* {
            scroll-behavior: smooth;
        }
        
        body {
            font-family: 'Inter', sans-serif;
            background-color: #0a0a0a;
            color: #e5e7eb;
            overflow-x: hidden;
        }
        
        /* Header styles */
        .header-container {
            background: rgba(0, 0, 0, 0.9);
            border-radius: 9999px;
            box-shadow: 0 4px 30px rgba(0, 0, 0, 0.3);
            border: 1px solid rgba(255, 255, 255, 0.1);
        }
        .nav-item {
            position: relative;
            letter-spacing: 0.5px;
            transition: all 0.3s ease;
        }
        .nav-item:hover {
            transform: translateY(-2px);
            color: white;
        }
        .signin-btn {
            background: rgba(255, 255, 255, 0.1);
            border: 1px solid rgba(255, 255, 255, 0.2);
            transition: all 0.3s ease;
        }
        .signin-btn:hover {
            background: rgba(255, 255, 255, 0.2);
            transform: scale(1.05);
        }
        .download-btn {
            background: white;
            color: black;
            transition: all 0.3s ease;
        }
        .download-btn:hover {
            transform: scale(1.05);
            box-shadow: 0 0 15px rgba(255, 255, 255, 0.3);
        }
        
        /* Enhanced glass morphism */
        .glass-card {
            background: rgba(255, 255, 255, 0.03);
            backdrop-filter: blur(20px);
            -webkit-backdrop-filter: blur(20px);
            border: 1px solid rgba(255, 255, 255, 0.08);
            box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
            transition: all 0.4s cubic-bezier(0.25, 0.46, 0.45, 0.94);
        }
        
        .glass-card:hover {
            background: rgba(255, 255, 255, 0.05);
            border-color: rgba(255, 255, 255, 0.15);
            transform: translateY(-2px);
            box-shadow: 0 16px 64px rgba(0, 0, 0, 0.4);
        }
        
        /* Enhanced buttons */
        .btn-primary {
            background: rgba(255, 255, 255, 0.9);
            color: black;
            border: none;
            position: relative;
            overflow: hidden;
            transition: all 0.3s ease;
        }
        
        .btn-primary:hover {
            transform: translateY(-2px);
            box-shadow: 0 10px 25px rgba(255, 255, 255, 0.2);
        }
        
        .btn-secondary {
            background: rgba(255, 255, 255, 0.05);
            border: 1px solid rgba(255, 255, 255, 0.15);
            transition: all 0.3s ease;
        }
        
        .btn-secondary:hover {
            background: rgba(255, 255, 255, 0.1);
            border-color: rgba(255, 255, 255, 0.25);
            transform: translateY(-1px);
        }
        
        /* Enhanced active lesson */
        .active-lesson {
            background: rgba(255, 255, 255, 0.1);
            border: 1px solid rgba(255, 255, 255, 0.2);
            box-shadow: 0 0 30px rgba(255, 255, 255, 0.1);
            position: relative;
        }
        
        .active-lesson::before {
            content: '';
            position: absolute;
            left: 0;
            top: 0;
            bottom: 0;
            width: 4px;
            background: white;
            border-radius: 0 4px 4px 0;
        }
        
        /* Enhanced video container */
        .video-container {
            position: relative;
            border-radius: 16px;
            overflow: hidden;
            box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.6);
            background: #111;
        }
        
        /* Modern progress bar */
        .progress-container {
            height: 6px;
            background: rgba(255, 255, 255, 0.1);
            border-radius: 3px;
            overflow: hidden;
        }
        
        .progress-fill {
            height: 100%;
            background: white;
            border-radius: 3px;
            transition: width 0.3s ease;
            position: relative;
        }
        
        /* Enhanced status badges */
        .badge-in-progress {
            background: rgba(255, 255, 255, 0.9);
            color: black;
            border: none;
            font-weight: 600;
        }
        
        .badge-completed {
            background: rgba(255, 255, 255, 0.8);
            color: black;
            border: none;
            font-weight: 600;
        }
        
        .badge-not-started {
            background: rgba(255, 255, 255, 0.1);
            color: rgba(255, 255, 255, 0.7);
            border: 1px solid rgba(255, 255, 255, 0.2);
        }
        
        /* Enhanced star rating */
        .star-rating {
            display: flex;
            gap: 2px;
        }
        
        .star {
            color: white;
        }
        
        /* Enhanced chat button */
        .chat-btn {
            background: white;
            color: black;
            font-weight: 700;
            border: none;
            position: relative;
            overflow: hidden;
        }
        
        .chat-btn:hover {
            transform: translateY(-3px);
            box-shadow: 0 15px 35px rgba(255, 255, 255, 0.3);
        }
        
        /* Enhanced resource cards */
        .resource-card {
            transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
            border: 1px solid rgba(255, 255, 255, 0.08);
            position: relative;
            overflow: hidden;
        }
        
        .resource-card:hover {
            transform: translateY(-4px);
            border-color: rgba(255, 255, 255, 0.2);
            box-shadow: 0 12px 24px rgba(0, 0, 0, 0.3);
        }
        
        /* Enhanced session card */
        .session-card {
            position: relative;
            border-radius: 12px;
            overflow: hidden;
            transition: all 0.4s ease;
        }
        
        .session-card:hover {
            transform: translateY(-6px) scale(1.02);
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
        }
        
        .play-icon {
            opacity: 0;
            transition: all 0.3s ease;
            transform: scale(0.8);
        }
        
        .session-card:hover .play-icon {
            opacity: 1;
            transform: scale(1);
        }
        
        /* Enhanced search input */
        .search-input {
            background: rgba(255, 255, 255, 0.05);
            border: 1px solid rgba(255, 255, 255, 0.15);
            transition: all 0.3s ease;
        }
        
        .search-input:focus {
            background: rgba(255, 255, 255, 0.08);
            border-color: rgba(255, 255, 255, 0.3);
            box-shadow: 0 0 0 3px rgba(255, 255, 255, 0.1);
        }
        
        /* Floating elements animation */
        .floating {
            animation: float 6s ease-in-out infinite;
        }
        
        @keyframes float {
            0%, 100% { transform: translateY(0px); }
            50% { transform: translateY(-10px); }
        }
        
        /* Enhanced tabs */
        .tab-active {
            background: rgba(255, 255, 255, 0.1);
            border-bottom: 2px solid white;
            color: white;
        }
        
        /* Smooth scrollbar */
        ::-webkit-scrollbar {
            width: 8px;
        }
        
        ::-webkit-scrollbar-track {
            background: rgba(255, 255, 255, 0.05);
        }
        
        ::-webkit-scrollbar-thumb {
            background: rgba(255, 255, 255, 0.2);
            border-radius: 4px;
        }
        
        ::-webkit-scrollbar-thumb:hover {
            background: rgba(255, 255, 255, 0.3);
        }
        
        /* Enhanced lesson counter */
        .lesson-counter {
            background: rgba(255, 255, 255, 0.1);
            border: 1px solid rgba(255, 255, 255, 0.2);
        }
        
        /* Header spacing */
        .header-spacer {
            height: 80px;
        }
        
        /* Gradient text */
        .gradient-text {
            background: linear-gradient(to right, #fff, #ccc);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
        }

        /* Mobile menu specific styles */
        #mobileMenuButton {
            position: fixed;
            top: 1.5rem;
            right: 1rem;
            z-index: 55;
        }
        
        #mobileMenuOverlay {
            backdrop-filter: blur(10px);
            -webkit-backdrop-filter: blur(10px);
            z-index: 60;
        }
        
        #mobileMenu {
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
            z-index: 61;
            max-height: 100vh;
            overflow-y: auto;
        }
        
        /* Ensure mobile menu appears above header */
        header {
            z-index: 50;
        }

        /* Responsive adjustments */
        @media (max-width: 1024px) {
            .header-container {
                border-radius: 16px;
            }
            
            .header-spacer {
                height: 70px;
            }
        }

        @media (max-width: 768px) {
            .header-container {
                padding: 12px;
                border-radius: 12px;
            }
            
            .header-spacer {
                height: 60px;
            }
            
            .desktop-nav {
                display: none;
            }
            
            .course-header {
                flex-direction: column;
                align-items: flex-start;
            }
            
            .course-header-actions {
                flex-direction: column;
                width: 100%;
                margin-top: 16px;
            }
            
            .course-header-actions .btn-secondary {
                width: 100%;
                margin-bottom: 8px;
            }
            
            .search-input {
                width: 100%;
                margin-top: 8px;
            }
            
            .tabs {
                overflow-x: auto;
                white-space: nowrap;
                padding-bottom: 8px;
            }
            
            .tabs::-webkit-scrollbar {
                height: 4px;
            }
            
            .tab {
                display: inline-block;
                margin-right: 8px;
            }
            
            .resource-card {
                flex-direction: column;
                align-items: flex-start;
            }
            
            .resource-card > div:first-child {
                margin-bottom: 12px;
            }
            
            .resource-card button {
                align-self: flex-end;
            }
        }

        @media (max-width: 640px) {
            .header-container {
                padding: 8px;
            }
            
            .header-spacer {
                height: 50px;
            }
            
            .course-title {
                font-size: 1.5rem;
            }
            
            .instructor-card {
                flex-direction: column;
                align-items: flex-start;
            }
            
            .instructor-card > div:first-child {
                margin-bottom: 12px;
            }
            
            .homework-item {
                flex-direction: column;
            }
            
            .homework-item > div:first-child {
                margin-bottom: 12px;
            }
            
            .homework-actions {
                flex-direction: column;
                align-items: flex-start;
            }
            
            .homework-actions > div:first-child {
                margin-bottom: 8px;
            }
            
            .lesson-item {
                flex-direction: column;
                align-items: flex-start;
            }
            
            .lesson-item > div:first-child {
                margin-bottom: 8px;
            }
            
            .lesson-item > div:last-child {
                margin-top: 8px;
            }
        }

        /* Modal styles */
        .modal {
            animation: modalFadeIn 0.3s ease-out;
        }
        @keyframes modalFadeIn {
            from { opacity: 0; transform: translateY(10px); }
            to { opacity: 1; transform: translateY(0); }
        }
        .loader {
            animation: spin 1s linear infinite;
        }
        @keyframes spin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }
        .toggle {
            transition: all 0.3s ease;
        }
        .toggle-checked {
            background-color: white;
        }
        .toggle-dot {
            transition: all 0.3s ease;
        }
        .toggle-checked .toggle-dot {
            transform: translateX(24px);
            background-color: black;
        }
        .vercel-btn {
            background: white;
            color: black;
            border-radius: 5px;
            padding: 0.5rem 1rem;
            font-weight: 500;
            transition: all 0.2s ease;
        }
        .vercel-btn:hover {
            background: #e5e5e5;
            transform: translateY(-1px);
        }