/* ============================================
   IOSE - Intent-Oriented Software Engineering
   Modern CSS Design System
   ============================================ */
/* Breakpoints (keep in sync with scripts.html): 1024 sidebar, 768 tablet, 640 large phone, 480 small phone */

/* CSS Variables */
:root {
    /* Colors - Primary */
    --color-primary-50: #eff6ff;
    --color-primary-100: #dbeafe;
    --color-primary-200: #bfdbfe;
    --color-primary-300: #93c5fd;
    --color-primary-400: #60a5fa;
    --color-primary-500: #3b82f6;
    --color-primary-600: #2563eb;
    --color-primary-700: #1d4ed8;
    --color-primary-800: #1e40af;
    --color-primary-900: #1e3a8a;

    /* Colors - Accent */
    --color-accent-cyan: #06b6d4;
    --color-accent-purple: #8b5cf6;
    --color-accent-pink: #ec4899;
    --color-accent-orange: #f97316;

    /* Colors - Neutral */
    --color-gray-50: #f8fafc;
    --color-gray-100: #f1f5f9;
    --color-gray-200: #e2e8f0;
    --color-gray-300: #cbd5e1;
    --color-gray-400: #94a3b8;
    --color-gray-500: #64748b;
    --color-gray-600: #475569;
    --color-gray-700: #334155;
    --color-gray-800: #1e293b;
    --color-gray-900: #0f172a;

    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-secondary: linear-gradient(135deg, #06b6d4 0%, #3b82f6 100%);
    --gradient-accent: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --gradient-dark: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    --gradient-hero: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);

    /* Typography */
    --font-sans: 'Inter', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    --space-16: 4rem;
    --space-20: 5rem;
    --space-24: 6rem;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    --shadow-glow: 0 0 40px rgba(102, 126, 234, 0.3);

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

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
}

/* Reset & Base */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

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

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-gray-800);
    background-color: #ffffff;
}

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

img {
    max-width: 100%;
    height: auto;
}

/* Container */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-6);
}

/* ============================================
   Header
   ============================================ */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid rgba(226, 232, 240, 0.6);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: flex-start;
    height: 64px;
    gap: var(--space-6);
}

.header-inner .logo {
    flex-shrink: 0;
}

.header-inner .header-actions {
    margin-left: auto;
    flex-shrink: 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--color-gray-900);
}

.logo-icon {
    font-size: 1.5rem;
}

.main-nav {
    display: flex;
    align-items: center;
    gap: var(--space-8);
}

.nav-link {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-gray-600);
    transition: color var(--transition-fast);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--gradient-primary);
    transition: width var(--transition-base);
}

.nav-link:hover,
.nav-link.active {
    color: var(--color-primary-600);
}

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.header-slogan {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.slogan-main .mobile-br {
    display: none;
}

.slogan-main {
    font-size: 1.25rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: 0.02em;
}

.slogan-divider {
    width: 4px;
    height: 20px;
    background: var(--color-gray-300);
    border-radius: var(--radius-full);
}

.slogan-sub {
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--color-gray-600);
    letter-spacing: 0.02em;
}

/* 768px–1023px: keep main + sub, hide divider */
@media (max-width: 1023px) {
    .slogan-divider {
        display: none;
    }
}

@media (max-width: 768px) {
    .header-inner {
        gap: var(--space-3);
    }

    .header-slogan {
        flex-direction: column;
        gap: var(--space-1);
        min-width: 0;
        flex-shrink: 1;
    }

    .slogan-main {
        font-size: 1rem;
        line-height: 1.35;
        text-align: center;
    }

    .slogan-main .mobile-br {
        display: inline;
    }

    .slogan-sub {
        font-size: 0.75rem;
    }

    .header-actions {
        gap: var(--space-1);
    }

    .header-actions .btn {
        padding: var(--space-2) var(--space-2);
        font-size: 0.75rem;
    }
}

/* 640px and below: only main slogan, tighter header */
@media (max-width: 640px) {
    .slogan-sub {
        display: none;
    }

    .header-inner {
        gap: var(--space-2);
    }

    .header-actions {
        gap: var(--space-1);
    }

    .header-actions .btn {
        padding: var(--space-2) 0.375rem;
        font-size: 0.6875rem;
    }
}

/* 480px: compact main slogan and header buttons */
@media (max-width: 480px) {
    .slogan-main {
        font-size: 0.9375rem;
    }

    .header-actions .btn {
        padding: var(--space-2) 0.25rem;
        font-size: 0.625rem;
    }
}

/* Header TOC button: only on chapter pages at mobile breakpoint (see scripts.html MOBILE_BREAKPOINT) */
.header-toc-btn {
    display: none;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-4);
    margin-right: var(--space-2);
    border: none;
    background: var(--color-gray-100);
    color: var(--color-gray-700);
    font-size: 0.875rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.header-toc-btn:hover {
    background: var(--color-primary-100);
    color: var(--color-primary-600);
}

@media (max-width: 1024px) {
    body.has-sidebar .header-toc-btn {
        display: flex;
    }
}

@media (max-width: 640px) {
    .header-toc-btn .header-toc-btn-text {
        display: none;
    }

    .header-toc-btn {
        padding: var(--space-2);
    }
}

.header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    min-width: 0;
}

.header-actions .btn {
    white-space: nowrap;
    flex-shrink: 0;
}

.language-switch {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-size: 0.875rem;
}

.lang-current {
    font-weight: 600;
    color: var(--color-gray-900);
}

.lang-link {
    color: var(--color-gray-500);
    transition: color var(--transition-fast);
}

.lang-link:hover {
    color: var(--color-primary-600);
}

/* ============================================
   Buttons
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-5);
    font-size: 0.875rem;
    font-weight: 600;
    border-radius: var(--radius-lg);
    transition: all var(--transition-base);
    cursor: pointer;
    border: none;
}

.btn-sm {
    padding: var(--space-2) var(--space-4);
    font-size: 0.8125rem;
}

.btn-large {
    padding: var(--space-4) var(--space-8);
    font-size: 1rem;
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 14px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.5);
}

.btn-secondary {
    background: white;
    color: var(--color-gray-700);
    border: 1px solid var(--color-gray-200);
}

.btn-secondary:hover {
    background: var(--color-gray-50);
    border-color: var(--color-gray-300);
}

.btn-icon {
    display: flex;
    align-items: center;
}

.btn-arrow {
    margin-left: var(--space-2);
    transition: transform var(--transition-base);
}

.btn:hover .btn-arrow {
    transform: translateX(4px);
}

/* ============================================
   Hero Section
   ============================================ */
/* Reserve top space for fixed header (64px) so hero is not covered */
.hero {
    position: relative;
    min-height: 85vh;
    display: flex;
    align-items: center;
    padding: calc(64px + var(--space-8)) var(--space-6) var(--space-12);
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    inset: 0;
    z-index: 0;
    overflow: hidden;
}

.gradient-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(80px);
    opacity: 0.5;
    animation: float 20s ease-in-out infinite;
}

.orb-1 {
    width: 600px;
    height: 600px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    top: -200px;
    right: -100px;
    animation-delay: 0s;
}

.orb-2 {
    width: 400px;
    height: 400px;
    background: linear-gradient(135deg, #06b6d4 0%, #3b82f6 100%);
    bottom: -100px;
    left: -100px;
    animation-delay: -5s;
}

.orb-3 {
    width: 300px;
    height: 300px;
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    top: 50%;
    left: 30%;
    animation-delay: -10s;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    25% { transform: translate(30px, -30px) scale(1.05); }
    50% { transform: translate(-20px, 20px) scale(0.95); }
    75% { transform: translate(20px, 30px) scale(1.02); }
}

.hero .container {
    position: relative;
    z-index: 1;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-16);
    align-items: center;
}

.hero-badge {
    display: inline-flex;
    margin-bottom: var(--space-6);
}

.badge-text {
    padding: var(--space-2) var(--space-4);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-primary-700);
    background: var(--color-primary-50);
    border: 1px solid var(--color-primary-200);
    border-radius: var(--radius-full);
}

.hero-title {
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
    margin-bottom: var(--space-6);
}

.title-main {
    font-size: 3.5rem;
    font-weight: 700;
    line-height: 1.1;
    color: var(--color-gray-900);
    letter-spacing: -0.02em;
}

.title-divider {
    width: 60px;
    height: 4px;
    background: var(--gradient-primary);
    border-radius: var(--radius-full);
}

.title-sub {
    font-size: 1.5rem;
    font-weight: 500;
    color: var(--color-gray-600);
    line-height: 1.4;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--color-gray-600);
    line-height: 1.8;
    margin-bottom: var(--space-8);
    max-width: 540px;
}

.hero-actions {
    display: flex;
    gap: var(--space-4);
}

/* Hero Visual - Book Cover */
.hero-visual {
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}

.book-cover {
    position: relative;
    width: 280px;
    height: 380px;
    perspective: 1000px;
}

.book-front {
    position: absolute;
    inset: 0;
    background: var(--gradient-dark);
    border-radius: var(--radius-xl);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    box-shadow: var(--shadow-xl), var(--shadow-glow);
    transform: rotateY(-15deg);
    transform-style: preserve-3d;
}

.book-spine {
    position: absolute;
    left: -20px;
    top: 10px;
    bottom: 10px;
    width: 40px;
    background: linear-gradient(90deg, #1e293b 0%, #334155 50%, #1e293b 100%);
    border-radius: var(--radius-md) 0 0 var(--radius-md);
    transform: rotateY(90deg);
    transform-origin: right;
}

.book-shadow {
    position: absolute;
    bottom: -40px;
    left: 20px;
    right: -20px;
    height: 40px;
    background: radial-gradient(ellipse at center, rgba(0,0,0,0.3) 0%, transparent 70%);
    filter: blur(10px);
}

.book-content {
    text-align: center;
    color: white;
    padding: var(--space-8);
}

.book-icon {
    font-size: 4rem;
    margin-bottom: var(--space-6);
}

.book-title-small {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: 0.1em;
    margin-bottom: var(--space-3);
    background: var(--gradient-hero);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.book-subtitle-small {
    font-size: 1rem;
    opacity: 0.8;
    display: block;
    margin-top: var(--space-2);
}

.floating-elements {
    position: absolute;
    inset: 0;
    pointer-events: none;
}

.float-element {
    position: absolute;
    padding: var(--space-2) var(--space-4);
    background: white;
    border-radius: var(--radius-lg);
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-gray-700);
    box-shadow: var(--shadow-lg);
    animation: float-element 6s ease-in-out infinite;
}

.el-1 {
    top: 10%;
    right: -10%;
    animation-delay: 0s;
}

.el-2 {
    bottom: 30%;
    left: -10%;
    animation-delay: -2s;
}

.el-3 {
    bottom: 10%;
    right: 0;
    animation-delay: -4s;
}

.el-4 {
    top: 35%;
    left: -5%;
    animation-delay: -1s;
}

.el-5 {
    bottom: 25%;
    right: -8%;
    animation-delay: -3s;
}

@keyframes float-element {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-15px); }
}

/* ============================================
   Stats Section
   ============================================ */
.stats {
    padding: var(--space-16) 0;
    background: var(--color-gray-50);
    border-top: 1px solid var(--color-gray-200);
    border-bottom: 1px solid var(--color-gray-200);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-8);
}

.stat-item {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 3rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
    margin-bottom: var(--space-2);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--color-gray-500);
    font-weight: 500;
}

/* ============================================
   Features Section
   ============================================ */
.features {
    padding: var(--space-24) 0;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    color: var(--color-gray-900);
    margin-bottom: var(--space-16);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-6);
    list-style: none;
    padding: 0;
    margin: 0;
}

.feature-card {
    padding: var(--space-8);
    background: white;
    border: 1px solid var(--color-gray-200);
    border-radius: var(--radius-xl);
    transition: all var(--transition-base);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: var(--color-primary-200);
}

.feature-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.75rem;
    background: var(--color-primary-50);
    border-radius: var(--radius-lg);
    margin-bottom: var(--space-5);
}

.feature-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--color-gray-900);
    margin-bottom: var(--space-3);
}

.feature-desc {
    font-size: 0.9375rem;
    color: var(--color-gray-600);
    line-height: 1.6;
}

/* ============================================
   TOC Preview Section
   ============================================ */
.toc-preview {
    padding: var(--space-24) 0;
    background: var(--color-gray-900);
    color: white;
}

.toc-preview .section-title {
    color: white;
}

.toc-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-6);
}

.toc-part {
    padding: var(--space-6);
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-xl);
    transition: all var(--transition-base);
}

.toc-part:hover {
    background: rgba(255, 255, 255, 0.08);
    border-color: rgba(255, 255, 255, 0.2);
}

.part-number {
    font-size: 2.5rem;
    font-weight: 700;
    background: var(--gradient-hero);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
    margin-bottom: var(--space-2);
}

.part-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--space-1);
}

.part-desc {
    font-size: 0.875rem;
    color: var(--color-gray-400);
    margin-bottom: var(--space-4);
}

.chapter-list {
    list-style: none;
}

.chapter-list li {
    font-size: 0.875rem;
    color: var(--color-gray-300);
    padding: var(--space-2) 0;
    padding-left: var(--space-4);
    position: relative;
}

.chapter-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 6px;
    height: 6px;
    background: var(--color-primary-400);
    border-radius: 50%;
}

/* ============================================
   Audience Section
   ============================================ */
.audience {
    padding: var(--space-24) 0;
}

.audience-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-4);
    list-style: none;
    padding: 0;
    margin: 0;
}

.audience-item {
    padding: var(--space-6);
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
    transition: all var(--transition-base);
}

.audience-item:hover {
    background: var(--color-primary-50);
}

.audience-role {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-gray-900);
}

.audience-need {
    font-size: 0.875rem;
    color: var(--color-gray-600);
}

/* ============================================
   CTA Section
   ============================================ */
.cta {
    padding: var(--space-24) 0;
    background: var(--gradient-dark);
    position: relative;
    overflow: hidden;
}

.cta::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(circle at 30% 50%, rgba(102, 126, 234, 0.15) 0%, transparent 50%);
}

.cta-content {
    position: relative;
    z-index: 1;
    text-align: center;
    max-width: 640px;
    margin: 0 auto;
}

.cta-title {
    font-size: 2.5rem;
    font-weight: 700;
    color: white;
    margin-bottom: var(--space-4);
}

.cta-desc {
    font-size: 1.125rem;
    color: var(--color-gray-300);
    margin-bottom: var(--space-8);
}

.cta-actions {
    display: flex;
    justify-content: center;
}

/* ============================================
   Footer
   ============================================ */
.site-footer {
    padding: var(--space-6) 0 var(--space-8);
    background: var(--color-gray-50);
    border-top: 1px solid var(--color-gray-200);
}

/* Footer with sidebar - offset for chapter navigation */
body.has-sidebar .site-footer {
    margin-left: 280px;
    transition: margin-left var(--transition-base);
}

body.has-sidebar.sidebar-collapsed .site-footer {
    margin-left: 68px;
}

body.has-sidebar .site-footer .container {
    max-width: calc(1200px - var(--space-16));
}

.footer-inner {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-16);
    margin-bottom: var(--space-12);
    align-items: center;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--color-gray-900);
    margin-bottom: var(--space-4);
}

.footer-desc {
    font-size: 0.9375rem;
    color: var(--color-gray-600);
    line-height: 1.7;
    margin-top: var(--space-6);
    max-width: 420px;
}

/* Buy Me Coffee - Donate Section */
.footer-donate {
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.footer-donate h4 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-gray-900);
    margin-bottom: var(--space-3);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.donate-text {
    font-size: 0.875rem;
    color: var(--color-gray-600);
    margin-bottom: var(--space-3);
    line-height: 1.5;
}

.footer-donate img {
    width: 140px;
    height: 140px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.footer-donate img:hover {
    transform: scale(1.02);
    box-shadow: var(--shadow-lg);
}

.footer-copyright {
    font-size: 0.75rem;
    color: var(--color-gray-500);
    margin-top: var(--space-4);
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 1024px) {
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-content {
        order: 1;
    }

    .hero-visual {
        order: 0;
    }

    .title-divider {
        margin: 0 auto;
    }

    .hero-description {
        margin-left: auto;
        margin-right: auto;
    }

    .hero-actions {
        justify-content: center;
    }

    .book-cover {
        width: 220px;
        height: 300px;
    }

    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .main-nav {
        display: none;
    }

    .title-main {
        font-size: 2.5rem;
    }

    .title-sub {
        font-size: 1.125rem;
    }

    .section-title {
        font-size: 2rem;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .toc-grid {
        grid-template-columns: 1fr;
    }

    .audience-grid {
        grid-template-columns: 1fr;
    }

    .footer-inner {
        grid-template-columns: 1fr;
        gap: var(--space-10);
        text-align: center;
    }

    .footer-desc {
        margin: var(--space-6) auto 0;
        max-width: 480px;
    }

    body.has-sidebar .site-footer,
    body.has-sidebar.sidebar-collapsed .site-footer {
        margin-left: 0;
    }

    body.has-sidebar .site-footer .container,
    body.has-sidebar.sidebar-collapsed .site-footer .container {
        max-width: 1200px;
    }

    .cta-title {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--space-4);
    }

    .hero-actions {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

    .hero {
        padding: calc(64px + var(--space-4)) 0 var(--space-8);
    }

    .gradient-orb {
        filter: blur(50px);
    }

    .section-title {
        font-size: 1.75rem;
        margin-bottom: var(--space-10);
    }

    .stats {
        padding: var(--space-10) 0;
    }

    .stats-grid {
        grid-template-columns: 1fr 1fr;
        gap: var(--space-6);
    }

    .stat-number {
        font-size: 2rem;
    }

    .features {
        padding: var(--space-16) 0;
    }

    .feature-card {
        padding: var(--space-6);
    }

    .toc-preview {
        padding: var(--space-16) 0;
    }

    .cta-title {
        font-size: 1.5rem;
    }
}

/* ============================================
   Chapter Navigation (Left Sidebar)
   ============================================ */
.chapter-nav {
    position: fixed;
    left: 0;
    top: 64px;
    bottom: 0;
    width: 280px;
    background: white;
    border-right: 1px solid var(--color-gray-200);
    z-index: 90;
    transform: translateX(0);
    transition: transform var(--transition-base), width var(--transition-base);
    display: flex;
    flex-direction: column;
}

.chapter-nav.collapsed {
    width: 68px;
}

.chapter-nav.collapsed .chapter-nav-content,
.chapter-nav.collapsed .chapter-nav-title {
    opacity: 0;
    visibility: hidden;
}

.chapter-nav-header {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-4);
    border-bottom: 1px solid var(--color-gray-200);
    height: 56px;
    flex-shrink: 0;
}

.chapter-nav-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border: none;
    background: var(--color-gray-100);
    border-radius: var(--radius-md);
    cursor: pointer;
    color: var(--color-gray-600);
    transition: all var(--transition-fast);
    flex-shrink: 0;
}

.chapter-nav-toggle:hover {
    background: var(--color-primary-100);
    color: var(--color-primary-600);
}

.chapter-nav.collapsed .chapter-nav-toggle {
    transform: rotate(180deg);
}

.chapter-nav-title {
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--color-gray-900);
    white-space: nowrap;
    transition: opacity var(--transition-fast), visibility var(--transition-fast);
}

.chapter-nav-content {
    flex: 1;
    overflow-y: auto;
    padding: var(--space-4);
    transition: opacity var(--transition-fast), visibility var(--transition-fast);
}

.chapter-part {
    margin-bottom: var(--space-6);
}

.chapter-part-header {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    margin-bottom: var(--space-3);
    padding: var(--space-2) var(--space-3);
    background: var(--color-gray-50);
    border-radius: var(--radius-md);
}

.chapter-part-number {
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--gradient-primary);
    color: white;
    font-size: 0.75rem;
    font-weight: 700;
    border-radius: var(--radius-full);
    flex-shrink: 0;
}

.chapter-part-title {
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--color-gray-700);
    line-height: 1.4;
}

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

.chapter-item {
    margin-bottom: var(--space-1);
}

.chapter-item.active .chapter-link {
    background: var(--color-primary-50);
    color: var(--color-primary-700);
    border-left-color: var(--color-primary-500);
}

.chapter-link {
    display: flex;
    align-items: flex-start;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-3);
    border-radius: var(--radius-md);
    border-left: 3px solid transparent;
    transition: all var(--transition-fast);
    text-decoration: none;
    color: var(--color-gray-600);
}

.chapter-link:hover {
    background: var(--color-gray-50);
    color: var(--color-gray-900);
}

.chapter-num {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--color-gray-400);
    flex-shrink: 0;
    min-width: 20px;
}

.chapter-item.active .chapter-num {
    color: var(--color-primary-500);
}

.chapter-title {
    font-size: 0.8125rem;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* Chapter Nav Overlay for Mobile */
.chapter-nav-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 85;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
}

.chapter-nav-overlay.active {
    opacity: 1;
    visibility: visible;
}

/* ============================================
   Content TOC (Float right, after H1)
   ============================================ */
.content-toc-wrapper {
    float: right;
    clear: right;
    width: 240px;
    margin-left: var(--space-6);
    margin-bottom: var(--space-6);
    margin-top: var(--space-2);
}

.content-toc {
    background: var(--color-gray-50);
    border: 1px solid var(--color-gray-200);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.content-toc-header {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-4);
    background: white;
    border-bottom: 1px solid var(--color-gray-200);
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-gray-700);
}

.content-toc-header svg:first-child {
    color: var(--color-primary-500);
}

.content-toc-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 20px;
    height: 20px;
    margin-left: auto;
    border: none;
    background: transparent;
    border-radius: var(--radius-sm);
    cursor: pointer;
    color: var(--color-gray-400);
    transition: all var(--transition-fast);
}

.content-toc-toggle:hover {
    background: var(--color-gray-100);
    color: var(--color-gray-600);
}

.content-toc-toggle.collapsed svg {
    transform: rotate(-90deg);
}

.content-toc-body {
    max-height: 400px;
    overflow-y: auto;
    transition: max-height var(--transition-base), padding var(--transition-base);
}

.content-toc-body.collapsed {
    max-height: 0;
    padding-top: 0;
    padding-bottom: 0;
}

.content-toc-list {
    list-style: none;
    padding: var(--space-3) 0;
    margin: 0;
}

.content-toc-item {
    padding: var(--space-1) var(--space-4);
}

.content-toc-item.toc-h3 {
    padding-left: var(--space-8);
}

.content-toc-link {
    display: block;
    font-size: 0.8125rem;
    color: var(--color-gray-600);
    text-decoration: none;
    line-height: 1.5;
    transition: color var(--transition-fast);
    border-bottom: none;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.content-toc-link:hover {
    color: var(--color-primary-600);
    border-bottom: none;
}

.content-toc-item.active .content-toc-link {
    color: var(--color-primary-600);
    font-weight: 600;
}

/* Clear float after content */
.content-wrapper::after {
    content: "";
    display: table;
    clear: both;
}

/* ============================================
   Content Layout with Sidebar (100% minus nav)
   ============================================ */
.page-content.with-sidebar {
    display: flex;
    width: 100%;
    min-height: calc(100vh - 64px);
    position: relative;
    padding: 0;
}

.page-content.with-sidebar .content-main {
    flex: 1;
    margin-left: 280px;
    padding: var(--space-4) var(--space-10) var(--space-8) var(--space-8);
    transition: margin-left var(--transition-base);
    min-width: 0;
    max-width: calc(100% - 280px);
}

.page-content.with-sidebar .chapter-nav.collapsed ~ .content-main {
    margin-left: 68px;
    max-width: calc(100% - 68px);
}

.page-content.with-sidebar .content-wrapper {
    width: 100%;
    min-height: calc(100vh - 160px);
    background: white;
    padding: 0 var(--space-10) var(--space-8);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
}

/* Scroll margin for anchor links */
/* Content Typography - Wider Layout */
.page-content.with-sidebar .content-wrapper h1 {
    font-size: 2.25rem;
    font-weight: 700;
    color: var(--color-gray-900);
    margin-bottom: var(--space-6);
    padding-bottom: var(--space-4);
    border-bottom: 2px solid var(--color-gray-200);
    scroll-margin-top: 88px;
}

.page-content.with-sidebar .content-wrapper h2 {
    font-size: 1.625rem;
    font-weight: 600;
    color: var(--color-gray-800);
    margin-top: var(--space-10);
    margin-bottom: var(--space-5);
    scroll-margin-top: 88px;
}

.page-content.with-sidebar .content-wrapper h3 {
    font-size: 1.375rem;
    font-weight: 600;
    color: var(--color-gray-800);
    margin-top: var(--space-8);
    margin-bottom: var(--space-4);
    scroll-margin-top: 88px;
}

.page-content.with-sidebar .content-wrapper p {
    font-size: 1.0625rem;
    line-height: 1.85;
    color: var(--color-gray-700);
    margin-bottom: var(--space-5);
}

.page-content.with-sidebar .content-wrapper ul,
.page-content.with-sidebar .content-wrapper ol {
    margin-bottom: var(--space-6);
    padding-left: var(--space-7);
}

.page-content.with-sidebar .content-wrapper li {
    margin-bottom: var(--space-2);
    line-height: 1.75;
    color: var(--color-gray-700);
}

.page-content.with-sidebar .content-wrapper blockquote {
    border-left: 4px solid var(--color-primary-500);
    padding-left: var(--space-6);
    margin: var(--space-8) 0;
    color: var(--color-gray-600);
    font-style: italic;
    font-size: 1.0625rem;
}

.page-content.with-sidebar .content-wrapper pre {
    background: var(--color-gray-900);
    color: var(--color-gray-50);
    padding: var(--space-6);
    border-radius: var(--radius-lg);
    overflow-x: auto;
    margin-bottom: var(--space-6);
    font-size: 0.9375rem;
}

.page-content.with-sidebar .content-wrapper table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: var(--space-6);
    font-size: 0.9375rem;
}

.page-content.with-sidebar .content-wrapper hr {
    border: none;
    height: 1px;
    background: var(--color-gray-200);
    margin: var(--space-12) 0;
}

/* ============================================
   Responsive Design for Sidebar Navigation
   ============================================ */
@media (max-width: 1280px) {
    .page-content.with-sidebar .content-wrapper {
        padding: var(--space-6);
    }

    .page-content.with-sidebar .content-main {
        padding: var(--space-6) var(--space-8) var(--space-6) var(--space-6);
    }
}

@media (max-width: 1024px) {
    .page-content.with-sidebar .content-main {
        margin-left: 0;
        max-width: 100%;
        padding: var(--space-4);
    }

    .page-content.with-sidebar .chapter-nav.collapsed ~ .content-main {
        margin-left: 0;
        max-width: 100%;
    }

    .content-toc-wrapper {
        float: none;
        width: 100%;
        margin-left: 0;
        margin-bottom: var(--space-6);
        order: -1;
    }

    .page-content.with-sidebar .content-wrapper {
        padding: var(--space-5);
    }

    .page-content.with-sidebar .content-wrapper h1 {
        font-size: 1.75rem;
    }
}

@media (max-width: 1024px) {
    .chapter-nav {
        transform: translateX(-100%);
        width: 280px;
    }

    .chapter-nav.open {
        transform: translateX(0);
    }

    .chapter-nav.collapsed {
        width: 280px;
    }

    .chapter-nav.collapsed .chapter-nav-content,
    .chapter-nav.collapsed .chapter-nav-title {
        opacity: 1;
        visibility: visible;
    }

    .chapter-nav-toggle {
        transform: rotate(180deg);
    }

    .chapter-nav.open .chapter-nav-toggle {
        transform: rotate(0);
    }

    .page-content.with-sidebar .content-main {
        margin-left: 0;
        padding: var(--space-6);
    }

    .page-content.with-sidebar .chapter-nav.collapsed + .content-main {
        margin-left: 0;
    }

    .page-content.with-sidebar .content-wrapper {
        padding: var(--space-6);
    }
}

@media (max-width: 768px) {
    .page-content.with-sidebar .content-wrapper {
        padding: var(--space-5);
    }

    .page-content.with-sidebar .content-wrapper h1 {
        font-size: 1.5rem;
    }

    .page-content.with-sidebar .content-wrapper h2 {
        font-size: 1.25rem;
    }
}

/* ============================================
   Dark Mode Support (Future)
   ============================================ */
@media (prefers-color-scheme: dark) {
    /* Dark mode styles can be added here */
}

/* ============================================
   Chapter Navigation Footer (Prev/Next)
   ============================================ */
.chapter-nav-footer {
    display: flex;
    justify-content: space-between;
    align-items: stretch;
    gap: var(--space-6);
    margin-top: var(--space-12);
    padding-top: var(--space-8);
    border-top: 1px solid var(--color-gray-200);
}

.chapter-nav-prev,
.chapter-nav-next {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
    padding: var(--space-5) var(--space-6);
    background: var(--color-gray-50);
    border: 1px solid var(--color-gray-200);
    border-radius: var(--radius-lg);
    text-decoration: none;
    transition: all var(--transition-base);
    flex: 1;
    max-width: 320px;
}

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

.chapter-nav-prev:hover,
.chapter-nav-next:hover {
    background: var(--color-primary-50);
    border-color: var(--color-primary-200);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.chapter-nav-prev.disabled,
.chapter-nav-next.disabled {
    opacity: 0.5;
    cursor: not-allowed;
    background: var(--color-gray-100);
}

.chapter-nav-prev.disabled:hover,
.chapter-nav-next.disabled:hover {
    transform: none;
    box-shadow: none;
    border-color: var(--color-gray-200);
}

.chapter-nav-label {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--color-gray-500);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.chapter-nav-next .chapter-nav-label {
    flex-direction: row-reverse;
}

.chapter-nav-title {
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--color-gray-800);
    line-height: 1.4;
}

.chapter-nav-prev:hover .chapter-nav-title,
.chapter-nav-next:hover .chapter-nav-title {
    color: var(--color-primary-700);
}

/* Responsive for chapter nav footer */
@media (max-width: 640px) {
    .chapter-nav-footer {
        flex-direction: column;
        gap: var(--space-4);
    }

    .chapter-nav-prev,
    .chapter-nav-next {
        max-width: 100%;
        align-items: flex-start;
        text-align: left;
    }

    .chapter-nav-next .chapter-nav-label {
        flex-direction: row;
    }
}

/* ============================================
   Print Styles
   ============================================ */
@media print {
    .site-header,
    .hero-visual,
    .cta,
    .site-footer {
        display: none;
    }

    .hero {
        min-height: auto;
        padding: 2rem 0;
    }
}

/* ============================================
   Main Content & Page Content
   ============================================ */
.main-content {
    padding-top: 64px;
    min-height: 100vh;
}

.page-content {
    padding: var(--space-10) 0;
    background: var(--color-gray-50);
}

.page-header {
    margin-bottom: var(--space-10);
    text-align: center;
}

.page-header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--color-gray-900);
    margin-bottom: var(--space-4);
}

.content-wrapper {
    max-width: 1200px;
    margin: 0 auto;
    background: white;
    padding: var(--space-6) var(--space-12) var(--space-12);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
}

/* ============================================
   Typography - Content Styles
   ============================================ */
.content-wrapper h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--color-gray-900);
    margin-top: var(--space-2);
    margin-bottom: var(--space-6);
    padding-bottom: var(--space-4);
    border-bottom: 2px solid var(--color-gray-200);
}

.content-wrapper h2 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-gray-800);
    margin-top: var(--space-10);
    margin-bottom: var(--space-5);
}

.content-wrapper h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-gray-800);
    margin-top: var(--space-8);
    margin-bottom: var(--space-4);
}

.content-wrapper h4 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--color-gray-700);
    margin-top: var(--space-6);
    margin-bottom: var(--space-3);
}

.content-wrapper p {
    font-size: 1rem;
    line-height: 1.8;
    color: var(--color-gray-700);
    margin-bottom: var(--space-5);
}

.content-wrapper ul,
.content-wrapper ol {
    margin-bottom: var(--space-5);
    padding-left: var(--space-6);
}

.content-wrapper li {
    margin-bottom: var(--space-2);
    line-height: 1.7;
    color: var(--color-gray-700);
}

.content-wrapper li::marker {
    color: var(--color-primary-500);
}

.content-wrapper a {
    color: var(--color-primary-600);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: border-color var(--transition-fast);
}

.content-wrapper a:hover {
    border-bottom-color: var(--color-primary-600);
}

.content-wrapper strong {
    color: var(--color-gray-900);
    font-weight: 700;
    background: linear-gradient(transparent 60%, rgba(102, 126, 234, 0.15) 60%);
    padding: 0 2px;
}

.content-wrapper code {
    font-family: var(--font-mono);
    font-size: 0.875em;
    background: var(--color-gray-100);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
    color: var(--color-gray-800);
}

.content-wrapper pre {
    background: var(--color-gray-900);
    color: var(--color-gray-50);
    padding: var(--space-6);
    border-radius: var(--radius-lg);
    overflow-x: auto;
    margin-bottom: var(--space-6);
}

.content-wrapper pre code {
    background: transparent;
    padding: 0;
    color: inherit;
}

.content-wrapper blockquote {
    border-left: 4px solid var(--color-primary-500);
    padding-left: var(--space-6);
    margin: var(--space-6) 0;
    color: var(--color-gray-600);
    font-style: italic;
}

.content-wrapper hr {
    border: none;
    height: 1px;
    background: var(--color-gray-200);
    margin: var(--space-10) 0;
}

.content-wrapper table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: var(--space-6);
}

.content-wrapper th,
.content-wrapper td {
    padding: var(--space-3) var(--space-4);
    border: 1px solid var(--color-gray-200);
    text-align: left;
}

.content-wrapper th {
    background: var(--color-gray-100);
    font-weight: 600;
    color: var(--color-gray-800);
}

.content-wrapper tr:nth-child(even) {
    background: var(--color-gray-50);
}

/* Page Item (for list pages) */
.page-item {
    padding: var(--space-6);
    border-bottom: 1px solid var(--color-gray-100);
    transition: background var(--transition-fast);
}

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

.page-item:hover {
    background: var(--color-gray-50);
}

.page-item h3 {
    margin-top: 0;
    margin-bottom: var(--space-2);
}

.page-item h3 a {
    color: var(--color-gray-900);
    border-bottom: none;
}

.page-item h3 a:hover {
    color: var(--color-primary-600);
}

.page-item p {
    margin-bottom: 0;
    color: var(--color-gray-600);
}

/* Mobile Responsive for Content */
@media (max-width: 768px) {
    .content-wrapper {
        padding: var(--space-6);
    }

    .page-content {
        padding: var(--space-10) 0;
    }

    .page-header h1 {
        font-size: 2rem;
    }

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

    .content-wrapper h2 {
        font-size: 1.25rem;
    }

    .page-content.with-sidebar .content-wrapper h1 {
        font-size: 1.5rem;
    }

    .page-content.with-sidebar .content-wrapper h2 {
        font-size: 1.375rem;
    }

    .page-content.with-sidebar .content-wrapper h3 {
        font-size: 1.125rem;
    }

    .page-content.with-sidebar .content-wrapper p {
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .content-wrapper {
        padding: var(--space-4);
    }

    .page-content.with-sidebar .content-wrapper {
        padding: var(--space-4);
    }

    .page-content.with-sidebar .content-wrapper h1 {
        font-size: 1.375rem;
    }

    .page-content.with-sidebar .content-wrapper h2 {
        font-size: 1.125rem;
    }
}

/* ============================================
   Unpublished Chapter Styles
   ============================================ */

/* Sidebar: Unpublished chapter styling */
.chapter-item.unpublished .chapter-link {
    color: var(--color-gray-400);
}

.chapter-item.unpublished .chapter-link:hover {
    background: var(--color-gray-50);
    color: var(--color-gray-500);
}

.chapter-item.unpublished .chapter-num {
    color: var(--color-gray-300);
}

.chapter-item.unpublished .chapter-title {
    color: var(--color-gray-400);
}

.chapter-item.unpublished .chapter-badge {
    font-size: 0.6875rem;
    font-weight: 600;
    color: var(--color-accent-orange);
    background: rgba(249, 115, 22, 0.1);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
    margin-left: auto;
    flex-shrink: 0;
}

/* Unpublished Placeholder Page */
.unpublished-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: var(--space-16) var(--space-8);
    min-height: 400px;
}

.unpublished-icon {
    color: var(--color-gray-300);
    margin-bottom: var(--space-6);
}

.unpublished-title {
    font-size: 1.75rem;
    font-weight: 600;
    color: var(--color-gray-700);
    margin-bottom: var(--space-4);
}

.unpublished-badge {
    display: inline-block;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-accent-orange);
    background: rgba(249, 115, 22, 0.1);
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-full);
    margin-bottom: var(--space-6);
}

.unpublished-message {
    font-size: 1.25rem;
    font-weight: 500;
    color: var(--color-gray-600);
    margin-bottom: var(--space-4);
}

.unpublished-description {
    font-size: 1rem;
    color: var(--color-gray-500);
    max-width: 400px;
    margin-bottom: var(--space-8);
}

.unpublished-actions {
    display: flex;
    gap: var(--space-4);
}

.unpublished-actions .btn {
    color: white;
}

/* Read Page: Chapter link styling */
.chapter-link-published {
    color: var(--color-primary-600);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: border-color var(--transition-fast);
}

.chapter-link-published:hover {
    border-bottom-color: var(--color-primary-600);
}

.chapter-link-unpublished {
    color: var(--color-gray-400);
    text-decoration: none;
    cursor: default;
}

.chapter-status-badge {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--color-accent-orange);
    background: rgba(249, 115, 22, 0.1);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
    margin-left: var(--space-2);
}