/**
 * HSK Vocabulary Learning System - Dual Theme (Dark/Light)
 * Gaming-inspired design with theme toggle support
 * Default: Dark Theme | Add class "light-theme" for Light Theme
 */

html {
    height: 100vh;
    background: black;
}

/* ========================================
   Fullscreen / Auto-hide Header Mode
   ======================================== */
/* When body has fullscreen-mode class, hide header */
body.fullscreen-mode #header-container,
body.fullscreen-mode #header-container header,
body.fullscreen-mode > .header,
html.fullscreen-mode #header-container {
    transform: translateY(-100%) !important;
    transition: transform 0.3s ease !important;
    position: fixed !important;
    top: 0 !important;
    left: 0 !important;
    right: 0 !important;
    z-index: 9999 !important;
}

body.fullscreen-mode #header-container:hover,
body.fullscreen-mode #header-container:hover header,
body.fullscreen-mode > .header:hover,
html.fullscreen-mode #header-container:hover,
body.fullscreen-mode #header-container.visible,
body.fullscreen-mode #header-container.visible header,
html.fullscreen-mode #header-container.visible {
    transform: translateY(0) !important;
}

/* Invisible hover trigger area at top */
.fullscreen-hover-trigger {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 15px;
    z-index: 10000;
    background: transparent;
    display: none;
}

body.fullscreen-mode .fullscreen-hover-trigger {
    display: block;
}

body.fullscreen-mode .main-content,
body.fullscreen-mode .vocabulary-app {
    padding-top: 0 !important;
    margin-top: 0 !important;
}

/* Show header indicator when hidden */
.fullscreen-header-indicator {
    position: fixed;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    background: linear-gradient(135deg, rgba(0, 240, 255, 0.2), rgba(0, 255, 136, 0.2));
    padding: 4px 20px;
    border-radius: 0 0 12px 12px;
    font-size: 0.75rem;
    color: #94a3b8;
    z-index: 9998;
    cursor: pointer;
    transition: all 0.3s ease;
    opacity: 0;
    pointer-events: none;
}

.vocabulary-app.fullscreen-mode .fullscreen-header-indicator {
    opacity: 1;
    pointer-events: auto;
}

.vocabulary-app.fullscreen-mode .fullscreen-header-indicator:hover {
    background: linear-gradient(135deg, rgba(0, 240, 255, 0.4), rgba(0, 255, 136, 0.4));
    color: #f1f5f9;
}

/* ========================================
   CSS Variables - Dark Theme (Default)
   ======================================== */
:root {
    /* Dark Theme Colors */
    --vg-bg-primary: #0a0e17;
    --vg-bg-secondary: #111827;
    --vg-bg-tertiary: #1a2332;
    --vg-bg-card: rgba(17, 24, 39, 0.95);
    --vg-bg-card-hover: rgba(30, 41, 59, 0.98);
    
    /* Accent Colors */
    --vg-accent-cyan: #00f0ff;
    --vg-accent-green: #00ff88;
    --vg-accent-blue: #0ea5e9;
    --vg-accent-red: #ef4444;
    --vg-accent-orange: #ff6600;
    --vg-accent-yellow: #ffee00;
    
    /* Gradient Accents */
    --vg-gradient-primary: linear-gradient(135deg, #00f0ff 0%, #0ea5e9 100%);
    --vg-gradient-success: linear-gradient(135deg, #00ff88 0%, #00cc6a 100%);
    --vg-gradient-warning: linear-gradient(135deg, #ffee00 0%, #ff9900 100%);
    --vg-gradient-danger: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
    --vg-gradient-card: linear-gradient(145deg, rgba(17, 24, 39, 0.9) 0%, rgba(30, 41, 59, 0.7) 100%);
    
    /* Text Colors */
    --vg-text-primary: #f1f5f9;
    --vg-text-secondary: #cbd5e1;
    --vg-text-muted: #94a3b8;
    --vg-text-accent: #00f0ff;
    
    /* Glow Effects */
    --vg-glow-primary: 0 0 20px rgba(0, 240, 255, 0.5), 0 0 40px rgba(0, 240, 255, 0.3);
    --vg-glow-success: 0 0 20px rgba(0, 255, 136, 0.5), 0 0 40px rgba(0, 255, 136, 0.3);
    
    /* Borders */
    --vg-border-color: rgba(100, 116, 139, 0.3);
    --vg-border-glow: rgba(0, 240, 255, 0.3);
    
    /* Spacing */
    --vg-space-1: 0.25rem;
    --vg-space-2: 0.5rem;
    --vg-space-3: 0.75rem;
    --vg-space-4: 1rem;
    --vg-space-5: 1.25rem;
    --vg-space-6: 1.5rem;
    --vg-space-8: 2rem;
    --vg-space-10: 2.5rem;
    --vg-space-12: 3rem;
    
    /* Border Radius */
    --vg-radius-sm: 0.5rem;
    --vg-radius-md: 0.75rem;
    --vg-radius-lg: 1rem;
    --vg-radius-xl: 1.5rem;
    --vg-radius-2xl: 2rem;
    --vg-radius-full: 9999px;
    
    /* Transitions */
    --vg-transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --vg-transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --vg-transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    --vg-transition-bounce: 0.6s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    
    /* Header */
    --vg-header-height: 72px;
}

/* ========================================
   Light Theme Override
   ======================================== */
.vocabulary-app.light-theme {
    --vg-bg-primary: #ffffff;
    --vg-bg-secondary: #f8fafc;
    --vg-bg-tertiary: #f1f5f9;
    --vg-bg-card: rgba(255, 255, 255, 0.95);
    --vg-bg-card-hover: rgba(248, 250, 252, 0.98);
    
    --vg-gradient-primary: linear-gradient(135deg, #0ea5e9 0%, #10b981 100%);
    --vg-gradient-card: linear-gradient(145deg, rgba(255, 255, 255, 0.95) 0%, rgba(248, 250, 252, 0.9) 100%);
    
    --vg-text-primary: #1e293b;
    --vg-text-secondary: #475569;
    --vg-text-muted: #64748b;
    --vg-text-accent: #0ea5e9;
    
    --vg-glow-primary: 0 4px 14px rgba(14, 165, 233, 0.25);
    --vg-glow-success: 0 4px 14px rgba(16, 185, 129, 0.25);
    
    --vg-border-color: rgba(226, 232, 240, 0.8);
    --vg-border-glow: rgba(14, 165, 233, 0.3);
}

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

/* Prevent pseudo-elements from blocking clicks */
.vocabulary-app *::before,
.vocabulary-app *::after {
    pointer-events: none;
}

/* Vocabulary App Container - Uses CSS Variables */
.vocabulary-app {
    background: var(--vg-bg-primary) !important;
    color: var(--vg-text-primary) !important;
    min-height: 100vh;
    transition: background 0.3s ease, color 0.3s ease;
}

/* Light Theme Background Gradient */
.vocabulary-app.light-theme {
    background: linear-gradient(135deg, #ffffff 0%, #f0f9ff 50%, #f0fdf4 100%) !important;
}

.vocabulary-app * {
    color: inherit;
}

.vocabulary-app h1, 
.vocabulary-app h2, 
.vocabulary-app h3, 
.vocabulary-app h4, 
.vocabulary-app h5, 
.vocabulary-app h6 {
    color: #f1f5f9 !important;
}

.vocabulary-app p,
.vocabulary-app span,
.vocabulary-app div,
.vocabulary-app label {
    color: inherit;
}

.vocabulary-app a {
    color: #00f0ff;
}

/* Input and form elements */
.vocabulary-app input, 
.vocabulary-app textarea, 
.vocabulary-app select, 
.vocabulary-app button {
    color: #f1f5f9;
    background-color: #1a2332;
    border: 1px solid rgba(100, 116, 139, 0.3);
}

.vocabulary-app input::placeholder, 
.vocabulary-app textarea::placeholder {
    color: #94a3b8;
}

html {
    font-family: 'Inter', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
    font-size: 16px;
    scroll-behavior: smooth;
}

/* Animated Background Pattern - Light Theme */
body::before {
    content: '';
    position: fixed;
    inset: 0;
    background: 
        linear-gradient(rgba(0, 240, 255, 0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(0, 255, 136, 0.03) 1px, transparent 1px);
    background-size: 60px 60px;
    pointer-events: none;
    z-index: -1;
}

/* Colorful Gradient Orbs */
body::after {
    content: '';
    position: fixed;
    inset: 0;
    background: 
        radial-gradient(circle at 10% 20%, rgba(0, 240, 255, 0.08) 0%, transparent 35%),
        radial-gradient(circle at 90% 80%, rgba(0, 255, 136, 0.08) 0%, transparent 35%),
        radial-gradient(circle at 50% 50%, rgba(239, 68, 68, 0.05) 0%, transparent 40%);
    pointer-events: none;
    z-index: -1;
}

/* ========================================
   Main Layout
   ======================================== */
.main {
    min-height: 100dvh;
    padding-top: var(--vg-header-height);
    display: flex;
    flex-direction: column;
}

.hidden {
    display: none !important;
}

/* ========================================
   Loading Overlay - Gaming Style
   ======================================== */
.loading-overlay {
    position: fixed;
    inset: 0;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(20px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9999;
    transition: opacity var(--vg-transition-normal);
}

.loading-overlay.hidden {
    opacity: 0;
    pointer-events: none;
}

.loading-spinner {
    text-align: center;
    padding: var(--vg-space-8);
    background: var(--vg-gradient-card);
    border: 1px solid var(--vg-border-glow);
    border-radius: var(--vg-radius-xl);
    box-shadow: var(--vg-glow-cyan);
}

.loading-spinner i {
    font-size: 3rem;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    animation: spinGlow 1s linear infinite;
}

.loading-spinner p {
    color: var(--vg-text-secondary);
    font-weight: 500;
    margin-top: var(--vg-space-4);
    text-transform: uppercase;
    letter-spacing: 2px;
    font-size: 0.85rem;
}

@keyframes spinGlow {
    0% { transform: rotate(0deg); filter: drop-shadow(0 0 10px var(--vg-neon-cyan)); }
    50% { filter: drop-shadow(0 4px 14px var(--vg-neon-purple)); }
    100% { transform: rotate(360deg); filter: drop-shadow(0 0 10px var(--vg-neon-cyan)); }
}

/* ========================================
   System Selection Screen - Gaming UI
   ======================================== */
.system-selection-screen {
    min-height: calc(100vh - var(--vg-header-height));
    padding: var(--vg-space-6) var(--vg-space-4);
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
}

/* Selection Header */
.selection-header {
    text-align: center;
    margin-bottom: var(--vg-space-8);
    position: relative;
    z-index: 1;
    background: var(--vg-gradient-card);
    border: 1px solid var(--vg-border-glow);
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-6) var(--vg-space-8);
    box-shadow: var(--vg-glow-cyan);
    max-width: 600px;
    width: 100%;
}

.header-icon {
    width: 80px;
    height: 80px;
    background: var(--vg-gradient-primary);
    border-radius: var(--vg-radius-xl);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--vg-space-4);
    box-shadow: var(--vg-glow-cyan);
    animation: iconPulse 2s ease-in-out infinite;
    position: relative;
}

.header-icon::before {
    content: '';
    position: absolute;
    inset: -4px;
    background: var(--vg-gradient-primary);
    border-radius: var(--vg-radius-xl);
    opacity: 0.3;
    filter: blur(10px);
    animation: iconGlow 2s ease-in-out infinite alternate;
}

.header-icon i {
    font-size: 2rem;
    color: var(--vg-bg-primary);
    position: relative;
    z-index: 1;
}

@keyframes iconPulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.05); }
}

@keyframes iconGlow {
    0% { opacity: 0.3; transform: scale(1); }
    100% { opacity: 0.6; transform: scale(1.1); }
}

.selection-header h1 {
    font-size: clamp(1.5rem, 4vw, 2rem);
    font-weight: 800;
    margin-bottom: var(--vg-space-2);
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-transform: uppercase;
    letter-spacing: 2px;
}

.selection-header p {
    color: var(--vg-text-secondary);
    font-size: 1rem;
}

/* System Cards Container */
.system-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--vg-space-6);
    max-width: 900px;
    width: 100%;
}

/* System Card - Gaming Style */
.system-card {
    background: rgba(17, 24, 39, 0.95) !important;
    border: 2px solid rgba(0, 240, 255, 0.2);
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-6);
    cursor: pointer;
    transition: all var(--vg-transition-normal);
    position: relative;
    overflow: hidden;
    min-height: 280px;
    display: flex;
    flex-direction: column;
    color: #f1f5f9 !important;
}

.system-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--vg-gradient-primary);
    opacity: 0;
    transition: opacity var(--vg-transition-normal);
    z-index: 0;
}

.system-card::after {
    content: '';
    position: absolute;
    inset: 0;
    border-radius: var(--vg-radius-xl);
    padding: 2px;
    background: var(--vg-gradient-primary);
    mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
    mask-composite: exclude;
    opacity: 0.5;
    transition: opacity var(--vg-transition-normal);
}

.system-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: var(--vg-glow-cyan);
}

.system-card:hover::before {
    opacity: 0.05;
}

.system-card:hover::after {
    opacity: 1;
}

/* System Card Header */
.system-card-header {
    display: flex;
    align-items: center;
    gap: var(--vg-space-4);
    margin-bottom: var(--vg-space-4);
    position: relative;
    z-index: 1;
}

.system-icon {
    width: 60px;
    height: 60px;
    border-radius: var(--vg-radius-lg);
    background: var(--vg-bg-tertiary);
    border: 2px solid var(--vg-border-glow);
    padding: 8px;
    box-shadow: var(--vg-glow-cyan);
    transition: all var(--vg-transition-normal);
}

.system-card:hover .system-icon {
    transform: rotate(5deg) scale(1.1);
    box-shadow: var(--vg-glow-purple);
}

/* System Logo Wrapper - NEW */
.system-logo-wrap {
    width: 100%;
    height: 140px;
    border-radius: var(--vg-radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--vg-space-4);
    position: relative;
    z-index: 1;
    overflow: hidden;
}

.system-logo {
    max-width: 80%;
    max-height: 100px;
    object-fit: contain;
    filter: drop-shadow(0 4px 12px rgba(0,0,0,0.3));
    transition: all var(--vg-transition-normal);
}

.system-card:hover .system-logo {
    transform: scale(1.08);
}

.hsk-logo {
    border-radius: var(--vg-radius-md);
}

.tocfl-logo {
    max-height: 90px;
}

/* System Badge */
.system-badge {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: #fff;
    margin-bottom: var(--vg-space-2);
}

/* Select System Button */
.btn-select-system {
    width: 100%;
    padding: var(--vg-space-3) var(--vg-space-4);
    background: var(--vg-gradient-primary);
    border: none;
    border-radius: var(--vg-radius-md);
    color: var(--vg-bg-primary);
    font-weight: 700;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all var(--vg-transition-normal);
    position: relative;
    z-index: 1;
    margin-top: auto;
}

.btn-select-system:hover {
    transform: translateY(-2px);
    box-shadow: var(--vg-glow-cyan);
}

.system-card.system-hsk .btn-select-system {
    background: linear-gradient(135deg, #DC2626, #EF4444);
}

.system-card.system-hsk:hover {
    box-shadow: 0 0 30px rgba(220, 38, 38, 0.4);
}

.system-card.system-tocfl .btn-select-system {
    background: linear-gradient(135deg, #7C3AED, #A855F7);
}

.system-card.system-tocfl:hover {
    box-shadow: 0 0 30px rgba(124, 58, 237, 0.4);
}

.system-info h3 {
    font-size: 1.5rem;
    font-weight: 800;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: var(--vg-space-1);
}

.system-info {
    text-align: center;
    margin-bottom: var(--vg-space-4);
    position: relative;
    z-index: 1;
}

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

/* System Features */
.system-features {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--vg-space-2);
    margin-bottom: var(--vg-space-4);
    flex: 1;
    position: relative;
    z-index: 1;
}

.feature {
    display: flex;
    align-items: center;
    gap: var(--vg-space-2);
    padding: var(--vg-space-2) var(--vg-space-3);
    background: rgba(0, 240, 255, 0.05);
    border: 1px solid rgba(0, 240, 255, 0.2);
    border-radius: var(--vg-radius-sm);
    color: var(--vg-text-secondary);
    font-size: 0.8rem;
    transition: all var(--vg-transition-fast);
}

.feature:hover {
    background: rgba(0, 240, 255, 0.1);
    border-color: var(--vg-neon-cyan);
    color: var(--vg-neon-cyan);
}

.feature i {
    width: 18px;
    height: 18px;
    background: var(--vg-gradient-success);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.6rem;
    color: var(--vg-bg-primary);
    flex-shrink: 0;
}

/* System Stats */
.system-stats {
    display: flex;
    justify-content: space-between;
    padding: var(--vg-space-4);
    background: rgba(0, 0, 0, 0.05);
    border-radius: var(--vg-radius-lg);
    border: 1px solid var(--vg-border-color);
    position: relative;
    z-index: 1;
}

.stat {
    text-align: center;
    flex: 1;
}

.stat strong {
    display: block;
    font-size: 1.2rem;
    font-weight: 800;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: var(--vg-space-1);
}

.stat span:not(strong) {
    color: var(--vg-text-muted);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* ========================================
   Level Selection Screen
   ======================================== */
.level-selection-screen {
    min-height: calc(100vh - var(--vg-header-height));
    padding: var(--vg-space-6) var(--vg-space-4);
    display: flex;
    flex-direction: column;
}

.level-header {
    background: var(--vg-gradient-card);
    border: 1px solid var(--vg-border-glow);
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-5);
    margin-bottom: var(--vg-space-6);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: var(--vg-space-4);
    box-shadow: var(--vg-glow-cyan);
}

.selected-system-info {
    display: flex;
    align-items: center;
    gap: var(--vg-space-4);
}

.selected-logo-wrap {
    width: 56px;
    height: 56px;
    border-radius: var(--vg-radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.selected-logo-wrap img {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
}

.selected-icon {
    width: 56px;
    height: 56px;
    border-radius: var(--vg-radius-lg);
    border: 2px solid var(--vg-border-glow);
    padding: 6px;
    background: var(--vg-bg-tertiary);
}

.selected-system-info h2 {
    font-size: 1.5rem;
    font-weight: 700;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.selected-system-info p {
    color: var(--vg-text-secondary);
    font-size: 0.9rem;
}

/* Level Cards Grid */
.level-cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--vg-space-4);
    max-width: 1000px;
    margin: 0 auto;
    flex: 1;
}

/* Level Card - Gaming Style */
.level-card {
    background: var(--vg-gradient-card);
    border: 2px solid transparent;
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-5);
    cursor: pointer;
    transition: all var(--vg-transition-bounce);
    text-align: center;
    position: relative;
    overflow: hidden;
}

.level-card::after {
    content: '';
    position: absolute;
    inset: 0;
    border-radius: var(--vg-radius-xl);
    padding: 2px;
    background: var(--vg-gradient-primary);
    mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
    mask-composite: exclude;
    opacity: 0.3;
    transition: opacity var(--vg-transition-normal);
}

.level-card:hover {
    transform: translateY(-10px) scale(1.05);
    box-shadow: var(--vg-glow-purple);
}

.level-card:hover::after {
    opacity: 1;
}

.level-card:nth-child(1):hover { box-shadow: 0 6px 16px rgba(0, 255, 136, 0.5); }
.level-card:nth-child(2):hover { box-shadow: 0 6px 16px rgba(0, 240, 255, 0.5); }
.level-card:nth-child(3):hover { box-shadow: 0 6px 16px rgba(0, 255, 136, 0.5); }
.level-card:nth-child(4):hover { box-shadow: 0 6px 16px rgba(239, 68, 68, 0.5); }
.level-card:nth-child(5):hover { box-shadow: 0 6px 16px rgba(255, 238, 0, 0.5); }
.level-card:nth-child(6):hover { box-shadow: 0 6px 16px rgba(255, 102, 0, 0.5); }

/* Version Selector Container */
.version-selector-container {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
}

.version-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--vg-text-primary);
    margin-bottom: var(--vg-space-6);
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.version-cards {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--vg-space-6);
}

.version-card {
    background: var(--vg-gradient-card);
    border: 2px solid rgba(0, 240, 255, 0.2);
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-6);
    cursor: pointer;
    transition: all var(--vg-transition-bounce);
    text-align: center;
    position: relative;
    overflow: hidden;
}

.version-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--vg-gradient-primary);
    opacity: 0;
    transition: opacity var(--vg-transition-normal);
    z-index: 0;
}

.version-card:hover {
    transform: translateY(-8px) scale(1.02);
}

.version-card:hover::before {
    opacity: 0.05;
}

.version-card.version-hsk2 {
    border-color: rgba(220, 38, 38, 0.3);
}

.version-card.version-hsk2:hover {
    box-shadow: 0 0 30px rgba(220, 38, 38, 0.4);
}

.version-card.version-hsk3 {
    border-color: rgba(124, 58, 237, 0.3);
}

.version-card.version-hsk3:hover {
    box-shadow: 0 0 30px rgba(124, 58, 237, 0.4);
}

.version-badge {
    display: inline-block;
    padding: 12px 28px;
    font-size: 1.5rem;
    font-weight: 800;
    border-radius: var(--vg-radius-lg);
    margin-bottom: var(--vg-space-4);
    position: relative;
    z-index: 1;
}

.version-hsk2 .version-badge {
    background: linear-gradient(135deg, #DC2626, #EF4444);
    color: #fff;
    box-shadow: 0 4px 15px rgba(220, 38, 38, 0.4);
}

.version-hsk3 .version-badge {
    background: linear-gradient(135deg, #7C3AED, #A855F7);
    color: #fff;
    box-shadow: 0 4px 15px rgba(124, 58, 237, 0.4);
}

.version-desc {
    color: var(--vg-text-secondary);
    font-size: 1rem;
    margin-bottom: var(--vg-space-4);
    position: relative;
    z-index: 1;
}

.version-levels-count {
    font-size: 1.2rem;
    color: var(--vg-text-primary);
    margin-bottom: var(--vg-space-5);
    position: relative;
    z-index: 1;
}

.version-levels-count strong {
    font-size: 2rem;
    font-weight: 800;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.btn-select-version {
    width: 100%;
    padding: var(--vg-space-3) var(--vg-space-4);
    border: none;
    border-radius: var(--vg-radius-md);
    color: #fff;
    font-weight: 700;
    font-size: 1rem;
    cursor: pointer;
    transition: all var(--vg-transition-normal);
    position: relative;
    z-index: 1;
}

.version-hsk2 .btn-select-version {
    background: linear-gradient(135deg, #DC2626, #EF4444);
}

.version-hsk3 .btn-select-version {
    background: linear-gradient(135deg, #7C3AED, #A855F7);
}

.btn-select-version:hover {
    transform: translateY(-2px);
    box-shadow: var(--vg-glow-cyan);
}

/* CEFR Badge for TOCFL */
.cefr-badge {
    display: inline-block;
    padding: 2px 8px;
    font-size: 0.7rem;
    font-weight: 600;
    background: rgba(124, 58, 237, 0.2);
    color: #A855F7;
    border-radius: 4px;
    margin-left: 8px;
}

/* Loading Spinner */
.loading-spinner {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--vg-space-3);
    padding: var(--vg-space-8);
    color: var(--vg-text-secondary);
    font-size: 1.1rem;
}

.loading-spinner i {
    font-size: 1.5rem;
    color: var(--vg-neon-cyan);
}

.level-card .level-header {
    margin-bottom: var(--vg-space-3);
    background: none;
    border: none;
    padding: 0;
    box-shadow: none;
}

.level-badge {
    display: inline-block;
    width: 60px;
    height: 60px;
    line-height: 60px;
    background: var(--vg-gradient-primary);
    color: var(--vg-bg-primary);
    font-size: 1.5rem;
    font-weight: 900;
    border-radius: var(--vg-radius-lg);
    box-shadow: var(--vg-glow-cyan);
    margin-bottom: var(--vg-space-2);
    position: relative;
    z-index: 1;
}

.level-badges {
    display: flex;
    justify-content: center;
    gap: var(--vg-space-2);
}

.level-badge-small {
    width: 35px;
    height: 35px;
    line-height: 35px;
    font-size: 0.9rem;
}

.level-difficulty {
    color: var(--vg-text-muted);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.level-card h3 {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--vg-text-primary);
    margin-bottom: var(--vg-space-1);
    position: relative;
    z-index: 1;
}

.level-card p {
    color: var(--vg-text-secondary);
    font-size: 0.8rem;
    margin-bottom: var(--vg-space-4);
    position: relative;
    z-index: 1;
}

.level-stats {
    display: flex;
    justify-content: center;
    gap: var(--vg-space-6);
    position: relative;
    z-index: 1;
}

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

.level-stat-number {
    display: block;
    font-size: 1.2rem;
    font-weight: 800;
    color: var(--vg-neon-cyan);
}

.level-stat-label {
    color: var(--vg-text-muted);
    font-size: 0.7rem;
    text-transform: uppercase;
}

/* ========================================
   Unit Tree Screen - Gaming RPG Style
   ======================================== */
.unit-tree-screen {
    min-height: calc(100vh - var(--vg-header-height));
    padding: var(--vg-space-6) var(--vg-space-4);
    display: flex;
    flex-direction: column;
}

.tree-header {
    background: var(--vg-gradient-card);
    border: 1px solid var(--vg-border-glow);
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-5);
    margin-bottom: var(--vg-space-6);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: var(--vg-space-4);
    box-shadow: var(--vg-glow-cyan);
}

.selected-level-info h2 {
    font-size: 1.5rem;
    font-weight: 700;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.selected-level-info p {
    color: var(--vg-text-secondary);
}

.tree-actions .btn-primary {
    background: var(--vg-gradient-primary);
    color: var(--vg-bg-primary);
    font-weight: 700;
    padding: var(--vg-space-3) var(--vg-space-5);
    border-radius: var(--vg-radius-lg);
    border: none;
    cursor: pointer;
    transition: all var(--vg-transition-normal);
    box-shadow: var(--vg-glow-cyan);
}

.tree-actions .btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: var(--vg-glow-purple);
}

/* Unit Tree Container */
.unit-tree {
    display: flex;
    flex-direction: column;
    gap: var(--vg-space-4);
    max-width: 900px;
    margin: 0 auto;
    width: 100%;
    flex: 1;
}

/* Unit Node - RPG Quest Style */
.unit-node {
    background: rgba(17, 24, 39, 0.95) !important;
    border: 2px solid rgba(100, 116, 139, 0.3);
    border-radius: var(--vg-radius-xl);
    overflow: hidden;
    transition: all var(--vg-transition-normal);
    position: relative;
    color: #f1f5f9 !important;
}

.unit-node * {
    color: inherit;
}

.unit-node::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--vg-gradient-primary);
    opacity: 0.5;
    transition: opacity var(--vg-transition-normal);
    pointer-events: none;
}

.unit-node:hover {
    border-color: rgba(0, 240, 255, 0.3);
    box-shadow: var(--vg-glow-cyan);
}

.unit-node:hover::before {
    opacity: 1;
}

.unit-node.expanded {
    border-color: #00ff88;
    box-shadow: var(--vg-glow-green);
}

.unit-node.expanded::before {
    background: var(--vg-gradient-success);
    opacity: 1;
}

/* Unit Header */
.unit-header {
    padding: var(--vg-space-4) var(--vg-space-5);
    display: flex;
    align-items: center;
    gap: var(--vg-space-4);
    cursor: pointer;
    transition: all var(--vg-transition-fast);
    background: transparent;
    position: relative;
    z-index: 1;
    user-select: none;
}

.unit-header:hover {
    background: rgba(0, 240, 255, 0.08);
}

.unit-node.expanded .unit-header {
    background: rgba(0, 255, 136, 0.08);
}

.unit-icon {
    width: 50px;
    height: 50px;
    background: var(--vg-gradient-primary);
    border-radius: var(--vg-radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--vg-bg-primary);
    font-size: 1.3rem;
    flex-shrink: 0;
    box-shadow: var(--vg-glow-cyan);
    transition: all var(--vg-transition-normal);
}

.unit-node.expanded .unit-icon {
    background: var(--vg-gradient-success);
    box-shadow: var(--vg-glow-green);
    animation: iconBounce 0.5s ease;
}

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

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

.unit-info h3 {
    font-size: 1.1rem;
    font-weight: 700;
    color: #f1f5f9 !important;
    margin-bottom: var(--vg-space-1);
}

.unit-info h4 {
    font-size: 0.9rem;
    font-weight: 500;
    color: #cbd5e1 !important;
    margin-bottom: var(--vg-space-2);
}

.unit-stats {
    display: flex;
    gap: var(--vg-space-4);
    font-size: 0.8rem;
    color: #94a3b8 !important;
}

.unit-stats span {
    display: flex;
    align-items: center;
    gap: var(--vg-space-1);
    color: #94a3b8 !important;
}

.unit-stats i {
    color: #00f0ff !important;
}

.unit-toggle {
    width: 40px;
    height: 40px;
    background: rgba(0, 240, 255, 0.1);
    border: 2px solid var(--vg-border-glow);
    border-radius: var(--vg-radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--vg-transition-normal);
}

.unit-toggle:hover {
    background: rgba(0, 240, 255, 0.2);
    transform: scale(1.1);
}

.unit-toggle i {
    color: var(--vg-neon-cyan);
    font-size: 0.9rem;
    transition: transform var(--vg-transition-normal);
}

.unit-node.expanded .unit-toggle {
    background: rgba(0, 255, 136, 0.1);
    border-color: var(--vg-neon-green);
}

.unit-node.expanded .unit-toggle i {
    transform: rotate(180deg);
    color: var(--vg-neon-green);
}

/* Unit Content - Expandable */
.vocabulary-app .unit-content,
.unit-content {
    max-height: 0 !important;
    overflow: hidden !important;
    transition: max-height 0.4s ease-out, padding 0.3s ease;
    background: rgba(10, 14, 23, 0.95) !important;
    padding: 0 1rem !important;
    display: block !important;
}

.vocabulary-app .unit-node.expanded .unit-content,
.unit-node.expanded .unit-content {
    max-height: 2000px !important;
    padding: 1rem !important;
    transition: max-height 0.5s ease-in, padding 0.3s ease;
    background: rgba(17, 24, 39, 0.95) !important;
}

/* Lesson List */
.lesson-list {
    display: flex;
    flex-direction: column;
    gap: var(--vg-space-3);
}

/* Lesson Item - Quest Style */
.lesson-item {
    background: rgba(0, 240, 255, 0.05);
    border: 1px solid rgba(0, 240, 255, 0.2);
    border-radius: var(--vg-radius-lg);
    padding: var(--vg-space-3) var(--vg-space-4);
    display: flex;
    align-items: center;
    gap: var(--vg-space-3);
    cursor: pointer;
    transition: all var(--vg-transition-normal);
    position: relative;
    overflow: hidden;
    opacity: 0;
    transform: translateY(10px);
}

/* Staggered animation for lesson items when unit expands */
.unit-node.expanded .lesson-item {
    animation: lessonSlideIn 0.3s ease forwards;
}

.unit-node.expanded .lesson-item:nth-child(1) { animation-delay: 0.05s; }
.unit-node.expanded .lesson-item:nth-child(2) { animation-delay: 0.1s; }
.unit-node.expanded .lesson-item:nth-child(3) { animation-delay: 0.15s; }
.unit-node.expanded .lesson-item:nth-child(4) { animation-delay: 0.2s; }
.unit-node.expanded .lesson-item:nth-child(5) { animation-delay: 0.25s; }
.unit-node.expanded .lesson-item:nth-child(6) { animation-delay: 0.3s; }
.unit-node.expanded .lesson-item:nth-child(7) { animation-delay: 0.35s; }
.unit-node.expanded .lesson-item:nth-child(8) { animation-delay: 0.4s; }

@keyframes lessonSlideIn {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.lesson-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background: var(--vg-neon-cyan);
    opacity: 0;
    transition: opacity var(--vg-transition-fast);
}

.lesson-item:hover {
    background: rgba(0, 240, 255, 0.1);
    border-color: var(--vg-neon-cyan);
    transform: translateX(8px);
    box-shadow: 0 3px 10px rgba(0, 240, 255, 0.2);
}

.lesson-item:hover::before {
    opacity: 1;
}

.lesson-item.locked {
    opacity: 0.5;
    cursor: not-allowed;
}

.lesson-item.locked:hover {
    transform: none;
    box-shadow: none;
}

.lesson-item.completed {
    background: rgba(0, 255, 136, 0.1);
    border-color: rgba(0, 255, 136, 0.3);
}

.lesson-item.completed::before {
    background: var(--vg-neon-green);
    opacity: 1;
}

.lesson-icon {
    width: 36px;
    height: 36px;
    background: var(--vg-gradient-primary);
    border-radius: var(--vg-radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--vg-bg-primary);
    font-size: 0.9rem;
    flex-shrink: 0;
}

.lesson-item.locked .lesson-icon {
    background: var(--vg-bg-tertiary);
    color: var(--vg-text-muted);
}

.lesson-item.completed .lesson-icon {
    background: var(--vg-gradient-success);
}

.lesson-info {
    flex: 1;
}

.lesson-info h4 {
    font-size: 0.95rem;
    font-weight: 600;
    color: #f1f5f9 !important;
    margin-bottom: var(--vg-space-1);
}

.lesson-info span {
    font-size: 0.8rem;
    color: #94a3b8 !important;
}

.lesson-progress {
    display: flex;
    align-items: center;
    gap: var(--vg-space-2);
}

.progress-circle {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: rgba(30, 41, 59, 0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.7rem;
    font-weight: 700;
    color: #94a3b8;
    position: relative;
    border: 3px solid rgba(100, 116, 139, 0.3);
    box-sizing: border-box;
}

/* iOS-style circular progress ring */
.progress-circle.partial {
    background: rgba(17, 24, 39, 0.95);
    border: none;
    color: #00ff88;
}

.progress-circle.partial::before {
    content: '';
    position: absolute;
    inset: 0;
    border-radius: 50%;
    background: conic-gradient(
        from -90deg,
        #00ff88 calc(var(--progress, 0) * 3.6deg),
        rgba(100, 116, 139, 0.3) calc(var(--progress, 0) * 3.6deg)
    );
    -webkit-mask: radial-gradient(
        farthest-side,
        transparent calc(100% - 4px),
        #fff calc(100% - 4px)
    );
    mask: radial-gradient(
        farthest-side,
        transparent calc(100% - 4px),
        #fff calc(100% - 4px)
    );
}

/* Inner circle background */
.progress-circle.partial::after {
    content: '';
    position: absolute;
    inset: 4px;
    border-radius: 50%;
    background: rgba(17, 24, 39, 0.95);
    z-index: 0;
}

.progress-circle.partial span {
    position: relative;
    z-index: 1;
    font-size: 0.65rem;
}

/* Completed state - green checkmark */
.progress-circle.complete,
.progress-circle.completed {
    background: linear-gradient(135deg, #00ff88 0%, #00cc6a 100%);
    color: #0a0e17;
    box-shadow: 
        0 0 15px rgba(0, 255, 136, 0.5),
        0 0 30px rgba(0, 255, 136, 0.3);
    animation: completeGlow 2s ease-in-out infinite;
}

.progress-circle.complete i,
.progress-circle.completed i {
    color: #0a0e17;
    font-size: 0.9rem;
    font-weight: bold;
}

@keyframes completeGlow {
    0%, 100% { 
        box-shadow: 0 0 15px rgba(0, 255, 136, 0.5), 0 0 30px rgba(0, 255, 136, 0.3); 
    }
    50% { 
        box-shadow: 0 0 20px rgba(0, 255, 136, 0.7), 0 0 40px rgba(0, 255, 136, 0.4); 
    }
}

/* In-progress state with ring */
.progress-circle.progress {
    background: rgba(17, 24, 39, 0.9);
    color: #ffee00;
}

.progress-circle.progress::before {
    content: '';
    position: absolute;
    inset: 0;
    border-radius: 50%;
    padding: 3px;
    background: conic-gradient(
        #ffee00 calc(var(--progress, 50) * 1%),
        rgba(100, 116, 139, 0.3) calc(var(--progress, 50) * 1%)
    );
    -webkit-mask: 
        linear-gradient(#fff 0 0) content-box, 
        linear-gradient(#fff 0 0);
    -webkit-mask-composite: xor;
    mask-composite: exclude;
}

/* ========================================
   Buttons - Gaming Style
   ======================================== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--vg-space-2);
    padding: var(--vg-space-3) var(--vg-space-5);
    border-radius: var(--vg-radius-lg);
    font-weight: 600;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all var(--vg-transition-normal);
    border: none;
    text-decoration: none;
}

.btn-primary {
    background: var(--vg-gradient-primary);
    color: var(--vg-bg-primary);
    box-shadow: var(--vg-glow-cyan);
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 16px rgba(0, 240, 255, 0.6);
}

.btn-secondary {
    background: rgba(100, 116, 139, 0.2);
    color: var(--vg-text-secondary);
    border: 1px solid var(--vg-border-color);
}

.btn-secondary:hover {
    background: rgba(100, 116, 139, 0.3);
    border-color: var(--vg-text-secondary);
    transform: translateY(-2px);
}

.btn-success {
    background: var(--vg-gradient-success);
    color: var(--vg-bg-primary);
    box-shadow: var(--vg-glow-green);
}

.btn-large {
    padding: var(--vg-space-4) var(--vg-space-8);
    font-size: 1rem;
}

/* ========================================
   Learning Interface - Gaming Style
   ======================================== */
.learning-interface {
    padding: var(--vg-space-6) var(--vg-space-4);
    max-width: 800px;
    margin: 0 auto;
    width: 100%;
}

/* Progress Section */
.progress-section {
    background: var(--vg-gradient-card);
    border: 1px solid var(--vg-border-glow);
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-4);
    margin-bottom: var(--vg-space-6);
    box-shadow: var(--vg-glow-cyan);
}

.progress-info-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--vg-space-3);
    font-size: 0.9rem;
}

#currentProgress {
    color: var(--vg-neon-cyan);
    font-weight: 600;
}

#lessonProgress {
    color: var(--vg-text-secondary);
}

.progress-bar {
    height: 8px;
    background: rgba(100, 116, 139, 0.3);
    border-radius: var(--vg-radius-full);
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--vg-gradient-primary);
    border-radius: var(--vg-radius-full);
    transition: width var(--vg-transition-slow);
    box-shadow: var(--vg-glow-cyan);
}

/* ========================================
   Flashcard Container - 3D Flip Effect
   ======================================== */
.flashcard-container {
    perspective: 1500px;
    margin-bottom: var(--vg-space-6);
    min-height: 500px;
}

.flashcard {
    position: relative;
    width: 100%;
    min-height: 480px;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

.flashcard.flipped {
    transform: rotateY(180deg);
}

/* Front and Back sides */
.flashcard-front,
.flashcard-back {
    position: absolute;
    width: 100%;
    min-height: 480px;
    max-height: fit-content;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    background: rgba(17, 24, 39, 0.95);
    border: 2px solid rgba(0, 240, 255, 0.3);
    border-radius: var(--vg-radius-2xl);
    padding: 26px;
    box-shadow: 0 4px 20px rgba(0, 240, 255, 0.15);
    overflow: visible;
}

.flashcard-front::before,
.flashcard-back::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, rgba(0, 240, 255, 0.05) 0%, transparent 50%, rgba(0, 255, 136, 0.05) 100%);
    pointer-events: none;
    border-radius: var(--vg-radius-2xl);
}

.flashcard-front {
    z-index: 2;
    text-align: center;
}

.flashcard-back {
    transform: rotateY(180deg);
    z-index: 1;
    border-color: rgba(139, 92, 246, 0.3);
    box-shadow: 0 4px 20px rgba(139, 92, 246, 0.15);
}

.flashcard-back::before {
    background: linear-gradient(135deg, rgba(139, 92, 246, 0.05) 0%, transparent 50%, rgba(14, 165, 233, 0.05) 100%);
}

/* Chinese Character Display */
.chinese-character {
    margin-bottom: var(--vg-space-6);
    position: relative;
    z-index: 1;
}

#vocaText {
    font-size: clamp(3rem, 10vw, 5rem);
    font-weight: 900;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: none;
    filter: drop-shadow(0 4px 14px rgba(0, 240, 255, 0.5));
    display: inline-block;
    animation: textGlow 2s ease-in-out infinite alternate;
}

@keyframes textGlow {
    0% { filter: drop-shadow(0 4px 14px rgba(0, 240, 255, 0.5)); }
    100% { filter: drop-shadow(0 6px 16px rgba(0, 255, 136, 0.7)); }
}

/* Flashcard Details */
.flashcard-details {
    position: relative;
    z-index: 1;
    text-align: left;
}

.pinyin {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--vg-space-2);
    font-size: 1.3rem;
    color: var(--vg-neon-cyan);
    margin-bottom: var(--vg-space-4);
}

.audio-icon {
    cursor: pointer;
    transition: all var(--vg-transition-fast);
}

.audio-icon:hover {
    color: var(--vg-neon-purple);
    transform: scale(1.2);
}

.hanviet, .meaning {
    background: rgba(0, 0, 0, 0.05);
    padding: var(--vg-space-3) var(--vg-space-4);
    border-radius: var(--vg-radius-lg);
    margin-bottom: var(--vg-space-3);
    border-left: 3px solid var(--vg-neon-cyan);
}

.hanviet strong, .meaning strong {
    color: var(--vg-neon-cyan);
}

.example {
    background: rgba(0, 255, 136, 0.05);
    border: 1px solid rgba(0, 255, 136, 0.2);
    border-radius: var(--vg-radius-lg);
    padding: var(--vg-space-4);
    margin-top: var(--vg-space-4);
}

.example strong {
    color: var(--vg-neon-green);
}

.example-text {
    margin-top: var(--vg-space-3);
}

.chinese-example {
    font-size: 1.2rem;
    color: var(--vg-text-primary);
    margin-bottom: var(--vg-space-2);
}

.pinyin-example {
    color: var(--vg-neon-cyan);
    font-size: 0.9rem;
    margin-bottom: var(--vg-space-2);
}

.vietnamese-example {
    color: var(--vg-text-secondary);
    font-style: italic;
}

/* Flashcard Actions */
.flashcard-actions {
    display: flex;
    justify-content: center;
    gap: var(--vg-space-4);
    margin-top: var(--vg-space-6);
    position: relative;
    z-index: 1;
}

/* Rating Section */
.rating-section {
    margin-top: var(--vg-space-6);
    padding: var(--vg-space-4);
    background: rgba(0, 0, 0, 0.05);
    border-radius: var(--vg-radius-lg);
    text-align: center;
    position: relative;
    z-index: 1;
}

.star-rating {
    display: flex;
    justify-content: center;
    gap: var(--vg-space-2);
    margin: var(--vg-space-4) 0;
}

.star-rating i {
    font-size: 1.5rem;
    color: var(--vg-text-muted);
    cursor: pointer;
    transition: all var(--vg-transition-fast);
}

.star-rating i:hover,
.star-rating i.active {
    color: var(--vg-neon-yellow);
    transform: scale(1.2);
    filter: drop-shadow(0 0 10px rgba(255, 238, 0, 0.5));
}

/* Navigation Controls */
.navigation-controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--vg-space-4);
}

.navigation-controls .btn {
    padding: var(--vg-space-3) var(--vg-space-5);
    font-weight: 600;
    border-radius: var(--vg-radius-lg);
    transition: all 0.3s ease;
    cursor: pointer;
}

.navigation-controls .btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none !important;
}

.navigation-controls .btn-secondary {
    background: rgba(100, 116, 139, 0.2) !important;
    border: 2px solid rgba(100, 116, 139, 0.4) !important;
    color: #cbd5e1 !important;
}

.navigation-controls .btn-secondary:hover:not(:disabled) {
    background: rgba(100, 116, 139, 0.3) !important;
    border-color: #94a3b8 !important;
    transform: translateY(-2px);
}

.navigation-controls .btn-success {
    background: linear-gradient(135deg, #00ff88, #00cc6a) !important;
    border: none !important;
    color: #0a0e17 !important;
    box-shadow: 0 4px 15px rgba(0, 255, 136, 0.4);
}

.navigation-controls .btn-success:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 255, 136, 0.6);
}

.navigation-controls .btn-info {
    background: linear-gradient(135deg, #0ea5e9, #00f0ff) !important;
    border: none !important;
    color: #0a0e17 !important;
    box-shadow: 0 4px 15px rgba(14, 165, 233, 0.4);
}

.navigation-controls .btn-info:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(14, 165, 233, 0.6);
}

.nav-spacer {
    flex: 1;
}

/* ========================================
   Modals - Gaming Style
   ======================================== */
.modal {
    position: fixed;
    inset: 0;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 10000;
    padding: var(--vg-space-4);
}

.modal-content {
    background: var(--vg-gradient-card);
    border: 2px solid var(--vg-border-glow);
    border-radius: var(--vg-radius-2xl);
    max-width: 500px;
    width: 100%;
    box-shadow: var(--vg-glow-cyan);
    overflow: hidden;
}

.modal-header {
    padding: var(--vg-space-5);
    background: rgba(0, 0, 0, 0.05);
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--vg-border-color);
}

.modal-header h3 {
    font-size: 1.2rem;
    background: var(--vg-gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.modal-body {
    padding: var(--vg-space-5);
}

.modal-footer {
    padding: var(--vg-space-4) var(--vg-space-5);
    background: rgba(0, 0, 0, 0.03);
    display: flex;
    justify-content: flex-end;
    gap: var(--vg-space-3);
    border-top: 1px solid var(--vg-border-color);
}

/* Settings */
.setting-group {
    margin-bottom: var(--vg-space-4);
}

.setting-group label {
    display: flex;
    align-items: center;
    gap: var(--vg-space-3);
    color: var(--vg-text-primary);
    cursor: pointer;
}

.setting-group input[type="checkbox"] {
    width: 20px;
    height: 20px;
    accent-color: var(--vg-neon-cyan);
}

.setting-group select {
    width: 100%;
    padding: var(--vg-space-3);
    background: var(--vg-bg-tertiary);
    border: 1px solid var(--vg-border-color);
    border-radius: var(--vg-radius-md);
    color: var(--vg-text-primary);
    margin-top: var(--vg-space-2);
}

.setting-hint {
    display: block;
    font-size: 0.75rem;
    color: #94a3b8;
    margin-top: 4px;
    margin-left: 32px;
}

/* Settings Button in Header */
#settingsBtn {
    display: flex !important;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    padding: 0;
    background: rgba(100, 116, 139, 0.2) !important;
    border: 2px solid rgba(100, 116, 139, 0.4) !important;
    border-radius: 10px;
    color: #cbd5e1 !important;
    cursor: pointer;
    transition: all 0.3s ease;
}

#settingsBtn:hover {
    background: rgba(0, 240, 255, 0.2) !important;
    border-color: #00f0ff !important;
    color: #00f0ff !important;
    transform: rotate(90deg);
}

#settingsBtn i {
    font-size: 1.1rem;
}

/* Floating Settings Button */
.floating-settings-btn {
    position: fixed;
    top: 80px;
    right: 20px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: linear-gradient(135deg, rgba(0, 240, 255, 0.3), rgba(0, 255, 136, 0.3));
    border: 2px solid rgba(0, 240, 255, 0.5);
    color: #00f0ff;
    font-size: 1.3rem;
    cursor: pointer;
    z-index: 9000;
    display: flex !important;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(0, 240, 255, 0.4);
}

/* Move button up when header is hidden */
body.fullscreen-mode .floating-settings-btn {
    top: 20px;
}

.floating-settings-btn:hover {
    background: linear-gradient(135deg, rgba(0, 240, 255, 0.5), rgba(0, 255, 136, 0.5));
    border-color: #00ff88;
    color: #00ff88;
    transform: rotate(90deg) scale(1.1);
    box-shadow: 0 6px 20px rgba(0, 255, 136, 0.5);
}

.floating-settings-btn i {
    transition: transform 0.3s ease;
}

/* User actions container */
.header .user-actions {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

/* Completion Stats - Using vg- prefix to avoid homepage.css conflict */
.vg-completion-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
    margin-bottom: 1rem;
}

.vg-stat-item {
    text-align: center;
    padding: 1rem;
    background: rgba(0, 0, 0, 0.06);
    border-radius: 0.75rem;
    border: 1px solid rgba(0, 240, 255, 0.3);
    opacity: 1; /* Override homepage.css opacity: 0 */
    transform: none; /* Override homepage.css transform */
}

.vg-stat-item i {
    font-size: 1.5rem;
    color: #00f0ff;
    margin-bottom: 0.5rem;
    display: block;
}

.vg-stat-item span {
    color: #cbd5e1;
    font-size: 0.9rem;
    display: block;
    line-height: 1.5;
}

.vg-stat-item strong {
    color: #00ff88;
    font-weight: 700;
}

/* Completion Message */
.completion-message {
    color: #f1f5f9 !important;
    text-align: center;
    padding: var(--vg-space-4);
    background: rgba(0, 255, 136, 0.1);
    border-radius: var(--vg-radius-lg);
    border: 1px solid rgba(0, 255, 136, 0.3);
    margin-top: var(--vg-space-4);
}

.completion-message #essayUnlockMessage {
    display: block;
    margin-top: var(--vg-space-2);
    color: #00f0ff !important;
    font-weight: 600;
}

/* Modal Body Text */
.modal-body {
    padding: var(--vg-space-5);
    color: #f1f5f9 !important;
}

.modal-body p,
.modal-body span,
.modal-body div {
    color: inherit;
}

/* ========================================
   Responsive Design
   ======================================== */
@media (max-width: 768px) {
    .system-cards {
        grid-template-columns: 1fr;
    }
    
    .level-cards-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .flashcard {
        padding: var(--vg-space-6);
    }
    
    #vocaText {
        font-size: 3rem;
    }
    
    .flashcard-actions {
        flex-direction: column;
    }
    
    .navigation-controls {
        flex-wrap: wrap;
    }
    
    .completion-stats {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .level-cards-grid {
        grid-template-columns: 1fr;
    }
    
    .unit-header {
        flex-wrap: wrap;
    }
    
    .unit-stats {
        width: 100%;
        justify-content: flex-start;
        margin-top: var(--vg-space-2);
    }
}

/* ========================================
   Animations
   ======================================== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.system-card,
.level-card,
.unit-node {
    animation: fadeInUp 0.5s ease forwards;
}

.system-card:nth-child(1) { animation-delay: 0.1s; }
.system-card:nth-child(2) { animation-delay: 0.2s; }
.system-card:nth-child(3) { animation-delay: 0.3s; }

.level-card:nth-child(1) { animation-delay: 0.05s; }
.level-card:nth-child(2) { animation-delay: 0.1s; }
.level-card:nth-child(3) { animation-delay: 0.15s; }
.level-card:nth-child(4) { animation-delay: 0.2s; }
.level-card:nth-child(5) { animation-delay: 0.25s; }
.level-card:nth-child(6) { animation-delay: 0.3s; }
.level-card:nth-child(7) { animation-delay: 0.35s; }

.unit-node:nth-child(1) { animation-delay: 0.1s; }
.unit-node:nth-child(2) { animation-delay: 0.15s; }
.unit-node:nth-child(3) { animation-delay: 0.2s; }
.unit-node:nth-child(4) { animation-delay: 0.25s; }
.unit-node:nth-child(5) { animation-delay: 0.3s; }

/* Loading Placeholder */
.loading-placeholder {
    text-align: center;
    padding: var(--vg-space-12);
    color: var(--vg-text-secondary);
}

.spinner {
    width: 50px;
    height: 50px;
    margin: 0 auto var(--vg-space-4);
    border: 3px solid var(--vg-border-color);
    border-top-color: var(--vg-neon-cyan);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

/* Limit Notice */
.limit-notice {
    position: fixed;
    top: var(--vg-header-height);
    left: 0;
    right: 0;
    z-index: 1000;
    transform: translateY(-100%);
    transition: transform var(--vg-transition-normal);
}

.limit-notice:not(.hidden) {
    transform: translateY(0);
}

.notice-content {
    background: var(--vg-gradient-warning);
    color: var(--vg-bg-primary);
    padding: var(--vg-space-4);
    display: flex;
    align-items: center;
    gap: var(--vg-space-3);
}

.close-btn {
    background: transparent;
    border: none;
    color: inherit;
    font-size: 1.5rem;
    cursor: pointer;
    margin-left: auto;
}

/* ========================================
   Exercise Card (Back of Flashcard)
   ======================================== */
.exercise-card {
    position: relative;
    z-index: 1;
    height: 100%;
    display: flex;
    flex-direction: column;
}

.exercise-vocab-hint {
    text-align: center;
    margin-bottom: var(--vg-space-4);
    padding: var(--vg-space-3);
    background: linear-gradient(135deg, rgba(139, 92, 246, 0.15), rgba(14, 165, 233, 0.15));
    border-radius: var(--vg-radius-lg);
    border: 1px solid rgba(139, 92, 246, 0.3);
}

.exercise-vocab-hint span {
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, #8b5cf6, #0ea5e9);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    filter: drop-shadow(0 2px 8px rgba(139, 92, 246, 0.4));
}

/* ========================================
   Exercise Section - Gaming Style
   ======================================== */
.exercise-section {
    background: rgba(17, 24, 39, 0.95);
    border: 2px solid rgba(0, 240, 255, 0.2);
    border-radius: var(--vg-radius-xl);
    padding: var(--vg-space-6);
    margin-top: var(--vg-space-6);
    position: relative;
    overflow: hidden;
}

.exercise-section::before,
.exercise-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, #8b5cf6, #0ea5e9, #8b5cf6);
    background-size: 200% 100%;
    animation: gradientMove 3s linear infinite;
}

.exercise-card::before {
    border-radius: var(--vg-radius-2xl) var(--vg-radius-2xl) 0 0;
}

@keyframes gradientMove {
    0% { background-position: 0% 0%; }
    100% { background-position: 200% 0%; }
}

.exercise-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--vg-space-4);
    padding-bottom: var(--vg-space-3);
    border-bottom: 1px solid rgba(139, 92, 246, 0.2);
}

.exercise-header h3 {
    font-size: 1.1rem;
    font-weight: 700;
    color: #f1f5f9 !important;
    display: flex;
    align-items: center;
    gap: var(--vg-space-2);
    margin: 0;
}

.exercise-header h3 i {
    color: #8b5cf6;
    font-size: 1rem;
}

.exercise-info {
    display: flex;
    gap: var(--vg-space-4);
}

.exercise-info span {
    font-size: 0.8rem;
    color: #94a3b8 !important;
    background: rgba(139, 92, 246, 0.1);
    padding: var(--vg-space-1) var(--vg-space-3);
    border-radius: var(--vg-radius-full);
    border: 1px solid rgba(139, 92, 246, 0.2);
}

.exercise-content {
    display: flex;
    flex-direction: column;
    gap: var(--vg-space-4);
    flex: 1;
}

.question-text {
    font-size: 1.1rem;
    font-weight: 600;
    color: #f1f5f9 !important;
    text-align: center;
    padding: var(--vg-space-3);
    background: rgba(0, 0, 0, 0.2);
    border-radius: var(--vg-radius-lg);
    border: 1px solid rgba(100, 116, 139, 0.3);
}

/* Exercise Options - Gaming Buttons */
.exercise-options {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--vg-space-3);
}

.option-btn {
    background: rgba(139, 92, 246, 0.05) !important;
    border: 2px solid rgba(139, 92, 246, 0.3) !important;
    border-radius: var(--vg-radius-lg);
    padding: var(--vg-space-3);
    font-size: 0.95rem;
    font-weight: 500;
    color: #f1f5f9 !important;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.option-btn::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, rgba(139, 92, 246, 0.2), rgba(14, 165, 233, 0.2));
    opacity: 0;
    transition: opacity 0.3s ease;
}

.option-btn:hover:not(:disabled) {
    border-color: #8b5cf6 !important;
    transform: translateY(-2px);
    box-shadow: 0 4px 14px rgba(139, 92, 246, 0.3);
}

.option-btn:hover:not(:disabled)::before {
    opacity: 1;
}

.option-btn.selected {
    background: rgba(0, 240, 255, 0.2) !important;
    border-color: #00f0ff !important;
    box-shadow: 0 3px 10px rgba(0, 240, 255, 0.4);
}

.option-btn.correct {
    background: rgba(0, 255, 136, 0.3) !important;
    border-color: #00ff88 !important;
    box-shadow: 
        0 0 20px rgba(0, 255, 136, 0.5),
        0 0 40px rgba(0, 255, 136, 0.3),
        inset 0 0 20px rgba(0, 255, 136, 0.1) !important;
    animation: correctPulse 0.6s ease, correctGlow 1s ease-in-out infinite;
    transform: scale(1.02);
}

.option-btn.correct::after {
    content: '✓';
    position: absolute;
    right: 10px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 1.2rem;
    color: #00ff88;
    animation: checkAppear 0.3s ease;
}

.option-btn.incorrect {
    background: rgba(239, 68, 68, 0.3) !important;
    border-color: #ef4444 !important;
    box-shadow: 
        0 0 20px rgba(239, 68, 68, 0.5),
        0 0 40px rgba(239, 68, 68, 0.3) !important;
    animation: incorrectShake 0.6s ease;
}

.option-btn.incorrect::after {
    content: '✗';
    position: absolute;
    right: 10px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 1.2rem;
    color: #ef4444;
    animation: checkAppear 0.3s ease;
}

@keyframes correctPulse {
    0% { transform: scale(1); }
    30% { transform: scale(1.05); }
    60% { transform: scale(0.98); }
    100% { transform: scale(1.02); }
}

@keyframes correctGlow {
    0%, 100% { box-shadow: 0 0 20px rgba(0, 255, 136, 0.5), 0 0 40px rgba(0, 255, 136, 0.3); }
    50% { box-shadow: 0 0 30px rgba(0, 255, 136, 0.7), 0 0 60px rgba(0, 255, 136, 0.4); }
}

@keyframes incorrectShake {
    0%, 100% { transform: translateX(0); }
    10%, 30%, 50%, 70%, 90% { transform: translateX(-8px); }
    20%, 40%, 60%, 80% { transform: translateX(8px); }
}

@keyframes checkAppear {
    0% { opacity: 0; transform: translateY(-50%) scale(0); }
    50% { transform: translateY(-50%) scale(1.3); }
    100% { opacity: 1; transform: translateY(-50%) scale(1); }
}

.exercise-actions {
    display: flex;
    justify-content: center;
    margin-top: var(--vg-space-4);
}

/* Exercise Result - on back of card */
.exercise-result {
    margin-top: var(--vg-space-4);
    padding: var(--vg-space-4);
    border-radius: var(--vg-radius-lg);
    background: rgba(0, 0, 0, 0.3);
    border: 1px solid rgba(100, 116, 139, 0.3);
}

.exercise-result.hidden {
    display: none;
}

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

.result-icon {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--vg-space-3);
    font-size: 1.8rem;
    animation: iconBounceIn 0.5s cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

.result-icon.success {
    background: rgba(0, 255, 136, 0.2);
    color: #00ff88;
    box-shadow: 
        0 0 20px rgba(0, 255, 136, 0.4),
        0 0 40px rgba(0, 255, 136, 0.2);
    animation: iconBounceIn 0.5s cubic-bezier(0.68, -0.55, 0.265, 1.55), 
               successPulse 1.5s ease-in-out infinite;
}

.result-icon.error {
    background: rgba(239, 68, 68, 0.2);
    color: #ef4444;
    box-shadow: 
        0 0 20px rgba(239, 68, 68, 0.4),
        0 0 40px rgba(239, 68, 68, 0.2);
    animation: iconBounceIn 0.5s cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

.result-icon i {
    color: inherit;
}

@keyframes iconBounceIn {
    0% { transform: scale(0); opacity: 0; }
    50% { transform: scale(1.3); }
    100% { transform: scale(1); opacity: 1; }
}

@keyframes successPulse {
    0%, 100% { box-shadow: 0 0 20px rgba(0, 255, 136, 0.4), 0 0 40px rgba(0, 255, 136, 0.2); }
    50% { box-shadow: 0 0 30px rgba(0, 255, 136, 0.6), 0 0 60px rgba(0, 255, 136, 0.3); }
}

.result-message {
    font-size: 1rem;
    font-weight: 600;
    color: #f1f5f9 !important;
    margin-bottom: var(--vg-space-3);
}

.correct-answer {
    font-size: 0.9rem;
    color: #cbd5e1 !important;
    padding: var(--vg-space-2) var(--vg-space-3);
    background: rgba(0, 255, 136, 0.1);
    border-radius: var(--vg-radius-sm);
    border-left: 3px solid #00ff88;
    margin-bottom: var(--vg-space-3);
    text-align: left;
}

.correct-answer strong {
    color: #00ff88 !important;
}

.result-actions {
    display: flex;
    justify-content: center;
    gap: var(--vg-space-3);
    margin-top: var(--vg-space-3);
    animation: fadeInUp 0.4s ease 0.3s both;
}

.result-actions .btn {
    padding: var(--vg-space-3) var(--vg-space-5);
    font-weight: 600;
    border-radius: var(--vg-radius-lg);
    transition: all 0.3s ease;
}

.result-actions .btn-secondary {
    background: rgba(100, 116, 139, 0.2) !important;
    border: 2px solid rgba(100, 116, 139, 0.4) !important;
    color: #cbd5e1 !important;
}

.result-actions .btn-secondary:hover {
    background: rgba(100, 116, 139, 0.3) !important;
    border-color: #94a3b8 !important;
    transform: translateY(-2px);
}

.result-actions .btn-primary {
    background: linear-gradient(135deg, #00ff88, #00cc6a) !important;
    border: none !important;
    color: #0a0e17 !important;
    box-shadow: 0 4px 15px rgba(0, 255, 136, 0.4);
}

.result-actions .btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 255, 136, 0.6);
}

/* Result appear animation */
.exercise-result:not(.hidden) {
    animation: resultSlideUp 0.4s ease;
}

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

.result-actions {
    display: flex;
    justify-content: center;
    gap: var(--vg-space-4);
}

/* Buttons in exercise */
.exercise-section .btn {
    padding: var(--vg-space-3) var(--vg-space-6);
    border-radius: var(--vg-radius-lg);
    font-weight: 600;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.3s ease;
    display: inline-flex;
    align-items: center;
    gap: var(--vg-space-2);
}

.exercise-section .btn-primary {
    background: linear-gradient(135deg, #00f0ff, #00ff88) !important;
    border: none;
    color: #f1f5f9 !important;
}

.exercise-section .btn-primary:hover:not(:disabled) {
    box-shadow: 0 5px 12px rgba(0, 240, 255, 0.5);
    transform: translateY(-2px);
}

.exercise-section .btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.exercise-section .btn-secondary {
    background: transparent !important;
    border: 2px solid rgba(0, 240, 255, 0.3) !important;
    color: #00f0ff !important;
}

.exercise-section .btn-secondary:hover {
    background: rgba(0, 240, 255, 0.1) !important;
    border-color: #00f0ff !important;
}

/* Direct ID targeting for stats */
#completedWords,
#accuracyRate, 
#studyTime {
    color: #00ff88;
}

.completion-message {
    color: #f1f5f9;
    text-align: center;
    padding: 1rem;
    background: rgba(0, 255, 136, 0.1);
    border-radius: 0.75rem;
    border: 1px solid rgba(0, 255, 136, 0.3);
    margin-top: 1rem;
}

/* ========================================
   Lesson Transition Notification
   ======================================== */
.lesson-transition-notification {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 10000;
    background: linear-gradient(135deg, rgba(0, 255, 136, 0.95) 0%, rgba(0, 204, 106, 0.95) 100%);
    color: #0a0e17;
    padding: 1.5rem 2.5rem;
    border-radius: 1rem;
    box-shadow: 
        0 0 30px rgba(0, 255, 136, 0.6),
        0 0 60px rgba(0, 255, 136, 0.4),
        0 10px 30px rgba(0, 0, 0, 0.3);
    animation: notificationSlideIn 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

.lesson-transition-notification .notification-content {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.1rem;
    font-weight: 600;
}

.lesson-transition-notification .notification-content i {
    font-size: 1.5rem;
}

.lesson-transition-notification.fade-out {
    animation: notificationFadeOut 0.3s ease-out forwards;
}

@keyframes notificationSlideIn {
    from {
        opacity: 0;
        transform: translate(-50%, -50%) scale(0.8);
    }
    to {
        opacity: 1;
        transform: translate(-50%, -50%) scale(1);
    }
}

@keyframes notificationFadeOut {
    from {
        opacity: 1;
        transform: translate(-50%, -50%) scale(1);
    }
    to {
        opacity: 0;
        transform: translate(-50%, -50%) scale(0.8);
    }
}

/* Light theme variant */
.vocabulary-app.light-theme .lesson-transition-notification {
    background: linear-gradient(135deg, rgba(16, 185, 129, 0.95) 0%, rgba(5, 150, 105, 0.95) 100%);
    color: #ffffff;
}

/* Unit complete notification - special styling */
.lesson-transition-notification.unit-complete {
    background: linear-gradient(135deg, rgba(14, 165, 233, 0.95) 0%, rgba(139, 92, 246, 0.95) 100%);
    box-shadow: 
        0 0 30px rgba(14, 165, 233, 0.6),
        0 0 60px rgba(139, 92, 246, 0.4),
        0 10px 30px rgba(0, 0, 0, 0.3);
}

.lesson-transition-notification.unit-complete .notification-content i {
    color: #fbbf24;
}

/* ========================================
   Restart Lesson Button
   ======================================== */
.restart-btn-container {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid rgba(0, 240, 255, 0.2);
    text-align: center;
}

.restart-lesson-btn {
    background: linear-gradient(135deg, #0ea5e9 0%, #00f0ff 100%) !important;
    color: #0a0e17 !important;
    font-weight: 600 !important;
    padding: 0.875rem 2rem !important;
    border-radius: 0.75rem !important;
    border: none !important;
    cursor: pointer !important;
    transition: all 0.3s ease !important;
    box-shadow: 0 4px 15px rgba(0, 240, 255, 0.3);
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.restart-lesson-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 240, 255, 0.5);
}

.restart-lesson-btn i {
    font-size: 1rem;
}

/* Light theme */
.vocabulary-app.light-theme .restart-btn-container {
    border-top-color: rgba(14, 165, 233, 0.2);
}

.vocabulary-app.light-theme .restart-lesson-btn {
    background: linear-gradient(135deg, #0ea5e9 0%, #10b981 100%) !important;
    color: #ffffff !important;
}

/* Light theme - Exercise result and options */
.vocabulary-app.light-theme .exercise-result {
    background: rgba(255, 255, 255, 0.9);
    border-color: rgba(14, 165, 233, 0.3);
}

.vocabulary-app.light-theme .result-message {
    color: #1f2937 !important;
}

.vocabulary-app.light-theme .correct-answer {
    color: #374151 !important;
    background: rgba(16, 185, 129, 0.1);
    border-left-color: #10b981;
}

.vocabulary-app.light-theme .correct-answer strong {
    color: #10b981 !important;
}

.vocabulary-app.light-theme .option-btn.correct {
    background: rgba(16, 185, 129, 0.3) !important;
    border-color: #10b981 !important;
    box-shadow: 0 0 20px rgba(16, 185, 129, 0.4);
}

.vocabulary-app.light-theme .option-btn.incorrect {
    background: rgba(239, 68, 68, 0.3) !important;
    border-color: #ef4444 !important;
    box-shadow: 0 0 20px rgba(239, 68, 68, 0.4);
}

.vocabulary-app.light-theme .result-actions .btn-secondary {
    background: rgba(107, 114, 128, 0.2) !important;
    border-color: rgba(107, 114, 128, 0.4) !important;
    color: #374151 !important;
}

.vocabulary-app.light-theme .result-actions .btn-primary {
    background: linear-gradient(135deg, #10b981, #059669) !important;
    color: #ffffff !important;
}