:root {
            --primary-color: #2563eb;
            --hover-color: #1d4ed8;
            --background-color: #ffffff;
            --card-background: #ffffff;
            --text-primary: #1f2937;
            --text-secondary: #4b5563;
            --spacing-unit: 1rem;
            --transition-speed: 0.3s;
            --header-background: #ffffff;
            --topic-number-bg: #2563eb;
            --topic-border: #e5e7eb;
            --card-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
        }

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

        body {
            font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
            background-color: var(--background-color);
            color: var(--text-primary);
            line-height: 1.5;
            min-height: 100vh;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 1.5rem var(--spacing-unit);
        }

        .header {
            background-color: var(--header-background);
            padding: 2rem;
            margin-bottom: 2rem;
            border-radius: 1rem;
            box-shadow: var(--card-shadow);
            text-align: center;
        }

        .header h1 {
            font-size: 2.5rem;
            color: var(--primary-color);
            margin-bottom: 1rem;
            font-weight: 700;
            letter-spacing: -0.025em;
        }

        .header-divider {
            height: 3px;
            background: linear-gradient(to right, transparent, var(--primary-color), transparent);
            margin: 1rem auto;
            max-width: 200px;
        }

        .topics-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
            gap: 1.5rem;
            padding: 1rem 0;
        }

        .topic {
            background-color: var(--card-background);
            border-radius: 1rem;
            padding: 1.5rem;
            transition: all var(--transition-speed) ease;
            border: 1px solid var(--topic-border);
            text-decoration: none;
            display: flex;
            align-items: center;
            box-shadow: var(--card-shadow);
            position: relative;
            overflow: hidden;
        }

        .topic:hover {
            transform: translateY(-2px);
            box-shadow: 0 8px 16px rgba(0, 0, 0, 0.1);
            border-color: var(--primary-color);
            background-color: #f8faff;
        }

        .topic-number {
            background-color: var(--topic-number-bg);
            color: white;
            width: 2.5rem;
            height: 2.5rem;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            margin-right: 1.25rem;
            flex-shrink: 0;
            font-size: 1rem;
            font-weight: 600;
            transition: transform var(--transition-speed) ease;
        }

        .topic:hover .topic-number {
            transform: scale(1.1);
        }

        .topic-title {
            color: var(--text-primary);
            font-size: 1.1rem;
            font-weight: 500;
            line-height: 1.4;
        }

        @media (max-width: 768px) {
            :root {
                --primary-color: #4f46e5;
                --background-color: #f8fafc;
                --card-background: #ffffff;
                --text-primary: #1e293b;
                --header-background: #ffffff;
                --topic-number-bg: #4f46e5;
                --topic-border: #e2e8f0;
                --card-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
            }

            body {
                background: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
            }

            .container {
                padding: 0.75rem;
            }

            .header {
                padding: 1.5rem 1rem;
                margin-bottom: 1rem;
                border: 1px solid var(--topic-border);
                background: linear-gradient(145deg, #ffffff, #f8fafc);
            }

            .header h1 {
                font-size: 1.75rem;
                background: linear-gradient(45deg, #4f46e5, #6366f1);
                -webkit-background-clip: text;
                background-clip: text;
                -webkit-text-fill-color: transparent;
            }

            .header-divider {
                background: linear-gradient(to right, transparent, #4f46e5, transparent);
            }

            .topics-grid {
                grid-template-columns: 1fr;
                gap: 0.75rem;
                padding: 0.5rem 0;
            }

            .topic {
                padding: 1.25rem;
                margin: 0 0.25rem;
                background: linear-gradient(145deg, #ffffff, #fafafa);
                border: 1px solid var(--topic-border);
            }

            .topic:hover {
                background: linear-gradient(145deg, #f8faff, #f0f7ff);
                border-color: #4f46e5;
            }

            .topic-number {
                width: 2.25rem;
                height: 2.25rem;
                margin-right: 1rem;
                background: linear-gradient(145deg, #4f46e5, #6366f1);
            }

            .topic-title {
                font-size: 1rem;
                color: #1e293b;
            }

            /* Add subtle inner shadow to cards */
            .topic {
                box-shadow: 
                    0 4px 6px rgba(0, 0, 0, 0.05),
                    inset 0 1px 0 rgba(255, 255, 255, 0.1);
            }

            /* Enhanced touch feedback */
            .topic:active {
                transform: translateY(1px);
                box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
            }
        }