/* Layout - Book-like Reading Experience with Sidebar Navigation */

:root {
    /* Light Theme Colors */
    --color-bg: #FAF9F7;
    --color-bg-secondary: #F3F1EE;
    --color-text: #2C2C2C;
    --color-text-secondary: #5C5C5C;
    --color-text-strong: #1A1A1A;
    --color-primary: #2563EB;
    --color-border: #E0DED9;
    --color-code-bg: #F5F3F0;
    --color-code-block-bg: #1E293B;
    --color-code-text: #E2E8F0;

    /* Spacing */
    --space-xs: 0.5rem;
    --space-sm: 1rem;
    --space-md: 1.5rem;
    --space-lg: 2rem;
    --space-xl: 3rem;
    --space-2xl: 4rem;

    /* Container Widths */
    --width-reading: 1000px;
    --width-wide: 1200px;
    --sidebar-width: 260px;
    --outline-width: 220px;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;
}

/* Global Reset */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* Body */
body {
    background: var(--color-bg);
    color: var(--color-text);
    margin: 0;
    padding: 0;
    min-height: 100vh;
    transition: background-color var(--transition-base), color var(--transition-base);
}

/* Progress Bar */
.progress-bar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--color-bg-secondary);
    z-index: 1000;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--color-primary), #3B82F6);
    transition: width var(--transition-slow);
}

/* Chapter Header */
.chapter-header {
    position: sticky;
    top: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    padding: 0 1.25rem;
    height: 44px;
    display: flex;
    align-items: center;
    z-index: 100;
    backdrop-filter: blur(10px);
    background: rgba(250, 249, 247, 0.95);
}

.header-content {
    max-width: 1600px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    height: 100%;
}

.home-link {
    font-family: var(--font-sans);
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--color-primary);
    text-decoration: none;
    padding: 0;
    border-radius: 6px;
    transition: all var(--transition-fast);
    line-height: 1;
}

.home-link:hover {
    opacity: 0.8;
}
span.home-link:hover {
    opacity: 1;
    cursor: default;
}

.header-controls {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.chapter-num {
    font-family: var(--font-sans);
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
}

/* Sidebar Toggle (Hamburger) */
.sidebar-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: var(--space-xs);
    border-radius: 6px;
    color: var(--color-text);
    transition: all var(--transition-fast);
    line-height: 1;
}

.sidebar-toggle:hover {
    background: var(--color-bg-secondary);
}

/* ===== Page Layout: 3-Column Grid ===== */
.page-wrapper {
    display: grid;
    grid-template-columns: var(--sidebar-width) 1fr var(--outline-width);
    max-width: 1600px;
    margin: 0 auto;
    min-height: calc(100vh - 60px);
}

/* ===== Left Sidebar: Chapter List ===== */
.sidebar {
    position: sticky;
    top: 57px; /* header height */
    height: calc(100vh - 57px);
    overflow-y: auto;
    border-right: 1px solid var(--color-border);
    background: var(--color-bg);
    padding: var(--space-md) 0;
    font-family: var(--font-sans);
    scrollbar-width: thin;
    scrollbar-color: var(--color-border) transparent;
    z-index: 10;
}

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

.sidebar::-webkit-scrollbar-thumb {
    background: var(--color-border);
    border-radius: 4px;
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 var(--space-md) var(--space-md);
    font-size: 0.8125rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-secondary);
}

.sidebar-close {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--color-text-secondary);
    padding: 0;
    line-height: 1;
}

.sidebar-part {
    margin-bottom: var(--space-md);
}

.part-title {
    font-size: 0.6875rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--color-text-secondary);
    padding: var(--space-xs) var(--space-md);
    margin: 0;
    opacity: 0.7;
}

.sidebar-chapters {
    list-style: none;
    padding: 0;
    margin: var(--space-xs) 0 0 0;
}

.sidebar-link {
    display: flex;
    align-items: baseline;
    gap: 0.5rem;
    padding: 0.4rem var(--space-md);
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    text-decoration: none;
    transition: all var(--transition-fast);
    border-left: 3px solid transparent;
    line-height: 1.4;
}

.sidebar-link:hover {
    color: var(--color-primary);
    background: var(--color-bg-secondary);
}

.sidebar-link.active {
    color: var(--color-primary);
    font-weight: 600;
    border-left-color: var(--color-primary);
    background: rgba(37, 99, 235, 0.06);
}

.sidebar-link.completed {
    color: #10B981;
}

.sidebar-link.completed::after {
    content: '\2713';
    margin-left: auto;
    font-size: 0.75rem;
    opacity: 0.7;
}

.sidebar-num {
    font-size: 0.75rem;
    font-weight: 600;
    min-width: 1.25rem;
    opacity: 0.6;
}

/* ===== Right Sidebar: On This Page Outline ===== */
.outline-sidebar {
    position: sticky;
    top: 57px;
    height: calc(100vh - 57px);
    overflow-y: auto;
    border-left: 1px solid var(--color-border);
    background: var(--color-bg);
    padding: var(--space-md) 0;
    font-family: var(--font-sans);
    scrollbar-width: thin;
    scrollbar-color: var(--color-border) transparent;
}

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

.outline-sidebar::-webkit-scrollbar-thumb {
    background: var(--color-border);
    border-radius: 4px;
}

.outline-header {
    font-size: 0.8125rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-secondary);
    padding: 0 var(--space-md) var(--space-md);
}

.outline-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.outline-list li {
    margin: 0;
}

.outline-link {
    display: block;
    padding: 0.3rem var(--space-md);
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    text-decoration: none;
    transition: all var(--transition-fast);
    border-left: 2px solid transparent;
    line-height: 1.4;
}

.outline-link:hover {
    color: var(--color-primary);
}

.outline-link.active {
    color: var(--color-primary);
    border-left-color: var(--color-primary);
    font-weight: 500;
}

.outline-link.outline-h3 {
    padding-left: calc(var(--space-md) + 0.75rem);
    font-size: 0.75rem;
}

/* Sidebar Overlay (mobile) */
.sidebar-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 90;
    opacity: 0;
    transition: opacity var(--transition-base);
}

.sidebar-overlay.visible {
    display: block;
    opacity: 1;
}

/* Main Content */
.chapter-content {
    padding: var(--space-2xl) var(--space-lg);
    min-width: 0; /* prevent grid blowout */
}

.book-page {
    background: white;
    padding: var(--space-2xl);
    border-radius: 12px;
    box-shadow: var(--shadow-lg);
    margin-bottom: var(--space-xl);
    overflow: hidden;
    max-width: 100%;
}

/* Chapter Navigation */
.chapter-nav {
    margin: var(--space-2xl) 0;
}

.nav-buttons {
    display: flex;
    justify-content: space-between;
    gap: var(--space-md);
    flex-wrap: wrap;
}

.nav-btn {
    font-family: var(--font-sans);
    font-size: var(--text-sm);
    font-weight: 600;
    padding: var(--space-sm) var(--space-lg);
    border-radius: 8px;
    text-decoration: none;
    transition: all var(--transition-base);
    display: inline-flex;
    align-items: center;
    gap: var(--space-xs);
}

.prev-btn, .next-btn {
    background: var(--color-primary);
    color: white;
}

.prev-btn:hover, .next-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.toc-btn {
    background: var(--color-bg-secondary);
    color: var(--color-text);
}

.toc-btn:hover {
    background: var(--color-border);
}

.nav-btn.disabled {
    background: var(--color-bg-secondary);
    color: var(--color-text-secondary);
    opacity: 0.5;
    cursor: not-allowed;
}

/* Buttons */
.icon-btn {
    background: none;
    border: none;
    font-size: 1.1rem;
    cursor: pointer;
    padding: 0.25rem;
    border-radius: 6px;
    transition: all var(--transition-fast);
    line-height: 1;
}

.icon-btn:hover {
    background: var(--color-bg-secondary);
}

/* Back to Top */
.back-to-top {
    position: fixed;
    bottom: var(--space-xl);
    right: var(--space-xl);
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--color-primary);
    color: white;
    border: none;
    font-size: var(--text-xl);
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    transform: scale(0.8);
    transition: all var(--transition-base);
    z-index: 50;
}

.back-to-top.visible {
    opacity: 1;
    transform: scale(1);
}

.back-to-top:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-xl);
}

/* Images */
img {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 2em auto;
    border-radius: 4px;
}

/* Ensure images stay within reading container */
.book-page img {
    max-width: 100% !important;
    width: auto !important;
    height: auto !important;
    object-fit: contain;
    box-sizing: border-box;
}

/* Images in paragraphs */
.book-page p img {
    max-width: 100% !important;
}

/* Figure captions */
.book-page figure {
    margin: 2em 0;
    text-align: center;
}

.book-page figcaption {
    font-family: var(--font-sans);
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
    margin-top: var(--space-sm);
    font-style: italic;
    text-align: center;
}

/* ===== Responsive Design ===== */

/* Hide outline on medium screens */
@media (max-width: 1279px) {
    .page-wrapper {
        grid-template-columns: var(--sidebar-width) 1fr;
    }
    .outline-sidebar {
        display: none;
    }
}

/* Collapse sidebar on tablet/mobile */
@media (max-width: 1023px) {
    .sidebar-toggle {
        display: block;
    }

    .sidebar-close {
        display: block;
    }

    .page-wrapper {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: fixed;
        top: 0;
        left: 0;
        bottom: 0;
        width: var(--sidebar-width);
        transform: translateX(-100%);
        transition: transform var(--transition-base);
        z-index: 200;
        padding-top: var(--space-md);
        box-shadow: none;
    }

    .sidebar.open {
        transform: translateX(0);
        box-shadow: var(--shadow-xl);
    }
}

@media (max-width: 768px) {
    .chapter-content {
        padding: var(--space-lg) var(--space-sm);
    }

    .book-page {
        padding: var(--space-lg) var(--space-md);
        border-radius: 0;
        box-shadow: none;
    }

    /* Mobile image adjustments */
    .book-page img {
        margin: 1.5em auto;
        max-width: 100% !important;
    }

    .nav-buttons {
        flex-direction: column;
    }

    .nav-btn {
        width: 100%;
        justify-content: center;
    }

    .back-to-top {
        bottom: var(--space-md);
        right: var(--space-md);
        width: 40px;
        height: 40px;
    }

    .header-content {
        gap: var(--space-sm);
    }

    .chapter-num {
        display: none;
    }
}

/* Print Styles */
@media print {
    .progress-bar,
    .chapter-header,
    .chapter-nav,
    .back-to-top,
    .sidebar,
    .outline-sidebar,
    .sidebar-overlay {
        display: none;
    }

    .page-wrapper {
        grid-template-columns: 1fr;
    }

    .book-page {
        box-shadow: none;
        padding: 0;
    }

    body {
        background: white;
    }
}