/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #94a3b8;
    --border: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    --radius: 8px;
    --radius-lg: 12px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow-sm);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.status-badge {
    padding: 0.375rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.875rem;
    font-weight: 500;
}

.status-badge.online {
    background: #dcfce7;
    color: #166534;
}

.status-badge.offline {
    background: #fef3c7;
    color: #92400e;
}

/* Search Section */
.search-section {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border);
    padding: 1.5rem 0;
}

.search-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.search-box {
    position: relative;
    display: flex;
    align-items: center;
}

.search-icon {
    position: absolute;
    left: 1rem;
    color: var(--text-tertiary);
    pointer-events: none;
}

#search-input {
    width: 100%;
    padding: 0.875rem 3rem 0.875rem 3rem;
    border: 2px solid var(--border);
    border-radius: var(--radius-lg);
    font-size: 1rem;
    background: var(--bg-primary);
    transition: all 0.2s;
}

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

.clear-btn {
    position: absolute;
    right: 1rem;
    background: none;
    border: none;
    color: var(--text-tertiary);
    cursor: pointer;
    padding: 0.25rem;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    transition: all 0.2s;
}

.clear-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-secondary);
}

.filter-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

.chip {
    padding: 0.375rem 0.875rem;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 9999px;
    font-size: 0.875rem;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text-secondary);
}

.chip:hover {
    background: var(--bg-secondary);
    border-color: var(--primary-light);
}

.chip.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Main Content */
.main-content {
    flex: 1;
    max-width: 1200px;
    width: 100%;
    margin: 0 auto;
    padding: 2rem 1.5rem;
}

.results-info {
    margin-bottom: 1rem;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* Article Grid */
.article-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.5rem;
}

.article-card {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    cursor: pointer;
    transition: all 0.2s;
    box-shadow: var(--shadow-sm);
}

.article-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary-light);
}

.article-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.article-card .tldr {
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-bottom: 0.75rem;
    line-height: 1.5;
}

.article-card .tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.375rem;
    margin-top: 0.75rem;
}

.tag {
    padding: 0.25rem 0.625rem;
    background: var(--bg-tertiary);
    border-radius: 0.375rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.difficulty-beginner { background: #dcfce7; color: #166534; }
.difficulty-intermediate { background: #fef3c7; color: #92400e; }
.difficulty-advanced { background: #fee2e2; color: #991b1b; }

/* Article View */
.article-view {
    animation: fadeIn 0.3s;
}

.back-button {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.625rem 1rem;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 1.5rem;
    transition: all 0.2s;
}

.back-button:hover {
    background: var(--bg-tertiary);
    border-color: var(--primary-light);
}

.article-content {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 2.5rem;
    box-shadow: var(--shadow-sm);
}

.article-content h1 {
    font-size: 2.25rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.article-content h2 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-top: 2rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.article-content h3 {
    font-size: 1.375rem;
    font-weight: 600;
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.article-content p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
    line-height: 1.75;
}

.article-content ul,
.article-content ol {
    margin-bottom: 1rem;
    padding-left: 1.5rem;
    color: var(--text-secondary);
}

.article-content li {
    margin-bottom: 0.5rem;
    line-height: 1.75;
}

.article-content strong {
    color: var(--text-primary);
    font-weight: 600;
}

.article-content code {
    background: var(--bg-tertiary);
    padding: 0.125rem 0.375rem;
    border-radius: 0.25rem;
    font-size: 0.875em;
    font-family: 'Courier New', monospace;
}

.article-content pre {
    background: var(--bg-tertiary);
    padding: 1rem;
    border-radius: var(--radius);
    overflow-x: auto;
    margin-bottom: 1rem;
}

.article-content pre code {
    background: none;
    padding: 0;
}

.article-content blockquote {
    border-left: 4px solid var(--primary);
    padding-left: 1rem;
    margin: 1rem 0;
    color: var(--text-secondary);
    font-style: italic;
}

/* Loading State */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 4rem 0;
}

.spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

.loading p {
    margin-top: 1rem;
    color: var(--text-secondary);
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 4rem 1rem;
    color: var(--text-tertiary);
}

.empty-state svg {
    margin-bottom: 1rem;
    opacity: 0.5;
}

.empty-state h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

/* Footer */
.footer {
    background: var(--bg-primary);
    border-top: 1px solid var(--border);
    padding: 1.5rem;
    text-align: center;
    color: var(--text-tertiary);
    font-size: 0.875rem;
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Responsive */
@media (max-width: 768px) {
    .article-grid {
        grid-template-columns: 1fr;
    }
    
    .article-content {
        padding: 1.5rem;
    }
    
    .article-content h1 {
        font-size: 1.875rem;
    }
    
    .article-content h2 {
        font-size: 1.5rem;
    }
}

/* Print Styles */
@media print {
    .header,
    .search-section,
    .back-button,
    .footer {
        display: none;
    }
    
    .article-content {
        border: none;
        box-shadow: none;
        padding: 0;
    }
}