/* ============================================================
   DRAFT EBOOK — Styles
   Design: Light theme matching getdraft.dev, optimized for reading
   ============================================================ */

/* ============================================================
   VARIABLES (extends site tokens)
   ============================================================ */
:root {
    /* Backgrounds */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #f1f3f5;
    --bg-sidebar: #f8f9fa;
    --bg-code: #f5f7f9;

    /* Accents */
    --accent-cyan: #2563eb;
    --accent-amber: #d97706;
    --accent-rose: #e11d48;
    --accent-emerald: #059669;
    --accent-violet: #7c3aed;

    /* Text */
    --text-primary: #111827;
    --text-secondary: #334155;
    --text-muted: #475569;
    --text-reading: #1f2937;

    /* Borders */
    --border: #e2e8f0;
    --border-subtle: rgba(0, 0, 0, 0.06);

    /* Glass */
    --glass-bg: rgba(255, 255, 255, 0.85);
    --glass-border: rgba(0, 0, 0, 0.06);

    /* Sidebar */
    --sidebar-width: 300px;

    /* Transitions */
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

/* ============================================================
   RESET & BASE
   ============================================================ */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: 'DM Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.7;
    overflow-x: hidden;
}

::selection {
    background: rgba(37, 99, 235, 0.2);
    color: var(--text-primary);
}

::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-secondary); }
::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: #94a3b8; }

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

/* ============================================================
   READING PROGRESS BAR
   ============================================================ */
.reading-progress {
    position: fixed;
    top: 0;
    left: 0;
    width: 0%;
    height: 3px;
    background: linear-gradient(90deg, #2563eb, #7c3aed);
    z-index: 200;
    transition: width 0.15s ease-out;
}

/* ============================================================
   BOOK LAYOUT
   ============================================================ */
.book-layout {
    min-height: 100vh;
}

/* ============================================================
   TOP BAR
   ============================================================ */
.book-topbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 56px;
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 1.5rem;
    z-index: 150;
}

.book-topbar-left {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.book-topbar-logo {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.03em;
}

.book-topbar-logo span {
    color: var(--text-muted);
    font-weight: 400;
    font-size: 0.9rem;
    margin-left: 0.25rem;
}

.book-topbar-divider {
    width: 1px;
    height: 24px;
    background: var(--border);
}

.book-topbar-chapter {
    font-size: 0.85rem;
    color: var(--text-secondary);
    max-width: 300px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.book-topbar-right {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.book-topbar-link {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: color 0.2s;
}

.book-topbar-link:hover {
    color: var(--text-primary);
}

.topbar-github {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.4rem 0.8rem;
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-primary);
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 6px;
    transition: border-color 0.2s;
}

.topbar-github:hover {
    border-color: var(--accent-cyan);
}

/* Mobile sidebar toggle */
.sidebar-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}

.sidebar-toggle span {
    width: 20px;
    height: 2px;
    background: var(--text-secondary);
    border-radius: 1px;
    transition: transform 0.3s, opacity 0.3s;
}

/* ============================================================
   SIDEBAR
   ============================================================ */
.book-sidebar {
    position: fixed;
    top: 56px;
    left: 0;
    bottom: 0;
    width: var(--sidebar-width);
    background: var(--bg-sidebar);
    border-right: 1px solid var(--border);
    overflow-y: auto;
    overflow-x: hidden;
    padding: 1.5rem 0;
    z-index: 100;
    scrollbar-width: thin;
    scrollbar-color: #cbd5e1 transparent;
}

.book-sidebar::-webkit-scrollbar { width: 4px; }
.book-sidebar::-webkit-scrollbar-track { background: transparent; }
.book-sidebar::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 2px; }

/* Sidebar search */
.sidebar-search {
    padding: 0 1.25rem 1rem;
    position: relative;
}

.sidebar-search input {
    width: 100%;
    padding: 0.5rem 0.75rem 0.5rem 2rem;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.8rem;
    outline: none;
    transition: border-color 0.2s;
}

.sidebar-search input:focus {
    border-color: var(--accent-cyan);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.sidebar-search input::placeholder {
    color: var(--text-muted);
}

.sidebar-search-icon {
    position: absolute;
    left: 1.75rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    pointer-events: none;
    margin-top: -0.5rem;
}

/* Sidebar parts & chapters */
.sidebar-part {
    padding: 0 1.25rem;
    margin-bottom: 0.25rem;
}

.sidebar-part-title {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    font-weight: 500;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-muted);
    padding: 1rem 0 0.5rem;
    border-top: 1px solid var(--border-subtle);
}

.sidebar-part:first-child .sidebar-part-title {
    border-top: none;
    padding-top: 0.5rem;
}

.sidebar-chapters {
    list-style: none;
}

.sidebar-chapter {
    display: block;
    padding: 0.4rem 0.75rem;
    margin: 1px 0;
    font-size: 0.85rem;
    color: var(--text-secondary);
    border-radius: 6px;
    transition: color 0.15s, background 0.15s;
    cursor: pointer;
    line-height: 1.4;
}

.sidebar-chapter:hover {
    color: var(--text-primary);
    background: rgba(0, 0, 0, 0.04);
}

.sidebar-chapter.active {
    color: var(--accent-cyan);
    background: rgba(37, 99, 235, 0.08);
    font-weight: 500;
}

.sidebar-chapter .ch-num {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-right: 0.4rem;
    min-width: 1.5rem;
    display: inline-block;
}

.sidebar-chapter.active .ch-num {
    color: var(--accent-cyan);
    opacity: 0.7;
}

/* ============================================================
   MAIN CONTENT AREA
   ============================================================ */
.book-content {
    margin-left: var(--sidebar-width);
    padding-top: 56px;
    padding-right: 220px; /* reserve space for the fixed page-toc (200px + gap) */
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.chapter-wrapper {
    width: 100%;
    max-width: 860px;
    padding: 3rem 2.5rem 4rem;
}

/* Loading state */
.chapter-loading {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 50vh;
    color: var(--text-muted);
    font-size: 0.9rem;
}

.chapter-loading::after {
    content: '';
    width: 20px;
    height: 20px;
    border: 2px solid var(--border);
    border-top-color: var(--accent-cyan);
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
    margin-left: 0.75rem;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ============================================================
   CHAPTER TYPOGRAPHY
   ============================================================ */
.chapter-wrapper h1 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: clamp(2rem, 4vw, 2.75rem);
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.15;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
}

.chapter-meta {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 0.5rem;
    letter-spacing: 0.02em;
}

.chapter-meta .part-name {
    color: var(--accent-cyan);
}

.read-time {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 2.5rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--border);
}

.chapter-intro {
    font-size: 1.15rem;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 2rem;
}

.chapter-wrapper h2 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    line-height: 1.2;
    color: var(--text-primary);
    margin-top: 3rem;
    margin-bottom: 1rem;
    padding-top: 1rem;
}

.chapter-wrapper h3 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-top: 2rem;
    margin-bottom: 0.75rem;
}

.chapter-wrapper h4 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-top: 1.5rem;
    margin-bottom: 0.5rem;
}

.chapter-wrapper p {
    font-size: 1.0625rem;
    color: var(--text-reading);
    line-height: 1.85;
    margin-bottom: 1.25rem;
}

.chapter-wrapper strong {
    color: var(--text-primary);
    font-weight: 600;
}

.chapter-wrapper em {
    color: var(--text-secondary);
    font-style: italic;
}

.chapter-wrapper ul,
.chapter-wrapper ol {
    padding-left: 1.5rem;
    margin-bottom: 1.25rem;
}

.chapter-wrapper li {
    font-size: 1rem;
    color: var(--text-reading);
    line-height: 1.8;
    margin-bottom: 0.4rem;
}

.chapter-wrapper li::marker {
    color: var(--accent-cyan);
}

.chapter-wrapper blockquote {
    border-left: 3px solid var(--accent-violet);
    padding: 0.75rem 1.25rem;
    margin: 1.5rem 0;
    background: rgba(124, 58, 237, 0.04);
    border-radius: 0 8px 8px 0;
}

.chapter-wrapper blockquote p {
    font-size: 1rem;
    color: var(--text-secondary);
    font-style: italic;
    margin-bottom: 0;
}

.chapter-wrapper hr {
    border: none;
    height: 1px;
    background: var(--border);
    margin: 2.5rem 0;
}

/* Inline links */
.chapter-wrapper a {
    color: var(--accent-cyan);
    text-decoration: underline;
    text-underline-offset: 3px;
    text-decoration-color: rgba(37, 99, 235, 0.3);
    transition: text-decoration-color 0.2s;
}

.chapter-wrapper a:hover {
    text-decoration-color: var(--accent-cyan);
}

/* ============================================================
   CODE BLOCKS
   ============================================================ */
.chapter-wrapper code {
    font-family: 'JetBrains Mono', monospace;
    background: var(--bg-code);
    padding: 0.15rem 0.4rem;
    border-radius: 4px;
    font-size: 0.85em;
    color: #b35900;
    border: 1px solid var(--border);
}

.chapter-wrapper pre {
    background: var(--bg-code);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.25rem 1.5rem;
    margin: 1.5rem 0;
    overflow-x: auto;
    position: relative;
}

.chapter-wrapper pre code {
    background: none;
    border: none;
    padding: 0;
    font-size: 0.875rem;
    color: var(--text-reading);
    line-height: 1.7;
}

/* Terminal-style code block */
.chapter-wrapper pre.terminal {
    background: #eef0f4;
    border-color: rgba(37, 99, 235, 0.15);
    padding-top: 1.75rem;
}

.chapter-wrapper pre.terminal::before {
    content: 'Terminal';
    position: absolute;
    top: 0;
    left: 1.25rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    background: #eef0f4;
    padding: 0 0.5rem;
    transform: translateY(-50%);
}

.chapter-wrapper pre.terminal code {
    color: var(--accent-emerald);
    white-space: pre;
    word-break: keep-all;
}

/* Copy button on code blocks */
.copy-btn {
    position: absolute;
    top: 0.4rem;
    right: 0.5rem;
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(255, 255, 255, 0.7);
    border: 1px solid var(--border);
    border-radius: 5px;
    cursor: pointer;
    color: var(--text-muted);
    transition: color 0.15s, background 0.15s, border-color 0.15s;
    z-index: 2;
    padding: 0;
}

.copy-btn:hover {
    color: var(--text-primary);
    background: var(--bg-primary);
    border-color: rgba(37, 99, 235, 0.3);
}

.copy-btn.copied {
    color: var(--accent-emerald);
    border-color: rgba(5, 150, 105, 0.3);
}

.copy-btn svg {
    width: 14px;
    height: 14px;
}

/* File path label on code blocks */
.chapter-wrapper pre[data-file]::before {
    content: attr(data-file);
    position: absolute;
    top: 0;
    left: 1.25rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    color: var(--text-muted);
    letter-spacing: 0.02em;
    background: var(--bg-code);
    padding: 0 0.5rem;
    transform: translateY(-50%);
}

/* ============================================================
   CALLOUT BOXES
   ============================================================ */
.callout {
    border-radius: 12px;
    padding: 1.25rem 1.5rem;
    margin: 1.5rem 0;
    border: 1px solid;
}

.callout-title {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 0.85rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.callout p {
    font-size: 0.95rem;
    margin-bottom: 0.5rem;
}

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

/* Concept callout */
.callout-concept {
    background: rgba(37, 99, 235, 0.04);
    border-color: rgba(37, 99, 235, 0.15);
}

.callout-concept .callout-title {
    color: var(--accent-cyan);
}

/* Example callout */
.callout-example {
    background: rgba(124, 58, 237, 0.04);
    border-color: rgba(124, 58, 237, 0.15);
}

.callout-example .callout-title {
    color: var(--accent-violet);
}

/* Tip callout */
.callout-tip {
    background: rgba(5, 150, 105, 0.04);
    border-color: rgba(5, 150, 105, 0.15);
}

.callout-tip .callout-title {
    color: var(--accent-emerald);
}

/* Warning callout */
.callout-warning {
    background: rgba(217, 119, 6, 0.04);
    border-color: rgba(217, 119, 6, 0.15);
}

.callout-warning .callout-title {
    color: var(--accent-amber);
}

/* Insight callout */
.callout-insight {
    background: rgba(225, 29, 72, 0.04);
    border-color: rgba(225, 29, 72, 0.15);
}

.callout-insight .callout-title {
    color: var(--accent-rose);
}

/* ============================================================
   TABLES
   ============================================================ */
.chapter-wrapper table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
    font-size: 0.9rem;
}

.chapter-wrapper thead th {
    font-family: 'Space Grotesk', sans-serif;
    font-weight: 600;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-muted);
    text-align: left;
    padding: 0.75rem 1rem;
    border-bottom: 2px solid var(--border);
}

.chapter-wrapper tbody td {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border-subtle);
    color: var(--text-reading);
    vertical-align: top;
}

.chapter-wrapper tbody tr:hover {
    background: rgba(0, 0, 0, 0.02);
}

/* ============================================================
   DIAGRAM / FIGURE
   ============================================================ */
.figure {
    margin: 2rem 0;
    text-align: center;
}

.figure-content {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 2rem;
    overflow-x: auto;
}

.figure-caption {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: 0.75rem;
    font-style: italic;
}

/* ASCII diagrams */
.diagram {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    line-height: 1.5;
    color: var(--text-secondary);
    white-space: pre;
    text-align: left;
    display: inline-block;
}

.diagram .highlight {
    color: var(--accent-cyan);
    font-weight: 500;
}

/* ============================================================
   CHAPTER NAVIGATION (prev/next — compact top bar)
   ============================================================ */
.chapter-nav {
    order: -1;
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    max-width: 860px;
    padding: 0.6rem 1rem;
    margin-bottom: 0;
    border-bottom: 1px solid var(--border-subtle);
}

.chapter-nav-link {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    padding: 0.35rem 0.85rem;
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 100px;
    text-decoration: none !important;
    transition: border-color 0.2s, color 0.2s, background 0.2s;
    white-space: nowrap;
}

.chapter-nav-link:hover {
    border-color: rgba(37, 99, 235, 0.3);
    color: var(--accent-cyan);
    background: rgba(37, 99, 235, 0.04);
}

.chapter-nav-link--next {
    text-align: right;
}

.chapter-nav-label {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
}

.chapter-nav-title {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 0.8rem;
    font-weight: 500;
    color: inherit;
}

/* ============================================================
   ON THIS PAGE (mini-TOC)
   ============================================================ */
.page-toc {
    position: fixed;
    right: 2rem;
    top: 56px;
    width: 200px;
    padding: 1.5rem 0;
    max-height: calc(100vh - 56px);
    overflow-y: auto;
    z-index: 50;
}

.page-toc-title {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    font-weight: 500;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-muted);
    margin-bottom: 0.75rem;
}

.page-toc-list {
    list-style: none;
}

.page-toc-item {
    display: block;
    font-size: 0.8rem;
    color: var(--text-muted);
    padding: 0.25rem 0;
    padding-left: 0.75rem;
    border-left: 1px solid var(--border-subtle);
    transition: color 0.15s, border-color 0.15s;
    line-height: 1.4;
}

.page-toc-item:hover {
    color: var(--text-secondary);
}

.page-toc-item.active {
    color: var(--accent-cyan);
    border-left-color: var(--accent-cyan);
}

.page-toc-item--h3 {
    padding-left: 1.5rem;
    font-size: 0.75rem;
}

/* ============================================================
   LANDING PAGE (chapter 0 / TOC)
   ============================================================ */
.book-landing {
    text-align: center;
    padding: 4rem 0 2rem;
}

.book-landing h1 {
    font-size: clamp(2.5rem, 5vw, 3.5rem);
    margin-bottom: 1rem;
}

.book-landing .gradient-text {
    background: linear-gradient(135deg, var(--accent-cyan), var(--accent-violet), var(--accent-rose), var(--accent-cyan));
    background-size: 300% 300%;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: gradient-shift 8s ease infinite;
}

@keyframes gradient-shift {
    0%   { background-position: 0% 50%; }
    50%  { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

.book-landing-subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
    max-width: 550px;
    margin: 0 auto 3rem;
}

.book-toc {
    text-align: left;
    max-width: 600px;
    margin: 0 auto;
}

.book-toc-part {
    margin-bottom: 1.5rem;
}

.book-toc-part-title {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    font-weight: 500;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--accent-cyan);
    margin-bottom: 0.5rem;
}

.book-toc-list {
    list-style: none;
}

.book-toc-entry {
    display: flex;
    align-items: baseline;
    gap: 0.75rem;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-subtle);
    cursor: pointer;
    transition: background 0.15s;
}

.book-toc-entry:hover {
    background: rgba(0, 0, 0, 0.02);
}

.book-toc-num {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    color: var(--text-muted);
    min-width: 2rem;
}

.book-toc-name {
    font-size: 1rem;
    color: var(--text-primary);
    font-weight: 500;
}

.book-toc-time {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-left: auto;
}

/* ============================================================
   FOOTER
   ============================================================ */
.book-footer {
    border-top: 1px solid var(--border);
    padding: 2rem 0;
    margin-top: 2rem;
    text-align: center;
    font-size: 0.8rem;
    color: var(--text-muted);
}

.book-footer a {
    color: var(--accent-cyan);
}

/* ============================================================
   RESPONSIVE
   ============================================================ */

/* Hide page-toc below 1200px */
@media (max-width: 1200px) {
    .page-toc { display: none; }
    .book-content { padding-right: 0; }
}

/* Tablet */
@media (max-width: 1024px) {
    :root {
        --sidebar-width: 260px;
    }

    .chapter-wrapper {
        padding: 2.5rem 2rem 3rem;
    }
}

/* Mobile */
@media (max-width: 768px) {
    .book-sidebar {
        transform: translateX(-100%);
        transition: transform 0.3s var(--ease-out);
        width: 280px;
        z-index: 140;
        background: var(--bg-primary);
    }

    .book-sidebar.open {
        transform: translateX(0);
    }

    .sidebar-backdrop {
        display: none;
        position: fixed;
        inset: 0;
        background: rgba(0, 0, 0, 0.3);
        z-index: 130;
    }

    .sidebar-backdrop.visible {
        display: block;
    }

    .sidebar-toggle {
        display: flex;
    }

    .book-content {
        margin-left: 0;
    }

    .chapter-wrapper {
        padding: 2rem 1.25rem 3rem;
    }

    .chapter-wrapper h1 {
        font-size: 1.75rem;
    }

    .chapter-wrapper h2 {
        font-size: 1.3rem;
    }

    .chapter-wrapper h3 {
        font-size: 1.1rem;
    }

    /* Tables: horizontal scroll on mobile */
    .chapter-wrapper table {
        display: block;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        white-space: nowrap;
    }

    /* Code blocks: bleed slightly for more width */
    .chapter-wrapper pre {
        border-radius: 8px;
        padding: 1rem;
        margin-left: -0.5rem;
        margin-right: -0.5rem;
        font-size: 0.82rem;
    }

    .chapter-wrapper pre code {
        font-size: 0.82rem;
    }

    /* Diagrams: allow scroll */
    .figure-content {
        padding: 1rem;
    }

    .diagram {
        font-size: 0.68rem;
        overflow-x: auto;
        max-width: 100%;
        display: block;
    }

    /* Callouts: tighter on mobile */
    .callout {
        padding: 1rem 1.1rem;
        border-radius: 10px;
    }

    /* Chapter nav: hide titles, keep arrow labels */
    .chapter-nav {
        padding: 0.5rem 0.75rem;
    }
    .chapter-nav-title {
        display: none;
    }
    .chapter-nav-link {
        padding: 0.3rem 0.7rem;
        font-size: 0.75rem;
    }

    .book-topbar-chapter {
        display: none;
    }

    .book-topbar-divider {
        display: none;
    }

    .book-topbar-right .book-topbar-link {
        display: none;
    }

    /* Book landing page on mobile */
    .book-landing {
        padding: 2rem 0 1rem;
    }

    .book-toc-entry {
        padding: 0.6rem 0.25rem;
    }

    .book-toc-time {
        display: none;
    }
}

/* Small mobile */
@media (max-width: 480px) {
    .chapter-wrapper {
        padding: 1.5rem 0.75rem 2.5rem;
    }

    .chapter-wrapper h1 {
        font-size: 1.5rem;
    }

    .chapter-wrapper p {
        font-size: 1rem;
    }

    .chapter-wrapper pre {
        border-radius: 8px;
        padding: 0.85rem;
        margin-left: -0.75rem;
        margin-right: -0.75rem;
    }

    .chapter-wrapper pre code {
        font-size: 0.78rem;
    }

    .book-topbar {
        padding: 0 1rem;
    }

    .book-topbar-logo span {
        display: none;
    }

    .chapter-nav-link {
        padding: 0.25rem 0.6rem;
        font-size: 0.7rem;
    }
}

/* ============================================================
   PRINT
   ============================================================ */
@media print {
    .book-sidebar,
    .book-topbar,
    .reading-progress,
    .page-toc,
    .chapter-nav,
    .sidebar-toggle,
    .sidebar-backdrop {
        display: none !important;
    }

    .book-content {
        margin-left: 0;
    }

    .chapter-wrapper {
        max-width: 100%;
        padding: 0;
    }

    body {
        background: white;
        color: #1a1a1a;
    }

    .chapter-wrapper p,
    .chapter-wrapper li {
        color: #333;
    }

    .chapter-wrapper pre {
        border: 1px solid #ccc;
        background: #f5f5f5;
    }
}