/* ===================================
   CSS Variables & Reset
   =================================== */
:root {
    /* Colors */
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #8b5cf6;
    --accent-color: #06b6d4;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --text-light: #9ca3af;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, monospace;

    /* Spacing */
    --container-max-width: 1280px;
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;

    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    color: var(--text-primary);
    background-color: var(--bg-primary);
    line-height: 1.6;
    font-size: 16px;
}

/* ===================================
   Typography
   =================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: var(--spacing-sm);
    color: var(--text-secondary);
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* ===================================
   Layout Components
   =================================== */
.container {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.content-wrapper {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.main-area {
    min-width: 0;
}

/* ===================================
   Header
   =================================== */
.site-header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-md) 0;
}

.logo a {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--text-primary);
}

.logo-icon {
    width: 40px;
    height: 40px;
    border-radius: 8px;
    object-fit: cover;
}

.main-nav ul {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
}

.main-nav a {
    color: var(--text-secondary);
    font-weight: 500;
    transition: color var(--transition-fast);
    position: relative;
}

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

.main-nav a::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width var(--transition-base);
}

.main-nav a:hover::after {
    width: 100%;
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
}

.mobile-menu-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    transition: var(--transition-fast);
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    background: var(--bg-primary);
    color: var(--text-primary);
    padding: var(--spacing-2xl) 0;
    margin-bottom: var(--spacing-xl);
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-xl);
    align-items: center;
}

.hero-left {
    text-align: left;
}

.hero h1 {
    color: var(--text-primary);
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.hero-cta {
    display: flex;
    gap: var(--spacing-md);
}

.hero-right {
    display: flex;
    justify-content: center;
    align-items: center;
}

.hero-video {
    width: 100%;
    max-width: 560px;
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    overflow: hidden;
    border-radius: 12px;
    box-shadow: var(--shadow-xl);
}

.hero-video iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}

/* ===================================
   Buttons
   =================================== */
.btn {
    display: inline-block;
    padding: 12px 28px;
    font-weight: 600;
    border-radius: 8px;
    transition: all var(--transition-fast);
    border: 2px solid transparent;
    cursor: pointer;
    font-size: 1rem;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: transparent;
    color: var(--primary-color);
    border-color: var(--primary-color);
}

.btn-secondary:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

/* ===================================
   Section Styles
   =================================== */
.section {
    margin-bottom: var(--spacing-2xl);
}

.section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--spacing-lg);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--border-color);
}

.section-header h2 {
    margin-bottom: 0;
    font-size: 1.75rem;
}

.view-all {
    color: var(--primary-color);
    font-weight: 600;
    transition: transform var(--transition-fast);
    display: inline-block;
}

.view-all:hover {
    transform: translateX(4px);
}

/* ===================================
   News Cards
   =================================== */
.news-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

.news-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    overflow: hidden;
    transition: all var(--transition-base);
}

.news-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-color);
}

.news-card.featured {
    grid-column: 1 / -1;
}

.news-card.featured .news-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
}

.news-image {
    background: var(--bg-tertiary);
    aspect-ratio: 16/9;
    overflow: hidden;
}

.news-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.news-card:hover .news-image img {
    transform: scale(1.05);
}

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

.news-tag {
    display: inline-block;
    padding: 4px 12px;
    background: var(--primary-color);
    color: white;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: 4px;
    text-transform: uppercase;
    margin-bottom: var(--spacing-xs);
}

.news-content h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-xs);
}

.news-content h3 a {
    color: var(--text-primary);
}

.news-content h3 a:hover {
    color: var(--primary-color);
}

.news-excerpt {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.6;
}

.news-meta {
    display: flex;
    gap: var(--spacing-md);
    font-size: 0.875rem;
    color: var(--text-light);
}

/* ===================================
   Tutorial Cards
   =================================== */
.tutorial-grid {
    display: grid;
    gap: var(--spacing-lg);
}

.tutorial-card {
    display: flex;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    transition: all var(--transition-base);
}

.tutorial-card:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-lg);
    transform: translateX(4px);
}

.tutorial-icon {
    flex-shrink: 0;
    width: 64px;
    height: 64px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: 12px;
    color: white;
}

.tutorial-content h3 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-xs);
}

.tutorial-content h3 a {
    color: var(--text-primary);
}

.tutorial-content h3 a:hover {
    color: var(--primary-color);
}

.tutorial-content p {
    margin-bottom: var(--spacing-md);
    font-size: 0.9375rem;
}

.tutorial-meta {
    display: flex;
    gap: var(--spacing-md);
    align-items: center;
    font-size: 0.875rem;
}

.difficulty {
    padding: 4px 10px;
    border-radius: 4px;
    font-weight: 600;
    font-size: 0.75rem;
    text-transform: uppercase;
}

.difficulty.beginner {
    background: #d1fae5;
    color: #065f46;
}

.difficulty.intermediate {
    background: #fed7aa;
    color: #92400e;
}

.difficulty.advanced {
    background: #fecaca;
    color: #991b1b;
}

.duration {
    color: var(--text-light);
}

/* ===================================
   Recommended Content
   =================================== */
.recommended-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

.recommended-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    overflow: hidden;
    transition: all var(--transition-base);
}

.recommended-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.recommended-image {
    position: relative;
    background: var(--bg-tertiary);
    aspect-ratio: 16/9;
    overflow: hidden;
}

.recommended-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.recommended-card:hover .recommended-image img {
    transform: scale(1.05);
}

.recommended-badge {
    position: absolute;
    top: var(--spacing-sm);
    right: var(--spacing-sm);
    padding: 6px 12px;
    background: rgba(0, 0, 0, 0.75);
    color: white;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: 6px;
    backdrop-filter: blur(4px);
}

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

.recommended-content h3 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-xs);
}

.recommended-content h3 a {
    color: var(--text-primary);
}

.recommended-content h3 a:hover {
    color: var(--primary-color);
}

.recommended-content p {
    font-size: 0.9375rem;
}

/* ===================================
   Sidebar
   =================================== */
.sidebar {
    position: sticky;
    top: 100px;
    height: fit-content;
}

.sidebar-section {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: 12px;
    margin-bottom: var(--spacing-lg);
    border: 1px solid var(--border-color);
}

.sidebar-section h3 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--border-color);
}

.sidebar-list {
    list-style: none;
}

.sidebar-list li {
    margin-bottom: var(--spacing-sm);
}

.sidebar-list a {
    color: var(--text-secondary);
    font-size: 0.9375rem;
    display: block;
    padding: var(--spacing-xs);
    border-radius: 6px;
    transition: all var(--transition-fast);
}

.sidebar-list a:hover {
    background: var(--bg-primary);
    color: var(--primary-color);
    padding-left: var(--spacing-sm);
}

/* ===================================
   Footer
   =================================== */
.site-footer {
    background: var(--text-primary);
    color: white;
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section h3 {
    color: white;
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
}

.footer-section p {
    color: rgba(255, 255, 255, 0.8);
    font-size: 0.9375rem;
}

.footer-section ul {
    list-style: none;
}

.footer-section li {
    margin-bottom: var(--spacing-xs);
}

.footer-section a {
    color: rgba(255, 255, 255, 0.7);
    transition: color var(--transition-fast);
}

.footer-section a:hover {
    color: white;
}

.social-links {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-sm);
}

.social-links a {
    padding: var(--spacing-xs) var(--spacing-sm);
    background: rgba(255, 255, 255, 0.1);
    border-radius: 6px;
    transition: background var(--transition-fast);
}

.social-links a:hover {
    background: rgba(255, 255, 255, 0.2);
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.875rem;
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 1024px) {
    .content-wrapper {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: static;
    }

    .sidebar-section {
        display: inline-block;
        width: calc(50% - var(--spacing-sm));
        margin-right: var(--spacing-md);
        vertical-align: top;
    }
}

@media (max-width: 768px) {
    .hero-content {
        grid-template-columns: 1fr;
        gap: var(--spacing-lg);
    }

    .hero-left {
        text-align: center;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .hero-cta {
        justify-content: center;
    }

    .main-nav {
        display: none;
    }

    .mobile-menu-toggle {
        display: flex;
    }

    .news-card.featured .news-content {
        grid-template-columns: 1fr;
    }

    .news-grid,
    .tutorial-grid,
    .recommended-grid {
        grid-template-columns: 1fr;
    }

    .tutorial-card {
        flex-direction: column;
    }

    .sidebar-section {
        display: block;
        width: 100%;
        margin-right: 0;
    }

    .footer-content {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    :root {
        --spacing-xl: 2rem;
        --spacing-2xl: 2.5rem;
    }

    h1 { font-size: 1.75rem; }
    h2 { font-size: 1.5rem; }
    h3 { font-size: 1.25rem; }

    .container {
        padding: 0 var(--spacing-sm);
    }
}

/* ===================================
   Page Header
   =================================== */
.page-header {
    background: var(--bg-secondary);
    padding: var(--spacing-2xl) 0;
    margin-bottom: var(--spacing-xl);
    border-bottom: 1px solid var(--border-color);
}

.page-header h1 {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
    text-align: center;
}

.page-description {
    font-size: 1.125rem;
    color: var(--text-secondary);
    text-align: center;
    max-width: 700px;
    margin: 0 auto;
}

/* Category Filters */
.category-filters {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: var(--spacing-lg);
}

.filter-btn {
    padding: var(--spacing-xs) var(--spacing-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-secondary);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.filter-btn:hover {
    background: var(--bg-tertiary);
    border-color: var(--primary-color);
    color: var(--primary-color);
}

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

/* ===================================
   Privacy Policy Page
   =================================== */
.privacy-content {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-xl) 0;
}

.privacy-section {
    margin-bottom: var(--spacing-2xl);
}

.privacy-section h2 {
    font-size: 1.75rem;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--border-color);
}

.privacy-section h3 {
    font-size: 1.25rem;
    color: var(--text-primary);
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-sm);
}

.privacy-section p {
    margin-bottom: var(--spacing-md);
    line-height: 1.8;
}

.privacy-section ul {
    margin-bottom: var(--spacing-md);
    padding-left: var(--spacing-xl);
}

.privacy-section ul li {
    margin-bottom: var(--spacing-xs);
    color: var(--text-secondary);
    line-height: 1.7;
}

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

.privacy-section a {
    color: var(--primary-color);
    text-decoration: underline;
}

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

/* ===================================
   FAQ Page
   =================================== */
.faq-category-title {
    font-size: 1.75rem;
    color: var(--text-primary);
    margin-bottom: var(--spacing-lg);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--border-color);
}

.faq-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.faq-item {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
    transition: all var(--transition-base);
}

.faq-item:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

.faq-question {
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-md);
    background: none;
    border: none;
    text-align: left;
    cursor: pointer;
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    transition: background var(--transition-fast);
}

.faq-question:hover {
    background: var(--bg-secondary);
}

.faq-icon {
    flex-shrink: 0;
    color: var(--primary-color);
    transition: transform var(--transition-base);
}

.faq-item.active .faq-icon {
    transform: rotate(180deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-base);
}

.faq-item.active .faq-answer {
    max-height: 1000px;
}

.faq-answer p,
.faq-answer ul,
.faq-answer ol {
    padding: 0 var(--spacing-md) var(--spacing-md);
    margin: 0;
}

.faq-answer p {
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: var(--spacing-sm);
}

.faq-answer ul,
.faq-answer ol {
    padding-left: var(--spacing-xl);
    padding-right: var(--spacing-md);
}

.faq-answer li {
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: var(--spacing-xs);
}

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

.faq-answer a {
    color: var(--primary-color);
    text-decoration: underline;
}

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

/* ===================================
   404 Error Page
   =================================== */
.error-page {
    min-height: 60vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-2xl) 0;
}

.error-content {
    text-align: center;
    max-width: 600px;
    margin: 0 auto;
}

.error-code {
    font-size: 8rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
    margin-bottom: var(--spacing-md);
}

.error-content h1 {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-md);
}

.error-message {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
}

.error-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    margin-bottom: var(--spacing-2xl);
    flex-wrap: wrap;
}

.error-suggestions {
    margin-top: var(--spacing-2xl);
    padding-top: var(--spacing-xl);
    border-top: 1px solid var(--border-color);
}

.error-suggestions h2 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.error-suggestions ul {
    list-style: none;
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    justify-content: center;
}

.error-suggestions li a {
    display: inline-block;
    padding: var(--spacing-xs) var(--spacing-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.error-suggestions li a:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

@media (max-width: 768px) {
    .error-code {
        font-size: 5rem;
    }

    .error-content h1 {
        font-size: 1.75rem;
    }

    .error-actions {
        flex-direction: column;
    }
}