/* ============================================
   CSS Variables - Light & Dark Themes
   ============================================ */
:root {
    /* Light Theme Colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-card: #ffffff;
    --text-primary: #1a1a1a;
    --text-secondary: #6c757d;
    --border-color: #e9ecef;
    --shadow: rgba(0, 0, 0, 0.1);
    
    /* Brand Colors */
    --accent-primary: #d32f2f;
    --accent-secondary: #ff6b35;
    --accent-gradient: linear-gradient(135deg, #d32f2f 0%, #ff6b35 100%);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    
    /* Typography */
    --font-tamil: 'Noto Sans Tamil', sans-serif;
    --font-english: 'Inter', sans-serif;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
}

[data-theme="dark"] {
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-card: #1c2128;
    --text-primary: #e6edf3;
    --text-secondary: #8b949e;
    --border-color: #30363d;
    --shadow: rgba(0, 0, 0, 0.3);
}

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

body {
    font-family: var(--font-english);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
}

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

/* ============================================
   Header
   ============================================ */
.header {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 8px var(--shadow);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.logo h1 {
    font-size: clamp(1.5rem, 4vw, 2rem);
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 0.25rem;
}

.tagline {
    font-family: var(--font-tamil);
    font-size: clamp(0.875rem, 2vw, 1rem);
    color: var(--text-secondary);
}

.subtitle {
    font-family: var(--font-tamil);
    color: var(--text-secondary);
    margin-top: var(--spacing-sm);
    font-size: clamp(0.875rem, 2vw, 1rem);
}

.header-controls {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
}

/* ============================================
   Toggle Buttons
   ============================================ */
.toggle-btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    padding: 0.5rem 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.875rem;
}

.toggle-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px var(--shadow);
}

.toggle-label {
    font-family: var(--font-tamil);
    color: var(--text-secondary);
    transition: color 0.3s ease;
}

.toggle-label.active {
    color: var(--accent-primary);
    font-weight: 600;
}

.toggle-switch {
    width: 40px;
    height: 20px;
    background: var(--border-color);
    border-radius: 10px;
    position: relative;
    transition: background 0.3s ease;
}

.toggle-switch::after {
    content: '';
    position: absolute;
    width: 16px;
    height: 16px;
    background: white;
    border-radius: 50%;
    top: 2px;
    left: 2px;
    transition: transform 0.3s ease;
}

.toggle-btn.active .toggle-switch {
    background: var(--accent-primary);
}

.toggle-btn.active .toggle-switch::after {
    transform: translateX(20px);
}

.theme-toggle {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.3s ease;
}

.theme-toggle:hover {
    transform: rotate(15deg) scale(1.1);
    box-shadow: 0 4px 12px var(--shadow);
}

.sun-icon,
.moon-icon {
    color: var(--text-primary);
    transition: opacity 0.3s ease;
}

[data-theme="dark"] .sun-icon {
    display: none;
}

[data-theme="light"] .moon-icon {
    display: none;
}

/* ============================================
   Main Content
   ============================================ */
.main {
    min-height: calc(100vh - 200px);
    padding: var(--spacing-xl) 0;
}

/* Loading State */
.loading {
    text-align: center;
    padding: var(--spacing-xl);
}

.spinner {
    width: 50px;
    height: 50px;
    border: 4px solid var(--border-color);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto var(--spacing-md);
}

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

/* Articles Grid */
.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    animation: fadeIn 0.6s ease;
}

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

/* Article Card */
.article-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all 0.3s ease;
    cursor: pointer;
    animation: slideUp 0.6s ease;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.article-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 24px var(--shadow);
    border-color: var(--accent-primary);
}

.article-image {
    width: 100%;
    height: 200px;
    object-fit: cover;
    background: var(--bg-secondary);
}

.article-content {
    padding: var(--spacing-md);
}

.article-category {
    display: inline-block;
    background: var(--accent-gradient);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 50px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    margin-bottom: var(--spacing-sm);
}

.article-title {
    font-family: var(--font-tamil);
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    line-height: 1.4;
    color: var(--text-primary);
}

.article-description {
    font-family: var(--font-tamil);
    color: var(--text-secondary);
    font-size: 0.9375rem;
    line-height: 1.6;
    margin-bottom: var(--spacing-md);
}

.article-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: var(--spacing-sm);
    border-top: 1px solid var(--border-color);
}

.article-source {
    font-size: 0.875rem;
    color: var(--accent-primary);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.3s ease;
}

.article-source:hover {
    color: var(--accent-secondary);
}

.article-date {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: var(--spacing-xl);
    font-family: var(--font-tamil);
}

.empty-subtitle {
    color: var(--text-secondary);
    margin-top: var(--spacing-sm);
}

/* ============================================
   Footer
   ============================================ */
.footer {
    background: var(--bg-card);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-lg) 0;
    text-align: center;
    margin-top: var(--spacing-xl);
}

.footer p {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.footer-tagline {
    font-family: var(--font-tamil);
    margin-top: var(--spacing-xs);
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .header-controls {
        width: 100%;
        justify-content: space-between;
    }
    
    .articles-grid {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }
    
    .toggle-btn {
        font-size: 0.75rem;
        padding: 0.4rem 0.8rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-sm);
    }
    
    .header {
        padding: var(--spacing-sm) 0;
    }
    
    .main {
        padding: var(--spacing-md) 0;
    }
}