:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #ec4899;
    --background: #0f172a;
    --surface: #1e293b;
    --surface-light: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --border: #334155;
    --success: #10b981;
    --shadow: rgba(0, 0, 0, 0.3);
    --gradient: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 20px;
}

/* Header Styles */
.header {
    background: var(--surface);
    border-radius: 16px;
    padding: 40px;
    margin-bottom: 40px;
    box-shadow: 0 4px 6px var(--shadow);
    position: relative;
    overflow: hidden;
}

.header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient);
}

.header-content {
    margin-bottom: 30px;
}

.header-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    background: var(--gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

.search-container {
    display: flex;
    gap: 10px;
    max-width: 600px;
}

.search-input {
    flex: 1;
    padding: 14px 20px;
    background: var(--surface-light);
    border: 2px solid var(--border);
    border-radius: 12px;
    color: var(--text-primary);
    font-size: 1rem;
    transition: all 0.3s ease;
}

.search-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.search-btn {
    padding: 14px 24px;
    background: var(--gradient);
    border: none;
    border-radius: 12px;
    color: white;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.search-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 16px rgba(99, 102, 241, 0.3);
}

/* Main Content */
.main {
    margin-bottom: 40px;
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 30px;
    color: var(--text-primary);
}

/* Categories Grid */
.categories-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 24px;
}

.category-card {
    background: var(--surface);
    border-radius: 16px;
    padding: 30px;
    cursor: pointer;
    transition: all 0.3s ease;
    border: 2px solid transparent;
    position: relative;
    overflow: hidden;
}

.category-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient);
    transform: scaleX(0);
    transition: transform 0.3s ease;
}

.category-card:hover {
    transform: translateY(-4px);
    border-color: var(--primary-color);
    box-shadow: 0 12px 24px var(--shadow);
}

.category-card:hover::before {
    transform: scaleX(1);
}

.category-icon {
    width: 48px;
    height: 48px;
    margin-bottom: 16px;
    border-radius: 12px;
    object-fit: contain;
}

.category-name {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.category-description {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 12px;
}

.category-count {
    display: inline-block;
    background: var(--surface-light);
    color: var(--primary-light);
    padding: 6px 12px;
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 600;
}

/* Questions Section */
.questions-section,
.search-results-section {
    animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.back-btn {
    background: var(--surface);
    border: 2px solid var(--border);
    color: var(--text-primary);
    padding: 12px 20px;
    border-radius: 12px;
    cursor: pointer;
    font-size: 1rem;
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 24px;
    transition: all 0.3s ease;
}

.back-btn:hover {
    background: var(--surface-light);
    border-color: var(--primary-color);
    transform: translateX(-4px);
}

.questions-header {
    margin-bottom: 30px;
}

.category-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    background: var(--gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.questions-count {
    color: var(--text-muted);
    font-size: 1.1rem;
}

.questions-list {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.question-item {
    background: var(--surface);
    border-radius: 12px;
    padding: 20px 24px;
    transition: all 0.3s ease;
    border-left: 4px solid transparent;
    display: flex;
    align-items: center;
    gap: 16px;
}

.question-item:hover {
    background: var(--surface-light);
    border-left-color: var(--primary-color);
    transform: translateX(4px);
}

.question-number {
    background: var(--gradient);
    color: white;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.9rem;
    flex-shrink: 0;
}

.question-link {
    color: var(--text-primary);
    text-decoration: none;
    flex: 1;
    font-size: 1.05rem;
    transition: color 0.3s ease;
}

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

.question-tag {
    background: var(--surface-light);
    color: var(--text-secondary);
    padding: 4px 12px;
    border-radius: 6px;
    font-size: 0.85rem;
    flex-shrink: 0;
}

/* Search Results */
.search-info {
    color: var(--text-secondary);
    margin-bottom: 24px;
    font-size: 1.1rem;
}

.search-results {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.search-result-category {
    background: var(--surface);
    border-radius: 16px;
    padding: 24px;
    border-left: 4px solid var(--primary-color);
}

.search-result-category-name {
    font-size: 1.4rem;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--primary-light);
}

.search-result-questions {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.search-highlight {
    background: var(--primary-color);
    color: white;
    padding: 2px 4px;
    border-radius: 4px;
}

/* Footer */
.footer {
    text-align: center;
    padding: 30px;
    background: var(--surface);
    border-radius: 16px;
    color: var(--text-secondary);
}

.footer a {
    color: var(--primary-light);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .header-title {
        font-size: 2rem;
    }

    .header {
        padding: 24px;
    }

    .categories-grid {
        grid-template-columns: 1fr;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .category-title {
        font-size: 1.8rem;
    }

    .search-container {
        flex-direction: column;
    }

    .search-btn {
        width: 100%;
    }
}

/* Loading State */
.loading {
    text-align: center;
    padding: 60px;
    color: var(--text-secondary);
    font-size: 1.2rem;
}

.loading::after {
    content: '';
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid var(--border);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin-left: 10px;
    vertical-align: middle;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-secondary);
}

.empty-state-icon {
    font-size: 4rem;
    margin-bottom: 20px;
    opacity: 0.5;
}

.empty-state-text {
    font-size: 1.2rem;
}