/* ===== CSS Variables ===== */
:root {
    /* Colors - Dark Theme (Default) */
    --bg-primary: #0a1628;
    --bg-secondary: #122036;
    --bg-card: #1a2d4a;
    --bg-card-hover: #223654;
    --text-primary: #ffffff;
    --text-secondary: #a0aec0;
    --text-muted: #718096;
    --accent-primary: #00d4aa;
    --accent-secondary: #00b894;
    --accent-gradient: linear-gradient(135deg, #00d4aa 0%, #00b894 100%);
    --border-color: #2d3748;
    --shadow-color: rgba(0, 0, 0, 0.3);
    --danger: #e53e3e;
    --warning: #ed8936;
    --success: #48bb78;
    --info: #4299e1;
    
    /* Spacing */
    --sidebar-width: 260px;
    --sidebar-collapsed: 70px;
    --header-height: 70px;
    --border-radius: 12px;
    --border-radius-sm: 8px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
}

/* Light Theme */
[data-theme="light"] {
    --bg-primary: #f7fafc;
    --bg-secondary: #ffffff;
    --bg-card: #ffffff;
    --bg-card-hover: #f0f4f8;
    --text-primary: #1a202c;
    --text-secondary: #4a5568;
    --text-muted: #718096;
    --border-color: #e2e8f0;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

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

a:hover {
    color: var(--accent-secondary);
}

/* ===== Sidebar ===== */
.sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: var(--sidebar-width);
    height: 100vh;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    z-index: 1000;
    transition: width var(--transition-normal);
    display: flex;
    flex-direction: column;
}

.sidebar.collapsed {
    width: var(--sidebar-collapsed);
}

.sidebar-header {
    padding: 20px;
    display: flex;
    align-items: center;
    gap: 12px;
    border-bottom: 1px solid var(--border-color);
    min-height: var(--header-height);
}

.sidebar-header i {
    font-size: 28px;
    color: var(--accent-primary);
}

.sidebar-header span {
    font-size: 20px;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    white-space: nowrap;
}

.sidebar.collapsed .sidebar-header span {
    display: none;
}

.sidebar-menu {
    list-style: none;
    padding: 15px 10px;
    flex: 1;
}

.sidebar-menu li {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 16px;
    margin-bottom: 5px;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    color: var(--text-secondary);
}

/* ====== Sidebar Bottom (GitHub + Coffee) ====== */
.sidebar-bottom {
    padding: 12px 10px;
    border-top: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.sidebar-github-btn {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 14px;
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    text-decoration: none;
    font-size: 13px;
    font-weight: 600;
    background: linear-gradient(135deg, rgba(36, 41, 47, 0.3), rgba(36, 41, 47, 0.1));
    border: 1px solid var(--border-color);
    transition: all var(--transition-fast);
    cursor: pointer;
}

.sidebar-github-btn:hover {
    background: linear-gradient(135deg, rgba(36, 41, 47, 0.5), rgba(36, 41, 47, 0.3));
    border-color: var(--accent-primary);
    transform: translateY(-1px);
}

.sidebar-github-btn .fab.fa-github {
    font-size: 18px;
}

.sidebar-star-icon {
    margin-left: auto;
    color: #f0c040;
    font-size: 12px;
    animation: starPulse 2s ease-in-out infinite;
}

@keyframes starPulse {
    0%, 100% { opacity: 0.6; transform: scale(1); }
    50% { opacity: 1; transform: scale(1.2); }
}

.sidebar-coffee-btn {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 14px;
    border-radius: var(--border-radius-sm);
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 12px;
    font-weight: 500;
    transition: all var(--transition-fast);
    cursor: pointer;
}

.sidebar-coffee-btn:hover {
    color: #ffdd00;
    background: rgba(255, 221, 0, 0.08);
}

/* Collapsed sidebar: hide text */
.sidebar.collapsed .sidebar-bottom span {
    display: none;
}

.sidebar.collapsed .sidebar-github-btn,
.sidebar.collapsed .sidebar-coffee-btn {
    justify-content: center;
    padding: 10px;
}

.sidebar.collapsed .sidebar-star-icon {
    display: none;
}

/* ====== Open Source Banner (Home Page) ====== */
.open-source-banner {
    margin-top: 60px;
    padding: 40px;
    background: linear-gradient(135deg, rgba(var(--accent-primary-rgb, 0, 255, 163), 0.05), rgba(var(--accent-secondary-rgb, 0, 209, 255), 0.05));
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    text-align: center;
}

.oss-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 6px 16px;
    background: var(--accent-gradient);
    border-radius: 20px;
    color: #000;
    font-size: 13px;
    font-weight: 700;
    margin-bottom: 16px;
}

.oss-badge i {
    font-size: 14px;
}

.oss-text {
    color: var(--text-secondary);
    font-size: 15px;
    max-width: 550px;
    margin: 0 auto 24px;
    line-height: 1.6;
}

.oss-actions {
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}

.oss-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    border-radius: var(--border-radius-sm);
    text-decoration: none;
    font-size: 14px;
    font-weight: 600;
    transition: all var(--transition-fast);
    cursor: pointer;
}

.oss-btn-star {
    background: #24292e;
    color: #fff;
    border: 1px solid #444;
}

.oss-btn-star:hover {
    background: #2d333b;
    border-color: var(--accent-primary);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
}

.oss-btn-contribute {
    background: transparent;
    color: var(--accent-primary);
    border: 1px solid var(--accent-primary);
}

.oss-btn-contribute:hover {
    background: rgba(0, 255, 163, 0.1);
    transform: translateY(-2px);
}

.oss-btn-coffee {
    background: #ffdd00;
    color: #000;
    border: 1px solid #ffdd00;
    font-weight: 700;
}

.oss-btn-coffee:hover {
    background: #ffe94a;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(255, 221, 0, 0.3);
}

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

.sidebar-menu li.active {
    background: var(--accent-gradient);
    color: white;
}

.sidebar-menu li i {
    font-size: 18px;
    width: 24px;
    text-align: center;
}

.sidebar.collapsed .sidebar-menu li span {
    display: none;
}

/* ===== Main Content ===== */
.main-content {
    margin-left: var(--sidebar-width);
    min-height: 100vh;
    transition: margin-left var(--transition-normal);
}

.sidebar.collapsed + .main-content {
    margin-left: var(--sidebar-collapsed);
}

/* ===== Header ===== */
.header {
    position: sticky;
    top: 0;
    min-height: var(--header-height);
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    padding: 15px 20px;
    gap: 15px;
    z-index: 100;
}

.menu-toggle {
    display: none;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    font-size: 18px;
    cursor: pointer;
    padding: 10px;
    border-radius: var(--border-radius-sm);
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    flex-shrink: 0;
    transition: all var(--transition-fast);
}

.menu-toggle:hover {
    background: var(--bg-card-hover);
}

/* Mobile Sidebar Overlay */
.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    z-index: 1000;
}

.sidebar-overlay.active {
    display: block;
}

.search-container {
    flex: 1;
    display: flex;
    gap: 10px;
    min-width: 0;
}

/* Header button should not be full width */
.search-container .btn-primary {
    flex-shrink: 0;
}

.search-container input {
    flex: 1;
    min-width: 0;
    padding: 12px 16px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    color: var(--text-primary);
    font-size: 14px;
    transition: all var(--transition-fast);
}

.search-container input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(0, 212, 170, 0.1);
}

.search-container input::placeholder {
    color: var(--text-muted);
}

.header-spacer {
    flex: 1;
    min-width: 10px;
}

.theme-toggle {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    width: 44px;
    height: 44px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    flex-shrink: 0;
    transition: all var(--transition-fast);
}

.theme-toggle:hover {
    background: var(--bg-card-hover);
    transform: rotate(15deg);
}

/* ===== Buttons ===== */
.btn-primary {
    padding: 12px 20px;
    background: var(--accent-gradient);
    border: none;
    border-radius: 50px;
    color: white;
    font-size: 14px;
    font-weight: 600;
    flex-shrink: 0;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(0, 212, 170, 0.4);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-secondary {
    padding: 10px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all var(--transition-fast);
    width: 100%;
    justify-content: center;
    margin-bottom: 10px;
}

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

.btn-danger {
    padding: 12px 24px;
    background: var(--danger);
    border: none;
    border-radius: var(--border-radius-sm);
    color: white;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all var(--transition-fast);
}

.btn-danger:hover {
    background: #c53030;
}

/* ===== Pages ===== */
.page {
    display: none;
    padding: 30px;
    animation: fadeIn 0.3s ease;
}

.page.active {
    display: block;
}

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

/* ===== Hero Section ===== */
.hero-section {
    text-align: center;
    padding: 60px 20px;
    max-width: 1000px;
    margin: 0 auto;
}

.hero-section h1 {
    font-size: 48px;
    margin-bottom: 20px;
    font-weight: 700;
}

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

.hero-section > p {
    font-size: 18px;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 40px;
}

/* ===== Topic Refinement Panel ===== */
.refinement-panel {
    margin: 0 20px 20px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    overflow: hidden;
    animation: refinementSlideIn 0.35s ease;
}

@keyframes refinementSlideIn {
    from { opacity: 0; transform: translateY(-15px); max-height: 0; }
    to { opacity: 1; transform: translateY(0); max-height: 600px; }
}

.refinement-content {
    padding: 30px 35px;
    position: relative;
}

.refinement-close {
    position: absolute;
    top: 15px;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 18px;
    cursor: pointer;
    padding: 5px 10px;
    border-radius: 50%;
    transition: all var(--transition-fast);
}

.refinement-close:hover {
    color: var(--text-primary);
    background: var(--bg-card);
}

.refinement-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 8px;
}

.refinement-header i {
    font-size: 22px;
    color: var(--accent-primary);
}

.refinement-header h2 {
    font-size: 20px;
    font-weight: 600;
    margin: 0;
}

.refinement-subtitle {
    color: var(--text-secondary);
    font-size: 15px;
    margin-bottom: 20px;
    line-height: 1.5;
}

.refinement-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 22px;
}

.refinement-chip {
    padding: 10px 18px;
    background: var(--bg-card);
    border: 1.5px solid var(--border-color);
    border-radius: 50px;
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.refinement-chip:hover {
    border-color: var(--accent-primary);
    background: var(--bg-card-hover);
    transform: translateY(-2px);
}

.refinement-chip.selected {
    border-color: var(--accent-primary);
    background: rgba(0, 212, 170, 0.12);
    color: var(--accent-primary);
    font-weight: 600;
    box-shadow: 0 0 0 1px var(--accent-primary);
}

.refinement-difficulty {
    display: flex;
    align-items: center;
    gap: 15px;
    margin-bottom: 22px;
    flex-wrap: wrap;
}

.difficulty-label {
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
}

.difficulty-buttons {
    display: flex;
    gap: 8px;
}

.diff-btn {
    padding: 8px 16px;
    background: var(--bg-card);
    border: 1.5px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    color: var(--text-secondary);
    font-size: 13px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.diff-btn:hover {
    border-color: var(--accent-primary);
    color: var(--text-primary);
}

.diff-btn.active {
    border-color: var(--accent-primary);
    background: rgba(0, 212, 170, 0.12);
    color: var(--accent-primary);
    font-weight: 600;
}

.refinement-actions {
    display: flex;
    align-items: center;
    gap: 20px;
    flex-wrap: wrap;
}

.refinement-actions .btn-primary {
    padding: 12px 24px;
    font-size: 15px;
}

.refinement-skip {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 14px;
    cursor: pointer;
    padding: 8px 4px;
    transition: color var(--transition-fast);
}

.refinement-skip:hover {
    color: var(--accent-primary);
}

/* ===== Topic Suggestions ===== */
.topic-suggestions {
    margin-bottom: 50px;
}

.topic-suggestions h3 {
    margin-bottom: 15px;
    color: var(--text-secondary);
    font-weight: 500;
}

.suggestion-chips {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
}

.chip {
    padding: 10px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.chip:hover {
    border-color: var(--accent-primary);
    background: var(--bg-card-hover);
    transform: translateY(-2px);
}

/* ===== Features Grid ===== */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-top: 40px;
}

.feature-card {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    transition: all var(--transition-fast);
}

.feature-card:hover {
    transform: translateY(-5px);
    border-color: var(--accent-primary);
    box-shadow: 0 10px 40px var(--shadow-color);
}

.feature-card i {
    font-size: 40px;
    color: var(--accent-primary);
    margin-bottom: 15px;
}

.feature-card h3 {
    font-size: 18px;
    margin-bottom: 10px;
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 14px;
}

/* ===== Course Header ===== */
.course-header {
    background: var(--bg-secondary);
    padding: 30px;
    border-radius: var(--border-radius);
    margin-bottom: 30px;
    border: 1px solid var(--border-color);
}

.course-title-section h1 {
    font-size: 28px;
    margin-bottom: 20px;
}

.progress-container {
    display: flex;
    align-items: center;
    gap: 15px;
}

.progress-bar {
    flex: 1;
    height: 12px;
    background: var(--bg-card);
    border-radius: 50px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent-gradient);
    border-radius: 50px;
    transition: width 0.5s ease;
    width: 0%;
}

.progress-text {
    font-weight: 600;
    color: var(--accent-primary);
    min-width: 50px;
}

/* ===== Course Content Layout ===== */
.course-content {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: 30px;
}

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

/* ===== Course Sections ===== */
.course-section {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 25px;
}

.section-title {
    font-size: 22px;
    color: var(--accent-primary);
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.section-content {
    color: var(--text-secondary);
    line-height: 1.8;
}

/* ===== Lesson Cards ===== */
.lesson-card {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 25px;
    overflow: hidden;
}

.lesson-header {
    padding: 20px 25px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.lesson-header h3 {
    color: var(--accent-primary);
    font-size: 18px;
}

.lesson-header i {
    color: var(--text-muted);
    transition: transform var(--transition-fast);
}

.lesson-card.expanded .lesson-header i {
    transform: rotate(180deg);
}

.lesson-content {
    padding: 25px;
    display: none;
}

.lesson-card.expanded .lesson-content {
    display: block;
}

.lesson-text {
    color: var(--text-secondary);
    margin-bottom: 25px;
    line-height: 1.8;
}

/* ===== Video Grid ===== */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.video-card {
    background: var(--bg-secondary);
    border-radius: var(--border-radius-sm);
    overflow: hidden;
    border: 1px solid var(--border-color);
    transition: all var(--transition-fast);
}

.video-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 30px var(--shadow-color);
}

.video-thumbnail {
    position: relative;
    aspect-ratio: 16/9;
    overflow: hidden;
}

.video-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.video-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.4);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.video-card:hover .video-overlay {
    opacity: 1;
}

.video-overlay i {
    font-size: 50px;
    color: white;
}

.video-info {
    padding: 15px;
}

.video-info h4 {
    font-size: 14px;
    margin-bottom: 8px;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.video-meta {
    display: flex;
    gap: 10px;
    color: var(--text-muted);
    font-size: 12px;
}

.video-completed {
    position: absolute;
    top: 10px;
    right: 10px;
    background: var(--success);
    color: white;
    padding: 5px 10px;
    border-radius: 50px;
    font-size: 11px;
    font-weight: 600;
}

/* ===== Course Sidebar ===== */
.course-sidebar {
    position: sticky;
    top: calc(var(--header-height) + 30px);
    height: fit-content;
}

.sidebar-card {
    background: var(--bg-card);
    padding: 20px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.sidebar-title {
    font-size: 16px;
    color: var(--accent-primary);
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-color);
}

/* ===== Progress Checklist ===== */
.progress-checklist {
    list-style: none;
}

.progress-checklist li {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 0;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 14px;
}

.progress-checklist li:last-child {
    border-bottom: none;
}

.progress-checklist li.completed {
    color: var(--success);
}

.progress-checklist li.completed i {
    color: var(--success);
}

.check-box {
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.check-box.checked {
    background: var(--accent-gradient);
    border-color: var(--accent-primary);
}

.check-box.checked::after {
    content: '✓';
    color: white;
    font-size: 12px;
    font-weight: bold;
}

/* ===== Share Buttons ===== */
.share-buttons {
    display: flex;
    gap: 10px;
}

.share-btn {
    flex: 1;
    padding: 12px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.share-btn:hover {
    background: var(--bg-card-hover);
    transform: translateY(-2px);
}

/* ===== Quiz Section ===== */
.quiz-container {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.quiz-question {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--border-color);
}

.quiz-question h4 {
    margin-bottom: 15px;
    font-size: 16px;
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.quiz-option {
    padding: 12px 16px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    gap: 10px;
}

.quiz-option:hover {
    border-color: var(--accent-primary);
}

.quiz-option.selected {
    border-color: var(--accent-primary);
    background: rgba(0, 212, 170, 0.1);
}

.quiz-option.correct {
    border-color: var(--success);
    background: rgba(72, 187, 120, 0.1);
}

.quiz-option.incorrect {
    border-color: var(--danger);
    background: rgba(229, 62, 62, 0.1);
}

.quiz-option input {
    display: none;
}

.option-marker {
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    font-weight: 600;
}

.quiz-option.selected .option-marker {
    border-color: var(--accent-primary);
    background: var(--accent-primary);
    color: white;
}

.quiz-submit {
    margin-top: 20px;
}

.quiz-results {
    text-align: center;
    padding: 30px;
}

.quiz-results h3 {
    margin-bottom: 20px;
}

.score-display {
    font-size: 48px;
    font-weight: 700;
    color: var(--accent-primary);
    margin-bottom: 20px;
}

/* ===== Resources Grid ===== */
.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 15px;
}

.resource-card {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 15px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.resource-card:hover {
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

.resource-card i {
    font-size: 24px;
    color: var(--accent-primary);
}

.resource-info h4 {
    font-size: 14px;
    margin-bottom: 4px;
}

.resource-info span {
    font-size: 12px;
    color: var(--text-muted);
}

/* ===== My Courses Page ===== */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 25px;
}

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

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 40px var(--shadow-color);
}

.course-card-header {
    padding: 20px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
}

.course-card-header h3 {
    font-size: 18px;
    margin-bottom: 5px;
}

.course-card-header span {
    color: var(--text-muted);
    font-size: 13px;
}

.course-card-body {
    padding: 20px;
}

.course-card-progress {
    margin-bottom: 15px;
}

.course-card-progress .progress-bar {
    height: 8px;
    margin-bottom: 5px;
}

.course-card-progress span {
    font-size: 13px;
    color: var(--text-secondary);
}

.course-card-actions {
    display: flex;
    gap: 10px;
}

.course-card-actions button {
    flex: 1;
    padding: 10px;
    border-radius: var(--border-radius-sm);
    font-size: 13px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

/* ===== Badges Page ===== */
.badges-container {
    max-width: 1000px;
    margin: 0 auto;
}

.badges-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    margin-bottom: 40px;
}

.stat-card {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    text-align: center;
}

.stat-card i {
    font-size: 36px;
    color: var(--accent-primary);
    margin-bottom: 15px;
}

.stat-number {
    display: block;
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 5px;
}

.stat-label {
    color: var(--text-secondary);
}

.badges-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 20px;
}

.badge-card {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    text-align: center;
    transition: all var(--transition-fast);
}

.badge-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px var(--shadow-color);
}

.badge-card.locked {
    opacity: 0.5;
}

.badge-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 15px;
    background: var(--accent-gradient);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.badge-icon i {
    font-size: 36px;
    color: white;
}

.badge-card.locked .badge-icon {
    background: var(--bg-secondary);
}

.badge-card.locked .badge-icon i {
    color: var(--text-muted);
}

.badge-card h4 {
    font-size: 16px;
    margin-bottom: 5px;
}

.badge-card p {
    font-size: 13px;
    color: var(--text-secondary);
}

/* ===== Settings Page ===== */
.settings-container {
    max-width: 600px;
}

.settings-section {
    background: var(--bg-card);
    padding: 25px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.settings-section h3 {
    margin-bottom: 10px;
}

.settings-description {
    color: var(--text-secondary);
    font-size: 14px;
    margin-bottom: 20px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
}

.form-group input[type="text"],
.form-group input[type="password"] {
    width: 100%;
    padding: 12px 16px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    font-size: 14px;
}

.form-group input:focus {
    outline: none;
    border-color: var(--accent-primary);
}

.help-link {
    font-size: 12px;
    display: inline-block;
    margin-top: 5px;
}

.toggle-group {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.toggle {
    position: relative;
    width: 50px;
    height: 26px;
}

.toggle input {
    opacity: 0;
    width: 0;
    height: 0;
}

.toggle-slider {
    position: absolute;
    cursor: pointer;
    inset: 0;
    background: var(--bg-secondary);
    border-radius: 26px;
    transition: var(--transition-fast);
}

.toggle-slider::before {
    content: '';
    position: absolute;
    width: 20px;
    height: 20px;
    left: 3px;
    bottom: 3px;
    background: white;
    border-radius: 50%;
    transition: var(--transition-fast);
}

.toggle input:checked + .toggle-slider {
    background: var(--accent-primary);
}

.toggle input:checked + .toggle-slider::before {
    transform: translateX(24px);
}

.danger-zone {
    border-color: var(--danger);
}

.danger-zone h3 {
    color: var(--danger);
}

/* ===== Modal ===== */
.modal {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.7);
    z-index: 2000;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    max-width: 500px;
    width: 100%;
    max-height: 80vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.modal-content.large {
    max-width: 800px;
}

.modal-header {
    padding: 20px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.modal-header h2 {
    font-size: 20px;
}

.modal-close {
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 28px;
    cursor: pointer;
    line-height: 1;
}

.modal-body {
    padding: 20px;
    overflow-y: auto;
    color: var(--text-secondary);
    line-height: 1.8;
}

/* ===== Notes Modal Tabs ===== */
.notes-tabs {
    display: flex;
    gap: 4px;
    border-bottom: 1px solid var(--border-color);
    margin: -20px -20px 20px;
    padding: 0 20px;
    background: var(--bg-secondary);
    position: sticky;
    top: -20px;
    z-index: 5;
}

.notes-tab {
    padding: 12px 20px;
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    border-bottom: 2px solid transparent;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 8px;
    white-space: nowrap;
}

.notes-tab:hover {
    color: var(--text-primary);
}

.notes-tab.active {
    color: var(--accent-primary);
    border-bottom-color: var(--accent-primary);
}

.notes-tab i {
    font-size: 13px;
}

.notes-tab-content {
    display: none;
}

.notes-tab-content.active {
    display: block;
    animation: fadeIn 0.2s ease;
}

/* ===== Study Guide ===== */
.study-guide {
    font-size: 14px;
    line-height: 1.75;
}

.study-guide .guide-title {
    font-size: 22px;
    color: var(--text-primary);
    margin-bottom: 20px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--accent-primary);
}

.study-guide .guide-phase {
    font-size: 17px;
    color: var(--accent-primary);
    margin-top: 28px;
    margin-bottom: 12px;
    padding: 8px 14px;
    background: rgba(139, 92, 246, 0.08);
    border-left: 3px solid var(--accent-primary);
    border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
}

.study-guide .guide-section {
    font-size: 14px;
    color: var(--text-primary);
    margin-top: 16px;
    margin-bottom: 8px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-size: 12px;
    opacity: 0.85;
}

.study-guide .guide-list {
    list-style: none;
    padding: 0;
    margin: 8px 0 16px;
}

.study-guide .guide-list li {
    padding: 6px 0 6px 24px;
    position: relative;
    line-height: 1.6;
}

.study-guide .guide-list li::before {
    content: '';
    position: absolute;
    left: 6px;
    top: 14px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent-primary);
    opacity: 0.6;
}

.study-guide p {
    margin: 8px 0;
}

/* ===== Community Cards ===== */
.communities-container {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.communities-intro {
    font-size: 14px;
    color: var(--text-secondary);
    padding: 14px 16px;
    background: rgba(139, 92, 246, 0.06);
    border-radius: var(--border-radius-sm);
    border: 1px solid rgba(139, 92, 246, 0.12);
    margin-bottom: 4px;
    line-height: 1.6;
}

.communities-intro i {
    color: var(--accent-primary);
    margin-right: 6px;
}

.community-card {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 16px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    text-decoration: none;
    color: inherit;
    transition: all 0.2s ease;
    cursor: pointer;
}

.community-card:hover {
    border-color: var(--accent-primary);
    transform: translateX(4px);
    box-shadow: 0 2px 12px rgba(139, 92, 246, 0.12);
}

.community-icon {
    font-size: 24px;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-primary);
    border-radius: 10px;
    flex-shrink: 0;
}

.community-info {
    flex: 1;
    min-width: 0;
}

.community-info h4 {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 3px;
}

.community-info p {
    font-size: 12px;
    color: var(--text-muted);
    line-height: 1.4;
    margin: 0;
}

.community-members {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: 11px;
    color: var(--text-muted);
    margin-top: 4px;
    opacity: 0.7;
}

.community-members i {
    font-size: 10px;
}

.community-arrow {
    color: var(--text-muted);
    font-size: 12px;
    opacity: 0;
    transition: all 0.2s ease;
    flex-shrink: 0;
}

.community-card:hover .community-arrow {
    opacity: 1;
    color: var(--accent-primary);
}

.communities-tip {
    font-size: 12px;
    color: var(--text-muted);
    padding: 12px 16px;
    background: var(--bg-secondary);
    border-radius: var(--border-radius-sm);
    margin-top: 8px;
    line-height: 1.5;
    font-style: italic;
}

.communities-tip i {
    margin-right: 6px;
    color: var(--accent-secondary);
}

.community-empty {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-muted);
}

.community-empty i {
    font-size: 40px;
    margin-bottom: 12px;
    opacity: 0.3;
}

/* ===== Video Modal ===== */
.video-modal-content {
    width: 90%;
    max-width: 900px;
    padding: 0;
}

.video-modal-content .modal-header {
    padding: 15px 20px;
    border-bottom: 1px solid var(--border-color);
}

.video-modal-content .modal-header h3 {
    font-size: 1rem;
    margin: 0;
    padding-right: 30px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.video-modal-content .close-btn {
    position: absolute;
    top: 10px;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 24px;
    cursor: pointer;
    transition: color 0.2s;
}

.video-modal-content .close-btn:hover {
    color: var(--accent);
}

.video-embed-container {
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    overflow: hidden;
}

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

.video-modal-actions {
    display: flex;
    gap: 10px;
    padding: 15px 20px;
    border-top: 1px solid var(--border-color);
    justify-content: flex-end;
}

.video-modal-actions button {
    padding: 10px 20px;
    font-size: 0.9rem;
}

/* ===== Loading Overlay ===== */
.loading-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(10, 22, 40, 0.95);
    z-index: 3000;
    align-items: center;
    justify-content: center;
}

.loading-overlay.active {
    display: flex;
}

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

.spinner {
    width: 60px;
    height: 60px;
    border: 4px solid var(--border-color);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

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

.loading-spinner p {
    font-size: 18px;
    margin-bottom: 30px;
}

.loading-steps {
    text-align: left;
    max-width: 300px;
    margin: 0 auto;
}

.loading-step {
    padding: 10px 0;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 12px;
}

.loading-step.active {
    color: var(--accent-primary);
}

.loading-step.completed {
    color: var(--success);
}

.loading-step i {
    width: 20px;
}

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

.empty-state {
    text-align: center;
    padding: 60px 20px;
    grid-column: 1 / -1;
}

.empty-state i {
    font-size: 60px;
    color: var(--text-muted);
    margin-bottom: 20px;
}

.empty-state h3 {
    margin-bottom: 10px;
    color: var(--text-secondary);
}

.empty-state p {
    color: var(--text-muted);
}

/* ===== Responsive Design ===== */

/* Tablets and below (768px and under) - Hide sidebar, show menu toggle */
@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        transform: translateX(-100%);
        width: 280px;
        z-index: 1001;
        transition: transform 0.3s ease;
    }
    
    .sidebar.active {
        transform: translateX(0);
    }
    
    .sidebar-overlay.active {
        display: block;
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .menu-toggle {
        display: flex;
    }
    
    .header {
        flex-wrap: wrap;
        padding: 10px;
        gap: 10px;
    }
    
    .search-container {
        order: 10;
        flex: 1 1 100%;
        width: 100%;
    }
    
    .header-spacer {
        display: none;
    }
    
    .hero-section {
        padding: 30px 15px;
    }
    
    .refinement-panel {
        margin: 0 10px 15px;
    }
    
    .refinement-content {
        padding: 20px 18px;
    }
    
    .refinement-header h2 {
        font-size: 17px;
    }
    
    .refinement-chips {
        gap: 8px;
    }
    
    .refinement-chip {
        padding: 8px 14px;
        font-size: 13px;
    }
    
    .refinement-difficulty {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }
    
    .refinement-actions {
        flex-direction: column;
        align-items: stretch;
        gap: 10px;
    }
    
    .refinement-actions .btn-primary {
        justify-content: center;
    }
    
    .refinement-skip {
        text-align: center;
    }
    
    .hero-section h1 {
        font-size: 26px;
    }
    
    .hero-section > p {
        font-size: 14px;
    }
    
    .page {
        padding: 15px;
    }
    
    .features-grid {
        grid-template-columns: 1fr 1fr;
        gap: 12px;
    }
    
    .feature-card {
        padding: 20px 15px;
    }
    
    .feature-card i {
        font-size: 28px;
    }
    
    .feature-card h3 {
        font-size: 14px;
    }
    
    .feature-card p {
        font-size: 12px;
    }
    
    .course-content {
        grid-template-columns: 1fr;
    }
    
    .course-sidebar {
        position: static;
        display: block;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .badges-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .badges-stats {
        grid-template-columns: 1fr;
    }
    
    .profile-dropdown {
        position: fixed;
        top: auto;
        bottom: 0;
        left: 0;
        right: 0;
        width: 100%;
        border-radius: var(--border-radius) var(--border-radius) 0 0;
        max-height: 80vh;
        overflow-y: auto;
    }
    
    .modal-content {
        width: 95%;
        max-height: 90vh;
        margin: 5vh auto;
    }
    
    .course-tabs {
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }
    
    .tab-btn {
        white-space: nowrap;
        flex-shrink: 0;
    }
    
    /* Notes modal mobile */
    .notes-tabs {
        margin: -20px -20px 16px;
        padding: 0 12px;
    }
    
    .notes-tab {
        padding: 10px 14px;
        font-size: 13px;
    }
    
    .community-card {
        padding: 12px;
        gap: 10px;
    }
    
    .community-icon {
        width: 38px;
        height: 38px;
        font-size: 20px;
    }
    
    .community-info h4 {
        font-size: 13px;
    }
    
    .study-guide .guide-phase {
        font-size: 15px;
        padding: 6px 10px;
    }
    
    .resources-grid {
        grid-template-columns: 1fr;
    }
}

/* Small phones (480px and under) */
@media (max-width: 480px) {
    .header {
        padding: 8px;
        gap: 8px;
    }
    
    .menu-toggle {
        width: 40px;
        height: 40px;
    }
    
    .theme-toggle {
        width: 40px;
        height: 40px;
    }
    
    .profile-avatar {
        width: 36px;
        height: 36px;
    }
    
    .search-container {
        flex-direction: column;
    }
    
    .search-container input {
        width: 100%;
    }
    
    .search-container .btn-primary {
        width: 100%;
        justify-content: center;
    }
    
    .hero-section h1 {
        font-size: 22px;
    }
    
    .hero-section > p {
        font-size: 13px;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .chip {
        padding: 8px 12px;
        font-size: 12px;
    }
    
    .course-header {
        padding: 15px;
    }
    
    .course-title-section h1 {
        font-size: 18px;
    }
    
    .video-card {
        flex-direction: row;
    }
    
    .video-thumbnail {
        width: 120px;
        min-width: 120px;
        height: 80px;
    }
    
    .video-info h4 {
        font-size: 13px;
    }
    
    .video-meta {
        display: none;
    }
    
    .badges-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 10px;
    }
    
    .badge-card {
        padding: 15px 10px;
    }
    
    .badge-card i {
        font-size: 24px;
    }
    
    .badge-card h3 {
        font-size: 11px;
    }
}

/* Tablets (769px to 1024px) - Collapsed sidebar */
@media (min-width: 769px) and (max-width: 1024px) {
    .sidebar {
        width: var(--sidebar-collapsed);
    }
    
    .sidebar .sidebar-header span,
    .sidebar-menu li span {
        display: none;
    }
    
    .sidebar-header {
        justify-content: center;
        padding: 20px 10px;
    }
    
    .sidebar-menu li {
        justify-content: center;
        padding: 14px;
    }
    
    .main-content {
        margin-left: var(--sidebar-collapsed);
    }
    
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .video-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .course-content {
        grid-template-columns: 1fr;
    }
    
    .course-sidebar {
        position: static;
        display: grid;
        grid-template-columns: repeat(3, 1fr);
        gap: 20px;
    }
}

/* Large screens (1025px and up) - Full layout */
@media (min-width: 1025px) {
    .course-content {
        grid-template-columns: 1fr 320px;
    }
    
    .video-grid {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .features-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

/* Touch devices - No hover effects */
@media (hover: none) {
    .btn-primary:hover,
    .chip:hover,
    .feature-card:hover,
    .video-card:hover {
        transform: none;
    }
}

/* Landscape phones */
@media (max-height: 500px) and (orientation: landscape) {
    .hero-section {
        padding: 15px;
    }
    
    .hero-section h1 {
        font-size: 20px;
        margin-bottom: 10px;
    }
    
    .hero-section > p {
        display: none;
    }
    
    .features-grid {
        display: none;
    }
}

/* ===== User Profile Styles ===== */
.profile-container {
    position: relative;
}

.profile-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
    border-radius: 50%;
    transition: all var(--transition-fast);
}

.profile-btn:hover {
    background: var(--bg-card);
}

.profile-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-gradient);
    color: white;
    font-weight: 600;
    font-size: 14px;
    overflow: hidden;
}

.profile-avatar.empty {
    background: var(--bg-card);
    border: 2px dashed var(--border-color);
    color: var(--text-muted);
}

.profile-avatar.guest {
    background: var(--bg-card);
    border: 2px solid var(--warning);
    color: var(--warning);
}

.profile-avatar.large {
    width: 56px;
    height: 56px;
    font-size: 18px;
}

.profile-avatar-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.profile-initials {
    font-size: inherit;
}

.profile-dropdown {
    position: absolute;
    top: calc(100% + 10px);
    right: 0;
    width: 280px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: 0 10px 40px var(--shadow-color);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-fast);
    z-index: 1001;
}

.profile-dropdown.active {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.profile-info {
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

.profile-details {
    margin-top: 12px;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.profile-name {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 16px;
}

.profile-email {
    font-size: 13px;
    color: var(--text-secondary);
}

.profile-badge {
    display: inline-block;
    padding: 4px 10px;
    background: var(--accent-primary);
    color: white;
    border-radius: 20px;
    font-size: 11px;
    font-weight: 600;
    margin-top: 6px;
}

.profile-badge.guest {
    background: var(--warning);
}

.profile-message {
    color: var(--text-secondary);
    font-size: 14px;
    line-height: 1.5;
}

.profile-warning {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 16px;
    background: rgba(237, 137, 54, 0.1);
    color: var(--warning);
    font-size: 12px;
    border-bottom: 1px solid var(--border-color);
}

.profile-warning i {
    font-size: 14px;
}

.profile-action {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    width: 100%;
    padding: 14px 20px;
    background: none;
    border: none;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 14px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.profile-action:first-of-type {
    border-top: none;
}

.profile-action:hover {
    background: var(--bg-card);
    color: var(--text-primary);
}

.profile-action.primary {
    background: var(--accent-gradient);
    color: white;
    border-radius: 0 0 var(--border-radius) var(--border-radius);
}

.profile-action.primary:hover {
    opacity: 0.9;
}

/* ===== Auth Modal Styles ===== */
.auth-modal .modal-content {
    max-width: 420px;
}

.auth-modal .modal-header {
    text-align: center;
    padding-bottom: 10px;
}

.auth-modal .modal-header h2 {
    font-size: 24px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.auth-subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 24px;
    font-size: 14px;
}

.auth-error {
    display: none;
    padding: 12px 16px;
    background: rgba(229, 62, 62, 0.1);
    border: 1px solid var(--danger);
    border-radius: var(--border-radius-sm);
    color: var(--danger);
    font-size: 13px;
    margin-bottom: 16px;
    text-align: center;
}

.auth-error.active {
    display: block;
}

.auth-buttons {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.auth-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    width: 100%;
    padding: 14px 20px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    background: var(--bg-card);
    color: var(--text-primary);
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.auth-btn:hover {
    background: var(--bg-card-hover);
    border-color: var(--text-muted);
    transform: translateY(-1px);
}

.auth-btn.google:hover {
    border-color: #4285F4;
    box-shadow: 0 4px 12px rgba(66, 133, 244, 0.2);
}

.auth-btn.microsoft:hover {
    border-color: #00A4EF;
    box-shadow: 0 4px 12px rgba(0, 164, 239, 0.2);
}

.auth-btn.guest {
    background: transparent;
    border-style: dashed;
    color: var(--text-secondary);
}

.auth-btn.guest:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
}

.auth-btn svg,
.auth-btn i {
    flex-shrink: 0;
}

.auth-divider {
    display: flex;
    align-items: center;
    margin: 24px 0;
    color: var(--text-muted);
    font-size: 13px;
}

.auth-divider::before,
.auth-divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--border-color);
}

.auth-divider span {
    padding: 0 16px;
}

.auth-guest-note {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    margin-top: 16px;
    padding: 12px;
    background: rgba(237, 137, 54, 0.1);
    border-radius: var(--border-radius-sm);
    color: var(--warning);
    font-size: 12px;
    line-height: 1.5;
}

.auth-guest-note i {
    margin-top: 2px;
    flex-shrink: 0;
}

/* ===== Auth Notification ===== */
.auth-notification {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 14px 24px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: 0 10px 40px var(--shadow-color);
    color: var(--text-primary);
    font-size: 14px;
    z-index: 2000;
    opacity: 0;
    transition: all 0.3s ease;
}

.auth-notification.active {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
}

.auth-notification.success i {
    color: var(--success);
}

.auth-notification.error i {
    color: var(--danger);
}

/* ===== Print Styles ===== */
@media print {
    .sidebar,
    .header,
    .course-sidebar,
    .video-grid,
    .quiz-section {
        display: none !important;
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .course-content {
        display: block;
    }
}

/* ===== Auth Prompt for My Courses ===== */
.auth-prompt-container {
    display: flex;
    flex-direction: column;
    gap: 30px;
    padding: 20px;
    width: 100%;
    max-width: 600px;
    margin: 0 auto;
}

.auth-prompt {
    background: var(--card-bg);
    border-radius: 16px;
    padding: 40px;
    text-align: center;
    border: 1px solid var(--border-color);
}

.auth-prompt i.fa-user-lock {
    font-size: 48px;
    color: var(--accent);
    margin-bottom: 20px;
}

.auth-prompt h3 {
    color: var(--text-primary);
    margin-bottom: 10px;
    font-size: 1.5rem;
}

.auth-prompt p {
    color: var(--text-secondary);
    margin-bottom: 15px;
}

.auth-prompt-note {
    font-size: 0.85rem;
    color: var(--warning) !important;
    background: rgba(255, 193, 7, 0.1);
    padding: 10px 15px;
    border-radius: 8px;
    margin-bottom: 20px !important;
}

.auth-prompt .btn-primary {
    margin-top: 10px;
}

.session-courses {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 20px;
    border: 1px dashed var(--border-color);
}

.session-courses h4 {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 10px;
}

.session-warning {
    color: var(--warning);
    font-size: 0.8rem;
    margin-bottom: 15px;
}

.session-course-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 15px;
    background: var(--bg-secondary);
    border-radius: 8px;
    margin-bottom: 8px;
    cursor: pointer;
    transition: all 0.2s;
}

.session-course-item:hover {
    background: var(--bg-primary);
    transform: translateX(5px);
}

.session-course-item span:first-child {
    color: var(--text-primary);
}

.session-course-item span:last-child {
    color: var(--accent);
    font-weight: 600;
}
/* ===== Additional Responsive for Auth Prompt ===== */
@media (max-width: 480px) {
    .auth-prompt-container {
        padding: 15px;
        gap: 20px;
    }
    
    .auth-prompt {
        padding: 25px 20px;
    }
    
    .auth-prompt i.fa-user-lock {
        font-size: 36px;
    }
    
    .auth-prompt h3 {
        font-size: 1.2rem;
    }
    
    .auth-prompt p {
        font-size: 0.9rem;
    }
    
    .session-courses {
        padding: 15px;
    }
    
    .session-course-item {
        padding: 10px 12px;
        flex-direction: column;
        align-items: flex-start;
        gap: 5px;
    }
    
    .session-course-item:hover {
        transform: none;
    }
}

/* =================================================================
   LEARNING BATTLES — 1v1 Quiz Challenges
   ================================================================= */

/* Battle Page Layout */
#battlePage.active {
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 80vh;
    padding: 40px 20px;
}

.battle-state {
    width: 100%;
    max-width: 700px;
    margin: 0 auto;
    animation: battleFadeIn 0.5s ease;
}

.battle-state.hidden {
    display: none;
}

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

/* Challenge Landing Card */
.battle-challenge-card {
    text-align: center;
    padding: 60px 40px;
    background: var(--card-bg);
    border-radius: 24px;
    border: 1px solid rgba(0, 212, 170, 0.2);
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

.battle-icon {
    font-size: 64px;
    margin-bottom: 20px;
    animation: battlePulse 2s ease-in-out infinite;
}

@keyframes battlePulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.15); }
}

.battle-challenge-card h1 {
    font-size: 2rem;
    margin-bottom: 20px;
}

.battle-challenger-info {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.battle-challenger-name {
    font-weight: 700;
    color: var(--primary);
}

.battle-topic-badge {
    display: inline-block;
    padding: 12px 28px;
    background: linear-gradient(135deg, rgba(0, 212, 170, 0.15), rgba(0, 212, 170, 0.05));
    border: 1px solid rgba(0, 212, 170, 0.3);
    border-radius: 50px;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary);
    margin: 15px 0 30px;
}

.battle-name-input {
    max-width: 350px;
    margin: 0 auto 25px;
}

.battle-name-input label {
    display: block;
    margin-bottom: 10px;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.battle-name-input input {
    width: 100%;
    padding: 14px 20px;
    border-radius: 12px;
    border: 2px solid var(--border);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 1rem;
    text-align: center;
    transition: border-color 0.3s;
    box-sizing: border-box;
}

.battle-name-input input:focus {
    outline: none;
    border-color: var(--primary);
}

.battle-accept-btn {
    font-size: 1.1rem;
    padding: 16px 40px;
    border-radius: 14px;
}

/* Shake animation for empty name */
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-8px); }
    75% { transform: translateX(8px); }
}

.shake {
    animation: shake 0.4s ease;
    border-color: #ff4444 !important;
}

/* Battle Quiz */
.battle-quiz-header {
    text-align: center;
    margin-bottom: 30px;
}

.battle-timer {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 8px;
}

#battleQuizTopic {
    color: var(--text-secondary);
    font-size: 1rem;
}

.battle-quiz-question {
    background: var(--card-bg);
    border-radius: 16px;
    padding: 24px;
    margin-bottom: 20px;
    border: 1px solid var(--border);
}

.battle-quiz-question h4 {
    margin-bottom: 16px;
    font-size: 1.05rem;
    line-height: 1.5;
}

.battle-quiz-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.battle-quiz-option {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 18px;
    border-radius: 12px;
    border: 2px solid var(--border);
    cursor: pointer;
    transition: all 0.2s;
    background: var(--bg-secondary);
}

.battle-quiz-option:hover {
    border-color: var(--primary);
    background: rgba(0, 212, 170, 0.05);
}

.battle-quiz-option.selected {
    border-color: var(--primary);
    background: rgba(0, 212, 170, 0.1);
}

.battle-quiz-option.correct {
    border-color: #4caf50;
    background: rgba(76, 175, 80, 0.1);
}

.battle-quiz-option.incorrect {
    border-color: #f44336;
    background: rgba(244, 67, 54, 0.1);
}

.battle-quiz-option input[type="radio"] {
    display: none;
}

.battle-quiz-option .option-marker {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    background: var(--border);
    font-weight: 700;
    font-size: 0.85rem;
    flex-shrink: 0;
}

.battle-submit-btn {
    display: block;
    margin: 30px auto 0;
    font-size: 1.1rem;
    padding: 16px 40px;
}

/* Battle Results */
.battle-results-card {
    text-align: center;
    padding: 50px 30px;
}

.battle-results-header h1 {
    font-size: 2rem;
    margin-bottom: 10px;
}

.battle-results-topic {
    color: var(--text-secondary);
    font-size: 1.1rem;
    margin-bottom: 40px;
}

/* Scoreboard */
.battle-scoreboard {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 30px;
    margin-bottom: 40px;
}

.battle-player {
    flex: 1;
    max-width: 220px;
    padding: 30px 20px;
    background: var(--card-bg);
    border-radius: 20px;
    border: 2px solid var(--border);
    transition: all 0.5s;
}

.battle-player.winner {
    border-color: var(--primary);
    box-shadow: 0 0 30px rgba(0, 212, 170, 0.2);
    transform: scale(1.05);
}

.battle-player-avatar {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background: var(--bg-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 15px;
    font-size: 1.5rem;
    color: var(--text-secondary);
}

.battle-player.winner .battle-player-avatar {
    background: linear-gradient(135deg, rgba(0, 212, 170, 0.2), rgba(0, 212, 170, 0.05));
    color: var(--primary);
}

.battle-player-name {
    font-weight: 700;
    font-size: 1.1rem;
    margin-bottom: 10px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.battle-player-score {
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--primary), #00f5d4);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.battle-player-label {
    margin-top: 8px;
    font-size: 0.9rem;
    min-height: 24px;
}

.battle-vs {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--text-secondary);
    padding: 10px;
    flex-shrink: 0;
}

/* Battle Results CTA */
.battle-results-cta {
    margin-top: 30px;
    padding-top: 30px;
    border-top: 1px solid var(--border);
}

.battle-results-cta p {
    color: var(--text-secondary);
    margin-bottom: 15px;
    font-size: 1.05rem;
}

/* Battle Error */
.battle-error-card {
    text-align: center;
    padding: 60px 40px;
    background: var(--card-bg);
    border-radius: 24px;
    border: 1px solid var(--border);
}

.battle-error-card i {
    font-size: 48px;
    color: #ff6b6b;
    margin-bottom: 20px;
}

.battle-error-card h2 {
    margin-bottom: 10px;
}

.battle-error-card p {
    color: var(--text-secondary);
    margin-bottom: 25px;
}

/* Challenge Button in Quiz Results */
.quiz-results-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
    margin-top: 15px;
}

.btn-battle {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 14px 28px;
    background: linear-gradient(135deg, #ff6b35, #ff4444);
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
}

.btn-battle:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(255, 107, 53, 0.3);
}

.btn-battle:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

/* Battle Share Modal */
.battle-share-modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 10000;
    opacity: 0;
    transition: opacity 0.3s;
    padding: 20px;
}

.battle-share-modal.active {
    opacity: 1;
}

.battle-share-content {
    background: var(--card-bg);
    border-radius: 24px;
    padding: 40px;
    max-width: 500px;
    width: 100%;
    position: relative;
    animation: battleSlideUp 0.4s ease;
}

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

.battle-share-close {
    position: absolute;
    top: 15px;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1.2rem;
    cursor: pointer;
    padding: 8px;
}

.battle-share-header {
    text-align: center;
    margin-bottom: 25px;
}

.battle-share-icon {
    font-size: 48px;
    margin-bottom: 10px;
}

.battle-share-header h2 {
    font-size: 1.5rem;
    margin-bottom: 8px;
}

.battle-share-header p {
    color: var(--text-secondary);
}

.battle-share-link {
    display: flex;
    gap: 10px;
    margin-bottom: 25px;
}

.battle-share-link input {
    flex: 1;
    padding: 12px 16px;
    border-radius: 12px;
    border: 2px solid var(--border);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.9rem;
}

.battle-share-link .btn-primary {
    white-space: nowrap;
}

.battle-share-buttons {
    display: flex;
    gap: 10px;
    justify-content: center;
}

.battle-share-btn {
    flex: 1;
    padding: 12px;
    border-radius: 12px;
    border: none;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    transition: transform 0.2s, opacity 0.2s;
    color: #fff;
}

.battle-share-btn:hover {
    transform: translateY(-2px);
    opacity: 0.9;
}

.battle-share-btn.whatsapp { background: #25D366; }
.battle-share-btn.twitter { background: #1DA1F2; }
.battle-share-btn.linkedin { background: #0077B5; }

/* Battle Responsive */
@media (max-width: 768px) {
    #battlePage {
        padding: 20px 15px;
    }

    .battle-challenge-card {
        padding: 40px 24px;
    }

    .battle-challenge-card h1 {
        font-size: 1.5rem;
    }

    .battle-topic-badge {
        font-size: 1rem;
        padding: 10px 20px;
    }

    .battle-scoreboard {
        flex-direction: column;
        gap: 15px;
    }

    .battle-player {
        max-width: 100%;
        width: 100%;
    }

    .battle-vs {
        transform: rotate(90deg);
        padding: 5px;
    }

    .battle-share-buttons {
        flex-direction: column;
    }

    .battle-share-content {
        padding: 30px 20px;
    }

    .quiz-results-actions {
        flex-direction: column;
        align-items: center;
    }
}

@media (max-width: 480px) {
    .battle-challenge-card {
        padding: 30px 16px;
    }

    .battle-icon {
        font-size: 48px;
    }

    .battle-player-score {
        font-size: 2rem;
    }
}

/* =================================================================
   STUDY DUO — Learn Together Feature
   ================================================================= */

/* Duo Page Layout */
#duoPage.active {
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 80vh;
    padding: 40px 20px;
}

.duo-state {
    width: 100%;
    max-width: 650px;
    margin: 0 auto;
    animation: battleFadeIn 0.5s ease;
}

.duo-state.hidden { display: none; }

/* Duo Loading */
.duo-loading-card {
    text-align: center;
    padding: 60px;
    color: var(--text-secondary);
}

/* Duo Landing Card */
.duo-landing-card {
    text-align: center;
    padding: 50px 40px;
    background: var(--card-bg);
    border-radius: 24px;
    border: 1px solid rgba(0, 212, 170, 0.2);
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

.duo-icon {
    font-size: 64px;
    margin-bottom: 15px;
}

.duo-landing-card h1 {
    font-size: 2rem;
    margin-bottom: 15px;
}

.duo-invite-info {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.duo-creator-name {
    font-weight: 700;
    color: var(--primary);
}

.duo-topic-badge {
    display: inline-block;
    padding: 12px 28px;
    background: linear-gradient(135deg, rgba(0, 212, 170, 0.15), rgba(0, 212, 170, 0.05));
    border: 1px solid rgba(0, 212, 170, 0.3);
    border-radius: 50px;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary);
    margin: 10px 0 25px;
}

/* Duo Perks */
.duo-perks {
    display: flex;
    gap: 15px;
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: 30px;
}

.duo-perk {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    background: var(--bg-secondary);
    border-radius: 10px;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.duo-perk i {
    color: var(--primary);
}

/* Duo Name Input */
.duo-name-input {
    max-width: 350px;
    margin: 0 auto 25px;
}

.duo-name-input label {
    display: block;
    margin-bottom: 10px;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.duo-name-input input {
    width: 100%;
    padding: 14px 20px;
    border-radius: 12px;
    border: 2px solid var(--border);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 1rem;
    text-align: center;
    transition: border-color 0.3s;
    box-sizing: border-box;
}

.duo-name-input input:focus {
    outline: none;
    border-color: var(--primary);
}

.duo-join-btn {
    font-size: 1.1rem;
    padding: 16px 40px;
    border-radius: 14px;
}

/* Duo Error */
.duo-error-card {
    text-align: center;
    padding: 60px 40px;
    background: var(--card-bg);
    border-radius: 24px;
    border: 1px solid var(--border);
}

.duo-error-card i {
    font-size: 48px;
    color: #ff6b6b;
    margin-bottom: 20px;
}

.duo-error-card h2 { margin-bottom: 10px; }
.duo-error-card p { color: var(--text-secondary); margin-bottom: 25px; }

/* Duo Banner (shown on course page during duo session) */
.duo-banner {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 24px;
    background: linear-gradient(135deg, rgba(0, 212, 170, 0.12), rgba(0, 212, 170, 0.04));
    border: 1px solid rgba(0, 212, 170, 0.25);
    border-radius: 14px;
    margin: 0 30px 20px;
    font-size: 0.95rem;
    color: var(--text-primary);
    animation: battleFadeIn 0.5s ease;
}

.duo-banner i {
    font-size: 1.3rem;
    color: var(--primary);
    flex-shrink: 0;
}

/* Duo Battle-Ready / Waiting Banner */
.duo-battle-banner {
    margin: 0 30px 20px;
    animation: battleFadeIn 0.5s ease;
}

.duo-battle-inner {
    display: flex;
    align-items: center;
    gap: 15px;
    padding: 16px 24px;
    background: linear-gradient(135deg, rgba(255, 107, 53, 0.12), rgba(255, 68, 68, 0.06));
    border: 1px solid rgba(255, 107, 53, 0.3);
    border-radius: 14px;
}

.duo-battle-banner.waiting .duo-battle-inner {
    background: linear-gradient(135deg, rgba(0, 212, 170, 0.1), rgba(0, 212, 170, 0.03));
    border-color: rgba(0, 212, 170, 0.25);
}

.duo-battle-icon {
    font-size: 1.8rem;
    flex-shrink: 0;
}

.duo-battle-text {
    flex: 1;
}

.duo-battle-text strong {
    display: block;
    font-size: 1.05rem;
    margin-bottom: 3px;
}

.duo-battle-text span {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.duo-battle-inner .btn-primary {
    white-space: nowrap;
    flex-shrink: 0;
}

/* Duo Sidebar Card (invite buddy button on course page) */
.duo-sidebar-card {
    text-align: center;
}

.btn-duo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    width: 100%;
    padding: 14px;
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    margin-bottom: 10px;
}

.btn-duo:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
}

.btn-duo:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.duo-sidebar-hint {
    font-size: 0.8rem;
    color: var(--text-secondary);
    line-height: 1.4;
}

/* Duo Share Modal (reuses battle share styling) */
.duo-share-modal {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 10000;
    opacity: 0;
    transition: opacity 0.3s;
    padding: 20px;
}

.duo-share-modal.active { opacity: 1; }

.duo-share-content {
    background: var(--card-bg);
    border-radius: 24px;
    padding: 40px;
    max-width: 500px;
    width: 100%;
    position: relative;
    animation: battleSlideUp 0.4s ease;
}

.duo-share-close {
    position: absolute;
    top: 15px; right: 15px;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1.2rem;
    cursor: pointer;
    padding: 8px;
}

.duo-share-header {
    text-align: center;
    margin-bottom: 25px;
}

.duo-share-icon { font-size: 48px; margin-bottom: 10px; }
.duo-share-header h2 { font-size: 1.5rem; margin-bottom: 8px; }
.duo-share-header p { color: var(--text-secondary); }

.duo-share-link {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.duo-share-link input {
    flex: 1;
    padding: 12px 16px;
    border-radius: 12px;
    border: 2px solid var(--border);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.9rem;
}

.duo-share-buttons {
    display: flex;
    gap: 10px;
    justify-content: center;
    margin-bottom: 20px;
}

.duo-share-btn {
    flex: 1;
    padding: 12px;
    border-radius: 12px;
    border: none;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    transition: transform 0.2s;
    color: #fff;
}

.duo-share-btn:hover { transform: translateY(-2px); }
.duo-share-btn.whatsapp { background: #25D366; }
.duo-share-btn.twitter { background: #1DA1F2; }
.duo-share-btn.linkedin { background: #0077B5; }

.duo-share-note {
    text-align: center;
    font-size: 0.85rem;
    color: var(--text-secondary);
    padding: 14px;
    background: var(--bg-secondary);
    border-radius: 10px;
}

.duo-share-note i {
    color: var(--primary);
    margin-right: 6px;
}

/* Duo Responsive */
@media (max-width: 768px) {
    #duoPage.active { padding: 20px 15px; }
    .duo-landing-card { padding: 35px 20px; }
    .duo-landing-card h1 { font-size: 1.5rem; }
    .duo-perks { flex-direction: column; align-items: center; }
    .duo-share-buttons { flex-direction: column; }
    .duo-share-content { padding: 30px 20px; }
    .duo-banner { margin: 0 15px 15px; padding: 12px 16px; font-size: 0.9rem; }
    .duo-battle-banner { margin: 0 15px 15px; }
    .duo-battle-inner { flex-direction: column; text-align: center; }
}

@media (max-width: 480px) {
    .duo-landing-card { padding: 25px 16px; }
    .duo-topic-badge { font-size: 1rem; padding: 10px 20px; }
}