:root {
    /* Color Palette - Light Mode */
    --bg-main-light: #f8fafc;
    --bg-card-light: #ffffff;
    --text-primary-light: #0f172a;
    --text-secondary-light: #475569;
    --border-color-light: #e2e8f0;
    
    /* Color Palette - Dark Mode (Default) */
    --bg-main-dark: #09090b;
    --bg-card-dark: #18181b;
    --text-primary-dark: #fafafa;
    --text-secondary-dark: #a1a1aa;
    --border-color-dark: #27272a;
    
    /* Accents */
    --accent-primary: #3b82f6; /* Blueish */
    --accent-glow: rgba(59, 130, 246, 0.5);
    --gradient-primary: linear-gradient(135deg, #3b82f6, #8b5cf6, #ec4899);
    
    /* Misc */
    --font-heading: 'Outfit', sans-serif;
    --font-body: 'Inter', sans-serif;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --transition-fast: 0.2s ease;
    --transition-smooth: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: var(--font-body);
    background-color: var(--bg-main-light);
    color: var(--text-primary-light);
    line-height: 1.6;
    transition: background-color var(--transition-smooth), color var(--transition-smooth);
}

body.dark-mode {
    background-color: var(--bg-main-dark);
    color: var(--text-primary-dark);
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    color: inherit;
    line-height: 1.2;
}

a {
    color: inherit;
    text-decoration: none;
}

ul {
    list-style: none;
}

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

/* Layout Elements */
.top-nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color-light);
    transition: all var(--transition-smooth);
}

body.dark-mode .top-nav {
    background-color: rgba(9, 9, 11, 0.8);
    border-bottom: 1px solid var(--border-color-dark);
}

.nav-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1.25rem;
    letter-spacing: -0.5px;
}

.logo-icon {
    color: var(--accent-primary);
}

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

.nav-link {
    font-weight: 500;
    color: var(--text-secondary-light);
    transition: color var(--transition-fast);
}

body.dark-mode .nav-link {
    color: var(--text-secondary-dark);
}

.nav-link:hover, .nav-link.active {
    color: var(--text-primary-light);
}

body.dark-mode .nav-link:hover, body.dark-mode .nav-link.active {
    color: var(--text-primary-dark);
}

.icon-btn {
    background: none;
    border: none;
    color: inherit;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color var(--transition-fast);
}

.icon-btn:hover {
    background-color: rgba(0, 0, 0, 0.05);
}

body.dark-mode .icon-btn:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-family: var(--font-heading);
    cursor: pointer;
    transition: all var(--transition-smooth);
    border: none;
    gap: 0.5rem;
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 14px var(--accent-glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px var(--accent-glow);
}

.btn-secondary {
    background-color: var(--bg-card-light);
    border: 1px solid var(--border-color-light);
    color: var(--text-primary-light);
}

body.dark-mode .btn-secondary {
    background-color: var(--bg-card-dark);
    border: 1px solid var(--border-color-dark);
    color: var(--text-primary-dark);
}

.btn-secondary:hover {
    background-color: rgba(0,0,0,0.05);
}

body.dark-mode .btn-secondary:hover {
    background-color: rgba(255,255,255,0.05);
}

/* Homepage Hero */
.hero-section {
    padding: 6rem 0;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero-bg-glow {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(139, 92, 246, 0.15) 0%, rgba(0,0,0,0) 70%);
    transform: translate(-50%, -50%);
    z-index: -1;
    pointer-events: none;
}

.hero-headline {
    font-size: 4rem;
    font-weight: 800;
    letter-spacing: -1.5px;
    margin-bottom: 1.5rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-subtext {
    font-size: 1.25rem;
    color: var(--text-secondary-light);
    max-width: 600px;
    margin: 0 auto 3rem auto;
}

body.dark-mode .hero-subtext {
    color: var(--text-secondary-dark);
}

/* Search Bar */
.search-container {
    max-width: 600px;
    margin: 0 auto;
    position: relative;
}

.search-input {
    width: 100%;
    padding: 1.25rem 1.5rem 1.25rem 3.5rem;
    border-radius: 99px;
    border: 1px solid var(--border-color-light);
    background-color: var(--bg-card-light);
    font-size: 1.1rem;
    color: var(--text-primary-light);
    box-shadow: 0 10px 25px rgba(0,0,0,0.05);
    transition: all var(--transition-smooth);
    font-family: var(--font-body);
}

body.dark-mode .search-input {
    border-color: var(--border-color-dark);
    background-color: var(--bg-card-dark);
    color: var(--text-primary-dark);
    box-shadow: 0 10px 25px rgba(0,0,0,0.2);
}

.search-input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.search-icon {
    position: absolute;
    left: 1.25rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary-light);
}

body.dark-mode .search-icon {
    color: var(--text-secondary-dark);
}

/* Categories Grid */
.section-title {
    font-size: 2rem;
    margin-bottom: 2rem;
}

.categories-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-bottom: 4rem;
}

.category-card {
    background-color: var(--bg-card-light);
    border: 1px solid var(--border-color-light);
    border-radius: var(--radius-lg);
    padding: 2rem;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition-smooth);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

body.dark-mode .category-card {
    background-color: var(--bg-card-dark);
    border: 1px solid rgba(255,255,255,0.05);
}

.category-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(0,0,0,0.08);
    border-color: var(--accent-primary);
}

body.dark-mode .category-card:hover {
    box-shadow: 0 10px 30px rgba(0,0,0,0.4);
}

.cat-icon-wrapper {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background: rgba(59, 130, 246, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent-primary);
}

/* Course Grid */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 2rem;
    margin-bottom: 4rem;
}

.course-card {
    background-color: var(--bg-card-light);
    border: 1px solid var(--border-color-light);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all var(--transition-smooth);
    display: flex;
    flex-direction: column;
}

body.dark-mode .course-card {
    background-color: var(--bg-card-dark);
    border: 1px solid rgba(255,255,255,0.05);
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 35px rgba(0,0,0,0.1);
}

body.dark-mode .course-card:hover {
    box-shadow: 0 15px 35px rgba(0,0,0,0.4);
}

.course-thumbnail {
    width: 100%;
    height: 180px;
    object-fit: cover;
    background-color: #333;
}

.course-content {
    padding: 1.5rem;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

.course-badges {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.badge {
    padding: 0.25rem 0.75rem;
    border-radius: 99px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.badge-beginner {
    background-color: rgba(34, 197, 94, 0.1);
    color: #16a34a;
}

.badge-intermediate {
    background-color: rgba(234, 179, 8, 0.1);
    color: #ca8a04;
}

.badge-advanced {
    background-color: rgba(239, 68, 68, 0.1);
    color: #dc2626;
}

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

.course-meta {
    display: flex;
    align-items: center;
    gap: 1rem;
    font-size: 0.875rem;
    color: var(--text-secondary-light);
    margin-bottom: 1rem;
}

body.dark-mode .course-meta {
    color: var(--text-secondary-dark);
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

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

body.dark-mode .course-card-footer {
    border-top: 1px solid var(--border-color-dark);
}

/* Page Headers */
.page-header {
    padding: 4rem 0;
    border-bottom: 1px solid var(--border-color-light);
    margin-bottom: 3rem;
}

body.dark-mode .page-header {
    border-bottom: 1px solid var(--border-color-dark);
}

.page-title {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.page-description {
    font-size: 1.25rem;
    color: var(--text-secondary-light);
    max-width: 800px;
}

body.dark-mode .page-description {
    color: var(--text-secondary-dark);
}

/* Course Detail Page */
.video-container {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 Aspect Ratio */
    height: 0;
    overflow: hidden;
    border-radius: var(--radius-lg);
    box-shadow: 0 15px 35px rgba(0,0,0,0.1);
    margin-bottom: 2rem;
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

.course-detail-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 3rem;
    margin-bottom: 4rem;
}

.course-sidebar {
    background-color: var(--bg-card-light);
    border: 1px solid var(--border-color-light);
    border-radius: var(--radius-lg);
    padding: 2rem;
}

body.dark-mode .course-sidebar {
    background-color: var(--bg-card-dark);
    border: 1px solid var(--border-color-dark);
}

.sidebar-item {
    margin-bottom: 1.5rem;
}

.sidebar-item h4 {
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-secondary-light);
    margin-bottom: 0.5rem;
}

body.dark-mode .sidebar-item h4 {
    color: var(--text-secondary-dark);
}

.tool-tag {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: rgba(59, 130, 246, 0.1);
    color: var(--accent-primary);
    border-radius: 99px;
    font-size: 0.875rem;
    margin-right: 0.5rem;
    margin-bottom: 0.5rem;
}

/* Task Learning Section */
.task-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.task-item {
    background-color: var(--bg-card-light);
    border: 1px solid var(--border-color-light);
    border-radius: var(--radius-lg);
    padding: 1.5rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    transition: all var(--transition-smooth);
}

body.dark-mode .task-item {
    background-color: var(--bg-card-dark);
    border: 1px solid var(--border-color-dark);
}

.task-item:hover {
    border-color: var(--accent-primary);
    transform: translateX(5px);
}

.task-item-left {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

/* Footer */
.app-footer {
    padding: 4rem 0 2rem 0;
    background-color: var(--bg-card-light);
    border-top: 1px solid var(--border-color-light);
    margin-top: 4rem;
}

body.dark-mode .app-footer {
    background-color: var(--bg-card-dark);
    border-top: 1px solid var(--border-color-dark);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 2rem;
    margin-bottom: 3rem;
}

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

body.dark-mode .footer-left p {
    color: var(--text-secondary-dark);
}

.newsletter-form {
    display: flex;
    gap: 0.5rem;
    margin-top: 1rem;
}

.newsletter-form input {
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color-light);
    background-color: var(--bg-main-light);
    color: var(--text-primary-light);
    flex-grow: 1;
}

body.dark-mode .newsletter-form input {
    border: 1px solid var(--border-color-dark);
    background-color: var(--bg-main-dark);
    color: var(--text-primary-dark);
}

.footer-bottom {
    text-align: center;
    border-top: 1px solid var(--border-color-light);
    padding-top: 2rem;
    color: var(--text-secondary-light);
}

body.dark-mode .footer-bottom {
    border-top: 1px solid var(--border-color-dark);
    color: var(--text-secondary-dark);
}

/* Page Fade Animation */
.page-content {
    animation: fadeIn var(--transition-smooth);
}

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

@media (max-width: 768px) {
    .nav-content {
        flex-direction: column;
        height: auto;
        padding: 1rem 0;
        gap: 1rem;
    }
    .hero-headline {
        font-size: 2.5rem;
    }
    .course-detail-content {
        grid-template-columns: 1fr;
    }
    .footer-content {
        flex-direction: column;
    }
}