:root {
            --primary: #6366f1;
            --primary-dark: #4f46e5;
            --secondary: #10b981;
            --danger: #ef4444;
            --warning: #f59e0b;
            --dark: #0f172a;
            --darker: #020617;
            --light: #f8fafc;
            --gray: #64748b;
            --glass: rgba(255, 255, 255, 0.05);
            --glass-border: rgba(255, 255, 255, 0.1);
        }
        
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
        }
        
        body {
            background: linear-gradient(135deg, var(--darker), #1e1b4b, var(--dark));
            color: var(--light);
            min-height: 100vh;
            overflow-x: hidden;
            position: relative;
        }
        
        /* Animated background */
        .bg-particles {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            z-index: -1;
            overflow: hidden;
        }
        
        .particle {
            position: absolute;
            border-radius: 50%;
            background: linear-gradient(45deg, var(--primary), transparent);
            animation: float 15s infinite linear;
        }
        
        @keyframes float {
            0%, 100% { transform: translate(0, 0) rotate(0deg); }
            25% { transform: translate(100px, 100px) rotate(90deg); }
            50% { transform: translate(0, 200px) rotate(180deg); }
            75% { transform: translate(-100px, 100px) rotate(270deg); }
        }
        
        .container {
            max-width: 1600px;
            margin: 0 auto;
            padding: 40px 20px;
            position: relative;
            z-index: 1;
        }
        
        /* Header */
        .header {
            text-align: center;
            padding: 80px 40px;
            background: var(--glass);
            backdrop-filter: blur(20px);
            border-radius: 32px;
            margin-bottom: 60px;
            border: 1px solid var(--glass-border);
            box-shadow: 
                0 20px 60px rgba(0, 0, 0, 0.3),
                inset 0 1px 0 rgba(255, 255, 255, 0.1);
            position: relative;
            overflow: hidden;
        }
        
        .header::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 1px;
            background: linear-gradient(90deg, transparent, var(--primary), transparent);
        }
        
        .header h1 {
            font-size: 4rem;
            font-weight: 800;
            background: linear-gradient(45deg, #fff, var(--primary), #a78bfa);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
            margin-bottom: 20px;
            line-height: 1.1;
            text-shadow: 0 0 30px rgba(99, 102, 241, 0.3);
        }
        
        .tagline {
            font-size: 1.3rem;
            color: #94a3b8;
            max-width: 800px;
            margin: 0 auto 40px;
            line-height: 1.6;
        }
        
        /* Progress Section */
        .progress-section {
            background: rgba(15, 23, 42, 0.8);
            border-radius: 20px;
            padding: 30px;
            margin: 30px 0;
            border: 1px solid rgba(255, 255, 255, 0.1);
        }
        
        .progress-title {
            font-size: 1.5rem;
            color: white;
            margin-bottom: 20px;
            display: flex;
            align-items: center;
            gap: 10px;
        }
        
        .progress-bar {
            height: 12px;
            background: rgba(255, 255, 255, 0.1);
            border-radius: 6px;
            overflow: hidden;
            margin: 15px 0;
        }
        
        .progress-fill {
            height: 100%;
            background: linear-gradient(90deg, var(--primary), var(--secondary));
            width: 0%;
            transition: width 0.5s ease;
            border-radius: 6px;
        }
        
        /* Stats */
        .stats-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 24px;
            margin: 50px 0;
        }
        
        .stat-card {
            background: var(--glass);
            backdrop-filter: blur(10px);
            border: 1px solid var(--glass-border);
            border-radius: 20px;
            padding: 30px;
            text-align: center;
            transition: all 0.3s;
            position: relative;
            overflow: hidden;
        }
        
        .stat-card::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 100%;
            background: linear-gradient(45deg, transparent, rgba(99, 102, 241, 0.1), transparent);
            transform: translateX(-100%);
            transition: transform 0.6s;
        }
        
        .stat-card:hover::before {
            transform: translateX(100%);
        }
        
        .stat-card:hover {
            transform: translateY(-5px);
            border-color: var(--primary);
            box-shadow: 0 10px 30px rgba(99, 102, 241, 0.2);
        }
        
        .stat-icon {
            font-size: 2.5rem;
            color: var(--primary);
            margin-bottom: 15px;
        }
        
        .stat-value {
            font-size: 3rem;
            font-weight: 800;
            color: white;
            display: block;
            line-height: 1;
        }
        
        .stat-label {
            color: #94a3b8;
            font-size: 0.9rem;
            text-transform: uppercase;
            letter-spacing: 1.5px;
            margin-top: 10px;
        }
        
        /* Category Tabs */
        .category-tabs {
            display: flex;
            gap: 10px;
            margin: 40px 0;
            flex-wrap: wrap;
            justify-content: center;
        }
        
        .category-tab {
            padding: 12px 25px;
            background: var(--glass);
            border: 1px solid var(--glass-border);
            border-radius: 12px;
            color: #94a3b8;
            cursor: pointer;
            transition: all 0.3s;
            font-weight: 500;
        }
        
        .category-tab.active {
            background: rgba(99, 102, 241, 0.2);
            border-color: var(--primary);
            color: var(--primary);
        }
        
        .category-tab:hover:not(.active) {
            background: rgba(255, 255, 255, 0.1);
        }
        
        /* Challenges Grid */
        .section-title {
            font-size: 2.2rem;
            font-weight: 700;
            margin: 60px 0 30px;
            color: white;
            display: flex;
            align-items: center;
            gap: 15px;
        }
        
        .section-title i {
            color: var(--primary);
            font-size: 1.8rem;
        }
        
        .challenges-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(380px, 1fr));
            gap: 30px;
            margin: 40px 0;
        }
        
        .challenge-card {
            background: var(--glass);
            backdrop-filter: blur(15px);
            border: 1px solid var(--glass-border);
            border-radius: 24px;
            padding: 35px;
            transition: all 0.4s;
            position: relative;
            overflow: hidden;
        }
        
        .challenge-card::after {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 4px;
            background: linear-gradient(90deg, var(--primary), var(--secondary));
        }
        
        .challenge-card:hover {
            transform: translateY(-10px) scale(1.02);
            border-color: var(--primary);
            box-shadow: 
                0 20px 40px rgba(0, 0, 0, 0.4),
                0 0 0 1px rgba(99, 102, 241, 0.2);
        }
        
        .challenge-header {
            display: flex;
            justify-content: space-between;
            align-items: flex-start;
            margin-bottom: 25px;
        }
        
        .challenge-icon {
            width: 70px;
            height: 70px;
            background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(16, 185, 129, 0.1));
            border-radius: 18px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 2rem;
            color: var(--primary);
        }
        
        .difficulty-badge {
            padding: 8px 20px;
            border-radius: 20px;
            font-size: 0.8rem;
            font-weight: 700;
            text-transform: uppercase;
            letter-spacing: 1px;
        }
        
        .medium-badge {
            background: rgba(245, 158, 11, 0.15);
            color: var(--warning);
            border: 1px solid rgba(245, 158, 11, 0.3);
        }
        
        .hard-badge {
            background: rgba(239, 68, 68, 0.15);
            color: var(--danger);
            border: 1px solid rgba(239, 68, 68, 0.3);
        }
        
        .challenge-card h3 {
            font-size: 1.6rem;
            font-weight: 700;
            margin-bottom: 15px;
            color: white;
            line-height: 1.3;
        }
        
        .challenge-card p {
            color: #94a3b8;
            margin-bottom: 25px;
            line-height: 1.6;
            font-size: 1.05rem;
        }
        
        .challenge-meta {
            display: flex;
            gap: 20px;
            margin-bottom: 25px;
            flex-wrap: wrap;
        }
        
        .meta-item {
            display: flex;
            align-items: center;
            gap: 8px;
            color: #cbd5e1;
            font-size: 0.9rem;
        }
        
        .meta-item i {
            color: var(--primary);
            font-size: 1rem;
        }
        
        .tags {
            display: flex;
            flex-wrap: wrap;
            gap: 10px;
            margin-bottom: 25px;
        }
        
        .tag {
            background: rgba(255, 255, 255, 0.05);
            padding: 6px 15px;
            border-radius: 15px;
            font-size: 0.85rem;
            color: #94a3b8;
            border: 1px solid rgba(255, 255, 255, 0.1);
        }
        
        .btn {
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 12px;
            padding: 16px 32px;
            background: linear-gradient(45deg, var(--primary), var(--primary-dark));
            color: white;
            text-decoration: none;
            border-radius: 14px;
            font-weight: 600;
            font-size: 1rem;
            transition: all 0.3s;
            border: none;
            cursor: pointer;
            width: 100%;
            position: relative;
            overflow: hidden;
        }
        
        .btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
            transition: left 0.6s;
        }
        
        .btn:hover::before {
            left: 100%;
        }
        
        .btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 10px 25px rgba(99, 102, 241, 0.4);
        }
        
        .btn.completed {
            background: linear-gradient(45deg, var(--secondary), #0d9668);
        }
        
        .btn.completed:hover {
            box-shadow: 0 10px 25px rgba(16, 185, 129, 0.4);
        }
        
        /* Completion Status */
        .completion-status {
            background: rgba(16, 185, 129, 0.15);
            border: 1px solid rgba(16, 185, 129, 0.3);
            border-radius: 12px;
            padding: 15px;
            margin: 15px 0;
            display: none;
            align-items: center;
            gap: 12px;
            color: var(--secondary);
            font-weight: 600;
            animation: fadeIn 0.5s ease;
        }
        
        .completion-status i {
            font-size: 1.2rem;
        }
        
        /* Completed Challenges List */
        .completed-list {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
            gap: 15px;
            margin-top: 20px;
        }
        
        .completed-item {
            background: rgba(255, 255, 255, 0.05);
            padding: 15px;
            border-radius: 12px;
            display: flex;
            align-items: center;
            gap: 15px;
            border-left: 4px solid var(--secondary);
        }
        
        .completed-icon {
            width: 40px;
            height: 40px;
            border-radius: 50%;
            background: rgba(16, 185, 129, 0.2);
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--secondary);
        }
        
        /* Footer */
        .footer {
            text-align: center;
            padding: 60px 20px;
            margin-top: 80px;
            border-top: 1px solid var(--glass-border);
            color: #94a3b8;
        }
        
        .footer-content {
            max-width: 800px;
            margin: 0 auto;
        }
        
        .footer h3 {
            font-size: 1.8rem;
            color: white;
            margin-bottom: 20px;
        }
        
        .footer-links {
            display: flex;
            justify-content: center;
            gap: 30px;
            margin: 30px 0;
            flex-wrap: wrap;
        }
        
        .footer-link {
            color: var(--primary);
            text-decoration: none;
            font-weight: 500;
            transition: color 0.3s;
            display: flex;
            align-items: center;
            gap: 8px;
        }
        
        .footer-link:hover {
            color: white;
        }
        
        .copyright {
            font-size: 0.9rem;
            margin-top: 30px;
            color: #64748b;
        }
        
        /* Animations */
        @keyframes fadeInUp {
            from {
                opacity: 0;
                transform: translateY(40px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }
        
        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(10px); }
            to { opacity: 1; transform: translateY(0); }
        }
        
        .challenge-card {
            animation: fadeInUp 0.6s ease-out forwards;
            opacity: 0;
        }
        
        /* Responsive */
        @media (max-width: 1024px) {
            .header h1 { font-size: 3rem; }
            .challenges-grid { grid-template-columns: repeat(2, 1fr); }
        }
        
        @media (max-width: 768px) {
            .header { padding: 50px 20px; }
            .header h1 { font-size: 2.5rem; }
            .challenges-grid { grid-template-columns: 1fr; }
            .stats-grid { grid-template-columns: repeat(2, 1fr); }
        }
        
        @media (max-width: 480px) {
            .header h1 { font-size: 2rem; }
            .stat-value { font-size: 2.5rem; }
            .stats-grid { grid-template-columns: 1fr; }
        }