    <style>
        @import url('https://fonts.googleapis.com/css2?family=Fira+Code:wght@400;500;600;700&family=JetBrains+Mono:wght@400;500;600;700&display=swap');

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

        body {
            font-family: 'JetBrains Mono', 'Fira Code', monospace;
            background: #0a0a0f;
            background-image:
                linear-gradient(rgba(0, 255, 255, 0.03) 1px, transparent 1px),
                linear-gradient(90deg, rgba(0, 255, 255, 0.03) 1px, transparent 1px);
            background-size: 50px 50px;
            min-height: 100vh;
            padding: 20px;
            color: #e0e0e0;
            position: relative;
        }

        body::before {
            content: '';
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: radial-gradient(circle at 50% 0%, rgba(0, 255, 255, 0.1) 0%, transparent 50%);
            pointer-events: none;
            z-index: 0;
        }

        .container {
            max-width: 1400px;
            margin: 0 auto;
            position: relative;
            z-index: 1;
        }

        header {
            text-align: center;
            color: #ffffff;
            margin-bottom: 50px;
            padding: 50px 0 30px;
            border-bottom: 2px solid transparent;
            border-image: linear-gradient(90deg, transparent, #00ffff, #ff00ff, transparent) 1;
            position: relative;
        }

        header::before {
            content: '< INIT_ENLIGHTENMENT_PROTOCOL />';
            position: absolute;
            top: 10px;
            left: 50%;
            transform: translateX(-50%);
            font-size: 0.7em;
            color: #00ffff;
            opacity: 0.4;
            font-family: 'Fira Code', monospace;
            letter-spacing: 2px;
        }

        header h1 {
            font-size: 3.5em;
            font-weight: 700;
            margin-bottom: 15px;
            letter-spacing: -2px;
            background: linear-gradient(135deg, #00ffff 0%, #ff00ff 50%, #ffff00 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            text-shadow: 0 0 40px rgba(0, 255, 255, 0.3);
            animation: glitch 3s infinite;
            position: relative;
        }

        @keyframes glitch {
            0%, 90%, 100% { transform: translate(0); }
            91% { transform: translate(-2px, 2px); }
            92% { transform: translate(2px, -2px); }
            93% { transform: translate(-2px, -2px); }
        }

        header p {
            font-size: 1em;
            color: #00ffff;
            font-weight: 400;
            text-transform: uppercase;
            letter-spacing: 4px;
            opacity: 0.8;
        }

        .category-nav {
            display: flex;
            gap: 15px;
            justify-content: center;
            margin-bottom: 40px;
            flex-wrap: wrap;
        }

        .category-btn {
            padding: 12px 28px;
            background: rgba(0, 255, 255, 0.05);
            color: #00ffff;
            border: 2px solid #00ffff;
            border-radius: 0;
            font-size: 0.9em;
            font-weight: 600;
            cursor: pointer;
            text-decoration: none;
            transition: all 0.3s ease;
            font-family: 'Fira Code', monospace;
            text-transform: uppercase;
            letter-spacing: 1px;
            position: relative;
            overflow: hidden;
        }

        .category-btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(0, 255, 255, 0.3), transparent);
            transition: left 0.5s;
        }

        .category-btn:hover::before {
            left: 100%;
        }

        .category-btn:hover {
            background: rgba(0, 255, 255, 0.1);
            box-shadow: 0 0 20px rgba(0, 255, 255, 0.5), inset 0 0 20px rgba(0, 255, 255, 0.1);
            transform: translateY(-2px);
        }

        .category-btn.active {
            background: #00ffff;
            color: #0a0a0f;
            border-color: #00ffff;
            box-shadow: 0 0 30px rgba(0, 255, 255, 0.6);
        }

        .success-message {
            background: rgba(0, 255, 0, 0.1);
            color: #00ff00;
            padding: 16px 24px;
            border-radius: 0;
            margin-bottom: 20px;
            border: 2px solid #00ff00;
            font-family: 'Fira Code', monospace;
            font-size: 0.9em;
            box-shadow: 0 0 20px rgba(0, 255, 0, 0.3);
            animation: pulse 2s infinite;
        }

        @keyframes pulse {
            0%, 100% { opacity: 1; }
            50% { opacity: 0.8; }
        }

        .exercise-card {
            background: rgba(20, 20, 30, 0.8);
            border-radius: 0;
            padding: 35px;
            margin-bottom: 30px;
            border: 2px solid #1a1a2e;
            transition: all 0.3s ease;
            position: relative;
            backdrop-filter: blur(10px);
        }

        .exercise-card::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            border: 2px solid transparent;
            border-image: linear-gradient(135deg, #00ffff, #ff00ff) 1;
            opacity: 0;
            transition: opacity 0.3s;
            pointer-events: none;
        }

        .exercise-card:hover::before {
            opacity: 1;
        }

        .exercise-card:hover {
            transform: translateX(5px);
            box-shadow: -5px 0 30px rgba(0, 255, 255, 0.3);
        }

        .exercise-header {
            display: flex;
            align-items: center;
            margin-bottom: 24px;
            padding-bottom: 20px;
            border-bottom: 2px solid transparent;
            border-image: linear-gradient(90deg, #00ffff, transparent) 1;
        }

        .exercise-number {
            background: linear-gradient(135deg, #00ffff, #0080ff);
            color: #0a0a0f;
            min-width: 50px;
            height: 50px;
            border-radius: 0;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 1.2em;
            margin-right: 20px;
            font-family: 'Fira Code', monospace;
            box-shadow: 0 0 20px rgba(0, 255, 255, 0.5);
            position: relative;
        }

        .exercise-number::after {
            content: '';
            position: absolute;
            top: -2px;
            left: -2px;
            right: -2px;
            bottom: -2px;
            background: linear-gradient(135deg, #00ffff, #0080ff);
            z-index: -1;
            filter: blur(5px);
        }

        .exercise-category {
            background: rgba(255, 0, 255, 0.1);
            padding: 8px 16px;
            border-radius: 0;
            font-size: 0.8em;
            color: #ff00ff;
            text-transform: uppercase;
            font-family: 'Fira Code', monospace;
            font-weight: 600;
            border: 1px solid #ff00ff;
            letter-spacing: 2px;
        }

        .question {
            font-size: 1.3em;
            color: #ffffff;
            margin-bottom: 28px;
            font-weight: 500;
            line-height: 1.6;
            text-shadow: 0 0 10px rgba(255, 255, 255, 0.1);
        }

        .question::before {
            content: '> ';
            color: #00ffff;
            font-weight: 700;
        }

        .answer-section {
            display: none;
            background: rgba(0, 255, 0, 0.03);
            padding: 24px;
            border-radius: 0;
            margin-bottom: 28px;
            border-left: 4px solid #00ff00;
            border-top: 1px solid rgba(0, 255, 0, 0.2);
            border-bottom: 1px solid rgba(0, 255, 0, 0.2);
            position: relative;
        }

        .answer-section::before {
            content: '// CORRECT_ANSWER';
            position: absolute;
            top: -12px;
            left: 24px;
            background: #0a0a0f;
            padding: 0 8px;
            font-size: 0.7em;
            color: #00ff00;
            font-family: 'Fira Code', monospace;
        }

        .answer-section h3 {
            color: #00ff00;
            margin-bottom: 14px;
            font-size: 0.95em;
            font-weight: 600;
            font-family: 'Fira Code', monospace;
            text-transform: uppercase;
            letter-spacing: 1px;
        }

        .answer-text {
            color: #e0e0e0;
            line-height: 1.8;
            font-size: 0.95em;
        }

        .exercise-card.answer-open .answer-section,
        .exercise-card.answer-peek .answer-section {
            display: block;
        }

        .toggle-answer-btn {
            background: rgba(0, 255, 255, 0.05);
            color: #00ffff;
            padding: 12px 22px;
            border: 2px solid #00ffff;
            border-radius: 0;
            font-size: 0.85em;
            font-weight: 700;
            cursor: pointer;
            transition: all 0.3s ease;
            font-family: 'Fira Code', monospace;
            text-transform: uppercase;
            letter-spacing: 2px;
            margin-bottom: 18px;
            position: relative;
            overflow: hidden;
        }

        .toggle-answer-btn:hover,
        .toggle-answer-btn:focus-visible {
            background: rgba(0, 255, 255, 0.1);
            box-shadow: 0 0 20px rgba(0, 255, 255, 0.5), inset 0 0 20px rgba(0, 255, 255, 0.1);
            transform: translateY(-1px);
            outline: none;
        }

        .user-answer-form textarea {
            width: 100%;
            min-height: 160px;
            padding: 20px;
            background: rgba(10, 10, 15, 0.8);
            border: 2px solid #1a1a2e;
            border-radius: 0;
            font-size: 0.95em;
            font-family: 'Fira Code', monospace;
            color: #e0e0e0;
            resize: vertical;
            transition: all 0.3s ease;
            line-height: 1.8;
        }

        .user-answer-form textarea:focus {
            outline: none;
            border-color: #ff00ff;
            box-shadow: 0 0 20px rgba(255, 0, 255, 0.3), inset 0 0 20px rgba(255, 0, 255, 0.05);
            background: rgba(10, 10, 15, 1);
        }

        .user-answer-form textarea.has-answer {
            background: rgba(0, 255, 0, 0.05);
            border-color: #00ff00;
            box-shadow: 0 0 15px rgba(0, 255, 0, 0.2);
        }

        .save-status {
            margin-top: 10px;
            font-size: 0.8em;
            color: rgba(224, 224, 224, 0.7);
            min-height: 1.2em;
        }

        .save-status.saving {
            color: rgba(0, 255, 255, 0.85);
        }

        .save-status.saved {
            color: rgba(0, 255, 0, 0.85);
        }

        .save-status.error {
            color: rgba(255, 0, 51, 0.9);
        }

        .user-answer-form h3 {
            margin-bottom: 14px;
            color: #ff00ff;
            font-size: 0.95em;
            font-weight: 600;
            font-family: 'Fira Code', monospace;
            text-transform: uppercase;
            letter-spacing: 2px;
        }

        .user-answer-form h3::before {
            content: '// ';
            color: #00ffff;
        }

        .submit-btn {
            background: linear-gradient(135deg, #ff00ff, #8000ff);
            color: #ffffff;
            padding: 14px 32px;
            border: 2px solid #ff00ff;
            border-radius: 0;
            font-size: 0.9em;
            font-weight: 700;
            cursor: pointer;
            transition: all 0.3s ease;
            margin-top: 16px;
            font-family: 'Fira Code', monospace;
            text-transform: uppercase;
            letter-spacing: 2px;
            position: relative;
            overflow: hidden;
        }

        .submit-btn::before {
            content: '';
            position: absolute;
            top: 50%;
            left: 50%;
            width: 0;
            height: 0;
            border-radius: 50%;
            background: rgba(255, 255, 255, 0.3);
            transform: translate(-50%, -50%);
            transition: width 0.6s, height 0.6s;
        }

        .submit-btn:hover::before {
            width: 300px;
            height: 300px;
        }

        .submit-btn:hover {
            box-shadow: 0 0 30px rgba(255, 0, 255, 0.6), inset 0 0 20px rgba(255, 0, 255, 0.2);
            transform: translateY(-2px);
        }

        .submit-btn:active {
            transform: translateY(0);
        }

        .stats {
            background: rgba(20, 20, 30, 0.8);
            border-radius: 0;
            padding: 30px;
            margin-bottom: 40px;
            text-align: center;
            border: 2px solid transparent;
            border-image: linear-gradient(135deg, #00ffff, #ff00ff) 1;
            position: relative;
            backdrop-filter: blur(10px);
        }

        .stats::before {
            content: '[ PROGRESS_TRACKER ]';
            position: absolute;
            top: -14px;
            left: 50%;
            transform: translateX(-50%);
            background: #0a0a0f;
            padding: 0 12px;
            font-size: 0.75em;
            color: #00ffff;
            font-family: 'Fira Code', monospace;
            letter-spacing: 2px;
        }

        .stats h2 {
            color: #ffffff;
            margin-bottom: 20px;
            font-size: 1.1em;
            font-weight: 600;
            font-family: 'Fira Code', monospace;
        }

        .progress-bar {
            background: rgba(10, 10, 15, 0.8);
            height: 36px;
            border-radius: 0;
            overflow: hidden;
            margin-top: 16px;
            border: 2px solid #1a1a2e;
            position: relative;
        }

        .progress-fill {
            background: linear-gradient(90deg, #00ffff 0%, #ff00ff 100%);
            height: 100%;
            transition: width 0.8s cubic-bezier(0.68, -0.55, 0.265, 1.55);
            display: flex;
            align-items: center;
            justify-content: center;
            color: #0a0a0f;
            font-weight: 700;
            font-family: 'Fira Code', monospace;
            font-size: 0.9em;
            position: relative;
            box-shadow: 0 0 20px rgba(0, 255, 255, 0.5);
        }

        .progress-fill::after {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
            animation: shimmer 2s infinite;
        }

        @keyframes shimmer {
            0% { left: -100%; }
            100% { left: 200%; }
        }

        .lang-switcher {
            position: fixed;
            top: 25px;
            right: 25px;
            display: flex;
            gap: 10px;
            z-index: 1000;
        }

        .lang-btn {
            padding: 10px 22px;
            background: rgba(0, 255, 255, 0.05);
            color: #00ffff;
            border: 2px solid #00ffff;
            border-radius: 0;
            font-size: 0.85em;
            font-weight: 700;
            cursor: pointer;
            text-decoration: none;
            transition: all 0.3s ease;
            font-family: 'Fira Code', monospace;
            letter-spacing: 2px;
        }

        .lang-btn:hover {
            background: rgba(0, 255, 255, 0.1);
            box-shadow: 0 0 20px rgba(0, 255, 255, 0.5);
            transform: scale(1.05);
        }

        .lang-btn.active {
            background: #00ffff;
            color: #0a0a0f;
            border-color: #00ffff;
            box-shadow: 0 0 30px rgba(0, 255, 255, 0.6);
        }

        /* Scrollbar styling */
        ::-webkit-scrollbar {
            width: 14px;
        }

        ::-webkit-scrollbar-track {
            background: #0a0a0f;
            border-left: 1px solid #1a1a2e;
        }

        ::-webkit-scrollbar-thumb {
            background: linear-gradient(180deg, #00ffff, #ff00ff);
            border: 2px solid #0a0a0f;
        }

        ::-webkit-scrollbar-thumb:hover {
            box-shadow: 0 0 10px rgba(0, 255, 255, 0.5);
        }

        /* Selection color */
        ::selection {
            background: rgba(0, 255, 255, 0.3);
            color: #ffffff;
        }

        /* User info styles */
        .user-info {
            margin-top: 10px;
            text-align: center;
        }

        .user-status {
            display: inline-block;
            padding: 8px 16px;
            border-radius: 20px;
            font-size: 14px;
            font-weight: 500;
        }

        .user-status.logged-in {
            background: linear-gradient(135deg, #4CAF50, #45a049);
            color: white;
        }

        .user-status.not-logged-in {
            background: linear-gradient(135deg, #ff9800, #f57c00);
            color: white;
        }

        .logout-btn, .login-btn {
            color: white;
            text-decoration: none;
            font-weight: bold;
            margin-left: 10px;
            padding: 4px 8px;
            border-radius: 12px;
            background: rgba(255, 255, 255, 0.2);
            transition: background 0.3s;
        }

        .logout-btn:hover, .login-btn:hover {
            background: rgba(255, 255, 255, 0.3);
        }
    </style>
