/* Desktop max-width for lesson content */
        @media (min-width: 769px) {
            #lessonContent {
                max-width: 80ch;
                margin: 0 auto;
            }
        }

        /* Base styles to prevent overflow */
        .lesson-markdown-content {
            max-width: 100%;
            overflow-wrap: break-word;
            word-wrap: break-word;
            word-break: break-word;
        }

        .lesson-markdown-content > *:not(.lesson-flashcard-set) {
            max-width: 100%;
        }

        /* Exclude flashcard elements from markdown styling */
        .lesson-markdown-content .lesson-flashcard-set,
        .lesson-markdown-content .lesson-flashcard-set * {
            max-width: none;
        }

        .lesson-markdown-content h1,
        .lesson-markdown-content h2,
        .lesson-markdown-content h3,
        .lesson-markdown-content h4 {
            color: var(--text-primary);
            scroll-margin-top: 100px;
        }

        /* H1 - Page title (rarely used in lesson content) */
        .lesson-markdown-content h1 {
            font-size: 1.8rem;
            border-bottom: 2px solid var(--border);
            padding-bottom: 0.5rem;
            margin-top: 2rem;
            margin-bottom: 1rem;
        }

        /* H2 - Main sections (clearly distinguished) */
        .lesson-markdown-content h2 {
            font-size: 1.6rem;
            font-weight: 700;
            margin-top: 5rem;
            margin-bottom: 1.5rem;
            padding-bottom: 0.5rem;
            border-bottom: 3px solid #e74c3c;
            color: #e74c3c;
            position: relative;
        }

        /* First h2 doesn't need as much top margin */
        .lesson-markdown-content > h2:first-child,
        .lesson-markdown-content > p:first-child + h2 {
            margin-top: 1rem;
        }

        /* H3 - Sub-sections (indented look) */
        .lesson-markdown-content h3 {
            font-size: 1.25rem;
            font-weight: 600;
            margin-top: 2rem;
            margin-bottom: 0.75rem;
            padding-left: 1rem;
            border-left: 3px solid var(--border);
            color: var(--text-primary);
        }

        /* H4 - Minor sub-sections */
        .lesson-markdown-content h4 {
            font-size: 1.1rem;
            font-weight: 600;
            margin-top: 1.5rem;
            margin-bottom: 0.5rem;
            padding-left: 1.5rem;
            color: var(--text-secondary);
        }
        .lesson-markdown-content p {
            margin-bottom: 1rem;
        }
        .lesson-markdown-content ul,
        .lesson-markdown-content ol {
            margin-left: 1.5rem;
            margin-bottom: 1rem;
        }
        .lesson-markdown-content li {
            margin-bottom: 0.5rem;
        }
        .lesson-markdown-content code {
            background: var(--surface);
            padding: 0.2rem 0.4rem;
            border-radius: 4px;
            font-family: 'Courier New', monospace;
            font-size: 0.9em;
        }
        .lesson-markdown-content pre {
            background: var(--surface);
            padding: 1rem;
            border-radius: 8px;
            overflow-x: auto;
            margin-bottom: 1rem;
            border: 1px solid var(--border);
        }
        .lesson-markdown-content pre code {
            background: none;
            padding: 0;
            font-family: 'Courier New', 'Consolas', 'Monaco', monospace;
            font-size: 0.9rem;
            line-height: 1.4;
            white-space: pre;
            display: block;
            color: var(--text-primary);
        }
        .lesson-markdown-content strong {
            font-weight: 600;
            color: var(--vocab-highlight);
            background: var(--vocab-bg);
            padding: 0.1rem 0.3rem;
            border-radius: 4px;
            transition: all 0.2s ease;
            cursor: pointer;
        }

        .lesson-markdown-content strong:hover {
            background: var(--vocab-bg-hover);
            transform: translateY(-1px);
        }
        .lesson-markdown-content em {
            font-style: italic;
        }

        /* Link styles */
        .lesson-markdown-content a {
            color: var(--accent);
            text-decoration: underline;
            text-underline-offset: 2px;
            transition: color 0.2s ease, opacity 0.2s ease;
        }

        .lesson-markdown-content a:hover {
            color: var(--primary-color);
            opacity: 0.9;
        }

        .lesson-markdown-content a:visited {
            color: var(--accent);
            opacity: 0.85;
        }
        .lesson-markdown-content blockquote {
            border-left: 4px solid var(--accent);
            padding: 1rem 1rem 1rem 1.25rem;
            margin: 1.5rem 0;
            border-radius: 8px;
            background: var(--surface);
            color: var(--text-primary);
            box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
            overflow-wrap: break-word;
            word-wrap: break-word;
        }

        /* Callout box paragraph spacing */
        .lesson-markdown-content blockquote p:first-child {
            margin-top: 0;
        }
        .lesson-markdown-content blockquote p:last-child {
            margin-bottom: 0;
        }

        /* Emoji in blockquotes should be larger and prominent */
        .lesson-markdown-content blockquote p:first-child::first-line {
            font-size: 1.1em;
            font-weight: 500;
        }

        /* Table styles */
        .lesson-markdown-content table {
            width: 100%;
            border-collapse: collapse;
            margin: 1.5rem 0;
            background: var(--surface);
            border-radius: 8px;
            overflow: hidden;
            border: 1px solid var(--border);
        }

        .lesson-markdown-content table th {
            background: var(--background);
            color: var(--text-primary);
            font-weight: 600;
            text-align: left;
            padding: 0.75rem 1rem;
            border-bottom: 2px solid var(--border);
        }

        .lesson-markdown-content table td {
            padding: 0.75rem 1rem;
            border-bottom: 1px solid var(--border);
            color: var(--text-primary);
        }

        .lesson-markdown-content table td:first-child,
        .lesson-markdown-content table th:first-child {
            white-space: nowrap;
        }

        .lesson-markdown-content table tr:last-child td {
            border-bottom: none;
        }

        .lesson-markdown-content table tr:hover {
            background: var(--background);
        }

        /* Button styles */
        .complete-button:disabled {
            opacity: 0.6;
            cursor: not-allowed;
            background: var(--text-secondary) !important;
        }

        /* Mobile responsive styles */
        @media (max-width: 768px) {
            .study-container {
                padding-inline: 0.75rem !important;
            }

            .study-container .container {
                padding-inline: 0.5rem !important;
            }

            .back-button {
                margin-bottom: 1rem !important;
                padding: 0.625rem 1rem !important;
                font-size: 0.9rem !important;
            }

            #lessonContent {
                max-width: 100% !important;
                padding: 0 !important;
            }

            .lesson-container {
                padding: 1.25rem !important;
                border-radius: 8px !important;
            }

            .lesson-header {
                font-size: 1.5rem !important;
                margin: 0 0 0.75rem 0 !important;
                line-height: 1.3 !important;
                word-wrap: break-word !important;
                overflow-wrap: break-word !important;
            }

            .lesson-description {
                font-size: 0.95rem !important;
                line-height: 1.5 !important;
            }

            .lesson-content-box {
                margin: 1.5rem 0 !important;
                padding: 1rem !important;
            }

            .lesson-markdown-content {
                font-size: 1rem !important;
                line-height: 1.6 !important;
            }

            .lesson-markdown-content h1 {
                font-size: 1.4rem !important;
            }

            .lesson-markdown-content h2 {
                font-size: 1.3rem !important;
                margin-top: 3.5rem !important;
                padding-bottom: 0.4rem !important;
            }

            .lesson-markdown-content h3 {
                font-size: 1.1rem !important;
                margin-top: 1.5rem !important;
                padding-left: 0.75rem !important;
            }

            .lesson-markdown-content h4 {
                font-size: 1rem !important;
                padding-left: 1rem !important;
            }

            .lesson-markdown-content pre {
                padding: 0.75rem !important;
                overflow-x: auto !important;
                -webkit-overflow-scrolling: touch !important;
                max-width: 100% !important;
            }

            .lesson-markdown-content pre code {
                font-size: 0.85rem !important;
                white-space: pre !important;
                word-wrap: normal !important;
            }

            .lesson-markdown-content code {
                font-size: 0.85em !important;
                word-wrap: break-word !important;
            }

            .lesson-footer {
                padding-top: 1.5rem !important;
                margin-top: 1.5rem !important;
            }

            .practice-box {
                padding: 0.75rem !important;
                flex-direction: column !important;
                text-align: center !important;
                gap: 0.5rem !important;
            }

            .complete-button {
                padding: 1rem !important;
                font-size: 0.95rem !important;
                line-height: 1.4 !important;
            }

            .lesson-markdown-content blockquote {
                padding: 0.75rem !important;
                margin: 1rem 0 !important;
            }

            .lesson-markdown-content table {
                font-size: 0.85rem !important;
                display: block !important;
                overflow-x: auto !important;
                -webkit-overflow-scrolling: touch !important;
                width: 100% !important;
            }

            .lesson-markdown-content table th,
            .lesson-markdown-content table td {
                padding: 0.5rem !important;
                min-width: 80px !important;
            }

            .lesson-markdown-content ul,
            .lesson-markdown-content ol {
                margin-left: 1rem !important;
            }
        }

        /* Extra small screens (iPhone SE, small phones) */
        @media (max-width: 375px) {
            .lesson-container {
                padding: 1rem !important;
            }

            .lesson-header {
                font-size: 1.35rem !important;
            }

            .lesson-description {
                font-size: 0.9rem !important;
            }

            .lesson-markdown-content {
                font-size: 0.9rem !important;
            }

            .complete-button {
                padding: 0.875rem !important;
                font-size: 0.9rem !important;
            }
        }

        /* ========================================
           LESSON TABLE OF CONTENTS (SIDEBAR)
           ======================================== */

        /* Container for lesson content + ToC on desktop */
        .lesson-with-toc {
            display: flex;
            gap: 2rem;
            align-items: flex-start;
        }

        .lesson-main-content {
            flex: 1;
            min-width: 0; /* Prevent flex item from overflowing */
        }

        /* ToC Sidebar - Desktop only */
        .lesson-toc-sidebar {
            display: none; /* Hidden by default, shown on desktop */
            width: 320px;
            flex-shrink: 0;
            position: sticky;
            top: 100px;
            max-height: calc(100vh - 150px);
            overflow-y: auto;
            padding: 1.25rem;
            background: var(--surface);
            border-radius: 12px;
            border: 1px solid var(--border);
        }

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

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

        .lesson-toc-header {
            font-size: 0.85rem;
            font-weight: 600;
            color: var(--text-secondary);
            text-transform: uppercase;
            letter-spacing: 0.05em;
            margin-bottom: 1rem;
            padding-bottom: 0.5rem;
            border-bottom: 1px solid var(--border);
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .lesson-toc-header-icon {
            font-size: 1rem;
        }

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

        .lesson-toc-item {
            margin-bottom: 0.25rem;
        }

        .lesson-toc-link {
            display: block;
            padding: 0.5rem 0.75rem;
            font-size: 1rem;
            color: var(--text-secondary);
            text-decoration: none;
            border-radius: 6px;
            border-left: 2px solid transparent;
            transition: all 0.2s ease;
            line-height: 1.4;
        }

        .lesson-toc-link:hover {
            color: var(--text-primary);
            background: var(--background);
        }

        /* Main section (h2) links */
        .lesson-toc-link.toc-h2 {
            font-size: 1.15rem;
            font-weight: 600;
            padding-left: 0.75rem;
        }

        /* Sub-section (h3) links - indented */
        .lesson-toc-link.toc-h3 {
            font-size: 0.95rem;
            padding-left: 1.5rem;
            color: var(--text-secondary);
            opacity: 0.85;
        }

        /* Active state - current section */
        .lesson-toc-link.active {
            color: var(--accent);
            background: rgba(var(--accent-rgb, 0, 212, 255), 0.1);
            border-left-color: var(--accent);
        }

        .lesson-toc-link.toc-h3.active {
            opacity: 1;
        }

        /* Progress indicator */
        .lesson-toc-progress {
            margin-top: 1rem;
            padding-top: 0.75rem;
            border-top: 1px solid var(--border);
        }

        .lesson-toc-progress-bar {
            height: 4px;
            background: var(--border);
            border-radius: 2px;
            overflow: hidden;
        }

        .lesson-toc-progress-fill {
            height: 100%;
            background: var(--accent);
            border-radius: 2px;
            transition: width 0.3s ease;
            width: 0%;
        }

        .lesson-toc-progress-text {
            font-size: 0.75rem;
            color: var(--text-secondary);
            margin-top: 0.5rem;
            text-align: center;
        }

        /* Show ToC on desktop (wide screens) */
        @media (min-width: 1200px) {
            .lesson-toc-sidebar {
                display: block;
            }

            /* Adjust main content max-width when ToC is visible */
            .lesson-with-toc .lesson-main-content #lessonContent {
                max-width: none;
            }
        }

        /* Very wide screens - more room for ToC */
        @media (min-width: 1400px) {
            .lesson-toc-sidebar {
                width: 320px;
            }
        }

        /* ========================================
           LESSON FLASHCARDS
           ======================================== */

        .lesson-flashcard-set {
            margin: 2rem 0 !important;
            padding: 1.5rem !important;
            background: var(--surface) !important;
            border-radius: 12px !important;
            border: 1px solid var(--border) !important;
        }

        .lesson-flashcard-header {
            display: flex;
            align-items: center;
            gap: 0.5rem;
            margin-bottom: 1rem;
            font-weight: 600;
            color: var(--text-primary);
            font-size: 1.1rem;
        }

        .lesson-flashcard-icon {
            font-size: 1.3rem;
        }

        .lesson-flashcard-container {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 1rem;
        }

        .lesson-flashcard {
            position: relative;
            perspective: 1000px;
            height: 180px;
            cursor: pointer;
        }

        .lesson-flashcard-inner {
            position: relative !important;
            width: 100% !important;
            height: 100% !important;
            transition: transform 0.6s !important;
            transform-style: preserve-3d !important;
            -webkit-transform-style: preserve-3d !important;
        }

        .lesson-flashcard.flipped .lesson-flashcard-inner {
            transform: rotateY(180deg);
        }

        .lesson-flashcard .lesson-flashcard-inner .lesson-flashcard-front,
        .lesson-flashcard .lesson-flashcard-inner .lesson-flashcard-back {
            position: absolute !important;
            top: 0 !important;
            left: 0 !important;
            right: 0 !important;
            bottom: 0 !important;
            width: 100% !important;
            height: 100% !important;
            backface-visibility: hidden !important;
            -webkit-backface-visibility: hidden !important;
            border-radius: 12px !important;
            padding: 1.25rem !important;
            display: flex !important;
            flex-direction: column !important;
            justify-content: center !important;
            align-items: center !important;
            border: 2px solid var(--border, #333) !important;
            background: var(--background, #1a1a2e) !important;
            box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3) !important;
        }

        .lesson-flashcard .lesson-flashcard-inner .lesson-flashcard-front {
            background: linear-gradient(135deg, var(--background, #1a1a2e) 0%, var(--surface, #252542) 100%) !important;
        }

        .lesson-flashcard .lesson-flashcard-inner .lesson-flashcard-back {
            background: linear-gradient(135deg, var(--accent, #00d4ff) 0%, #5f4dee 100%) !important;
            transform: rotateY(180deg) !important;
        }

        .lesson-flashcard-number {
            position: absolute;
            top: 0.6rem;
            left: 0.6rem;
            width: 24px;
            height: 24px;
            border-radius: 50%;
            background: var(--accent, #00d4ff) !important;
            color: white !important;
            font-size: 0.75rem;
            font-weight: 600;
            display: flex;
            align-items: center;
            justify-content: center;
            z-index: 1;
        }

        .lesson-flashcard .lesson-flashcard-inner .lesson-flashcard-front .lesson-flashcard-question {
            font-size: 1rem !important;
            color: #ffffff !important;
            text-align: center !important;
            line-height: 1.5 !important;
            margin: 0 !important;
            padding: 0 0.5rem !important;
            background: transparent !important;
        }

        .lesson-flashcard .lesson-flashcard-inner .lesson-flashcard-front .lesson-flashcard-hint {
            position: absolute !important;
            bottom: 0.6rem !important;
            font-size: 0.75rem !important;
            color: #00d4ff !important;
            opacity: 0.9 !important;
            font-weight: 500 !important;
            background: transparent !important;
        }

        .lesson-flashcard-answer {
            font-size: 1rem;
            font-weight: 600;
            color: white;
            text-align: center;
            margin: 0 0 1rem 0;
            text-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
        }

        .flashcard-assessment {
            display: flex;
            gap: 0.5rem;
            margin-top: auto;
        }

        .flashcard-assessment button {
            padding: 0.5rem 0.75rem;
            border-radius: 6px;
            border: none;
            font-size: 0.8rem;
            font-weight: 500;
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .flashcard-got-it {
            background: rgba(255, 255, 255, 0.2);
            color: white;
        }

        .flashcard-got-it:hover {
            background: rgba(255, 255, 255, 0.35);
        }

        .flashcard-still-learning {
            background: rgba(0, 0, 0, 0.15);
            color: white;
        }

        .flashcard-still-learning:hover {
            background: rgba(0, 0, 0, 0.25);
        }

        /* Assessed states - keep cards interactive for review */
        .lesson-flashcard.assessed {
            /* Cards remain fully interactive after assessment */
        }

        .lesson-flashcard.assessed.got-it .lesson-flashcard-front {
            border-color: #22c55e;
            background: linear-gradient(135deg, rgba(34, 197, 94, 0.1) 0%, var(--surface) 100%);
        }

        .lesson-flashcard.assessed.got-it::after {
            content: '✓';
            position: absolute;
            top: 0.5rem;
            right: 0.5rem;
            color: #22c55e;
            font-size: 1.2rem;
            font-weight: bold;
        }

        .lesson-flashcard.assessed.still-learning .lesson-flashcard-front {
            border-color: #f59e0b;
            background: linear-gradient(135deg, rgba(245, 158, 11, 0.1) 0%, var(--surface) 100%);
        }

        .lesson-flashcard.assessed.still-learning::after {
            content: '↻';
            position: absolute;
            top: 0.5rem;
            right: 0.5rem;
            color: #f59e0b;
            font-size: 1.2rem;
            font-weight: bold;
        }

        /* Mobile responsive */
        @media (max-width: 768px) {
            .lesson-flashcard-set {
                margin: 1.5rem 0;
                padding: 1rem;
            }

            .lesson-flashcard-container {
                grid-template-columns: 1fr;
            }

            .lesson-flashcard {
                height: 160px;
            }

            .lesson-flashcard-question {
                font-size: 0.95rem;
            }

            .lesson-flashcard-answer {
                font-size: 1rem;
            }

            .flashcard-assessment button {
                padding: 0.4rem 0.6rem;
                font-size: 0.75rem;
            }
        }

        /* ========================================
           FULL-SCREEN LESSON PAGE - COLLAPSIBLE TOC
           ======================================== */

        .lesson-page-container {
            position: relative;
        }

        /* ToC Toggle Button - Fixed on right edge of viewport */
        .lesson-page-toc-toggle {
            display: none; /* Hidden by default, shown on desktop */
            position: fixed;
            right: 0;
            top: 50%;
            transform: translateY(-50%);
            width: 44px;
            height: 110px;
            background: linear-gradient(180deg, #e74c3c 0%, #c0392b 100%);
            border: none;
            border-radius: 12px 0 0 12px;
            cursor: pointer;
            z-index: 100;
            align-items: center;
            justify-content: center;
            color: white;
            transition: all 0.2s ease;
            writing-mode: vertical-rl;
            text-orientation: mixed;
            font-size: 0.85rem;
            font-weight: 700;
            letter-spacing: 0.05em;
            text-transform: uppercase;
            box-shadow: -2px 0 12px rgba(231, 76, 60, 0.4);
        }

        .lesson-page-toc-toggle:hover {
            background: linear-gradient(180deg, #c0392b 0%, #a93226 100%);
            color: white;
            width: 52px;
            box-shadow: -4px 0 16px rgba(231, 76, 60, 0.6);
        }

        .lesson-page-toc-toggle-icon {
            margin-bottom: 0.5rem;
            font-size: 1.2rem;
        }

        /* ToC Sidebar Panel - Slides out from right */
        .lesson-page-toc-panel {
            display: none; /* Hidden by default */
            position: fixed;
            right: 0;
            top: 80px; /* Below fixed nav */
            bottom: 0;
            width: 300px;
            background: var(--surface);
            border-left: 1px solid var(--border);
            transform: translateX(100%);
            transition: transform 0.3s ease;
            z-index: 99;
            overflow-y: auto;
            overflow-x: hidden; /* Prevent horizontal scrollbar */
            padding: 1.25rem;
            box-sizing: border-box;
        }

        .lesson-page-toc-panel.open {
            transform: translateX(0);
        }

        .lesson-page-toc-header {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding-bottom: 0.75rem;
            margin-bottom: 0.75rem;
            border-bottom: 1px solid var(--border);
        }

        .lesson-page-toc-title {
            font-size: 0.85rem;
            font-weight: 600;
            color: var(--text-secondary);
            text-transform: uppercase;
            letter-spacing: 0.05em;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .lesson-page-toc-close {
            background: none;
            border: none;
            color: var(--text-secondary);
            cursor: pointer;
            font-size: 1.5rem;
            padding: 0.25rem;
            line-height: 1;
            border-radius: 4px;
            transition: all 0.2s;
        }

        .lesson-page-toc-close:hover {
            color: var(--text-primary);
            background: var(--background);
        }

        .lesson-page-toc-list {
            list-style: none;
            margin: 0;
            padding: 0;
        }

        .lesson-page-toc-item {
            margin-bottom: 0.25rem;
        }

        .lesson-page-toc-link {
            display: block;
            padding: 0.5rem 0.75rem;
            font-size: 0.95rem;
            color: var(--text-secondary);
            text-decoration: none;
            border-radius: 6px;
            border-left: 2px solid transparent;
            transition: all 0.2s ease;
            line-height: 1.4;
            overflow-wrap: break-word;
            word-wrap: break-word;
            word-break: break-word;
        }

        .lesson-page-toc-link:hover {
            color: var(--text-primary);
            background: var(--background);
        }

        .lesson-page-toc-link.toc-h2 {
            font-weight: 600;
            color: #e74c3c;
        }

        .lesson-page-toc-link.toc-h3 {
            font-size: 0.85rem;
            padding-left: 1.25rem;
            opacity: 0.85;
        }

        .lesson-page-toc-link.active {
            color: var(--accent);
            background: rgba(var(--accent-rgb, 0, 212, 255), 0.1);
            border-left-color: var(--accent);
        }

        /* Progress indicator */
        .lesson-page-toc-progress {
            margin-top: 1rem;
            padding-top: 0.75rem;
            border-top: 1px solid var(--border);
        }

        .lesson-page-toc-progress-bar {
            height: 4px;
            background: var(--border);
            border-radius: 2px;
            overflow: hidden;
        }

        .lesson-page-toc-progress-fill {
            height: 100%;
            background: var(--accent);
            border-radius: 2px;
            transition: width 0.3s ease;
            width: 0%;
        }

        .lesson-page-toc-progress-text {
            font-size: 0.75rem;
            color: var(--text-secondary);
            margin-top: 0.5rem;
            text-align: center;
        }

        /* Show ToC on desktop */
        @media (min-width: 769px) {
            .lesson-page-toc-toggle {
                display: flex;
            }

            .lesson-page-toc-panel {
                display: block;
            }

            /* Adjust content margin when ToC is open */
            body.toc-open .container {
                margin-right: 300px;
                transition: margin-right 0.3s ease;
            }
        }

        /* Mobile ToC - Bottom sheet style */
        @media (max-width: 768px) {
            .lesson-page-toc-toggle {
                display: flex;
                position: fixed;
                right: 16px;
                bottom: 100px; /* Above the complete button */
                top: auto;
                transform: none;
                width: 56px;
                height: 56px;
                border-radius: 50%;
                border: none;
                background: linear-gradient(135deg, #e74c3c 0%, #c0392b 100%);
                color: white;
                writing-mode: horizontal-tb;
                font-size: 1.4rem;
                padding: 0;
                box-shadow: 0 4px 16px rgba(231, 76, 60, 0.5);
                z-index: 100;
            }

            .lesson-page-toc-toggle:active {
                transform: scale(0.95);
            }

            .lesson-page-toc-toggle span:last-child {
                display: none; /* Hide "ToC" text on mobile */
            }

            .lesson-page-toc-toggle-icon {
                margin: 0;
                font-size: 1.5rem;
            }

            .lesson-page-toc-panel {
                display: block;
                position: fixed;
                right: 0;
                left: 0;
                bottom: 0;
                top: 0;
                width: 100%;
                height: 100vh;
                max-height: none;
                border-radius: 0;
                border-left: none;
                border-top: none;
                transform: translateY(100%);
                z-index: 101;
                padding: 0;
                overflow-x: hidden;
            }

            .lesson-page-toc-panel.open {
                transform: translateY(0);
            }

            .lesson-page-toc-header {
                padding: 1.25rem 1.5rem;
                padding-top: calc(1.25rem + env(safe-area-inset-top, 0));
                border-bottom: 1px solid var(--border);
                position: sticky;
                top: 0;
                background: var(--surface);
                z-index: 10;
            }

            .lesson-page-toc-title {
                font-size: 1.1rem;
            }

            .lesson-page-toc-close {
                font-size: 2rem;
                padding: 0.5rem;
                min-width: 44px;
                min-height: 44px;
                display: flex;
                align-items: center;
                justify-content: center;
            }

            .lesson-page-toc-list {
                max-height: calc(100vh - 80px);
                overflow-y: auto;
                padding: 1.5rem;
                padding-top: 3.5rem;
            }

            .lesson-page-toc-item {
                margin-bottom: 0.5rem;
            }

            .lesson-page-toc-link {
                padding: 1rem 1.25rem;
                font-size: 1.1rem;
                line-height: 1.5;
                border-radius: 8px;
            }

            .lesson-page-toc-link.toc-h2 {
                font-size: 1.15rem;
            }

            .lesson-page-toc-link.toc-h3 {
                font-size: 1rem;
                padding-left: 2rem;
            }

            /* Don't shift content on mobile when ToC is open */
            body.toc-open .container {
                margin-right: 0;
            }
        }