:root {
            --primary: #3b82f6;
            --primary-dark: #1d4ed8;
            --accent: #8b5cf6;
            --success: #10b981;
            --warning: #f59e0b;
            --danger: #ef4444;
            --bg: #0f172a;
            --card-bg: #1e293b;
            --card-border: rgba(255, 255, 255, 0.08);
            --text: #f8fafc;
            --text-muted: #94a3b8;
            --radius-lg: 18px;
            --radius-md: 12px;
            --radius-sm: 8px;
        }

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

        body {
            font-family: 'Plus Jakarta Sans', sans-serif;
            background-color: var(--bg);
            color: var(--text);
            min-height: 100vh;
            display: flex;
            flex-direction: column;
            overflow-x: hidden;
        }

        /* Top Navbar */
        .vocab-nav {
            background: rgba(30, 41, 59, 0.8);
            backdrop-filter: blur(12px);
            border-bottom: 1px solid var(--card-border);
            height: 70px;
            padding: 0 28px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            position: sticky;
            top: 0;
            z-index: 1000;
        }

        .brand-link {
            display: flex;
            align-items: center;
            gap: 12px;
            text-decoration: none;
            color: var(--text);
        }

        .brand-icon {
            width: 40px;
            height: 40px;
            border-radius: 12px;
            background: linear-gradient(135deg, var(--primary), var(--accent));
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.2rem;
            color: white;
            box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
        }

        .brand-title {
            font-family: 'Outfit', sans-serif;
            font-size: 1.25rem;
            font-weight: 800;
            letter-spacing: -0.02em;
        }

        .brand-subtitle {
            font-size: 0.75rem;
            color: var(--text-muted);
            font-weight: 500;
        }

        .nav-right-tools {
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .btn-nav {
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 8px;
            height: 38px;
            padding: 0 16px;
            border-radius: 10px;
            font-size: 0.85rem;
            font-weight: 600;
            text-decoration: none;
            color: #e2e8f0;
            background: rgba(255, 255, 255, 0.06);
            border: 1px solid rgba(255, 255, 255, 0.12);
            transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
            cursor: pointer;
            outline: none;
            box-sizing: border-box;
            font-family: inherit;
        }

        .btn-nav:hover {
            background: rgba(255, 255, 255, 0.14);
            color: #ffffff;
            border-color: var(--primary, #3b82f6);
            transform: translateY(-1px);
        }

        /* Container */
        .container {
            max-width: 1140px;
            margin: 0 auto;
            padding: 32px 20px 60px;
            width: 100%;
            flex: 1;
        }

        /* Hero Stats Banner */
        .hero-banner {
            background: linear-gradient(135deg, rgba(59, 130, 246, 0.12), rgba(139, 92, 246, 0.12));
            border: 1px solid rgba(59, 130, 246, 0.25);
            border-radius: var(--radius-lg);
            padding: 28px 32px;
            margin-bottom: 32px;
            display: grid;
            grid-template-columns: 1fr auto;
            gap: 24px;
            align-items: center;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
        }

        .hero-text h1 {
            font-family: 'Outfit', sans-serif;
            font-size: 1.8rem;
            font-weight: 800;
            letter-spacing: -0.02em;
            margin-bottom: 8px;
            background: linear-gradient(135deg, #ffffff, #cbd5e1);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }

        .hero-text p {
            color: var(--text-muted);
            font-size: 0.95rem;
            max-width: 600px;
            line-height: 1.5;
        }

        .stats-grid {
            display: flex;
            gap: 16px;
            flex-wrap: wrap;
        }

        .stat-card {
            background: var(--card-bg);
            border: 1px solid var(--card-border);
            padding: 14px 20px;
            border-radius: var(--radius-md);
            text-align: center;
            min-width: 120px;
        }

        .stat-val {
            font-family: 'Outfit', sans-serif;
            font-size: 1.5rem;
            font-weight: 800;
            color: #38bdf8;
        }

        .stat-label {
            font-size: 0.75rem;
            color: var(--text-muted);
            text-transform: uppercase;
            font-weight: 600;
            letter-spacing: 0.05em;
            margin-top: 2px;
        }

        /* Tabs Navigation */
        .tabs-header {
            display: flex;
            gap: 8px;
            border-bottom: 1px solid var(--card-border);
            padding-bottom: 14px;
            margin-bottom: 28px;
            overflow-x: auto;
        }

        .tab-btn {
            background: transparent;
            border: 1px solid transparent;
            color: var(--text-muted);
            font-size: 0.95rem;
            font-weight: 600;
            padding: 10px 20px;
            border-radius: var(--radius-md);
            cursor: pointer;
            display: inline-flex;
            align-items: center;
            gap: 8px;
            transition: all 0.2s ease;
            white-space: nowrap;
        }

        .tab-btn:hover {
            color: var(--text);
            background: rgba(255, 255, 255, 0.05);
        }

        .tab-btn.active {
            color: #ffffff;
            background: var(--primary);
            box-shadow: 0 4px 14px rgba(59, 130, 246, 0.4);
        }

        .tab-badge {
            background: rgba(0, 0, 0, 0.25);
            padding: 2px 8px;
            border-radius: 12px;
            font-size: 0.75rem;
        }

        /* Topic Filter Pills */
        .topic-pills {
            display: flex;
            gap: 8px;
            flex-wrap: wrap;
            margin-bottom: 24px;
        }

        .topic-pill {
            background: rgba(255, 255, 255, 0.05);
            border: 1px solid var(--card-border);
            padding: 7px 16px;
            border-radius: 20px;
            font-size: 0.85rem;
            font-weight: 600;
            color: var(--text-muted);
            cursor: pointer;
            transition: all 0.15s ease;
        }

        .topic-pill:hover, .topic-pill.active {
            background: var(--primary);
            color: white;
            border-color: var(--primary);
        }

        .diff-pill, .diff-quiz-pill {
            background: rgba(255, 255, 255, 0.04);
            border: 1px solid var(--card-border);
            padding: 6px 14px;
            border-radius: 16px;
            font-size: 0.8rem;
            font-weight: 600;
            color: var(--text-muted);
            cursor: pointer;
            transition: all 0.15s ease;
        }

        .diff-pill:hover, .diff-pill.active,
        .diff-quiz-pill:hover, .diff-quiz-pill.active {
            background: linear-gradient(135deg, #8b5cf6, #3b82f6);
            color: white;
            border-color: #8b5cf6;
            box-shadow: 0 2px 10px rgba(139, 92, 246, 0.3);
        }

        /* 3D Flashcard Presentation */
        .flashcard-stage {
            perspective: 1200px;
            width: 100%;
            max-width: 680px;
            height: 420px;
            margin: 0 auto 28px;
            cursor: pointer;
        }

        .flashcard-inner {
            position: relative;
            width: 100%;
            height: 100%;
            text-align: center;
            transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
            transform-style: preserve-3d;
            border-radius: var(--radius-lg);
        }

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

        .flashcard-front, .flashcard-back {
            position: absolute;
            width: 100%;
            height: 100%;
            -webkit-backface-visibility: hidden;
            backface-visibility: hidden;
            border-radius: var(--radius-lg);
            background: var(--card-bg);
            border: 1px solid rgba(255, 255, 255, 0.12);
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.35), inset 0 1px 0 rgba(255, 255, 255, 0.1);
            padding: 32px;
            display: flex;
            flex-direction: column;
            justify-content: space-between;
        }

        .flashcard-back {
            transform: rotateY(180deg);
            text-align: left;
            overflow-y: auto;
            background: linear-gradient(145deg, #1e293b, #0f172a);
        }

        .card-top-row {
            display: flex;
            justify-content: space-between;
            align-items: center;
            width: 100%;
        }

        .card-topic-tag {
            font-size: 0.8rem;
            font-weight: 700;
            text-transform: uppercase;
            letter-spacing: 0.05em;
            color: #38bdf8;
            background: rgba(56, 189, 248, 0.12);
            padding: 4px 10px;
            border-radius: 6px;
        }

        .card-band-tag {
            font-size: 0.8rem;
            font-weight: 800;
            color: #a855f7;
            background: rgba(168, 85, 247, 0.12);
            padding: 4px 10px;
            border-radius: 6px;
        }

        .card-center-word {
            margin: auto 0;
        }

        .card-word {
            font-family: 'Outfit', sans-serif;
            font-size: 2.8rem;
            font-weight: 800;
            color: #ffffff;
            letter-spacing: -0.02em;
            margin-bottom: 8px;
        }

        .card-phonetic-wrap {
            display: inline-flex;
            align-items: center;
            gap: 10px;
            background: rgba(255, 255, 255, 0.06);
            padding: 6px 14px;
            border-radius: 20px;
            font-size: 0.95rem;
            color: var(--text-muted);
        }

        .speaker-btn {
            background: transparent;
            border: none;
            color: #38bdf8;
            cursor: pointer;
            font-size: 1rem;
            transition: transform 0.15s;
        }

        .speaker-btn:hover {
            transform: scale(1.2);
        }

        .card-hint {
            font-size: 0.8rem;
            color: #64748b;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 6px;
        }

        /* Vietnamese Translation Badges & Boxes */
        .vn-toggle-pill {
            background: rgba(56, 189, 248, 0.12);
            border: 1px solid rgba(56, 189, 248, 0.35);
            color: #f8fafc;
            padding: 6px 14px;
            border-radius: 20px;
            font-size: 0.8rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.2s ease;
            display: inline-flex;
            align-items: center;
            gap: 6px;
        }
        .vn-toggle-pill:hover {
            background: rgba(56, 189, 248, 0.22);
            border-color: #38bdf8;
            transform: translateY(-1px);
        }
        .vn-toggle-pill.off {
            background: rgba(255, 255, 255, 0.05);
            border-color: rgba(255, 255, 255, 0.12);
            color: var(--text-muted);
        }
        .card-vn-trans-front {
            font-size: 1.15rem;
            font-weight: 600;
            color: #38bdf8;
            margin-top: 10px;
            letter-spacing: -0.01em;
            background: rgba(56, 189, 248, 0.08);
            padding: 5px 18px;
            border-radius: 20px;
            border: 1px solid rgba(56, 189, 248, 0.25);
            display: inline-block;
            max-width: 90%;
            animation: fadeIn 0.2s ease;
        }
        .card-vn-box {
            background: rgba(56, 189, 248, 0.06);
            border: 1px solid rgba(56, 189, 248, 0.22);
            border-radius: 10px;
            padding: 10px 14px;
            margin: 8px 0 10px 0;
            text-align: left;
            animation: fadeIn 0.2s ease;
        }
        .card-vn-trans-highlight {
            font-size: 0.98rem;
            font-weight: 700;
            color: #38bdf8;
            margin-bottom: 3px;
            line-height: 1.35;
        }
        .card-vn-def-text {
            font-size: 0.85rem;
            color: #cbd5e1;
            line-height: 1.45;
        }

        /* Flashcard Back Sections */
        .card-def-title {
            font-size: 0.75rem;
            text-transform: uppercase;
            letter-spacing: 0.06em;
            color: var(--text-muted);
            font-weight: 700;
            margin-bottom: 4px;
        }

        .card-def-text {
            font-size: 1.1rem;
            font-weight: 600;
            color: #f1f5f9;
            line-height: 1.45;
            margin-bottom: 16px;
        }

        .collocations-box {
            background: rgba(255, 255, 255, 0.04);
            border: 1px solid rgba(255, 255, 255, 0.06);
            border-radius: var(--radius-sm);
            padding: 12px 14px;
            margin-bottom: 16px;
        }

        .colloc-item {
            display: inline-block;
            background: rgba(59, 130, 246, 0.15);
            color: #93c5fd;
            font-size: 0.85rem;
            font-weight: 600;
            padding: 3px 8px;
            border-radius: 6px;
            margin: 2px 4px 2px 0;
        }

        .example-box {
            border-left: 3px solid #8b5cf6;
            padding-left: 12px;
            margin-bottom: 12px;
            font-size: 0.95rem;
            color: #cbd5e1;
            font-style: italic;
            line-height: 1.5;
        }

        /* Card Controls Bar */
        .card-controls {
            max-width: 780px;
            margin: 0 auto 16px;
            display: flex;
            align-items: stretch;
            justify-content: space-between;
            gap: 8px;
            flex-wrap: wrap;
        }

        /* Anki SRS Rating Buttons */
        .btn-srs {
            flex: 1;
            min-width: 120px;
            padding: 12px 10px;
            border-radius: var(--radius-md);
            cursor: pointer;
            transition: all 0.18s cubic-bezier(0.4, 0, 0.2, 1);
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            gap: 4px;
            border: 1px solid transparent;
            text-align: center;
        }

        .btn-srs .srs-interval {
            font-size: 0.72rem;
            font-weight: 600;
            opacity: 0.85;
            letter-spacing: 0.02em;
        }

        .btn-srs .srs-label {
            font-size: 0.95rem;
            font-weight: 700;
            display: flex;
            align-items: center;
            gap: 6px;
        }

        .btn-srs-again {
            background: rgba(239, 68, 68, 0.12);
            border-color: rgba(239, 68, 68, 0.35);
            color: #f87171;
        }
        .btn-srs-again:hover {
            background: #ef4444;
            color: #fff;
            transform: translateY(-2px);
            box-shadow: 0 6px 16px rgba(239, 68, 68, 0.35);
        }

        .btn-srs-hard {
            background: rgba(245, 158, 11, 0.12);
            border-color: rgba(245, 158, 11, 0.35);
            color: #fbbf24;
        }
        .btn-srs-hard:hover {
            background: #f59e0b;
            color: #0f172a;
            transform: translateY(-2px);
            box-shadow: 0 6px 16px rgba(245, 158, 11, 0.35);
        }

        .btn-srs-good {
            background: rgba(59, 130, 246, 0.12);
            border-color: rgba(59, 130, 246, 0.35);
            color: #60a5fa;
        }
        .btn-srs-good:hover {
            background: #3b82f6;
            color: #fff;
            transform: translateY(-2px);
            box-shadow: 0 6px 16px rgba(59, 130, 246, 0.35);
        }

        .btn-srs-easy {
            background: rgba(16, 185, 129, 0.12);
            border-color: rgba(16, 185, 129, 0.35);
            color: #34d399;
        }
        .btn-srs-easy:hover {
            background: #10b981;
            color: #fff;
            transform: translateY(-2px);
            box-shadow: 0 6px 16px rgba(16, 185, 129, 0.35);
        }

        /* SRS Session Queue Header Bar */
        .srs-status-bar {
            max-width: 680px;
            margin: 0 auto 16px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 16px;
            padding: 10px 18px;
            background: rgba(255, 255, 255, 0.03);
            border: 1px solid var(--card-border);
            border-radius: var(--radius-md);
            font-size: 0.85rem;
        }

        .srs-queue-counters {
            display: flex;
            align-items: center;
            gap: 14px;
            flex-wrap: wrap;
        }

        .srs-badge-again {
            color: #f87171;
            font-weight: 700;
            display: flex;
            align-items: center;
            gap: 4px;
        }
        .srs-badge-hard {
            color: #fbbf24;
            font-weight: 700;
            display: flex;
            align-items: center;
            gap: 4px;
        }
        .srs-badge-good {
            color: #60a5fa;
            font-weight: 700;
            display: flex;
            align-items: center;
            gap: 4px;
        }
        .srs-badge-easy {
            color: #34d399;
            font-weight: 700;
            display: flex;
            align-items: center;
            gap: 4px;
        }

        .srs-progress-bar-wrap {
            flex: 1;
            height: 6px;
            background: rgba(255, 255, 255, 0.08);
            border-radius: 4px;
            overflow: hidden;
            min-width: 100px;
        }

        .srs-progress-bar-fill {
            height: 100%;
            background: linear-gradient(90deg, var(--primary), var(--success));
            width: 0%;
            transition: width 0.3s ease;
        }

        .srs-hotkey-guide {
            max-width: 780px;
            margin: 10px auto 25px;
            text-align: center;
            font-size: 0.78rem;
            color: #64748b;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 10px;
            flex-wrap: wrap;
        }

        .srs-hotkey-tag {
            background: rgba(255, 255, 255, 0.06);
            border: 1px solid rgba(255, 255, 255, 0.12);
            border-radius: 4px;
            padding: 2px 6px;
            font-family: monospace;
            font-weight: 700;
            color: #cbd5e1;
        }

        /* SRS Session Complete Screen */
        .srs-complete-card {
            max-width: 680px;
            margin: 40px auto;
            background: var(--card-bg);
            border: 1px solid rgba(16, 185, 129, 0.35);
            border-radius: var(--radius-lg);
            padding: 44px 30px;
            text-align: center;
            box-shadow: 0 16px 40px rgba(0, 0, 0, 0.4);
            animation: srsFadeIn 0.3s ease-out;
        }

        @keyframes srsFadeIn {
            from { opacity: 0; transform: translateY(14px); }
            to { opacity: 1; transform: translateY(0); }
        }

        .btn-nav-card {
            width: 48px;
            height: 48px;
            border-radius: var(--radius-md);
            background: var(--card-bg);
            border: 1px solid var(--card-border);
            color: var(--text);
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            transition: all 0.15s;
        }

        .btn-nav-card:hover {
            background: rgba(255, 255, 255, 0.15);
        }

        /* Diagnostic Quiz Container */
        .diag-wrapper {
            background: var(--card-bg);
            border: 1px solid var(--card-border);
            border-radius: var(--radius-lg);
            padding: 36px;
            max-width: 800px;
            margin: 0 auto;
        }

        .diag-header {
            text-align: center;
            margin-bottom: 32px;
        }

        .diag-header h2 {
            font-family: 'Outfit', sans-serif;
            font-size: 1.8rem;
            font-weight: 800;
            margin-bottom: 8px;
        }

        .q-block {
            margin-bottom: 28px;
            padding-bottom: 24px;
            border-bottom: 1px solid var(--card-border);
        }

        .q-number {
            font-size: 0.8rem;
            color: #38bdf8;
            font-weight: 700;
            text-transform: uppercase;
            margin-bottom: 6px;
        }

        .q-text {
            font-size: 1.05rem;
            font-weight: 600;
            color: #f8fafc;
            line-height: 1.45;
            margin-bottom: 16px;
        }

        .options-list {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 12px;
        }

        @media (max-width: 600px) {
            .options-list { grid-template-columns: 1fr; }
            .hero-banner { grid-template-columns: 1fr; }
        }

        .option-label {
            background: rgba(255, 255, 255, 0.04);
            border: 1px solid var(--card-border);
            padding: 12px 16px;
            border-radius: var(--radius-sm);
            cursor: pointer;
            display: flex;
            align-items: center;
            gap: 10px;
            font-size: 0.95rem;
            transition: all 0.15s ease;
        }

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

        .option-label input[type="radio"] {
            accent-color: var(--primary);
            width: 16px;
            height: 16px;
        }

        .btn-submit-diag {
            background: linear-gradient(135deg, var(--primary), var(--accent));
            color: white;
            border: none;
            padding: 14px 28px;
            border-radius: var(--radius-md);
            font-weight: 700;
            font-size: 1rem;
            cursor: pointer;
            width: 100%;
            box-shadow: 0 4px 15px rgba(59, 130, 246, 0.4);
            transition: transform 0.15s;
        }

        .btn-submit-diag:hover {
            transform: translateY(-2px);
        }

        /* Result Modal */
        .diag-result-card {
            text-align: center;
            padding: 20px;
        }

        .diag-band-badge {
            font-family: 'Outfit', sans-serif;
            font-size: 3.5rem;
            font-weight: 900;
            color: #38bdf8;
            margin: 12px 0;
            text-shadow: 0 0 30px rgba(56, 189, 248, 0.4);
        }

        .weak-topic-pill {
            background: rgba(239, 68, 68, 0.15);
            color: #f87171;
            padding: 4px 12px;
            border-radius: 20px;
            font-size: 0.85rem;
            font-weight: 600;
            display: inline-block;
            margin: 4px;
        }

        /* Collocations Matcher Mini-Game Styles */
        .game-bar {
            display: flex;
            justify-content: space-between;
            align-items: center;
            background: rgba(255, 255, 255, 0.03);
            border: 1px solid var(--card-border);
            border-radius: var(--radius-md);
            padding: 14px 20px;
            margin-bottom: 20px;
            flex-wrap: wrap;
            gap: 14px;
        }

        .game-metric {
            display: flex;
            align-items: center;
            gap: 8px;
            font-weight: 700;
            font-size: 1.05rem;
            color: #f8fafc;
        }

        .game-metric-label {
            font-size: 0.75rem;
            text-transform: uppercase;
            letter-spacing: 0.05em;
            color: var(--text-muted);
            display: block;
        }

        .combo-badge {
            background: linear-gradient(135deg, #f59e0b, #ef4444);
            color: white;
            padding: 3px 10px;
            border-radius: 12px;
            font-size: 0.8rem;
            font-weight: 800;
            display: inline-flex;
            align-items: center;
            gap: 4px;
        }

        .timer-badge {
            color: #38bdf8;
            font-family: monospace;
            font-size: 1.3rem;
            font-weight: 800;
        }

        .matcher-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 20px;
            margin-top: 16px;
        }

        @media (max-width: 640px) {
            .matcher-grid {
                grid-template-columns: 1fr;
            }
        }

        .tile-list {
            display: flex;
            flex-direction: column;
            gap: 10px;
        }

        .tile-col-title {
            font-size: 0.85rem;
            font-weight: 700;
            text-transform: uppercase;
            letter-spacing: 0.05em;
            color: #94a3b8;
            margin-bottom: 6px;
            display: flex;
            align-items: center;
            gap: 6px;
        }

        .tile-card {
            background: rgba(255, 255, 255, 0.04);
            border: 2px solid var(--card-border);
            border-radius: var(--radius-md);
            padding: 14px 18px;
            color: #f8fafc;
            font-size: 1rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.18s cubic-bezier(0.4, 0, 0.2, 1);
            user-select: none;
            display: flex;
            justify-content: space-between;
            align-items: center;
            min-height: 52px;
        }

        .tile-card:hover {
            background: rgba(255, 255, 255, 0.08);
            border-color: rgba(255, 255, 255, 0.25);
            transform: translateY(-2px);
        }

        .tile-card.selected {
            background: rgba(59, 130, 246, 0.2);
            border-color: #3b82f6;
            color: #93c5fd;
            box-shadow: 0 0 16px rgba(59, 130, 246, 0.4);
            transform: scale(1.02);
        }

        .tile-card.matched {
            animation: matchDisappear 0.4s forwards;
            pointer-events: none;
        }

        .tile-card.shake {
            animation: tileShake 0.4s cubic-bezier(0.36, 0.07, 0.19, 0.97) both;
            border-color: #ef4444 !important;
            background: rgba(239, 68, 68, 0.2) !important;
            color: #fca5a5 !important;
        }

        @keyframes matchDisappear {
            0% {
                background: rgba(16, 185, 129, 0.4);
                border-color: #10b981;
                color: #34d399;
                transform: scale(1.05);
                opacity: 1;
            }
            50% {
                background: rgba(16, 185, 129, 0.8);
                border-color: #10b981;
                transform: scale(1.1);
                opacity: 0.8;
            }
            100% {
                transform: scale(0.7);
                opacity: 0;
                height: 0;
                min-height: 0;
                padding: 0;
                margin: 0;
                border: none;
                visibility: hidden;
            }
        }

        /* ==========================================
           🏛️ Band 8.5 – 9.0 Elite Register & Elevation Lab Styles
           ========================================== */
        .elevation-hero-card {
            background: linear-gradient(135deg, rgba(30, 27, 75, 0.75), rgba(15, 23, 42, 0.9));
            border: 1px solid rgba(168, 85, 247, 0.35);
            border-radius: 20px;
            padding: 28px 32px;
            margin-bottom: 28px;
            position: relative;
            overflow: hidden;
            box-shadow: 0 12px 36px rgba(0, 0, 0, 0.35);
            backdrop-filter: blur(12px);
        }
        .elevation-hero-card::before {
            content: '';
            position: absolute;
            top: 0; left: 0; right: 0; height: 3px;
            background: linear-gradient(90deg, #c084fc, #3b82f6, #34d399);
        }
        .elevation-hero-title {
            font-size: 1.6rem;
            font-weight: 800;
            color: #fff;
            display: flex;
            align-items: center;
            gap: 12px;
            margin-bottom: 6px;
        }
        .elevation-hero-sub {
            font-size: 0.92rem;
            color: #cbd5e1;
            max-width: 820px;
            line-height: 1.55;
        }

        /* Sub-Navigation Pills */
        .elevation-nav-bar {
            display: flex;
            gap: 8px;
            background: rgba(15, 23, 42, 0.6);
            border: 1px solid rgba(255, 255, 255, 0.08);
            padding: 6px;
            border-radius: 14px;
            margin-bottom: 24px;
            flex-wrap: wrap;
        }
        .elevation-nav-btn {
            background: transparent;
            border: none;
            color: var(--text-muted);
            padding: 9px 18px;
            border-radius: 10px;
            font-size: 0.88rem;
            font-weight: 700;
            cursor: pointer;
            display: inline-flex;
            align-items: center;
            gap: 8px;
            transition: all 0.2s ease;
        }
        .elevation-nav-btn:hover {
            color: #fff;
            background: rgba(255, 255, 255, 0.06);
        }
        .elevation-nav-btn.active {
            background: linear-gradient(135deg, #8b5cf6, #3b82f6);
            color: #fff;
            box-shadow: 0 4px 14px rgba(139, 92, 246, 0.4);
        }

        /* Transformation Studio Cards */
        .transform-card {
            background: rgba(15, 23, 42, 0.7);
            border: 1px solid rgba(255, 255, 255, 0.08);
            border-radius: 18px;
            padding: 24px 28px;
            margin-bottom: 22px;
            transition: border-color 0.2s ease, box-shadow 0.2s ease;
        }
        .transform-card:hover {
            border-color: rgba(192, 132, 252, 0.35);
            box-shadow: 0 8px 24px rgba(0, 0, 0, 0.3);
        }
        .transform-header {
            display: flex;
            align-items: center;
            justify-content: space-between;
            margin-bottom: 16px;
            flex-wrap: wrap;
            gap: 10px;
        }
        .transform-topic-badge {
            background: rgba(192, 132, 252, 0.15);
            color: #c084fc;
            border: 1px solid rgba(192, 132, 252, 0.3);
            padding: 4px 12px;
            border-radius: 20px;
            font-size: 0.75rem;
            font-weight: 700;
            text-transform: uppercase;
            letter-spacing: 0.04em;
        }

        /* Register Segmented Control */
        .register-segmented-control {
            display: inline-flex;
            background: rgba(0, 0, 0, 0.35);
            border: 1px solid rgba(255, 255, 255, 0.1);
            padding: 3px;
            border-radius: 10px;
            gap: 2px;
        }
        .register-seg-btn {
            background: transparent;
            border: none;
            color: var(--text-muted);
            font-size: 0.78rem;
            font-weight: 700;
            padding: 5px 12px;
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.15s ease;
        }
        .register-seg-btn:hover { color: #fff; }
        .register-seg-btn.active.mode-standard {
            background: rgba(255, 255, 255, 0.15);
            color: #fff;
        }
        .register-seg-btn.active.mode-academic {
            background: linear-gradient(135deg, #3b82f6, #2563eb);
            color: #fff;
            box-shadow: 0 2px 8px rgba(59, 130, 246, 0.4);
        }
        .register-seg-btn.active.mode-classical {
            background: linear-gradient(135deg, #a855f7, #7e22ce);
            color: #fff;
            box-shadow: 0 2px 8px rgba(168, 85, 247, 0.4);
        }

        /* Sentence Display Box */
        .sentence-display-box {
            background: rgba(0, 0, 0, 0.25);
            border: 1px solid rgba(255, 255, 255, 0.06);
            border-left: 4px solid #3b82f6;
            border-radius: 12px;
            padding: 16px 20px;
            margin-bottom: 16px;
            font-size: 1.05rem;
            line-height: 1.65;
            color: #f1f5f9;
            position: relative;
            transition: all 0.25s ease;
        }
        .sentence-display-box.mode-academic {
            border-left-color: #60a5fa;
            background: rgba(59, 130, 246, 0.08);
        }
        .sentence-display-box.mode-classical {
            border-left-color: #c084fc;
            background: rgba(168, 85, 247, 0.08);
            font-family: 'Outfit', sans-serif;
            letter-spacing: 0.01em;
        }

        /* Chunks & Grammar Pills */
        .chunks-row {
            display: flex;
            align-items: center;
            gap: 8px;
            flex-wrap: wrap;
            margin-top: 10px;
        }
        .chunk-pill {
            background: rgba(139, 92, 246, 0.15);
            border: 1px solid rgba(139, 92, 246, 0.3);
            color: #c084fc;
            padding: 4px 10px;
            border-radius: 6px;
            font-size: 0.78rem;
            font-weight: 600;
        }
        .grammar-note-box {
            font-size: 0.8rem;
            color: #94a3b8;
            background: rgba(255, 255, 255, 0.03);
            border: 1px solid rgba(255, 255, 255, 0.06);
            border-radius: 8px;
            padding: 8px 14px;
            margin-top: 12px;
            display: flex;
            align-items: center;
            gap: 8px;
        }

        /* Pillar Grid & Cards */
        .pillar-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
            gap: 16px;
        }
        .pillar-word-card {
            background: rgba(15, 23, 42, 0.6);
            border: 1px solid rgba(255, 255, 255, 0.08);
            border-radius: 14px;
            padding: 18px 20px;
            display: flex;
            flex-direction: column;
            gap: 8px;
            transition: transform 0.2s ease, border-color 0.2s ease;
        }
        .pillar-word-card:hover {
            transform: translateY(-2px);
            border-color: rgba(192, 132, 252, 0.4);
            box-shadow: 0 6px 20px rgba(0, 0, 0, 0.25);
        }
        .pillar-word-title {
            font-size: 1.15rem;
            font-weight: 800;
            color: #fff;
            display: flex;
            align-items: center;
            justify-content: space-between;
        }

        /* Speaker audio button */
        .btn-speak-inline {
            background: transparent;
            border: none;
            color: var(--text-muted);
            cursor: pointer;
            font-size: 0.95rem;
            padding: 2px 6px;
            border-radius: 4px;
            transition: color 0.15s ease;
        }
        .btn-speak-inline:hover { color: #38bdf8; }

        /* Drills & Quiz */
        /* Gamified Arena & Drills */
        .arena-score-bar {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
            gap: 12px;
            background: rgba(15, 23, 42, 0.85);
            border: 1px solid rgba(168, 85, 247, 0.3);
            border-radius: 16px;
            padding: 16px 20px;
            margin-bottom: 24px;
            box-shadow: 0 8px 24px rgba(0, 0, 0, 0.3);
        }
        .arena-stat-item {
            text-align: center;
            position: relative;
        }
        .arena-stat-val {
            font-size: 1.4rem;
            font-weight: 800;
            color: #fff;
        }
        .arena-stat-lbl {
            font-size: 0.72rem;
            text-transform: uppercase;
            letter-spacing: 0.05em;
            color: var(--text-muted);
            margin-top: 2px;
            font-weight: 700;
        }

        /* Chunk Game Components */
        .chunk-game-board {
            background: rgba(15, 23, 42, 0.75);
            border: 1px solid rgba(255, 255, 255, 0.08);
            border-radius: 18px;
            padding: 24px;
            margin-bottom: 22px;
        }
        .chunk-sentence-slots {
            min-height: 80px;
            background: rgba(0, 0, 0, 0.35);
            border: 2px dashed rgba(168, 85, 247, 0.4);
            border-radius: 14px;
            padding: 14px;
            display: flex;
            flex-wrap: wrap;
            gap: 8px;
            align-items: center;
            margin-bottom: 18px;
            transition: border-color 0.2s ease;
        }
        .chunk-tile-pill {
            background: linear-gradient(135deg, rgba(139, 92, 246, 0.2), rgba(59, 130, 246, 0.2));
            border: 1px solid rgba(168, 85, 247, 0.4);
            color: #f1f5f9;
            padding: 8px 14px;
            border-radius: 10px;
            font-size: 0.9rem;
            font-weight: 600;
            cursor: pointer;
            user-select: none;
            transition: all 0.15s ease;
            display: inline-flex;
            align-items: center;
            gap: 6px;
        }
        .chunk-tile-pill:hover {
            transform: translateY(-2px);
            background: linear-gradient(135deg, rgba(139, 92, 246, 0.4), rgba(59, 130, 246, 0.4));
            border-color: #c084fc;
            box-shadow: 0 4px 12px rgba(168, 85, 247, 0.3);
        }
        .chunk-tile-pill.in-slot {
            background: linear-gradient(135deg, #8b5cf6, #3b82f6);
            color: #fff;
            box-shadow: 0 2px 8px rgba(139, 92, 246, 0.35);
        }
        .chunk-tile-pill.tile-distractor:hover {
            border-color: #f87171;
        }

        .drill-question-card {
            background: rgba(15, 23, 42, 0.7);
            border: 1px solid rgba(255, 255, 255, 0.08);
            border-radius: 16px;
            padding: 24px;
            margin-bottom: 20px;
        }
        .drill-option-btn {
            width: 100%;
            text-align: left;
            background: rgba(255, 255, 255, 0.03);
            border: 1px solid rgba(255, 255, 255, 0.08);
            color: #e2e8f0;
            padding: 14px 18px;
            border-radius: 12px;
            font-size: 0.92rem;
            font-family: inherit;
            margin-bottom: 10px;
            cursor: pointer;
            transition: all 0.15s ease;
            display: flex;
            align-items: flex-start;
            gap: 12px;
        }
        .drill-option-btn:hover {
            background: rgba(255, 255, 255, 0.08);
            border-color: rgba(255, 255, 255, 0.2);
            color: #fff;
        }
        .drill-option-btn.selected-correct {
            background: rgba(16, 185, 129, 0.15) !important;
            border-color: #10b981 !important;
            color: #34d399 !important;
        }
        .drill-option-btn.selected-wrong {
            background: rgba(239, 68, 68, 0.15) !important;
            border-color: #ef4444 !important;
            color: #f87171 !important;
        }