:root {
            --primary: #0056b3;
            --secondary: #28a745;
            --accent: #ffc107;
            --dark: #1a1a2e;
            --glass: rgba(255, 255, 255, 0.1);
            --glass-border: rgba(255, 255, 255, 0.2);
            --shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.37);
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        }

        body {
            color: white;
            line-height: 1.6;
            overflow-x: hidden;
            position: relative;
            min-height: 100vh;
        }

        #particles-js {
            position: fixed;
            width: 100%;
            height: 100%;
            background: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
            z-index: -1;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 20px;
        }

        /* Header Styles */
        header {
            background: var(--glass);
            backdrop-filter: blur(10px);
            -webkit-backdrop-filter: blur(10px);
            border-bottom: 1px solid var(--glass-border);
            padding: 40px 0 20px;
            text-align: center;
        }

        .breadcrumb {
            font-size: 0.9rem;
            margin-bottom: 15px;
            opacity: 0.8;
        }

        .breadcrumb a {
            color: var(--accent);
            text-decoration: none;
            transition: color 0.3s;
        }

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

        .page-title {
            font-size: 2.8rem;
            font-weight: 700;
            margin-bottom: 10px;
        }

        .page-subtitle {
            font-size: 1.2rem;
            opacity: 0.9;
            font-weight: 300;
            max-width: 800px;
            margin: 0 auto;
        }

        /* Main Content */
        main {
            padding: 40px 0;
        }

        .content-grid {
            display: grid;
            grid-template-columns: 1fr 320px;
            gap: 40px;
            align-items: start;
        }

        .lesson-content,
        .sidebar {
            background: var(--glass);
            border-radius: 15px;
            border: 1px solid var(--glass-border);
            backdrop-filter: blur(5px);
            box-shadow: var(--shadow);
            padding: 30px;
        }

        .lesson-section {
            margin-bottom: 40px;
        }

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

        .section-title {
            font-size: 2rem;
            margin-bottom: 25px;
            color: white;
            position: relative;
            padding-bottom: 15px;
        }

        .section-title::after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 0;
            width: 70px;
            height: 4px;
            background: linear-gradient(to right, var(--accent), var(--secondary));
            border-radius: 2px;
        }

        .subsection {
            margin-bottom: 30px;
        }

        .subsection-title {
            font-size: 1.3rem;
            color: var(--accent);
            margin-bottom: 10px;
        }

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

        li {
            margin-bottom: 8px;
        }

        /* Key Concept & Other Boxes */
        .key-concept,
        .warning,
        .example-box,
        .formula-box {
            border-left: 4px solid var(--accent);
            padding: 20px;
            margin: 20px 0;
            border-radius: 0 8px 8px 0;
            background: rgba(0, 0, 0, 0.2);
        }

        .warning {
            border-left-color: #f44336;
        }

        .formula-box {
            border-left-color: var(--primary);
        }

        .key-concept h4,
        .warning h4,
        .example-box h4,
        .formula-box h4 {
            margin-top: 0;
            color: var(--accent);
            margin-bottom: 10px;
            font-size: 1.2rem;
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .warning h4 {
            color: #f44336;
        }

        .formula-box h4 {
            color: var(--primary);
        }

        /* Calculators */
        .assessment-tool {
            background: rgba(0, 0, 0, 0.25);
            border-radius: 10px;
            padding: 25px;
            margin: 25px 0;
            border: 1px solid var(--glass-border);
        }

        .assessment-tool h3 {
            margin-bottom: 15px;
            color: var(--accent);
            text-align: center;
            font-size: 1.4rem;
        }

        .assessment-tool input,
        .assessment-tool button,
        .assessment-tool select,
        .assessment-tool textarea {
            padding: 12px 15px;
            margin: 8px 0;
            border-radius: 8px;
            width: 100%;
            background: rgba(255, 255, 255, 0.05);
            border: 1px solid var(--glass-border);
            color: white;
            font-size: 1rem;
        }

        .assessment-tool button {
            background: var(--accent);
            color: var(--dark);
            cursor: pointer;
            transition: background-color 0.3s, transform 0.2s;
            font-weight: bold;
        }

        .assessment-tool button:hover {
            background-color: #ffab00;
            transform: translateY(-2px);
        }

        .result {
            margin-top: 15px;
            padding: 15px;
            border-radius: 8px;
            display: none;
        }

        .result.good {
            background: rgba(40, 167, 69, 0.2);
            border-left: 4px solid var(--secondary);
        }

        .result.info {
            background: rgba(0, 86, 179, 0.2);
            border-left: 4px solid var(--primary);
        }

        .result.warning {
            background: rgba(255, 193, 7, 0.2);
            border-left: 4px solid var(--accent);
        }

        /* Tabs */
        .tabs {
            display: flex;
            margin-bottom: 20px;
            flex-wrap: wrap;
            border-bottom: 1px solid var(--glass-border);
        }

        .tab {
            padding: 10px 20px;
            cursor: pointer;
            border-bottom: 3px solid transparent;
            margin-right: 10px;
            transition: all 0.3s;
        }

        .tab:hover {
            color: var(--accent);
        }

        .tab.active {
            font-weight: bold;
            color: var(--accent);
            border-bottom: 3px solid var(--accent);
        }

        .tab-content {
            display: none;
        }

        .tab-content.active {
            display: block;
        }

        /* Sidebar */
        .sidebar {
            position: sticky;
            top: 90px;
        }

        .sidebar-title {
            font-size: 1.3rem;
            color: var(--accent);
            margin-bottom: 15px;
            padding-bottom: 10px;
            border-bottom: 1px solid var(--glass-border);
        }

        .module-nav {
            list-style: none;
            padding-left: 0;
            margin-bottom: 25px;
        }

        .module-nav a {
            text-decoration: none;
            color: white;
            display: block;
            padding: 10px 15px;
            border-radius: 8px;
            transition: background-color 0.3s;
            margin-bottom: 5px;
        }

        .module-nav a:hover {
            background-color: var(--glass);
        }

        .module-nav .active {
            background-color: var(--accent);
            color: var(--dark);
            font-weight: bold;
        }

        .resources-list {
            list-style: none;
            padding-left: 0;
        }

        .resources-list li {
            padding-left: 25px;
            position: relative;
        }

        .resources-list li:before {
            content: "📚";
            position: absolute;
            left: 0;
        }

        .resources-list a {
            text-decoration: none;
            color: var(--accent);
        }

        .resources-list a:hover {
            text-decoration: underline;
        }

        /* Footer */
        footer {
            background: rgba(0, 0, 0, 0.7);
            padding: 40px 0;
            margin-top: 60px;
            text-align: center;
            border-top: 1px solid var(--glass-border);
        }

        .copyright {
            margin-top: 20px;
            opacity: 0.7;
            font-size: 0.9rem;
        }

        .copyright a {
            color: var(--accent);
            text-decoration: none;
            transition: color 0.3s;
        }

        .copyright a:hover {
            color: white;
            text-decoration: underline;
        }

        /* Scroll to top */
        .scroll-to-top {
            position: fixed;
            bottom: 30px;
            right: 30px;
            width: 50px;
            height: 50px;
            background: var(--accent);
            color: var(--dark);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.5rem;
            cursor: pointer;
            opacity: 0;
            visibility: hidden;
            transition: all 0.3s;
            z-index: 1000;
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
        }

        .scroll-to-top.active {
            opacity: 1;
            visibility: visible;
        }

        .scroll-to-top:hover {
            transform: translateY(-5px);
        }

        /* Additional styles for content */
        .formula {
            font-family: 'Courier New', monospace;
            background: rgba(0, 0, 0, 0.3);
            padding: 15px;
            border-radius: 8px;
            margin: 15px 0;
            border-left: 4px solid var(--primary);
        }

        .concept-card {
            background: rgba(0, 0, 0, 0.2);
            border-radius: 8px;
            padding: 20px;
            margin: 15px 0;
            border-left: 4px solid var(--accent);
        }

        .concept-title {
            font-weight: bold;
            color: var(--accent);
            margin-bottom: 10px;
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .progress-section {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-top: 40px;
            padding-top: 20px;
            border-top: 1px solid var(--glass-border);
        }

        .btn {
            padding: 10px 20px;
            background: var(--accent);
            color: var(--dark);
            text-decoration: none;
            border-radius: 5px;
            transition: background-color 0.3s;
            border: none;
            cursor: pointer;
            font-size: 1rem;
            font-weight: bold;
        }

        .btn:hover {
            background-color: #ffab00;
            transform: translateY(-2px);
        }

        .btn-secondary {
            background: var(--secondary);
            color: white;
        }

        .btn-secondary:hover {
            background: #218838;
        }

        .btn-outline {
            background: transparent;
            border: 1px solid var(--accent);
            color: var(--accent);
        }

        .btn-outline:hover {
            background: var(--accent);
            color: var(--dark);
        }

        .progress-display {
            margin: 15px 0;
        }

        .progress-display p {
            margin-bottom: 5px;
        }

        .progress-bar-container {
            background-color: rgba(255, 255, 255, 0.1);
            border-radius: 5px;
            height: 10px;
            margin: 10px 0;
        }

        .progress-bar {
            background: var(--secondary);
            height: 100%;
            border-radius: 5px;
        }

        @media (max-width: 900px) {
            .content-grid {
                grid-template-columns: 1fr;
            }

            .sidebar {
                order: -1;
                margin-bottom: 40px;
                position: static;
            }

            .progress-section {
                flex-direction: column;
                gap: 15px;
            }

            .progress-section>div {
                display: flex;
                gap: 10px;
            }
        }