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

:root {
    /* Colors - Updated for blue theme */
    --primary: #306998;
    --primary-dark: #245c8a;
    --primary-light: #3a7ab8;
    --secondary: #f8f9fa;
    --accent: #4a90e2;
    --success: #306998;
    --warning: #306998;
    --danger: #306998;
    --purple: #306998;
    --blue-light: #e8f4ff;
    --blue-pale: #f0f8ff;

    
    /* Text colors */
    --text-dark: #1e3c72;
    --text-medium: #4a5568;
    --text-light: #666;
    --text-white: #ffffff;
    
    /* Background colors */
    --bg-white: #ffffff;
    --bg-light: #f8f9fa;
    --bg-dark: #1a202c;
    --bg-code: #2d2d2d;
    --bg-code-light: #f5f5f5;
    
    /* Border colors */
    --border-light: #eaeaea;
    --border-medium: #e5e7eb;
    --border-dark: #4a5568;
    --border-code: #007acc;
    
    /* Shadows */
    --shadow-sm: 0 2px 10px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 3px 15px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.05);
    
    /* Border radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 20px;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 2.5rem;
    --spacing-3xl: 3rem;

    /* Additional Badge bgcolors */
    --topic-badge-bg-color: #e92121;
    --author-badge-bg-color: #18c551;
    --duration-badge-bg-color: #81233b;
    
}

body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-medium);
    background: var(--bg-light);
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* ========== HEADER & NAVIGATION ========== */
.header {
    background: var(--primary);
    color: var(--text-white);
    box-shadow: var(--shadow-md);
}

.header-main {
    padding: var(--spacing-md) 0;
}

.header-main .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.breadcrumb-section {
    background: var(--primary-dark);
    border-top: 1px solid rgba(255, 255, 255, 0.2);
    padding: var(--spacing-sm) 0;
}

.breadcrumb {
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.9);
}

.breadcrumb a {
    color: inherit;
    text-decoration: none;
    transition: color 0.3s;
}

.breadcrumb a:hover {
    color: var(--text-white);
    text-decoration: underline;
}

.breadcrumb .sep {
    margin: 0 var(--spacing-xs);
    color: rgba(255, 255, 255, 0.6);
}

.breadcrumb .current {
    color: var(--text-white);
    font-weight: bold;
}

.main-nav {
    display: flex;
    gap: var(--spacing-md);
}

.main-nav a {
    color: var(--text-white);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s;
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--radius-sm);
}

.main-nav a:hover,
.main-nav a.active {
    background: rgba(255, 255, 255, 0.15);
    transform: translateY(-2px);
}

.logo h1 {
    margin: 0;
}

.logo h1 a {
    color: var(--text-white);
    text-decoration: none;
    font-size: 1.5rem;
    font-weight: 700;
}

/* ========== CARD COMPONENTS ========== */
.card {
    background: var(--bg-white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    text-decoration: none;
    color: inherit;
    border-top: 4px solid var(--primary);
    transition: all 0.3s;
    display: flex;
    flex-direction: column;
    height: 100%;
    border: 1px solid var(--border-light);
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
    border-top-color: var(--primary-light);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--spacing-md);
}

.card-header h2 {
    color: var(--primary);
    font-size: 1.25rem;
    margin: 0;
    flex: 1;
}

.card-description {
    color: var(--text-light);
    font-size: 0.95rem;
    line-height: 1.5;
    margin-bottom: var(--spacing-md);
    flex-grow: 1;
}

.card-footer {
    display: flex;
    gap: var(--spacing-xs);
    margin-top: auto;
    flex-wrap: wrap;
    align-items: center;
}

/* ========== HEADER CARDS ========== */
.page-header-card,
.chapter-header-card {
    background: var(--bg-white);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-2xl);
    color: var(--text-dark);
    border-left: 8px solid var(--primary);
    border-right: 8px solid var(--primary);
}

.page-header-card {
    margin-top: var(--spacing-xl);
    border-left: 8px solid var(--primary);
    border-right: 8px solid var(--blue-light);
}

.chapter-header-card {
    margin-top: var(--spacing-xl);
    border-left: 8px solid var(--accent);
    border-right: 8px solid var(--blue-pale);
}

.page-header-card h1,
.chapter-header-card h1 {
    color: var(--primary);
    margin-bottom: var(--spacing-sm);
    font-size: 2.2rem;
    font-weight: 700;
    line-height: 1.3;
}

.page-description {
    color: var(--text-medium);
    font-size: 1.2rem;
    margin-bottom: var(--spacing-lg);
    font-weight: 500;
    line-height: 1.6;
}

.page-intro {
    color: var(--text-dark);
    line-height: 1.8;
    margin-top: var(--spacing-lg);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-light);
    font-size: 1.05rem;
}

/* ========== BADGES ========== */
.badge {
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-xl);
    font-size: 0.8rem;
    font-weight: 500;
    display: inline-block;
    white-space: nowrap;
    border: 1px solid transparent;
}

.chapter-meta {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    align-items: center;
    margin-top: var(--spacing-sm);
}

.level-badge {
    background: var(--primary);
    color: white;
    border-color: var(--primary-dark);
}

.course-badge {
    background: var(--primary);
    color: white;
    border-color: var(--primary-dark);
}

.chapter-badge {
    background: var(--primary);
    color: white;
    border-color: var(--primary-dark);
}

.topic-badge {
    background: var(--topic-badge-bg-color);
    color: white;
    border-color: var(--topic-badge-bg-color);
}

.count-badge {
    background: var(--primary);
    color: white;
    border-color: var(--primary-dark);
}

.level-badge[data-level="beginner"] {
    background: var(--success);
    border-color: var(--primary-dark);
}

.level-badge[data-level="intermediate"] {
    background: var(--accent);
    border-color: var(--primary-dark);
}

.level-badge[data-level="advanced"] {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
}

/* ========== CHAPTER CONTENT ========== */
.chapter-content {
    background: var(--bg-white);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-md);
    max-width: 100%;
    margin: 0 auto;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-light);
}

.content {
    width: 100%;
    overflow-wrap: break-word;
}

/* Headings */
.content h1 {
    color: var(--text-dark);
    font-size: 2rem;
    margin: var(--spacing-xl) 0 var(--spacing-md);
    line-height: 1.3;
}

.content h2 {
    color: var(--text-dark);
    font-size: 1.75rem;
    margin: var(--spacing-xl) 0 var(--spacing-md);
    padding-bottom: var(--spacing-xs);
    border-bottom: 2px solid var(--border-light);
    line-height: 1.4;
}

.content h3 {
    color: var(--text-dark);
    font-size: 1.5rem;
    margin: var(--spacing-lg) 0 var(--spacing-sm);
    line-height: 1.4;
}

.content h4 {
    color: var(--text-medium);
    font-size: 1.25rem;
    margin: var(--spacing-md) 0 var(--spacing-xs);
}

.content h2[id],
.content h3[id],
.content h4[id] {
    scroll-margin-top: 1.5rem;
    position: relative;
}

/* Paragraphs */
.content p {
    margin-bottom: var(--spacing-md);
    line-height: 1.7;
    color: var(--text-medium);
}

/* Lists */
.content ul,
.content ol {
    margin-left: 1.5rem;
    margin-bottom: var(--spacing-md);
    padding-left: 1rem;
}

.content li {
    margin-bottom: var(--spacing-xs);
    line-height: 1.6;
    padding-left: 0.25rem;
}

.content ul li {
    list-style-type: disc;
}

.content ol li {
    list-style-type: decimal;
}

.content ul ul,
.content ol ol,
.content ul ol,
.content ol ul {
    margin-top: var(--spacing-xs);
    margin-bottom: 0;
    margin-left: 1.5rem;
}

.content ul ul li {
    list-style-type: circle;
}

.content ol ol li {
    list-style-type: lower-alpha;
}

/* Code blocks */
.content pre {
    background: var(--bg-code-light);
    border: 1px solid var(--border-light);
    border-left: 4px solid var(--primary);
    border-radius: var(--radius-sm);
    padding: var(--spacing-md);
    overflow-x: auto;
    margin: var(--spacing-md) 0;
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 0.95rem;
    line-height: 1.5;
}

.content code {
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
}

.content code:not(pre code) {
    background: var(--bg-code-light);
    padding: 0.2rem 0.4rem;
    border-radius: 3px;
    font-size: 0.9em;
    color: #d63384;
    border: 1px solid #ddd;
}

/* Blockquotes */
.content blockquote {
    border-left: 4px solid var(--primary);
    padding: var(--spacing-md) var(--spacing-lg);
    margin: var(--spacing-md) 0;
    background: var(--blue-pale);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.content blockquote p {
    margin-bottom: 0;
    color: var(--text-medium);
    font-style: italic;
}

/* Tables */
.content table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--spacing-md) 0;
    font-size: 0.95rem;
}

.content th,
.content td {
    padding: var(--spacing-xs) var(--spacing-sm);
    border: 1px solid var(--border-light);
    text-align: left;
}

.content th {
    background: var(--blue-light);
    font-weight: 600;
    color: var(--text-dark);
    border-bottom: 2px solid var(--primary);
}

/* Images */
.content img {
    max-width: 100%;
    height: auto;
    border-radius: var(--radius-sm);
    margin: var(--spacing-md) 0;
    border: 1px solid var(--border-light);
}

/* Horizontal rule */
.content hr {
    border: none;
    border-top: 1px solid var(--border-light);
    margin: var(--spacing-xl) 0;
}

/* Links */
.content a {
    color: var(--primary);
    text-decoration: none;
    transition: color 0.2s;
    font-weight: 500;
}

.content a:hover {
    color: var(--primary-dark);
    text-decoration: underline;
}

/* ========== LAYOUTS ========== */
.dynamic-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-lg);
    margin: var(--spacing-xl) 0;
}

.chapter-layout {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: var(--spacing-2xl);
    margin: var(--spacing-xl) 0;
}

/* ========== TOC SIDEBAR ========== */
.chapter-toc {
    position: sticky;
    top: var(--spacing-xl);
    align-self: start;
    background: var(--bg-white);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    border: 1px solid var(--border-medium);
    box-shadow: var(--shadow-lg);
    max-height: calc(100vh - 4rem);
    overflow-y: auto;
}

.toc-header {
    margin-bottom: var(--spacing-lg);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--primary);
}

.toc-header h3 {
    margin: 0;
    font-size: 1.1rem;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.toc-nav {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

/* Multi-level TOC items */
.toc-item {
    padding: 0.25rem 0;
    border-left: 3px solid transparent;
    transition: all 0.2s ease;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

.toc-item.level-2 {
    font-weight: 600;
    border-left-color: var(--primary);
    margin-top: 0.5rem;
}

.toc-item.level-3 {
    font-weight: 500;
    border-left-color: var(--accent);
    margin-top: 0.25rem;
    padding-left: 1rem;
}

.toc-item.level-4 {
    font-weight: normal;
    border-left-color: var(--success);
    margin-top: 0.25rem;
    padding-left: 2rem;
    font-size: 0.9rem;
}

.toc-link {
    display: block;
    padding: var(--spacing-xs) var(--spacing-sm);
    color: var(--text-medium);
    text-decoration: none;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    transition: all 0.2s ease;
    line-height: 1.4;
}

.toc-item.level-3 .toc-link {
    padding: 0.4rem 0.75rem;
}

.toc-item.level-4 .toc-link {
    padding: 0.35rem 0.75rem;
    color: var(--text-light);
}

.toc-link:hover {
    background-color: var(--blue-pale);
    color: var(--text-dark);
    transform: translateX(3px);
}

.toc-item.active {
    background-color: var(--blue-light);
}

.toc-item.active .toc-link {
    color: var(--primary);
    font-weight: 500;
}

.toc-item.level-2.active {
    border-left-color: var(--primary);
}

.toc-item.level-3.active {
    border-left-color: var(--accent);
}

.toc-item.level-4.active {
    border-left-color: var(--success);
}

.toc-empty {
    padding: var(--spacing-md);
    text-align: center;
    color: var(--text-light);
    font-style: italic;
}

/* ========== NAVIGATION ========== */
.chapter-navigation {
    display: flex;
    justify-content: space-between;
    margin-top: var(--spacing-3xl);
    padding-top: var(--spacing-xl);
    border-top: 1px solid var(--border-light);
}

.nav-btn {
    background: var(--primary);
    color: var(--text-white);
    text-decoration: none;
    padding: var(--spacing-sm) var(--spacing-lg);
    border: 2px solid var(--primary);
    border-radius: var(--radius-md);
    transition: all 0.3s;
    font-weight: 500;
    min-width: 200px;
    text-align: center;
}

.nav-btn:hover {
    background: var(--primary-dark);
    color: var(--text-white);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
    border-color: var(--primary-dark);
}

.nav-btn.prev {
    margin-right: auto;
}

.nav-btn.next {
    margin-left: auto;
}

/* ========== FOOTER ========== */
.footer {
    background: var(--primary);
    color: rgba(255, 255, 255, 0.9);
    padding: var(--spacing-2xl) 0;
    margin-top: var(--spacing-3xl);
    border-top: 4px solid var(--primary-light);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section h4 {
    color: var(--text-white);
    margin-bottom: var(--spacing-md);
    font-size: 1.1rem;
    font-weight: 600;
}

.footer-section ul {
    list-style: none;
    padding-left: 0;
}

.footer-section li {
    margin-bottom: var(--spacing-sm);
    padding-left: 1.5rem;
    position: relative;
}

.footer-section li:before {
    content: "→";
    position: absolute;
    left: 0;
    color: rgba(255, 255, 255, 0.7);
    font-weight: bold;
}

.footer-section a {
    color: rgba(255, 255, 255, 0.9);
    text-decoration: none;
    transition: all 0.3s;
    display: inline-block;
}

.footer-section a:hover {
    color: var(--text-white);
    padding-left: 0.25rem;
    text-decoration: underline;
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-xl);
    border-top: 1px solid rgba(255, 255, 255, 0.2);
    color: rgba(255, 255, 255, 0.7);
    font-size: 0.9rem;
}

/* ========== UTILITY ========== */
.no-items {
    text-align: center;
    padding: var(--spacing-2xl);
    background: var(--bg-light);
    border-radius: var(--radius-md);
    color: var(--text-light);
    grid-column: 1 / -1;
    border: 1px solid var(--border-light);
}

.page-content {
    background: var(--bg-white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-xl);
    border-left: 4px solid var(--primary);
    border: 1px solid var(--border-light);
    box-shadow: var(--shadow-sm);
}

/* ========== ANIMATIONS ========== */
@keyframes highlight-heading {
    0% {
        background-color: rgba(48, 105, 152, 0.3);
    }
    100% {
        background-color: transparent;
    }
}

.content h2[id]:target,
.content h3[id]:target,
.content h4[id]:target {
    animation: highlight-heading 1.5s ease;
}

/* ========== RESPONSIVE DESIGN ========== */
/* Tablet */
@media (max-width: 1024px) {
    .chapter-layout {
        grid-template-columns: 240px 1fr;
        gap: var(--spacing-lg);
    }
    
    .dynamic-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Mobile */
@media (max-width: 768px) {
    .header-main .container {
        flex-direction: column;
        text-align: center;
        gap: var(--spacing-md);
    }

    .main-nav {
        flex-wrap: wrap;
        justify-content: center;
        gap: var(--spacing-xs);
    }

    .main-nav a {
        margin: 0;
        padding: var(--spacing-xs) var(--spacing-sm);
        font-size: 0.95rem;
    }

    .dynamic-grid,
    .chapter-layout {
        grid-template-columns: 1fr;
    }

    .chapter-toc {
        position: static;
        max-height: none;
        margin-bottom: var(--spacing-lg);
    }

    .chapter-navigation {
        flex-direction: column;
        gap: var(--spacing-md);
    }

    .nav-btn {
        min-width: 100%;
        width: 100%;
    }

    .page-header-card,
    .chapter-header-card {
        padding: var(--spacing-lg);
        margin-bottom: var(--spacing-lg);
    }

    .page-header-card h1,
    .chapter-header-card h1 {
        font-size: 1.8rem;
    }

    .content h1 {
        font-size: 1.8rem;
    }

    .content h2 {
        font-size: 1.5rem;
    }

    .content h3 {
        font-size: 1.3rem;
    }
    
    .toc-item.level-3 {
        padding-left: 0.75rem;
    }
    
    .toc-item.level-4 {
        padding-left: 1.5rem;
    }
}

/* Small mobile */
@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-md);
    }

    .card {
        padding: var(--spacing-md);
    }

    .content ul,
    .content ol {
        margin-left: 1rem;
        padding-left: 0.5rem;
    }

    .content ul ul,
    .content ol ol {
        margin-left: 1rem;
    }

    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .footer-section li {
        padding-left: 0;
    }

    .footer-section li:before {
        display: none;
    }

    .chapter-meta {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-xs);
    }
}

/* Desktop optimization */
@media (min-width: 1200px) {
    .container {
        max-width: 1200px;
    }
    
    .dynamic-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-xl);
    }
}

/* ========== HIGHLIGHT.JS STYLES ========== */
.hljs {
    background: #1e1e1e;
    color: #d4d4d4;
    border-radius: var(--radius-sm);
    padding: var(--spacing-md) !important;
    font-size: 0.95rem;
    line-height: 1.5;
    border-left: 4px solid var(--primary);
}

/* ========== COPY BUTTON STYLES ========== */

pre {
    position: relative !important;
    margin: var(--spacing-md) 0 !important;
}

.copy-code-btn {
    position: absolute;
    top: 10px;
    right: 10px;
    background: var(--primary);
    color: var(--text-white);
    border: 1px solid var(--primary);
    padding: 6px 12px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.8rem;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    transition: all 0.2s;
    opacity: 0.8;
    z-index: 10;
}

.copy-code-btn:hover {
    opacity: 1;
    background: var(--primary-dark);
    color: var(--text-white);
    border-color: var(--primary-dark);
}

.copy-code-btn.copied {
    background: var(--success);
    border-color: var(--success);
    color: var(--text-white);
    opacity: 1;
}

/* Mobile responsive */
@media (max-width: 768px) {
    .copy-code-btn {
        top: 8px;
        right: 8px;
        padding: 4px 8px;
        font-size: 0.75rem;
    }
    
    .hljs {
        padding: var(--spacing-sm) !important;
        font-size: 0.85rem;
    }
}