;
        }

        .option-item span {
            font-size: 0.85rem;
            color: var(--text-secondary);
            line-height: 1.6;
        }

        /* ── Env table ── */
        .env-table {
            width: 100%;
            border-collapse: collapse;
            margin: 16px 0;
            font-size: 0.83rem;
            border: 1px solid var(--border);
            border-radius: var(--radius-sm);
            overflow: hidden;
        }

        .env-table th {
            padding: 9px 14px;
            text-align: left;
            font-size: 0.7rem;
            text-transform: uppercase;
            letter-spacing: 0.06em;
            color: var(--text-muted);
            background: var(--bg-warm);
            border-bottom: 1px solid var(--border);
        }

        .env-table td {
            padding: 10px 14px;
            border-bottom: 1px solid var(--border-light);
            vertical-align: top;
        }

        .env-table tr:last-child td {
            border-bottom: none;
        }

        .env-table td:first-child {
            font-family: var(--font-mono);
            font-size: 0.76rem;
            color: var(--code-accent);
        }

        .env-table td:nth-child(2) {
            color: var(--text-secondary);
        }

        .env-table td:last-child {
            color: var(--text-muted);
            font-size: 0.82rem;
        }

        /* ── Structure tree ── */
        .tree-block {
            background: var(--code-bg);
            border-radius: var(--radius);
            padding: 20px 24px;
            margin: 20px 0;
            font-family: var(--font-mono);
            font-size: 0.8rem;
            line-height: 1.8;
            color: var(--code-text);
            overflow-x: auto;
            white-space: pre;
        }

        .tree-block .tree-comment {
            color: var(--code-comment);
        }

        .tree-block .tree-accent {
            color: var(--code-accent);
        }

        .tree-block pre {
            margin: 0;
            font-family: inherit;
            font-size: inherit;
            line-height: inherit;
            color: inherit;
            white-space: pre;
            overflow-x: auto;
        }

        /* ── Divider ── */
        .doc-divider {
            border: none;
            border-top: 1px solid var(--border-light);
            margin: 56px 0;
        }

        /* ── Tag pill ── */
        .tag {
            display: inline-block;
            font-size: 0.65rem;
            text-transform: uppercase;
            letter-spacing: 0.08em;
            color: var(--accent);
            background: var(--tag-bg);
            padding: 3px 9px;
            border-radius: 4px;
            font-weight: 500;
            margin-bottom: 10px;
        }

        /* ── Mobile nav toggle ── */
        .sidebar-toggle {
            display: none;
            background: none;
            border: 1px solid var(--border);
            border-radius: 100px;
            width: 34px;
            height: 34px;
            cursor: pointer;
            align-items: center;
            justify-content: center;
            color: var(--text);
            transition: all 0.2s;
        }

        .sidebar-toggle svg {
            width: 17px;
            height: 17px;
            stroke: var(--text);
        }

        .mobile-sidebar-overlay {
            display: none;
            position: fixed;
            inset: 0;
            background: rgba(0, 0, 0, 0.4);
            z-index: 150;
        }

        .mobile-sidebar-overlay.open {
            display: block;
        }

        /* ── Why ci-pi ── */
        .why-cipi-intro {
            display: grid;
            grid-template-columns: 96px 1fr;
            gap: 32px;
            align-items: start;
            margin: 28px 0 32px;
        }

        .why-cipi-mascot {
            color: var(--accent);
            flex-shrink: 0;
        }

        .why-cipi-mascot svg {
            width: 96px;
            height: 96px;
        }

        .why-cipi-text p {
            font-size: 0.9rem;
            color: var(--text-secondary);
            line-height: 1.8;
            margin-bottom: 12px;
        }

        .why-cipi-text p:last-child {
            margin-bottom: 0;
        }

        @media (max-width: 600px) {
            .why-cipi-intro {
                grid-template-columns: 1fr;
            }
        }

        /* ── History Timeline ── */
        .timeline {
            margin-top: 40px;
            position: relative;
            padding-left: 28px;
        }

        .timeline::before {
            content: '';
            position: absolute;
            left: 7px;
            top: 8px;
            bottom: 8px;
            width: 1px;
            background: var(--border);
        }

        .timeline-item {
            position: relative;
            margin-bottom: 40px;
        }

        .timeline-item:last-child {
            margin-bottom: 0;
        }

        .timeline-marker {
            position: absolute;
            left: -25px;
            top: 6px;
            width: 10px;
            height: 10px;
            border-radius: 50%;
            background: var(--border);
            border: 2px solid var(--bg-card);
            box-shadow: 0 0 0 1px var(--border);
        }

        .timeline-item--current .timeline-marker {
            background: var(--accent);
            box-shadow: 0 0 0 1px var(--accent);
        }

        .timeline-body {
            display: flex;
            flex-direction: column;
            gap: 6px;
        }

        .timeline-version {
            font-family: var(--font-mono);
            font-size: 0.72rem;
            font-weight: 600;
            color: var(--accent);
            letter-spacing: 0.05em;
        }

        .timeline-date {
            font-size: 0.75rem;
            color: var(--text-muted);
            margin-top: -4px;
            margin-bottom: 2px;
        }

        .timeline-title {
            font-size: 1rem;
            font-weight: 500;
            color: var(--text);
            letter-spacing: -0.01em;
            margin-bottom: 4px;
        }

        .timeline-body>p {
            font-size: 0.875rem;
            color: var(--text-secondary);
            line-height: 1.75;
        }

        /* ── Footer ── */
        footer {
            border-top: 1px solid var(--border-light);
            padding: 40px 0;
            background: var(--sidebar-bg);
        }

        .footer-inner {
            max-width: 860px;
            margin-left: var(--sidebar-width);
            padding: 0 64px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            font-size: 0.82rem;
            color: var(--text-muted);
        }

        .footer-inner a {
            color: var(--text-secondary);
            text-decoration: none;
            transition: color 0.2s;
        }

        .footer-inner a:hover {
            color: var(--text);
        }

        .footer-links {
            display: flex;
            gap: 20px;
            list-style: none;
        }

        /* ── Responsive ── */
        @media (max-width: 900px) {
            .docs-layout {
                grid-template-columns: 1fr;
            }

            .docs-sidebar {
                position: fixed;
                top: var(--nav-height);
                left: -100%;
                width: min(var(--sidebar-width), 80vw);
                height: calc(100vh - var(--nav-height));
                z-index: 160;
                transition: left 0.3s ease;
                box-shadow: var(--shadow-md);
            }

            .docs-sidebar.open {
                left: 0;
            }

            .sidebar-toggle {
                display: flex;
            }

            .docs-content {
                padding: 36px 24px 80px;
            }

            .footer-inner {
                margin-left: 0;
                padding: 0 24px;
                flex-direction: column;
                gap: 16px;
                text-align: center;
            }
        }

        @media (max-width: 480px) {
            .nav-badge {
                display: none;
            }

            .cmd-table {
                font-size: 0.78rem;
            }

            .cmd-table td:first-child {
                white-space: normal;
            }
        }

/* ── Current chapter sidebar highlight ── */
.sidebar-group.current-chapter .sidebar-group-label {
    color: var(--accent);
}

/* ── Chapter grid (index page) ── */
.chapter-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 16px;
    margin-top: 8px;
}

.doc-chapter-card {
    display: block;
    padding: 24px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    transition: all 0.2s;
}

.doc-chapter-card:hover {
    border-color: var(--accent);
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.doc-chapter-card h3 {
    font-family: var(--font-display);
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 8px;
    letter-spacing: -0.01em;
}

.doc-chapter-card h3 a {
    color: var(--text);
    text-decoration: none;
    transition: color 0.15s;
}

.doc-chapter-card:hover h3 a {
    color: var(--accent);
}

.doc-chapter-card p {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 12px;
}

.chapter-sections {
    list-style: none;
    padding: 0;
    display: flex;
    flex-wrap: wrap;
    gap: 4px 8px;
}

.chapter-sections li {
    font-size: 0.72rem;
}

.chapter-sections a {
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.15s;
}

.chapter-sections a:hover {
    color: var(--accent);
}

@media (max-width: 480px) {
    .chapter-grid {
        grid-template-columns: 1fr;
    }
}

/* ── Sidebar group label as link ── */
a.sidebar-group-label {
    display: block;
    font-size: 0.65rem;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--text-muted);
    font-weight: 600;
    padding: 0 20px;
    margin-bottom: 6px;
    text-decoration: none;
    transition: color 0.15s;
}

a.sidebar-group-label:hover {
    color: var(--text);
}

/* ── Page Navigation (prev/next) ── */
.page-nav {
    display: flex;
    justify-content: space-between;
    align-items: stretch;
    gap: 16px;
    margin-top: 72px;
    padding-top: 40px;
    border-top: 1px solid var(--border-light);
}

.page-nav-link {
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 16px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    text-decoration: none;
    transition: all 0.2s;
    min-width: 0;
    flex: 1;
    max-width: 50%;
}

.page-nav-link:hover {
    border-color: var(--accent);
    box-shadow: var(--shadow-sm);
}

.page-nav-link--next {
    text-align: right;
    margin-left: auto;
}

.page-nav-label {
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    font-weight: 500;
}

.page-nav-title {
    font-family: var(--font-display);
    font-size: 1rem;
    font-weight: 600;
    color: var(--accent);
    letter-spacing: -0.01em;
}

.page-nav-link:hover .page-nav-title {
    color: var(--accent-light);
}

@media (max-width: 480px) {
    .page-nav {
        flex-direction: column;
    }
    .page-nav-link {
        max-width: 100%;
    }
}