:root {
            --proton: #ef4444;
            --neutron: #3b82f6;
            --electron: #eab308;
            --bg-dark: #020617;
            --glass-bg: rgba(255, 255, 255, 0.05);
            --glass-border: rgba(255, 255, 255, 0.1);
            --success: #22c55e;
            --error: #ef4444;
            --text-primary: #f1f5f9;
            --text-secondary: #94a3b8;
            --space-1: 8px;
            --space-2: 16px;
            --space-3: 24px;
            --space-4: 32px;
            --space-5: 40px;
            --space-6: 48px;
        }

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

        body {
            font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
            background: var(--bg-dark);
            color: var(--text-primary);
            min-height: 100vh;
            overflow: hidden;
        }

        /* Glass Card Effect */
        .glass-card {
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            backdrop-filter: blur(12px);
            -webkit-backdrop-filter: blur(12px);
            border-radius: 1rem;
        }

        /* Top Bar */
        .top-bar {
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            height: 60px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: 0 var(--space-4);
            background: rgba(2, 6, 23, 0.95);
            border-bottom: 1px solid var(--glass-border);
            z-index: 100;
        }

        .nav-left {
            display: flex;
            align-items: center;
            gap: var(--space-2);
        }

        .nav-brand {
            display: flex;
            align-items: center;
            gap: var(--space-2);
            margin-right: var(--space-2);
        }

        .nav-logo {
            height: 32px;
            width: auto;
            object-fit: contain;
        }

        .nav-company-name {
            font-family: 'Space Grotesk', sans-serif;
            font-size: 0.875rem;
            font-weight: 600;
            color: var(--text-primary);
            white-space: nowrap;
        }

        .home-btn {
            font-size: 1.25rem;
            padding: var(--space-1) var(--space-2);
        }

        .overview-logo-container {
            margin-bottom: var(--space-4);
        }

        .overview-logo {
            width: 200px;
            height: 200px;
            object-fit: contain;
        }

        .overview-company-name {
            font-family: 'Space Grotesk', sans-serif;
            font-size: clamp(2rem, 5vw, 3rem);
            font-weight: 700;
            color: var(--text-primary);
            margin-bottom: var(--space-4);
            letter-spacing: -0.02em;
        }

        .slide-select-wrapper {
            position: relative;
        }

        .slide-select {
            appearance: none;
            -webkit-appearance: none;
            padding: var(--space-1) var(--space-3);
            padding-right: 2rem;
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            color: var(--text-primary);
            border-radius: 0.5rem;
            font-size: 0.875rem;
            cursor: pointer;
            transition: all 0.2s ease;
            min-width: 180px;
        }

        .slide-select:hover {
            background: rgba(255, 255, 255, 0.15);
            border-color: var(--electron);
        }

        .slide-select:focus {
            outline: none;
            border-color: var(--electron);
        }

        .slide-select option {
            background: #1e293b;
            color: var(--text-primary);
            padding: var(--space-2);
        }

        .slide-counter {
            font-size: 1.25rem;
            font-weight: 700;
            color: var(--electron);
        }

        .nav-buttons {
            display: flex;
            gap: var(--space-2);
        }

        .nav-btn {
            padding: var(--space-1) var(--space-3);
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            color: var(--text-primary);
            border-radius: 0.5rem;
            cursor: pointer;
            font-size: 0.875rem;
            transition: all 0.2s ease;
        }

        .nav-btn:hover {
            background: rgba(255, 255, 255, 0.15);
            border-color: var(--electron);
        }

        .nav-btn:disabled {
            opacity: 0.3;
            cursor: not-allowed;
        }

        .keyboard-hints {
            font-size: 0.75rem;
            color: var(--text-secondary);
        }

        .keyboard-hints kbd {
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            border-radius: 4px;
            padding: 2px 6px;
            margin: 0 2px;
        }

        /* Main Split Layout */
        .main-container {
            position: fixed;
            top: 60px;
            left: 0;
            right: 0;
            bottom: 40px;
            display: flex;
        }

        .teacher-panel-header {
            font-size: 0.75rem;
            color: var(--electron);
            text-transform: uppercase;
            letter-spacing: 1px;
            margin-bottom: var(--space-3);
            padding-bottom: var(--space-1);
            border-bottom: 1px solid var(--glass-border);
        }

        /* Teacher Guidance Sections */
        .guidance-section {
            margin-bottom: var(--space-3);
            padding: var(--space-2);
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            border-radius: 0.75rem;
            border-left: 3px solid var(--electron);
        }

        .guidance-section.interaction {
            border-left-color: var(--success);
        }

        .guidance-section.watch {
            border-left-color: var(--proton);
        }

        .section-title {
            font-size: 0.8rem;
            font-weight: 700;
            color: var(--electron);
            margin-bottom: var(--space-1);
            text-transform: uppercase;
            letter-spacing: 0.5px;
        }

        .section-bullets {
            list-style: none;
        }

        .section-bullets li {
            font-size: 0.875rem;
            line-height: 1.5;
            margin-bottom: 6px;
            padding-left: var(--space-2);
            position: relative;
            color: var(--text-primary);
        }

        .section-bullets li::before {
            content: "•";
            position: absolute;
            left: 0;
            color: var(--text-secondary);
        }

        .section-bullets li:last-child {
            margin-bottom: 0;
        }

        /* Spoken/Non-Spoken Text Classes */
        .spoken {
            color: #ff8c00;
            font-weight: 700;
        }

        .non-spoken {
            color: #87CEEB;  /* Light blue for non-spoken content */
        }

        .heading {
            color: #eab308;
        }

        /* Tab Interface Styles */
        .tab-container {
            margin-bottom: var(--space-3);
        }

        .tab-list {
            display: flex;
            gap: var(--space-1);
            border-bottom: 1px solid var(--glass-border);
            margin-bottom: var(--space-2);
        }

        .tab-btn {
            padding: var(--space-1) var(--space-2);
            background: transparent;
            border: none;
            border-bottom: 2px solid transparent;
            color: var(--text-secondary);
            cursor: pointer;
            font-size: 0.8rem;
            font-weight: 600;
            transition: all 0.2s ease;
        }

        .tab-btn:hover {
            color: var(--text-primary);
        }

        .tab-btn[aria-selected="true"] {
            color: var(--electron);
            border-bottom-color: var(--electron);
        }

        .tab-panel {
            display: none;
        }

        .tab-panel[aria-hidden="false"] {
            display: block;
        }

        /* LHS Tab Interface */
        .lhs-tab-list {
            display: flex;
            gap: var(--space-1);
            padding: var(--space-2) var(--space-3);
            background: rgba(2, 6, 23, 0.8);
            border-bottom: 1px solid var(--glass-border);
        }

        .lhs-tab-btn {
            padding: var(--space-1) var(--space-2);
            background: transparent;
            border: none;
            border-bottom: 2px solid transparent;
            color: var(--text-secondary);
            cursor: pointer;
            font-size: 0.8rem;
            font-weight: 600;
            transition: all 0.2s ease;
        }

        .lhs-tab-btn:hover {
            color: var(--text-primary);
        }

        .lhs-tab-btn.active {
            color: var(--electron);
            border-bottom-color: var(--electron);
        }

        /* Pause/Wait Cues */
        .cue-pause {
            color: var(--success);
            font-weight: 600;
        }

        .cue-wait {
            color: var(--neutron);
            font-weight: 600;
        }

        /* Bottom Progress Bar */
        .bottom-bar {
            position: fixed;
            bottom: 0;
            left: 0;
            right: 0;
            height: 40px;
            display: flex;
            align-items: center;
            padding: 0 var(--space-4);
            background: rgba(2, 6, 23, 0.95);
            border-top: 1px solid var(--glass-border);
        }

        .progress-container {
            flex: 1;
            height: 8px;
            background: var(--glass-bg);
            border-radius: 4px;
            overflow: hidden;
            margin-right: var(--space-3);
        }

        .progress-bar {
            height: 100%;
            background: linear-gradient(90deg, var(--electron), var(--neutron));
            transition: width 0.3s ease;
            border-radius: 4px;
        }

        .progress-label {
            font-size: 0.75rem;
            color: var(--text-secondary);
            min-width: 80px;
            text-align: right;
        }

        /* Student Slide Styles (mirrored from main_lesson_01) */
        .slide-title {
            font-size: 1.5rem;
            font-weight: 700;
            margin-bottom: var(--space-2);
            color: var(--text-primary);
        }

        .slide-title .highlight {
            color: var(--electron);
        }

        .content-card {
            padding: var(--space-3);
            margin-bottom: var(--space-2);
        }

        .atom-visual {
            display: flex;
            justify-content: center;
            align-items: center;
            gap: var(--space-3);
            margin: var(--space-2) 0;
        }

        .atom-box {
            width: 100px;
            height: 140px;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            padding: var(--space-2);
            text-align: center;
        }

        .atom-symbol {
            font-size: 2.5rem;
            font-weight: 700;
        }

        .atom-mass {
            font-size: 1.25rem;
            color: var(--text-secondary);
        }

        .atom-label {
            font-size: 0.75rem;
            color: var(--text-secondary);
            margin-top: var(--space-1);
        }

        .vs-text {
            font-size: 1.25rem;
            font-weight: 700;
            color: var(--text-secondary);
        }

        .info-box {
            padding: var(--space-2);
            margin: var(--space-2) 0;
            border-left: 4px solid var(--electron);
            background: rgba(234, 179, 8, 0.1);
        }

        .info-box p {
            margin-bottom: var(--space-1);
            line-height: 1.5;
            font-size: 0.9rem;
        }

        .particle-legend {
            display: flex;
            justify-content: center;
            gap: var(--space-3);
            margin: var(--space-2) 0;
        }

        .legend-item {
            display: flex;
            align-items: center;
            gap: var(--space-1);
            font-size: 0.8rem;
        }

        .legend-dot {
            width: 10px;
            height: 10px;
            border-radius: 50%;
        }

        .legend-dot.proton { background: var(--proton); }
        .legend-dot.neutron { background: var(--neutron); }

        .formula-box {
            background: rgba(59, 130, 246, 0.15);
            border: 2px solid var(--neutron);
            border-radius: 0.5rem;
            padding: var(--space-2);
            text-align: center;
            font-size: 1rem;
            font-family: 'Courier New', monospace;
            margin: var(--space-2) 0;
        }

        .step-list {
            list-style: none;
            counter-reset: step-counter;
        }

        .step-list li {
            counter-increment: step-counter;
            display: flex;
            align-items: flex-start;
            gap: var(--space-1);
            margin-bottom: var(--space-1);
            padding: var(--space-1);
            background: rgba(255, 255, 255, 0.03);
            border-radius: 0.5rem;
            font-size: 0.85rem;
        }

        .step-list li::before {
            content: counter(step-counter);
            min-width: 20px;
            height: 20px;
            background: var(--electron);
            color: #000;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 0.75rem;
        }

        .quiz-options {
            display: flex;
            flex-direction: column;
            gap: var(--space-1);
            margin: var(--space-2) 0;
        }

        .quiz-option {
            padding: var(--space-1) var(--space-2);
            background: rgba(255, 255, 255, 0.05);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            font-size: 0.85rem;
        }

        .calculator-app {
            background: rgba(0, 0, 0, 0.3);
            border: 2px solid var(--glass-border);
            border-radius: 1rem;
            padding: var(--space-2);
            margin: var(--space-2) 0;
        }

        .calc-row {
            display: flex;
            align-items: center;
            gap: var(--space-1);
            margin-bottom: var(--space-1);
            flex-wrap: wrap;
        }

        .calc-label {
            min-width: 140px;
            font-weight: 600;
            font-size: 0.8rem;
        }

        .calc-input {
            width: 80px;
            padding: 0.35rem;
            background: rgba(255, 255, 255, 0.1);
            border: 1px solid rgba(255, 255, 255, 0.3);
            border-radius: 0.25rem;
            color: white;
            text-align: center;
            font-size: 0.8rem;
        }

        .btn {
            padding: var(--space-1) var(--space-2);
            border: none;
            border-radius: 0.5rem;
            font-size: 0.8rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .btn-primary {
            background: var(--electron);
            color: #000;
        }

        .btn-secondary {
            background: rgba(255, 255, 255, 0.1);
            color: white;
            border: 1px solid rgba(255, 255, 255, 0.2);
        }

        .data-table {
            width: 100%;
            border-collapse: collapse;
            margin: var(--space-2) 0;
            font-size: 0.75rem;
        }

        .data-table th,
        .data-table td {
            padding: var(--space-1);
            text-align: left;
            border: 1px solid var(--glass-border);
        }

        .data-table th {
            background: rgba(255, 255, 255, 0.05);
            font-weight: 600;
        }

        .data-table .result-row {
            background: rgba(34, 197, 94, 0.1) !important;
            font-weight: 600;
        }

        .input-group {
            display: flex;
            align-items: center;
            gap: var(--space-1);
            margin: var(--space-1) 0;
        }

        .input-label {
            min-width: 120px;
            font-size: 0.8rem;
            color: var(--text-secondary);
        }

        .fill-input {
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.3);
            color: white;
            padding: 0.4rem 0.8rem;
            border-radius: 0.5rem;
            width: 100px;
            text-align: center;
            font-size: 0.85rem;
        }

        .feedback {
            margin-top: var(--space-1);
            padding: var(--space-1);
            border-radius: 0.5rem;
            font-size: 0.8rem;
        }

        .particle-tray {
            display: flex;
            justify-content: center;
            gap: var(--space-3);
            margin: var(--space-2) 0;
        }

        .particle-source {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: var(--space-1);
        }

        .particle-btn {
            width: 40px;
            height: 40px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            cursor: grab;
        }

        .particle-btn.proton { background: var(--proton); }
        .particle-btn.neutron { background: var(--neutron); }

        .nucleus-area {
            width: 120px;
            height: 120px;
            border: 2px dashed var(--glass-border);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            margin: var(--space-2) auto;
        }

        .isotope-stats {
            display: flex;
            justify-content: center;
            gap: var(--space-2);
            margin: var(--space-2) 0;
        }

        .stat-box {
            text-align: center;
            padding: var(--space-1);
            background: var(--glass-bg);
            border-radius: 0.5rem;
            min-width: 60px;
        }

        .stat-value {
            font-size: 1.25rem;
            font-weight: 700;
            color: var(--electron);
        }

        .stat-label {
            font-size: 0.65rem;
            color: var(--text-secondary);
        }

        .checklist {
            list-style: none;
        }

        .checklist li {
            display: flex;
            align-items: center;
            gap: var(--space-1);
            padding: var(--space-1);
            margin-bottom: var(--space-1);
            background: rgba(255, 255, 255, 0.03);
            border-radius: 0.5rem;
            font-size: 0.85rem;
        }

        .check-box {
            width: 20px;
            height: 20px;
            border: 2px solid var(--glass-border);
            border-radius: 4px;
            cursor: pointer;
        }

        .confidence-rating {
            display: flex;
            justify-content: center;
            gap: var(--space-1);
            margin: var(--space-2) 0;
        }

        .confidence-btn {
            padding: var(--space-1);
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            color: var(--text-primary);
            border-radius: 0.5rem;
            cursor: pointer;
            font-size: 1rem;
            font-weight: 700;
        }

        .exam-game {
            padding: var(--space-2);
        }

        .question-card {
            padding: var(--space-2);
            margin-bottom: var(--space-2);
            background: var(--glass-bg);
            border: 2px solid var(--glass-border);
            border-radius: 0.75rem;
        }

        .question-card.locked {
            opacity: 0.5;
        }

        .question-number {
            display: inline-block;
            width: 24px;
            height: 24px;
            background: var(--electron);
            color: #000;
            border-radius: 50%;
            text-align: center;
            line-height: 24px;
            font-weight: 700;
            margin-right: var(--space-1);
        }

        /* NEW: Student Mirror Panel (LHS 60%) */
        .student-mirror-panel {
            width: 60%;
            display: flex;
            flex-direction: column;
            border-right: 1px solid var(--glass-border);
            background: rgba(0, 0, 0, 0.3);
        }

        .student-mirror-header {
            padding: var(--space-2) var(--space-3);
            background: rgba(2, 6, 23, 0.8);
            border-bottom: 1px solid var(--glass-border);
            font-size: 0.875rem;
            font-weight: 600;
            color: var(--text-secondary);
            display: flex;
            align-items: center;
            gap: var(--space-2);
        }

        .mirror-icon {
            font-size: 1.1rem;
        }

        .student-mirror-content {
            flex: 1;
            padding: var(--space-3);
            overflow-y: auto;
        }

        .student-mirror-content .glass-card {
            max-width: 800px;
            margin: 0 auto;
        }

        /* NEW: Teacher Panel (RHS 40%) */
        .teacher-panel {
            width: 40%;
            display: flex;
            flex-direction: column;
            background: rgba(2, 6, 23, 0.5);
        }

        /* Locked state: LHS takes full width, RHS is hidden */
        .main-container.notes-locked .student-mirror-panel {
            width: 100%;
            border-right: none;
        }

        .main-container.notes-locked .teacher-panel {
            display: none;
        }

        /* NEW: Visual Summary Styles */
        .visual-summary {
            padding: var(--space-2);
        }

        .visual-summary-box {
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            border-radius: 0.75rem;
            padding: var(--space-3);
            margin-bottom: var(--space-2);
        }

        .visual-summary-title {
            font-size: 1rem;
            font-weight: 700;
            color: var(--electron);
            margin-bottom: var(--space-2);
            display: flex;
            align-items: center;
            gap: var(--space-1);
        }

        .visual-summary-emoji {
            font-size: 1.5rem;
        }

        .visual-summary-svg {
            display: flex;
            justify-content: center;
            margin: var(--space-2) 0;
        }

        .visual-summary-keypoint {
            display: flex;
            align-items: flex-start;
            gap: var(--space-2);
            margin-bottom: var(--space-1);
            font-size: 0.8rem;
            color: var(--text-primary);
        }

        .visual-summary-keypoint::before {
            content: "•";
            color: var(--electron);
            font-weight: bold;
        }

        .color-box {
            display: inline-block;
            padding: 2px 8px;
            border-radius: 4px;
            font-weight: 600;
            font-size: 0.75rem;
        }
        .color-box.red { background: rgba(239, 68, 68, 0.3); color: var(--proton); }
        .color-box.blue { background: rgba(59, 130, 246, 0.3); color: var(--neutron); }
        .color-box.yellow { background: rgba(234, 179, 8, 0.3); color: var(--electron); }
        .color-box.green { background: rgba(34, 197, 94, 0.3); color: var(--success); }

        /* ==================== NEW INTRO SLIDE STYLES ==================== */

        /* Build an Atom Activity */
        .build-atom-container {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: var(--space-3);
        }

        .atom-diagram {
            position: relative;
            width: 200px;
            height: 200px;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .electron-orbit {
            position: absolute;
            border: 2px dashed rgba(234, 179, 8, 0.4);
            border-radius: 50%;
        }

        .electron-orbit:nth-child(1) { width: 120px; height: 120px; }
        .electron-orbit:nth-child(2) { width: 160px; height: 160px; }
        .electron-orbit:nth-child(3) { width: 200px; height: 200px; }

        .nucleus-center {
            width: 60px;
            height: 60px;
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid var(--glass-border);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 0.7rem;
            color: var(--text-secondary);
            z-index: 2;
        }

        .particle-label-row {
            display: flex;
            justify-content: center;
            gap: var(--space-3);
            flex-wrap: wrap;
        }

        .particle-label-item {
            display: flex;
            align-items: center;
            gap: var(--space-1);
            font-size: 0.85rem;
            font-weight: 600;
        }

        .particle-label-icon {
            width: 28px;
            height: 28px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 0.7rem;
        }

        .particle-label-icon.proton { background: var(--proton); }
        .particle-label-icon.neutron { background: var(--neutron); }
        .particle-label-icon.electron { background: var(--electron); }

        .identify-choices {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: var(--space-2);
            width: 100%;
            max-width: 350px;
        }

        .identify-choice {
            padding: var(--space-2);
            background: rgba(255, 255, 255, 0.05);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            text-align: center;
            cursor: pointer;
            transition: all 0.2s ease;
            font-size: 0.85rem;
        }

        .identify-choice:hover {
            border-color: var(--electron);
            background: rgba(234, 179, 8, 0.1);
        }

        .identify-choice.correct {
            border-color: var(--success);
            background: rgba(34, 197, 94, 0.2);
        }

        .identify-choice.incorrect {
            border-color: var(--error);
            background: rgba(239, 68, 68, 0.2);
        }

        /* Particle Calculator Activity */
        .particle-calc-container {
            display: flex;
            flex-direction: column;
            gap: var(--space-3);
        }

        .notation-diagram {
            text-align: center;
            padding: var(--space-3);
            background: rgba(59, 130, 246, 0.1);
            border: 2px solid var(--neutron);
            border-radius: 0.75rem;
            position: relative;
        }

        .notation-large {
            font-size: 2.5rem;
            font-weight: 700;
            font-family: 'Courier New', monospace;
            line-height: 1.2;
        }

        .notation-labels {
            display: flex;
            justify-content: center;
            gap: var(--space-4);
            margin-top: var(--space-2);
            font-size: 0.75rem;
            color: var(--text-secondary);
        }

        .notation-labels span {
            display: flex;
            align-items: center;
            gap: 4px;
        }

        .calc-input-row {
            display: flex;
            align-items: center;
            gap: var(--space-2);
            padding: var(--space-2);
            background: var(--glass-bg);
            border-radius: 0.5rem;
        }

        .calc-input-row label {
            min-width: 100px;
            font-size: 0.85rem;
            font-weight: 600;
        }

        .calc-result-box {
            text-align: center;
            padding: var(--space-2);
            background: rgba(34, 197, 94, 0.1);
            border: 2px solid var(--success);
            border-radius: 0.5rem;
            font-weight: 700;
            font-size: 1rem;
            color: var(--success);
            display: none;
        }

        .calc-result-box.show {
            display: block;
        }

        .calc-next-btn {
            margin-top: var(--space-2);
        }

        /* Atom Comparison Activity */
        .atom-compare-container {
            display: flex;
            flex-direction: column;
            gap: var(--space-3);
        }

        .atom-compare-grid {
            display: grid;
            grid-template-columns: 1fr auto 1fr;
            gap: var(--space-2);
            align-items: start;
        }

        .atom-compare-card {
            padding: var(--space-3);
            background: var(--glass-bg);
            border: 2px solid var(--glass-border);
            border-radius: 0.75rem;
            text-align: center;
        }

        .atom-compare-card h4 {
            font-size: 1.25rem;
            margin-bottom: var(--space-2);
        }

        .atom-compare-card .compare-symbol {
            font-size: 2rem;
            font-weight: 700;
            margin-bottom: var(--space-1);
        }

        .atom-compare-vs {
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.5rem;
            font-weight: 700;
            color: var(--text-secondary);
            padding-top: var(--space-4);
        }

        .compare-detail-list {
            list-style: none;
            text-align: left;
            font-size: 0.8rem;
        }

        .compare-detail-list li {
            padding: 4px 0;
            border-bottom: 1px solid var(--glass-border);
            display: flex;
            justify-content: space-between;
        }

        .compare-detail-list li:last-child {
            border-bottom: none;
        }

        .highlight-same {
            background: rgba(34, 197, 94, 0.15);
            border-left: 3px solid var(--success);
            padding-left: var(--space-1);
        }

        .highlight-different {
            background: rgba(239, 68, 68, 0.15);
            border-left: 3px solid var(--error);
            padding-left: var(--space-1);
        }

        .mystery-question {
            text-align: center;
            padding: var(--space-3);
            background: rgba(234, 179, 8, 0.1);
            border: 2px solid var(--electron);
            border-radius: 0.75rem;
            font-size: 1rem;
        }

        .compare-answer-btns {
            display: flex;
            justify-content: center;
            gap: var(--space-2);
            margin-top: var(--space-2);
        }

        .compare-answer-btn {
            padding: var(--space-1) var(--space-3);
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            color: var(--text-primary);
            cursor: pointer;
            font-weight: 600;
            transition: all 0.2s ease;
        }

        .compare-answer-btn:hover {
            border-color: var(--electron);
        }

        .compare-answer-btn.correct {
            border-color: var(--success);
            background: rgba(34, 197, 94, 0.3);
        }

        .compare-answer-btn.incorrect {
            border-color: var(--error);
            background: rgba(239, 68, 68, 0.3);
        }

        /* NEW: Transcript Section */
        .transcript-section {
            flex: 1;
            display: none;
            flex-direction: column;
            background: rgba(2, 6, 23, 0.7);
            overflow: hidden;
            min-height: 0;
        }

        .transcript-section.unlocked {
            display: flex;
        }

        .teacher-notes-lock-section {
            margin-bottom: var(--space-3);
            padding: var(--space-2) var(--space-3);
        }

        .teacher-notes-lock-box {
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            border-radius: 0.75rem;
            padding: var(--space-3);
        }

        .teacher-notes-lock-label {
            font-size: 0.8rem;
            font-weight: 700;
            color: var(--electron);
            text-transform: uppercase;
            letter-spacing: 0.5px;
            margin-bottom: var(--space-2);
        }

        .teacher-notes-lock-row {
            display: flex;
            gap: var(--space-2);
            align-items: center;
        }

        .teacher-notes-lock-input {
            flex: 1;
            padding: var(--space-1) var(--space-2);
            background: rgba(255, 255, 255, 0.1);
            border: 1px solid rgba(255, 255, 255, 0.3);
            border-radius: 0.5rem;
            color: var(--text-primary);
            font-size: 0.85rem;
            font-family: 'Courier New', monospace;
        }

        .teacher-notes-lock-input:focus {
            outline: none;
            border-color: var(--electron);
        }

        .teacher-notes-lock-btn {
            padding: var(--space-1) var(--space-2);
            background: var(--electron);
            color: #000;
            border: none;
            border-radius: 0.5rem;
            font-size: 0.8rem;
            font-weight: 700;
            cursor: pointer;
            transition: all 0.2s ease;
            white-space: nowrap;
        }

        .teacher-notes-lock-btn:hover {
            background: #fbbf24;
        }

        .teacher-notes-lock-feedback {
            margin-top: var(--space-1);
            font-size: 0.75rem;
            color: var(--error);
            min-height: 1.2em;
        }

        .transcript-header {
            padding: var(--space-2) var(--space-3);
            font-size: 0.75rem;
            font-weight: 700;
            text-transform: uppercase;
            letter-spacing: 1px;
            color: var(--text-secondary);
            display: flex;
            align-items: center;
            gap: var(--space-2);
        }

        .transcript-icon {
            font-size: 0.9rem;
        }

        .transcript-content {
            flex: 1;
            overflow-y: auto;
            padding: 0 var(--space-3) var(--space-3);
            font-size: 0.85rem;
            line-height: 1.6;
            min-height: 0;
        }

        .transcript-block {
            margin-bottom: var(--space-3);
            padding: var(--space-2);
            background: var(--glass-bg);
            border-radius: 0.5rem;
            border-left: 3px solid var(--electron);
        }

        .transcript-block-title {
            font-size: 0.7rem;
            font-weight: 700;
            text-transform: uppercase;
            color: var(--electron);
            margin-bottom: var(--space-1);
        }

        .spoken-text {
            color: #ff8c00;
            font-weight: 600;
        }

        .non-spoken-text {
            color: #87CEEB;
        }

        /* ==================== Interactive Activity Styles ==================== */

        .interactive-section {
            max-width: 800px;
            margin: var(--space-4) auto;
            padding: var(--space-4);
            background: rgba(0, 0, 0, 0.3);
            border-radius: 1rem;
            border: 2px solid var(--glass-border);
        }

        /* SLIDE 1: Emoji Reaction Poll */
        .emoji-poll {
            display: flex;
            justify-content: center;
            gap: var(--space-4);
            margin: var(--space-4) 0;
        }

        .emoji-btn {
            font-size: 3rem;
            cursor: pointer;
            transition: all 0.3s ease;
            filter: grayscale(0.5);
        }

        .emoji-btn:hover {
            transform: scale(1.3);
            filter: grayscale(0);
        }

        .emoji-btn.selected {
            transform: scale(1.4);
            filter: grayscale(0) drop-shadow(0 0 15px rgba(234, 179, 8, 0.8));
        }

        .poll-results {
            display: flex;
            flex-direction: column;
            gap: var(--space-2);
            margin-top: var(--space-3);
        }

        .poll-bar {
            display: flex;
            align-items: center;
            gap: var(--space-2);
        }

        .poll-bar-label { font-size: 2rem; min-width: 60px; }
        .poll-bar-track {
            flex: 1;
            height: 20px;
            background: rgba(255, 255, 255, 0.1);
            border-radius: 10px;
            overflow: hidden;
        }

        .poll-bar-fill {
            height: 100%;
            background: var(--electron);
            width: 0%;
            transition: width 0.5s ease;
        }

        /* SLIDE 2: Matching Game */
        .matching-area {
            display: flex;
            gap: var(--space-4);
            justify-content: space-around;
            margin: var(--space-4) 0;
        }

        .match-column {
            flex: 1;
            display: flex;
            flex-direction: column;
            gap: var(--space-2);
        }

        .match-label {
            font-size: 0.875rem;
            color: var(--text-secondary);
            text-align: center;
            margin-bottom: var(--space-1);
        }

        .match-item {
            padding: var(--space-2);
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            cursor: grab;
            text-align: center;
            font-weight: 600;
            transition: all 0.2s ease;
        }

        .match-item:hover { border-color: var(--electron); transform: scale(1.05); }
        .match-item.dragging { opacity: 0.5; }
        .match-item.matched { border-color: var(--success); background: rgba(34, 197, 94, 0.2); cursor: default; }
        .match-item.wrong { border-color: var(--error); animation: shake 0.3s ease; }

        @keyframes shake {
            0%, 100% { transform: translateX(0); }
            25% { transform: translateX(-5px); }
            75% { transform: translateX(5px); }
        }

        .match-target {
            padding: var(--space-2);
            min-height: 60px;
            border: 2px dashed rgba(255, 255, 255, 0.3);
            border-radius: 0.5rem;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .match-target.drag-over { border-color: var(--electron); background: rgba(234, 179, 8, 0.1); }

        /* SLIDE 3: Decision Spinner */
        .spinner-container {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: var(--space-4);
        }

        .spinner-wheel {
            width: 200px;
            height: 200px;
            border-radius: 50%;
            background: conic-gradient(
                var(--proton) 0deg 90deg,
                var(--neutron) 90deg 180deg,
                var(--electron) 180deg 270deg,
                var(--success) 270deg 360deg
            );
            display: flex;
            align-items: center;
            justify-content: center;
            position: relative;
            transition: transform 3s ease-out;
        }

        .spinner-wheel.spinning {
            transform: rotate(1800deg);
        }

        .spinner-center {
            width: 60px;
            height: 60px;
            background: var(--bg-dark);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 1.5rem;
        }

        .spinner-pointer {
            position: absolute;
            top: -20px;
            width: 0;
            height: 0;
            border-left: 15px solid transparent;
            border-right: 15px solid transparent;
            border-top: 25px solid var(--text-primary);
        }

        .spinner-options {
            display: grid;
            grid-template-columns: repeat(2, 1fr);
            gap: var(--space-2);
            width: 100%;
            max-width: 300px;
        }

        .spinner-option {
            padding: var(--space-2);
            text-align: center;
            font-weight: 600;
            border-radius: 0.5rem;
            transition: all 0.2s ease;
        }

        .spinner-option.selected {
            background: rgba(234, 179, 8, 0.3);
            border: 2px solid var(--electron);
        }

        /* SLIDE 4: Interactive Slider */
        .slider-container {
            margin: var(--space-4) 0;
        }

        .ratio-slider {
            width: 100%;
            height: 20px;
            -webkit-appearance: none;
            background: linear-gradient(90deg, var(--proton), var(--neutron));
            border-radius: 10px;
            outline: none;
        }

        .ratio-slider::-webkit-slider-thumb {
            -webkit-appearance: none;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            background: var(--electron);
            cursor: pointer;
            box-shadow: 0 0 15px rgba(234, 179, 8, 0.5);
        }

        .balance-visual {
            display: flex;
            justify-content: center;
            align-items: center;
            margin: var(--space-4) 0;
            gap: var(--space-4);
        }

        .balance-beam {
            width: 250px;
            height: 10px;
            background: linear-gradient(90deg, var(--proton), var(--electron));
            border-radius: 5px;
            position: relative;
            transition: transform 0.3s ease;
            transform-origin: center center;
        }

        .balance-fulcrum {
            position: absolute;
            left: 50%;
            top: 100%;
            transform: translateX(-50%);
            width: 0;
            height: 0;
            border-left: 20px solid transparent;
            border-right: 20px solid transparent;
            border-bottom: 30px solid var(--text-secondary);
        }

        .balance-pan {
            position: absolute;
            top: -60px;
            width: 80px;
            height: 40px;
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.3);
            border-radius: 0 0 40px 40px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 1.5rem;
            transition: all 0.3s ease;
        }

        .balance-pan.left { left: 0; }
        .balance-pan.right { right: 0; }

        .ratio-display {
            text-align: center;
            font-size: 1.5rem;
            font-weight: 700;
            margin-bottom: var(--space-3);
        }

        .ratio-display .cl-35 { color: var(--proton); }
        .ratio-display .cl-37 { color: var(--neutron); }
        .ratio-display .avg { color: var(--electron); font-size: 2rem; }

        /* SLIDE 5: Formula Puzzle Builder */
        .formula-puzzle {
            margin: var(--space-4) 0;
        }

        .puzzle-pieces {
            display: flex;
            flex-wrap: wrap;
            gap: var(--space-2);
            justify-content: center;
            margin-bottom: var(--space-3);
            padding: var(--space-3);
            background: rgba(0, 0, 0, 0.2);
            border-radius: 0.5rem;
            min-height: 80px;
        }

        .puzzle-piece {
            padding: var(--space-2) var(--space-3);
            background: rgba(59, 130, 246, 0.3);
            border: 2px solid var(--neutron);
            border-radius: 0.5rem;
            cursor: grab;
            font-family: 'Courier New', monospace;
            font-weight: 600;
            transition: all 0.2s ease;
        }

        .puzzle-piece:hover { transform: scale(1.1); border-color: var(--electron); }
        .puzzle-piece.selected { background: rgba(234, 179, 8, 0.3); border-color: var(--electron); }

        .puzzle-slot {
            display: inline-block;
            min-width: 80px;
            padding: var(--space-2);
            margin: var(--space-1);
            border: 2px dashed rgba(255, 255, 255, 0.3);
            border-radius: 0.5rem;
            text-align: center;
            font-family: 'Courier New', monospace;
            transition: all 0.2s ease;
        }

        .puzzle-slot.filled {
            border-style: solid;
            border-color: var(--success);
            background: rgba(34, 197, 94, 0.1);
        }

        .puzzle-target {
            display: flex;
            flex-wrap: wrap;
            gap: var(--space-1);
            justify-content: center;
            padding: var(--space-3);
            background: rgba(0, 0, 0, 0.3);
            border-radius: 0.5rem;
        }

        /* SLIDE 6: Step Calculator */
        .step-calculator {
            background: rgba(0, 0, 0, 0.3);
            border-radius: 1rem;
            padding: var(--space-4);
        }

        .calc-step-row {
            display: flex;
            align-items: center;
            gap: var(--space-2);
            padding: var(--space-2);
            margin-bottom: var(--space-2);
            background: rgba(255, 255, 255, 0.05);
            border-radius: 0.5rem;
            overflow: hidden;
        }

        .calc-step-num {
            width: 30px;
            height: 30px;
            background: var(--electron);
            color: #000;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            flex-shrink: 0;
        }

        .calc-step-content {
            flex: 1;
            font-family: 'Courier New', monospace;
            padding: var(--space-2);
            background: rgba(0, 0, 0, 0.2);
            border-radius: 0.25rem;
        }

        .calc-step-reveal {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.5s ease;
            color: var(--success);
            font-weight: 600;
            padding-left: 42px;
        }

        .calc-step-reveal.show {
            max-height: 50px;
            padding-top: var(--space-1);
        }

        .reveal-btn {
            margin-top: var(--space-3);
            width: 100%;
        }

        /* SLIDE 7: Step Sorter */
        .step-sorter {
            margin: var(--space-4) 0;
        }

        .scrambled-steps {
            display: flex;
            flex-direction: column;
            gap: var(--space-2);
            margin-bottom: var(--space-4);
            padding: var(--space-3);
            background: rgba(0, 0, 0, 0.2);
            border-radius: 0.5rem;
            min-height: 200px;
        }

        .sort-step {
            padding: var(--space-2) var(--space-3);
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            cursor: grab;
            display: flex;
            align-items: center;
            gap: var(--space-2);
            transition: all 0.2s ease;
        }

        .sort-step:hover { border-color: var(--electron); transform: scale(1.02); }
        .sort-step.dragging { opacity: 0.5; }
        .sort-step.in-place {
            border-color: var(--success);
            background: rgba(34, 197, 94, 0.1);
        }

        .sort-step .step-num-badge {
            width: 24px;
            height: 24px;
            background: var(--electron);
            color: #000;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 0.75rem;
        }

        .sort-step.in-place .step-num-badge {
            background: var(--success);
        }

        .target-sequence {
            display: flex;
            flex-direction: column;
            gap: var(--space-2);
            padding: var(--space-3);
            background: rgba(0, 0, 0, 0.3);
            border-radius: 0.5rem;
            min-height: 200px;
        }

        .target-slot {
            padding: var(--space-2) var(--space-3);
            min-height: 50px;
            border: 2px dashed rgba(255, 255, 255, 0.3);
            border-radius: 0.5rem;
            display: flex;
            align-items: center;
        }

        .target-slot.drag-over { border-color: var(--electron); background: rgba(234, 179, 8, 0.1); }

        /* SLIDE 8: Typing Race */
        .typing-race {
            text-align: center;
        }

        .typing-question {
            font-size: 1.5rem;
            margin-bottom: var(--space-4);
            padding: var(--space-3);
            background: rgba(255, 255, 255, 0.05);
            border-radius: 0.5rem;
        }

        .typing-timer {
            font-size: 3rem;
            font-weight: 700;
            color: var(--electron);
            margin-bottom: var(--space-3);
            font-variant-numeric: tabular-nums;
        }

        .typing-input {
            width: 200px;
            padding: var(--space-2);
            font-size: 1.5rem;
            text-align: center;
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.3);
            border-radius: 0.5rem;
            color: white;
            margin: 0 auto var(--space-3);
        }

        .typing-input:focus {
            outline: none;
            border-color: var(--electron);
        }

        .typing-start-btn {
            font-size: 1.25rem;
            padding: var(--space-3) var(--space-5);
        }

        /* SLIDE 9: Particle Catcher */
        .particle-catcher {
            position: relative;
            height: 300px;
            background: linear-gradient(180deg, #0a1628 0%, #1e3a5f 100%);
            border-radius: 1rem;
            overflow: hidden;
            border: 2px solid var(--glass-border);
        }

        .catcher-target {
            position: absolute;
            bottom: 20px;
            left: 50%;
            transform: translateX(-50%);
            width: 150px;
            height: 50px;
            background: rgba(234, 179, 8, 0.3);
            border: 3px solid var(--electron);
            border-radius: 0 0 75px 75px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 0.875rem;
        }

        .falling-particle {
            position: absolute;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 0.875rem;
            cursor: pointer;
            animation: fallDown 3s linear forwards;
            transition: transform 0.1s ease;
        }

        .falling-particle:hover { transform: scale(1.2); }

        .falling-particle.proton {
            background: var(--proton);
            color: white;
        }

        .falling-particle.neutron {
            background: var(--neutron);
            color: white;
        }

        @keyframes fallDown {
            from { top: -50px; }
            to { top: 350px; }
        }

        .catcher-score {
            position: absolute;
            top: 10px;
            right: 10px;
            font-size: 1.25rem;
            font-weight: 700;
        }

        .catcher-instructions {
            position: absolute;
            top: 10px;
            left: 10px;
            font-size: 0.875rem;
            color: var(--text-secondary);
        }

        /* SLIDE 10: Card Flip */
        .card-flip {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: var(--space-4);
        }

        .flip-card {
            width: 300px;
            height: 180px;
            perspective: 1000px;
            cursor: pointer;
        }

        .flip-card-inner {
            position: relative;
            width: 100%;
            height: 100%;
            transition: transform 0.6s;
            transform-style: preserve-3d;
        }

        .flip-card.flipped .flip-card-inner {
            transform: rotateY(180deg);
        }

        .flip-card-front, .flip-card-back {
            position: absolute;
            width: 100%;
            height: 100%;
            backface-visibility: hidden;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            border-radius: 1rem;
            padding: var(--space-3);
        }

        .flip-card-front {
            background: linear-gradient(135deg, rgba(59, 130, 246, 0.3), rgba(239, 68, 68, 0.3));
            border: 2px solid var(--glass-border);
        }

        .flip-card-front .card-icon {
            font-size: 4rem;
            margin-bottom: var(--space-2);
        }

        .flip-card-back {
            background: rgba(0, 0, 0, 0.5);
            border: 2px solid var(--glass-border);
            transform: rotateY(180deg);
        }

        .flip-card-back .result-icon {
            font-size: 4rem;
            margin-bottom: var(--space-2);
        }

        .flip-card-back .result-text {
            font-size: 1.25rem;
            font-weight: 700;
            margin-bottom: var(--space-2);
        }

        .flip-card-back .explanation {
            font-size: 0.875rem;
            color: var(--text-secondary);
            text-align: center;
        }

        .click-hint {
            font-size: 0.875rem;
            color: var(--text-secondary);
        }

        /* SLIDE 11: Fill-in-the-Blanks Animator */
        .fill-blanks {
            margin: var(--space-4) 0;
        }

        .blank-row {
            display: flex;
            align-items: center;
            gap: var(--space-2);
            padding: var(--space-2);
            margin-bottom: var(--space-2);
            background: rgba(255, 255, 255, 0.05);
            border-radius: 0.5rem;
            opacity: 0.5;
            transform: translateX(-20px);
            transition: all 0.4s ease;
        }

        .blank-row.active {
            opacity: 1;
            transform: translateX(0);
            border-left: 3px solid var(--electron);
        }

        .blank-row.completed {
            opacity: 1;
            border-left: 3px solid var(--success);
        }

        .blank-row .row-label {
            font-weight: 600;
            min-width: 80px;
        }

        .blank-input {
            flex: 1;
            max-width: 100px;
            padding: var(--space-1) var(--space-2);
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.3);
            border-radius: 0.25rem;
            color: white;
            text-align: center;
            font-family: 'Courier New', monospace;
        }

        .blank-input:focus {
            outline: none;
            border-color: var(--electron);
        }

        .blank-input.correct {
            border-color: var(--success);
            background: rgba(34, 197, 94, 0.2);
        }

        .blank-input.incorrect {
            border-color: var(--error);
            background: rgba(239, 68, 68, 0.2);
        }

        .blank-row .result {
            min-width: 120px;
            font-family: 'Courier New', monospace;
        }

        .blank-nav-btns {
            display: flex;
            gap: var(--space-2);
            justify-content: center;
            margin-top: var(--space-3);
        }

        /* SLIDE 12: Hint Ladder */
        .hint-ladder {
            margin: var(--space-4) 0;
        }

        .hint-step {
            display: flex;
            align-items: center;
            gap: var(--space-3);
            padding: var(--space-3);
            margin-bottom: var(--space-2);
            background: rgba(255, 255, 255, 0.05);
            border-radius: 0.5rem;
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .hint-step:hover { background: rgba(255, 255, 255, 0.1); }
        .hint-step.locked { opacity: 0.5; cursor: not-allowed; }
        .hint-step.revealed { border-left: 3px solid var(--electron); }

        .hint-cost {
            width: 40px;
            height: 40px;
            background: var(--electron);
            color: #000;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            flex-shrink: 0;
        }

        .hint-step.locked .hint-cost {
            background: rgba(255, 255, 255, 0.2);
            color: var(--text-secondary);
        }

        .hint-text {
            flex: 1;
            font-size: 0.875rem;
        }

        .hint-reveal-area {
            margin-top: var(--space-4);
            padding: var(--space-3);
            background: rgba(234, 179, 8, 0.1);
            border: 2px solid var(--electron);
            border-radius: 0.5rem;
            min-height: 60px;
        }

        .points-display-hint {
            font-size: 1.25rem;
            font-weight: 700;
            text-align: center;
            margin-bottom: var(--space-3);
        }

        .points-display-hint span { color: var(--electron); }

        /* SLIDE 13: Boss Health Bar */
        .boss-game {
            text-align: center;
        }

        .boss-container {
            position: relative;
            margin: var(--space-4) 0;
            padding: var(--space-4);
            background: linear-gradient(180deg, #1a0a0a 0%, #2d1515 100%);
            border-radius: 1rem;
            border: 2px solid var(--error);
        }

        .boss-health-bar {
            height: 30px;
            background: rgba(255, 255, 255, 0.1);
            border-radius: 15px;
            overflow: hidden;
            margin-bottom: var(--space-3);
        }

        .boss-health-fill {
            height: 100%;
            background: linear-gradient(90deg, var(--error), #ff6b6b);
            width: 100%;
            transition: width 0.5s ease;
        }

        .boss-name {
            font-size: 1.5rem;
            font-weight: 700;
            margin-bottom: var(--space-2);
        }

        .boss-emoji {
            font-size: 5rem;
            margin-bottom: var(--space-2);
            animation: bossBounce 1s ease infinite;
        }

        @keyframes bossBounce {
            0%, 100% { transform: translateY(0); }
            50% { transform: translateY(-10px); }
        }

        .boss-status {
            font-size: 1rem;
            color: var(--text-secondary);
        }

        .boss-question {
            margin: var(--space-3) 0;
            padding: var(--space-3);
            background: rgba(0, 0, 0, 0.3);
            border-radius: 0.5rem;
        }

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

        .boss-option {
            padding: var(--space-2);
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .boss-option:hover:not(:disabled) {
            border-color: var(--electron);
            transform: scale(1.05);
        }

        .boss-option:disabled { opacity: 0.5; cursor: not-allowed; }

        .boss-damage-effect {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            font-size: 3rem;
            font-weight: 700;
            opacity: 0;
            animation: damagePopup 0.8s ease forwards;
        }

        .boss-damage-effect.correct { color: var(--success); }
        .boss-damage-effect.wrong { color: var(--error); }

        @keyframes damagePopup {
            0% { opacity: 0; transform: translate(-50%, -50%) scale(0.5); }
            50% { opacity: 1; transform: translate(-50%, -50%) scale(1.5); }
            100% { opacity: 0; transform: translate(-50%, -50%) scale(2); }
        }

        /* SLIDE 14: Drag-to-Complete */
        .drag-complete {
            margin: var(--space-4) 0;
        }

        .drag-source {
            display: flex;
            flex-wrap: wrap;
            gap: var(--space-2);
            padding: var(--space-3);
            background: rgba(0, 0, 0, 0.2);
            border-radius: 0.5rem;
            margin-bottom: var(--space-3);
            min-height: 80px;
        }

        .drag-card {
            padding: var(--space-2) var(--space-3);
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            cursor: grab;
            transition: all 0.2s ease;
            font-size: 0.875rem;
        }

        .drag-card:hover {
            border-color: var(--electron);
            transform: scale(1.05);
        }

        .drag-card.dragging { opacity: 0.5; }
        .drag-card.completed { opacity: 0.3; cursor: default; }

        .drag-target-zone {
            padding: var(--space-4);
            background: rgba(34, 197, 94, 0.1);
            border: 3px dashed var(--success);
            border-radius: 1rem;
            min-height: 120px;
            display: flex;
            flex-wrap: wrap;
            gap: var(--space-2);
            align-items: flex-start;
        }

        .drag-target-zone.drag-over {
            background: rgba(34, 197, 94, 0.2);
            border-style: solid;
        }

        .drag-target-zone .zone-label {
            width: 100%;
            text-align: center;
            font-weight: 700;
            color: var(--success);
            margin-bottom: var(--space-2);
        }

        .drag-target-zone .drag-card {
            background: rgba(34, 197, 94, 0.2);
            border-color: var(--success);
        }

        /* SLIDE 15: Confetti Celebration */
        .celebration {
            text-align: center;
            padding: var(--space-4);
        }

        .celebration-emoji {
            font-size: 5rem;
            margin-bottom: var(--space-3);
            animation: celebrateBounce 0.5s ease infinite;
        }

        @keyframes celebrateBounce {
            0%, 100% { transform: scale(1); }
            50% { transform: scale(1.1); }
        }

        .celebration-btn {
            font-size: 1.5rem;
            padding: var(--space-3) var(--space-5);
            margin-top: var(--space-3);
        }

        .confetti-container {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            pointer-events: none;
            z-index: 1000;
            overflow: hidden;
        }

        /* SLIDE 6 (NEW): Property Sorting Game */
        .property-sort-game {
            display: flex;
            flex-direction: column;
            gap: var(--space-3);
        }

        .property-sort-source {
            display: flex;
            flex-wrap: wrap;
            gap: var(--space-2);
            justify-content: center;
            padding: var(--space-3);
            background: rgba(0, 0, 0, 0.2);
            border-radius: 0.5rem;
            min-height: 60px;
        }

        .property-tile {
            padding: var(--space-2) var(--space-3);
            background: rgba(255, 255, 255, 0.1);
            border: 2px solid rgba(255, 255, 255, 0.2);
            border-radius: 0.5rem;
            cursor: pointer;
            font-weight: 600;
            font-size: 0.85rem;
            transition: all 0.2s ease;
            user-select: none;
        }

        .property-tile:hover {
            border-color: var(--electron);
            transform: scale(1.05);
        }

        .property-tile.selected {
            border-color: var(--electron);
            background: rgba(234, 179, 8, 0.2);
            transform: scale(1.05);
        }

        .property-tile.sorted {
            opacity: 0.3;
            cursor: default;
            pointer-events: none;
        }

        .property-tile.correct-sort {
            border-color: var(--success);
            background: rgba(34, 197, 94, 0.2);
            opacity: 0.5;
        }

        .property-tile.wrong-sort {
            border-color: var(--error);
            animation: shake 0.3s ease;
        }

        .property-sort-bins {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: var(--space-3);
        }

        .sort-bin {
            padding: var(--space-3);
            border-radius: 0.75rem;
            min-height: 120px;
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: var(--space-1);
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .sort-bin.chemical-bin {
            background: rgba(34, 197, 94, 0.1);
            border: 2px dashed var(--success);
        }

        .sort-bin.physical-bin {
            background: rgba(59, 130, 246, 0.1);
            border: 2px dashed var(--neutron);
        }

        .sort-bin:hover {
            transform: scale(1.02);
        }

        .sort-bin.chemical-bin:hover {
            border-color: var(--success);
            background: rgba(34, 197, 94, 0.2);
        }

        .sort-bin.physical-bin:hover {
            border-color: var(--neutron);
            background: rgba(59, 130, 246, 0.2);
        }

        .sort-bin-label {
            font-size: 0.9rem;
            font-weight: 700;
            text-transform: uppercase;
            letter-spacing: 0.5px;
            margin-bottom: var(--space-1);
        }

        .sort-bin.chemical-bin .sort-bin-label {
            color: var(--success);
        }

        .sort-bin.physical-bin .sort-bin-label {
            color: var(--neutron);
        }

        .sort-bin-items {
            display: flex;
            flex-wrap: wrap;
            gap: var(--space-1);
            justify-content: center;
        }

        .sort-bin-item {
            padding: 4px 10px;
            border-radius: 0.25rem;
            font-size: 0.75rem;
            font-weight: 600;
        }

        .sort-bin.chemical-bin .sort-bin-item {
            background: rgba(34, 197, 94, 0.3);
            color: var(--success);
        }

        .sort-bin.physical-bin .sort-bin-item {
            background: rgba(59, 130, 246, 0.3);
            color: var(--neutron);
        }

        .property-sort-score {
            text-align: center;
            font-size: 0.85rem;
            color: var(--text-secondary);
        }

        .property-sort-score span {
            color: var(--electron);
            font-weight: 700;
        }

        /* Side-by-side isotope comparison for Slide 6 */
        .isotope-compare-side-by-side {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: var(--space-3);
            margin: var(--space-3) 0;
        }

        .isotope-compare-card {
            padding: var(--space-3);
            background: var(--glass-bg);
            border: 2px solid var(--glass-border);
            border-radius: 0.75rem;
            text-align: center;
        }

        .isotope-compare-card h4 {
            font-size: 1rem;
            margin-bottom: var(--space-2);
        }

        .isotope-compare-card .compare-symbol-big {
            font-size: 2.5rem;
            font-weight: 700;
            margin-bottom: var(--space-1);
        }

        .isotope-compare-card .compare-detail-list {
            list-style: none;
            text-align: left;
            font-size: 0.8rem;
        }

        .isotope-compare-card .compare-detail-list li {
            padding: 4px 0;
            border-bottom: 1px solid var(--glass-border);
            display: flex;
            justify-content: space-between;
        }

        .isotope-compare-card .compare-detail-list li:last-child {
            border-bottom: none;
        }

        .same-property {
            background: rgba(34, 197, 94, 0.1);
            border-left: 3px solid var(--success);
            padding-left: var(--space-1);
        }

        .diff-property {
            background: rgba(59, 130, 246, 0.1);
            border-left: 3px solid var(--neutron);
            padding-left: var(--space-1);
        }

        /* SLIDE 6 (NEW): Property Sorting Game */
        .property-sort-game { display: flex; flex-direction: column; gap: var(--space-3); }
        .property-sort-source { display: flex; flex-wrap: wrap; gap: var(--space-2); justify-content: center; padding: var(--space-3); background: rgba(0, 0, 0, 0.2); border-radius: 0.5rem; min-height: 60px; }
        .property-tile { padding: var(--space-2) var(--space-3); background: rgba(255, 255, 255, 0.1); border: 2px solid rgba(255, 255, 255, 0.2); border-radius: 0.5rem; cursor: pointer; font-weight: 600; font-size: 0.85rem; transition: all 0.2s ease; user-select: none; }
        .property-tile:hover { border-color: var(--electron); transform: scale(1.05); }
        .property-tile.selected { border-color: var(--electron); background: rgba(234, 179, 8, 0.2); transform: scale(1.05); }
        .property-tile.sorted { opacity: 0.3; cursor: default; pointer-events: none; }
        .property-tile.correct-sort { border-color: var(--success); background: rgba(34, 197, 94, 0.2); opacity: 0.5; }
        .property-tile.wrong-sort { border-color: var(--error); animation: shake 0.3s ease; }
        .property-sort-bins { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-3); }
        .sort-bin { padding: var(--space-3); border-radius: 0.75rem; min-height: 120px; display: flex; flex-direction: column; align-items: center; gap: var(--space-1); cursor: pointer; transition: all 0.2s ease; }
        .sort-bin.chemical-bin { background: rgba(34, 197, 94, 0.1); border: 2px dashed var(--success); }
        .sort-bin.physical-bin { background: rgba(59, 130, 246, 0.1); border: 2px dashed var(--neutron); }
        .sort-bin:hover { transform: scale(1.02); }
        .sort-bin.chemical-bin:hover { border-color: var(--success); background: rgba(34, 197, 94, 0.2); }
        .sort-bin.physical-bin:hover { border-color: var(--neutron); background: rgba(59, 130, 246, 0.2); }
        .sort-bin-label { font-size: 0.9rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.5px; margin-bottom: var(--space-1); }
        .sort-bin.chemical-bin .sort-bin-label { color: var(--success); }
        .sort-bin.physical-bin .sort-bin-label { color: var(--neutron); }
        .sort-bin-items { display: flex; flex-wrap: wrap; gap: var(--space-1); justify-content: center; }
        .sort-bin-item { padding: 4px 10px; border-radius: 0.25rem; font-size: 0.75rem; font-weight: 600; }
        .sort-bin.chemical-bin .sort-bin-item { background: rgba(34, 197, 94, 0.3); color: var(--success); }
        .sort-bin.physical-bin .sort-bin-item { background: rgba(59, 130, 246, 0.3); color: var(--neutron); }
        .property-sort-score { text-align: center; font-size: 0.85rem; color: var(--text-secondary); }
        .property-sort-score span { color: var(--electron); font-weight: 700; }
        .isotope-compare-side-by-side { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-3); margin: var(--space-3) 0; }
        .isotope-compare-card { padding: var(--space-3); background: var(--glass-bg); border: 2px solid var(--glass-border); border-radius: 0.75rem; text-align: center; }
        .isotope-compare-card h4 { font-size: 1rem; margin-bottom: var(--space-2); }
        .isotope-compare-card .compare-symbol-big { font-size: 2.5rem; font-weight: 700; margin-bottom: var(--space-1); }
        .isotope-compare-card .compare-detail-list { list-style: none; text-align: left; font-size: 0.8rem; }
        .isotope-compare-card .compare-detail-list li { padding: 4px 0; border-bottom: 1px solid var(--glass-border); display: flex; justify-content: space-between; }
        .isotope-compare-card .compare-detail-list li:last-child { border-bottom: none; }
        .same-property { background: rgba(34, 197, 94, 0.1); border-left: 3px solid var(--success); padding-left: var(--space-1); }
        .diff-property { background: rgba(59, 130, 246, 0.1); border-left: 3px solid var(--neutron); padding-left: var(--space-1); }
        .confetti {
            position: absolute;
            width: 10px;
            height: 10px;
            animation: confettiFall 3s ease-out forwards;
        }

        @keyframes confettiFall {
            0% { transform: translateY(-100vh) rotate(0deg); opacity: 1; }
            100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
        }

        /* Points Toast */
        .points-toast {
            position: fixed;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            padding: var(--space-3) var(--space-5);
            background: var(--electron);
            color: #000;
            font-size: 2rem;
            font-weight: 700;
            border-radius: 1rem;
            z-index: 200;
            animation: pointsPopup 1s ease forwards;
        }

        @keyframes pointsPopup {
            0% { opacity: 0; transform: translate(-50%, -50%) scale(0.5); }
            30% { opacity: 1; transform: translate(-50%, -50%) scale(1.2); }
            100% { opacity: 0; transform: translate(-50%, -50%) translateY(-50px); }
        }

        .lesson-overview {
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            padding: var(--space-4);
            z-index: 50;
        }

        .overview-badge {
            display: inline-block;
            background: rgba(234, 179, 8, 0.15);
            border: 1px solid var(--electron);
            color: var(--electron);
            padding: var(--space-1) var(--space-3);
            border-radius: 2rem;
            font-size: 0.75rem;
            font-weight: 600;
            text-transform: uppercase;
            letter-spacing: 0.05em;
            margin-bottom: var(--space-3);
        }

        .overview-title {
            font-size: 2.5rem;
            font-weight: 700;
            color: var(--text-primary);
            margin-bottom: var(--space-4);
            text-align: center;
        }

        .overview-points {
            max-width: 600px;
            width: 100%;
            margin-bottom: var(--space-5);
        }

        .overview-point {
            display: flex;
            align-items: center;
            gap: var(--space-3);
            padding: var(--space-3);
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            border-radius: 1rem;
            margin-bottom: var(--space-2);
            transition: all 0.2s ease;
        }

        .overview-point:hover {
            background: rgba(255, 255, 255, 0.1);
            border-color: var(--electron);
        }

        .overview-icon {
            font-size: 1.5rem;
            flex-shrink: 0;
        }

        .overview-point span:last-child {
            color: var(--text-primary);
            font-size: 1rem;
        }

        .start-lesson-btn {
            padding: var(--space-3) var(--space-6);
            background: var(--success);
            border: none;
            border-radius: 0.75rem;
            color: #000;
            font-size: 1.125rem;
            font-weight: 700;
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .start-lesson-btn:hover {
            background: #16a34a;
            transform: translateY(-2px);
            box-shadow: 0 8px 24px rgba(34, 197, 94, 0.3);
        }