:root {
            --primary: #6366f1;
            --primary-dark: #4f46e5;
            --secondary: #ec4899;
            --accent: #f59e0b;
            --dark-bg: #050810; /* Matching mainstyle.css */
            --glass-bg: rgba(255, 255, 255, 0.03);
            --glass-border: rgba(255, 255, 255, 0.1);
            --text-light: #f8fafc;
            --text-muted: #94a3b8;
            --primary-gradient: linear-gradient(135deg, #1d2671, #c33764);
        }

        body {
            font-family: "Poppins", sans-serif;
            background-color: var(--dark-bg);
            color: var(--text-light);
            overflow-x: hidden;
        }

        /* --- BACKGROUND SHAPES --- */
        .bg-glow {
            position: fixed;
            width: 40vw;
            height: 40vw;
            border-radius: 50%;
            background: radial-gradient(circle, rgba(99, 102, 241, 0.15) 0%, transparent 70%);
            z-index: -1;
            filter: blur(60px);
        }

        /* --- NAVBAR --- */
        .custom-navbar {
            background: rgba(15, 23, 42, 0.9);
            backdrop-filter: blur(15px);
            padding: 15px 0;
            border-bottom: 1px solid var(--glass-border);
        }

        .pi-logo {
            font-size: 2.8rem;
            font-weight: 700;
            color: #fff;
            line-height: 1;
            margin-right: 12px;
            display: inline-block;
        }

        .brand-text {
            font-family: 'Montserrat', sans-serif;
            font-size: 1.5rem;
            font-weight: 700;
            color: #fff;
        }

        .tagline {
            display: block;
            font-size: 0.75rem;
            color: var(--text-muted);
            text-transform: uppercase;
            letter-spacing: 2px;
        }

        /* --- COURSE HEADER --- */
        .course-header {
            padding: 120px 0 60px;
            text-align: center;
        }

        .section-title {
            font-family: 'Montserrat', sans-serif;
            font-weight: 800;
            font-size: 3.5rem;
            background: linear-gradient(to bottom, #fff, #94a3b8);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            margin-bottom: 20px;
        }

        /* --- FILTERS --- */
        .filter-container {
            background: var(--glass-bg);
            backdrop-filter: blur(10px);
            border: 1px solid var(--glass-border);
            border-radius: 20px;
            padding: 20px;
            margin-bottom: 50px;
        }

        .filter-btn {
            background: transparent;
            border: 1px solid var(--glass-border);
            color: var(--text-muted);
            padding: 8px 20px;
            border-radius: 50px;
            transition: all 0.3s ease;
            margin: 5px;
            font-weight: 500;
        }

        .filter-btn.active, .filter-btn:hover {
            background: var(--primary);
            border-color: var(--primary);
            color: white;
            box-shadow: 0 0 20px rgba(99, 102, 241, 0.4);
        }

        /* --- COURSE CARDS --- */
        .course-card {
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            border-radius: 24px;
            overflow: hidden;
            transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
            height: 100%;
            position: relative;
        }

        .course-card:hover {
            transform: translateY(-12px);
            border-color: var(--primary);
            background: rgba(255, 255, 255, 0.05);
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.5);
        }

        .card-badge {
            position: absolute;
            top: 20px;
            right: 20px;
            background: var(--primary-gradient);
            padding: 5px 15px;
            border-radius: 50px;
            font-size: 0.75rem;
            font-weight: 700;
            z-index: 2;
        }

        .subject-icon-box {
            height: 160px;
            display: flex;
            align-items: center;
            justify-content: center;
            background: linear-gradient(rgba(99, 102, 241, 0.1), transparent);
        }

        .card-content {
            padding: 25px;
        }

        .card-class-tag {
            color: var(--primary);
            font-weight: 600;
            font-size: 0.85rem;
            text-transform: uppercase;
            letter-spacing: 1px;
            display: block;
            margin-bottom: 8px;
        }

        .card-title {
            font-size: 1.5rem;
            font-weight: 700;
            margin-bottom: 15px;
            color: #fff;
        }

        .btn-download {
            background: var(--glass-bg);
            border: 1px solid var(--glass-border);
            color: #fff;
            width: 100%;
            padding: 12px;
            border-radius: 12px;
            font-weight: 600;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 10px;
            transition: all 0.3s;
            text-decoration: none;
        }

        .btn-download:hover {
            background: var(--primary);
            border-color: var(--primary);
            color: white;
        }

        /* --- FOOTER --- */
        .footer-section {
            background: rgba(15, 23, 42, 0.9);
            padding: 80px 0 40px;
            border-top: 1px solid var(--glass-border);
            margin-top: 100px;
        }

        .footer-link {
            color: var(--text-muted);
            text-decoration: none;
            transition: color 0.3s;
            display: block;
            margin-bottom: 10px;
        }

        .footer-link:hover { color: var(--primary); }

        /* Animation */
        .course-item {
            display: block;
            animation: fadeIn 0.6s ease forwards;
        }

        @keyframes fadeIn {
            from { opacity: 0; transform: scale(0.95); }
            to { opacity: 1; transform: scale(1); }
        }