/* ===================================
   Variables & Reset
   =================================== */
:root {
    /* Colors */
    --primary-color: #dd0031;
    --primary-dark: #c3002f;
    --primary-light: #ff4060;
    --secondary-color: #4f46e5;
    --accent-color: #0ea5e9;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #dd0031 0%, #c3002f 100%);
    --gradient-secondary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-accent: linear-gradient(135deg, #0ea5e9 0%, #06b6d4 100%);
    --gradient-hero: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #dd0031 100%);
    
    /* Neutral Colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #94a3b8;
    --border-color: #e2e8f0;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 300ms ease;
    --transition-slow: 500ms ease;
}

/* Dark Mode Variables */
body.dark-mode {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-tertiary: #64748b;
    --border-color: #334155;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Noto Sans TC', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color var(--transition-base), color var(--transition-base);
}

/* ===================================
   Typography
   =================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: 1rem;
}

h1 { font-size: 3rem; }
h2 { font-size: 2.5rem; }
h3 { font-size: 2rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

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

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

code {
    font-family: 'JetBrains Mono', monospace;
    background: var(--bg-tertiary);
    padding: 0.2rem 0.4rem;
    border-radius: var(--radius-sm);
    font-size: 0.9em;
}

/* ===================================
   Top Navigation
   =================================== */
.top-nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 70px;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    transition: all var(--transition-base);
}

body.dark-mode .top-nav {
    background: rgba(15, 23, 42, 0.95);
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    height: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 2rem;
}

.nav-left {
    display: flex;
    align-items: center;
    gap: 3rem;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 900;
    color: var(--primary-color);
}

.logo i {
    font-size: 2rem;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-link {
    color: var(--text-primary);
    font-weight: 500;
    padding: 0.5rem 0;
    position: relative;
    transition: color var(--transition-fast);
}

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

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.nav-right {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.search-btn,
.theme-toggle {
    width: 40px;
    height: 40px;
    border: none;
    background: var(--bg-secondary);
    color: var(--text-primary);
    border-radius: var(--radius-lg);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.search-btn:hover,
.theme-toggle:hover {
    background: var(--bg-tertiary);
    transform: translateY(-2px);
}

.login-btn {
    padding: 0.5rem 1.5rem;
    border: none;
    background: var(--gradient-primary);
    color: white;
    border-radius: var(--radius-lg);
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all var(--transition-fast);
}

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

/* ===================================
   Search Modal
   =================================== */
.search-modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(5px);
    z-index: 2000;
    display: none;
    align-items: flex-start;
    justify-content: center;
    padding-top: 10vh;
}

.search-modal.active {
    display: flex;
}

.search-modal-content {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    width: 90%;
    max-width: 600px;
    box-shadow: var(--shadow-2xl);
    position: relative;
}

.search-input {
    width: 100%;
    padding: 1.5rem 4rem 1.5rem 2rem;
    border: none;
    background: transparent;
    font-size: 1.25rem;
    color: var(--text-primary);
    outline: none;
}

.search-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    width: 40px;
    height: 40px;
    border: none;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.search-close:hover {
    background: var(--bg-tertiary);
}

.search-results {
    max-height: 400px;
    overflow-y: auto;
    padding: 1rem;
    border-top: 1px solid var(--border-color);
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    padding-top: 70px;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--gradient-hero);
    opacity: 0.05;
}

.hero-shapes {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
}

.shape {
    position: absolute;
    border-radius: 50%;
    filter: blur(80px);
    opacity: 0.3;
    animation: float 20s infinite ease-in-out;
}

.shape-1 {
    width: 400px;
    height: 400px;
    background: #667eea;
    top: 10%;
    left: 10%;
    animation-delay: 0s;
}

.shape-2 {
    width: 300px;
    height: 300px;
    background: #dd0031;
    top: 60%;
    right: 10%;
    animation-delay: 5s;
}

.shape-3 {
    width: 350px;
    height: 350px;
    background: #0ea5e9;
    bottom: 10%;
    left: 50%;
    animation-delay: 10s;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    33% { transform: translate(50px, -50px) scale(1.1); }
    66% { transform: translate(-50px, 50px) scale(0.9); }
}

.hero-content {
    position: relative;
    z-index: 1;
    text-align: center;
    padding: 2rem;
    max-width: 1000px;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1.5rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    animation: fadeInUp 0.8s ease;
}

.hero-title {
    font-size: 4rem;
    font-weight: 900;
    margin-bottom: 1.5rem;
    line-height: 1.1;
    animation: fadeInUp 0.8s ease 0.2s backwards;
}

.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-description {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 2.5rem;
    animation: fadeInUp 0.8s ease 0.4s backwards;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-bottom: 3rem;
    animation: fadeInUp 0.8s ease 0.6s backwards;
}

.btn {
    padding: 1rem 2rem;
    border: none;
    border-radius: var(--radius-lg);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: all var(--transition-base);
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: var(--shadow-lg);
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-xl);
}

.btn-secondary {
    background: var(--bg-primary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--bg-secondary);
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

.hero-stats {
    display: flex;
    gap: 3rem;
    justify-content: center;
    animation: fadeInUp 0.8s ease 0.8s backwards;
}

.stat {
    text-align: center;
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 900;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

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

/* ===================================
   Features Section
   =================================== */
.features {
    padding: var(--spacing-2xl) 2rem;
    background: var(--bg-secondary);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

.section-header {
    text-align: center;
    margin-bottom: 4rem;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 900;
    margin-bottom: 1rem;
}

.section-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: var(--radius-xl);
    border: 1px solid var(--border-color);
    transition: all var(--transition-base);
    cursor: pointer;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-color);
}

.feature-icon {
    width: 60px;
    height: 60px;
    background: var(--gradient-primary);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: white;
    margin-bottom: 1.5rem;
}

.feature-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ===================================
   Tutorial Section
   =================================== */
.tutorial-section {
    background: var(--bg-primary);
    min-height: 100vh;
    padding-top: 70px;
}

.tutorial-container {
    display: flex;
    max-width: 1600px;
    margin: 0 auto;
}

/* Sidebar */
.sidebar {
    width: 320px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    position: sticky;
    top: 70px;
    height: calc(100vh - 70px);
    overflow-y: auto;
    transition: transform var(--transition-base);
}

.sidebar-header {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.sidebar-header h3 {
    font-size: 1.25rem;
    margin: 0;
}

.sidebar-toggle {
    display: none;
    width: 36px;
    height: 36px;
    border: none;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    cursor: pointer;
}

.sidebar-content {
    padding: 1rem 0;
}

.sidebar-section {
    margin-bottom: 0.5rem;
}

.sidebar-section-title {
    padding: 0.75rem 1.5rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    transition: all var(--transition-fast);
    user-select: none;
}

.sidebar-section-title:hover {
    background: var(--bg-tertiary);
}

.sidebar-section-title i {
    font-size: 0.75rem;
    transition: transform var(--transition-base);
}

.sidebar-section-title.collapsed i {
    transform: rotate(-90deg);
}

.sidebar-menu {
    list-style: none;
    overflow: hidden;
    transition: max-height var(--transition-base);
}

.sidebar-menu.collapsed {
    max-height: 0 !important;
}

.sidebar-menu li {
    border-left: 2px solid transparent;
    transition: all var(--transition-fast);
}

.sidebar-menu a {
    display: block;
    padding: 0.75rem 1.5rem 0.75rem 2.5rem;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.sidebar-menu li:hover {
    border-left-color: var(--primary-color);
    background: var(--bg-primary);
}

.sidebar-menu li:hover a {
    color: var(--primary-color);
}

.sidebar-menu li.active {
    border-left-color: var(--primary-color);
    background: var(--bg-primary);
}

.sidebar-menu li.active a {
    color: var(--primary-color);
    font-weight: 600;
}

/* Main Content */
.main-content {
    flex: 1;
    padding: 3rem;
    max-width: 900px;
}

.content-header {
    margin-bottom: 2rem;
}

.content-title {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.content-meta {
    display: flex;
    gap: 1.5rem;
    color: var(--text-tertiary);
    font-size: 0.9rem;
}

.content-body {
    font-size: 1.1rem;
    line-height: 1.8;
}

.content-body h2 {
    margin-top: 2rem;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border-color);
}

.content-body h3 {
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
}

.content-body pre {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    overflow-x: auto;
    margin: 1.5rem 0;
}

.content-body pre code {
    background: transparent;
    padding: 0;
}

.code-example {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    overflow: hidden;
    margin: 2rem 0;
}

.code-example-header {
    background: var(--bg-tertiary);
    padding: 1rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
}

.code-example-title {
    font-weight: 600;
    font-size: 0.9rem;
}

.code-example-actions {
    display: flex;
    gap: 0.5rem;
}

.code-btn {
    padding: 0.4rem 1rem;
    border: none;
    background: var(--bg-primary);
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.code-example-body {
    padding: 1.5rem;
}

.note {
    background: #dbeafe;
    border-left: 4px solid #3b82f6;
    padding: 1rem 1.5rem;
    border-radius: var(--radius-md);
    margin: 1.5rem 0;
}

.warning {
    background: #fef3c7;
    border-left: 4px solid #f59e0b;
    padding: 1rem 1.5rem;
    border-radius: var(--radius-md);
    margin: 1.5rem 0;
}

.tip {
    background: #d1fae5;
    border-left: 4px solid #10b981;
    padding: 1rem 1.5rem;
    border-radius: var(--radius-md);
    margin: 1.5rem 0;
}

/* ===================================
   Examples Section
   =================================== */
.examples-section {
    padding: var(--spacing-2xl) 2rem;
    background: var(--bg-primary);
}

.examples-tabs {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-bottom: 3rem;
    flex-wrap: wrap;
}

.tab-btn {
    padding: 0.75rem 1.5rem;
    border: 2px solid var(--border-color);
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.tab-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

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

.examples-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 2rem;
}

.example-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    overflow: hidden;
    transition: all var(--transition-base);
    cursor: pointer;
}

.example-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.example-card-header {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.example-card-title {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

.example-card-description {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.example-card-tags {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
    margin-top: 1rem;
}

.tag {
    padding: 0.25rem 0.75rem;
    background: var(--bg-tertiary);
    border-radius: 50px;
    font-size: 0.75rem;
    font-weight: 600;
}

.example-card-body {
    padding: 1.5rem;
    background: var(--bg-primary);
}

.example-card-body pre {
    margin: 0;
    background: transparent;
    border: none;
    padding: 0;
}

.example-card-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.example-btn {
    padding: 0.5rem 1rem;
    border: none;
    background: var(--primary-color);
    color: white;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 600;
    transition: all var(--transition-fast);
}

.example-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
}

/* ===================================
   Playground Section
   =================================== */
.playground-section {
    padding: var(--spacing-2xl) 2rem;
    background: var(--bg-secondary);
}

.playground {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    overflow: hidden;
    box-shadow: var(--shadow-xl);
}

.playground-editor,
.playground-preview {
    display: flex;
    flex-direction: column;
}

.editor-tabs,
.preview-header {
    display: flex;
    gap: 0.5rem;
    padding: 1rem;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
}

.editor-tab {
    padding: 0.5rem 1rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 500;
    transition: all var(--transition-fast);
}

.editor-tab:hover {
    background: var(--bg-tertiary);
}

.editor-tab.active {
    background: var(--primary-color);
    color: white;
}

.preview-header {
    justify-content: space-between;
    align-items: center;
}

.preview-header span {
    font-weight: 600;
}

.btn-run {
    padding: 0.5rem 1.5rem;
    border: none;
    background: var(--gradient-accent);
    color: white;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all var(--transition-fast);
}

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

.editor-content,
.preview-content {
    flex: 1;
    padding: 1.5rem;
    overflow: auto;
}

.editor-content pre {
    margin: 0;
    background: transparent;
    border: none;
    padding: 0;
}

.preview-content .greeting {
    padding: 20px;
    text-align: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border-radius: 10px;
}

/* ===================================
   Exercises Section
   =================================== */
.exercises-section {
    padding: var(--spacing-2xl) 2rem;
    background: var(--bg-primary);
}

.exercise-container {
    max-width: 800px;
    margin: 0 auto;
}

.exercise-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: 2rem;
    margin-bottom: 2rem;
}

.exercise-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.exercise-number {
    background: var(--gradient-primary);
    color: white;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
}

.exercise-difficulty {
    padding: 0.25rem 1rem;
    border-radius: 50px;
    font-size: 0.85rem;
    font-weight: 600;
}

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

.difficulty-medium {
    background: #fef3c7;
    color: #92400e;
}

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

.exercise-question {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.exercise-options {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    margin-top: 1.5rem;
}

.option {
    padding: 1rem;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.option.selected {
    border-color: var(--primary-color);
    background: rgba(221, 0, 49, 0.05);
}

.option.correct {
    border-color: #10b981;
    background: rgba(16, 185, 129, 0.1);
}

.option.incorrect {
    border-color: #ef4444;
    background: rgba(239, 68, 68, 0.1);
}

.exercise-submit {
    margin-top: 1.5rem;
    padding: 0.75rem 2rem;
    border: none;
    background: var(--gradient-primary);
    color: white;
    border-radius: var(--radius-lg);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.exercise-submit:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.exercise-result {
    margin-top: 1.5rem;
    padding: 1rem;
    border-radius: var(--radius-lg);
    font-weight: 600;
}

.result-correct {
    background: #d1fae5;
    color: #065f46;
}

.result-incorrect {
    background: #fecaca;
    color: #991b1b;
}

/* ===================================
   Roadmap Section
   =================================== */
.roadmap-section {
    padding: var(--spacing-2xl) 2rem;
    background: var(--bg-secondary);
}

.roadmap {
    max-width: 900px;
    margin: 0 auto;
    position: relative;
}

.roadmap::before {
    content: '';
    position: absolute;
    left: 30px;
    top: 40px;
    bottom: 40px;
    width: 3px;
    background: var(--gradient-primary);
}

.roadmap-item {
    display: flex;
    gap: 2rem;
    margin-bottom: 3rem;
    position: relative;
}

.roadmap-number {
    width: 60px;
    height: 60px;
    background: var(--gradient-primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 900;
    flex-shrink: 0;
    box-shadow: var(--shadow-lg);
    z-index: 1;
}

.roadmap-content {
    flex: 1;
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: var(--radius-xl);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-md);
}

.roadmap-content h3 {
    font-size: 1.5rem;
    margin-bottom: 0.75rem;
}

.roadmap-content p {
    margin-bottom: 1rem;
}

.roadmap-topics {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.topic-tag {
    padding: 0.4rem 1rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    font-size: 0.85rem;
    font-weight: 600;
}

/* ===================================
   FAQ Section
   =================================== */
.faq-section {
    padding: var(--spacing-2xl) 2rem;
    background: var(--bg-primary);
}

.faq-list {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    margin-bottom: 1rem;
    overflow: hidden;
}

.faq-question {
    padding: 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    font-weight: 600;
    font-size: 1.1rem;
    transition: all var(--transition-fast);
}

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

.faq-question i {
    transition: transform var(--transition-base);
}

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

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

.faq-item.active .faq-answer {
    max-height: 500px;
    padding: 0 1.5rem 1.5rem;
}

/* ===================================
   Footer
   =================================== */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-xl) 2rem var(--spacing-md);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 3rem;
    margin-bottom: 2rem;
}

.footer-section h4 {
    margin-bottom: 1rem;
}

.footer-section p {
    margin-bottom: 1rem;
    font-size: 0.9rem;
}

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

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section ul li a {
    color: var(--text-secondary);
    transition: color var(--transition-fast);
}

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

.social-links {
    display: flex;
    gap: 1rem;
    margin-top: 1rem;
}

.social-links a {
    width: 40px;
    height: 40px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.social-links a:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    transform: translateY(-3px);
}

.footer-bottom {
    max-width: 1200px;
    margin: 0 auto;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    text-align: center;
    color: var(--text-secondary);
}

/* ===================================
   Scroll to Top Button
   =================================== */
.scroll-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 50px;
    height: 50px;
    background: var(--gradient-primary);
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: none;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    box-shadow: var(--shadow-xl);
    transition: all var(--transition-base);
    z-index: 999;
}

.scroll-top:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-2xl);
}

.scroll-top.visible {
    display: flex;
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 1024px) {
    .sidebar {
        position: fixed;
        left: 0;
        transform: translateX(-100%);
        z-index: 999;
    }
    
    .sidebar.active {
        transform: translateX(0);
    }
    
    .sidebar-toggle {
        display: block;
    }
    
    .main-content {
        padding: 2rem;
    }
    
    .playground {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-description {
        font-size: 1rem;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .hero-stats {
        flex-direction: column;
        gap: 1.5rem;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .examples-grid {
        grid-template-columns: 1fr;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .nav-container {
        padding: 0 1rem;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .main-content {
        padding: 1rem;
    }
}

/* ===================================
   Utility Classes
   =================================== */
.hidden {
    display: none !important;
}

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

.mt-1 { margin-top: var(--spacing-sm); }
.mt-2 { margin-top: var(--spacing-md); }
.mt-3 { margin-top: var(--spacing-lg); }

.mb-1 { margin-bottom: var(--spacing-sm); }
.mb-2 { margin-bottom: var(--spacing-md); }
.mb-3 { margin-bottom: var(--spacing-lg); }

.p-1 { padding: var(--spacing-sm); }
.p-2 { padding: var(--spacing-md); }
.p-3 { padding: var(--spacing-lg); }