:root {
    /* Color System - Premium */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #334155;
    --text-muted: #64748b;
    --accent-primary: #2563eb;
    --accent-secondary: #3b82f6;
    --accent-light: #dbeafe;
    --border-color: #e2e8f0;
    --border-light: #f1f5f9;
    --success: #10b981;
    --error: #ef4444;
    --warning: #f59e0b;
    --gradient-primary: linear-gradient(135deg, #2563eb 0%, #3b82f6 100%);
    --gradient-accent: linear-gradient(135deg, #06b6d4 0%, #0ea5e9 100%);
    --gradient-gold: linear-gradient(135deg, #f59e0b 0%, #eab308 100%);
    --gradient-success: linear-gradient(135deg, #10b981 0%, #059669 100%);
    --gradient-error: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
    /* Enhanced Color System */
    --dialogue-bg: #f8fafc;
    --dialogue-border: #e2e8f0;
    --speaker-a: #3b82f6;
    --speaker-b: #10b981;
    --question-main: #1e40af;
    --question-sub: #64748b;
    --phrase-bank-bg: #fef3c7;
    --phrase-bank-border: #f59e0b;
    --scenario-bg: #ecfdf5;
    --scenario-border: #10b981;
    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-12: 3rem;
    --space-16: 4rem;
    /* Shadows & Transitions */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
}

/* Dark Mode */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --accent-primary: #3b82f6;
    --accent-secondary: #60a5fa;
    --accent-light: #1e3a8a;
    --border-color: #334155;
    --border-light: #475569;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.6);
    /* Enhanced Dark Mode Colors */
    --dialogue-bg: #1e293b;
    --dialogue-border: #334155;
    --speaker-a: #60a5fa;
    --speaker-b: #34d399;
    --question-main: #93c5fd;
    --question-sub: #94a3b8;
    --phrase-bank-bg: #451a03;
    --phrase-bank-border: #f59e0b;
    --scenario-bg: #064e3b;
    --scenario-border: #10b981;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    transition: all var(--transition-normal);
}

/* Fixed Controls */
.fixed-controls {
    position: fixed;
    top: var(--space-4);
    right: var(--space-4);
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.theme-toggle {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
    color: var(--text-primary);
}

.theme-toggle:hover {
    background: var(--accent-primary);
    color: white;
    transform: scale(1.05);
}

.booking-link {
    background: var(--gradient-accent);
    color: white;
    border: none;
    border-radius: 24px;
    padding: var(--space-2) var(--space-4);
    font-size: var(--font-size-sm);
    font-weight: 600;
    text-decoration: none;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
    white-space: nowrap;
}

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

/* Quick Navigation */
.quick-nav-toggle {
    position: fixed;
    left: var(--space-4);
    top: var(--space-4);
    z-index: 1000;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
    color: var(--text-primary);
}

.quick-nav-toggle:hover {
    background: var(--accent-primary);
    color: white;
}

.quick-nav {
    position: fixed;
    left: var(--space-4);
    top: 100px;
    z-index: 900;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: var(--space-4);
    box-shadow: var(--shadow-lg);
    max-width: 280px;
    opacity: 0;
    visibility: hidden;
    transform: translateX(-20px);
    transition: all var(--transition-normal);
}

.quick-nav.visible {
    opacity: 1;
    visibility: visible;
    transform: translateX(0);
}

.quick-nav h3 {
    margin-bottom: var(--space-3);
    color: var(--text-primary);
    font-size: var(--font-size-base);
    font-weight: 600;
}

.quick-nav-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.quick-nav-item {
    padding: var(--space-3);
    border-radius: 8px;
    cursor: pointer;
    transition: all var(--transition-fast);
    border-left: 3px solid transparent;
    color: var(--text-secondary);
}

.quick-nav-item:hover {
    background: var(--bg-secondary);
    border-left-color: var(--accent-primary);
    color: var(--text-primary);
}

.quick-nav-item.completed {
    border-left-color: var(--success);
    color: var(--text-primary);
}

.quick-nav-item.completed::after {
    content: '✓';
    float: right;
    color: var(--success);
    font-weight: 600;
}

/* Timer Component */
.timer-container {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: var(--space-3) var(--space-4);
    margin-bottom: var(--space-4);
}

.timer-icon {
    color: var(--accent-primary);
    font-size: var(--font-size-lg);
}

.timer-display {
    font-weight: 600;
    color: var(--text-primary);
    font-size: var(--font-size-lg);
}

.timer-label {
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
}

/* Lesson Container */
.lesson-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--space-4);
}

/* Lesson Header */
.lesson-header {
    text-align: center;
    margin-bottom: var(--space-12);
}

.premium-border {
    background: var(--gradient-primary);
    padding: 2px;
    border-radius: 16px;
    display: inline-block;
    margin-bottom: var(--space-6);
}

.header-content {
    background: var(--bg-primary);
    padding: var(--space-8);
    border-radius: 14px;
}

.lesson-title {
    font-size: var(--font-size-4xl);
    font-weight: 800;
    color: var(--text-primary);
    margin-bottom: var(--space-4);
}

.lesson-subtitle {
    font-size: var(--font-size-xl);
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* Progress Bar */
.progress-container {
    max-width: 400px;
    margin: 0 auto;
}

.progress-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-2);
}

.progress-label {
    font-size: var(--font-size-sm);
    color: var(--text-muted);
}

.progress-percentage {
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--accent-primary);
}

.progress-bar {
    width: 100%;
    height: 12px;
    background: var(--bg-secondary);
    border-radius: 6px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    width: 0%;
    transition: width 0.5s ease;
    border-radius: 6px;
    max-width: 100%;
}

/* Module Styles */
.module {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    margin-bottom: var(--space-6);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: all var(--transition-normal);
    scroll-margin-top: 80px;
}

.module:hover {
    box-shadow: var(--shadow-lg);
}

.module-header {
    background: var(--bg-secondary);
    padding: var(--space-6);
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.module-header:hover {
    background: var(--bg-tertiary);
}

.module-title-container {
    display: flex;
    align-items: center;
    gap: var(--space-4);
}

.module-number {
    width: 48px;
    height: 48px;
    background: var(--gradient-primary);
    color: white;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: var(--font-size-lg);
}

.module-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--text-primary);
}

.module-controls {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.module-chevron {
    color: var(--text-muted);
    transition: transform var(--transition-fast);
    font-size: var(--font-size-lg);
}

.module.collapsed .module-chevron {
    transform: rotate(0deg);
}

.module:not(.collapsed) .module-chevron {
    transform: rotate(180deg);
}

.module-content {
    padding: var(--space-8);
    display: block;
}

.module.collapsed .module-content {
    display: none;
}

/* Objectives Grid */
.objectives-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-6);
    margin-bottom: var(--space-8);
}

.objectives-section h3 {
    color: var(--text-primary);
    font-size: var(--font-size-xl);
    margin-bottom: var(--space-4);
}

.objective-item {
    display: flex;
    align-items: flex-start;
    gap: var(--space-3);
    margin-bottom: var(--space-4);
}

.objective-icon {
    background: var(--accent-light);
    color: var(--accent-primary);
    width: 40px;
    height: 40px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.objective-content h4 {
    color: var(--text-primary);
    font-size: var(--font-size-base);
    margin-bottom: var(--space-1);
}

.objective-content p {
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
}

/* Phrase Bank */
.phrase-bank {
    background: var(--phrase-bank-bg);
    border: 1px solid var(--phrase-bank-border);
    border-radius: 12px;
    padding: var(--space-4);
    margin-top: var(--space-4);
}

.phrase-bank h4 {
    color: var(--text-primary);
    margin-bottom: var(--space-3);
}

.phrase-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: var(--space-2);
}

.phrase-item {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: var(--space-3);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-align: center;
    font-size: var(--font-size-sm);
}

.phrase-item:hover {
    background: var(--accent-light);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

/* Video Container */
.video-container {
    position: relative;
    width: 100%;
    height: 0;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    margin: var(--space-6) 0;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--shadow-lg);
}

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

/* Real Life Callout */
.real-life-callout {
    background: var(--scenario-bg);
    border: 1px solid var(--scenario-border);
    border-radius: 12px;
    padding: var(--space-6);
    margin: var(--space-6) 0;
}

.real-life-callout-content h4 {
    color: var(--scenario-border);
    margin-bottom: var(--space-3);
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

.real-life-callout-content h4::before {
    content: '💡';
}

/* Task Grid (Index Page) */
.task-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--space-6);
    margin: var(--space-8) 0;
}

.task-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    overflow: hidden;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
}

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

.task-header {
    background: var(--gradient-primary);
    color: white;
    padding: var(--space-4);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.task-number {
    font-size: var(--font-size-2xl);
    font-weight: 700;
}

.task-type {
    font-size: var(--font-size-sm);
    opacity: 0.9;
}

.task-content {
    padding: var(--space-6);
}

.task-content h3 {
    color: var(--text-primary);
    font-size: var(--font-size-xl);
    margin-bottom: var(--space-2);
}

.task-content p {
    color: var(--text-secondary);
    margin-bottom: var(--space-4);
}

.task-details {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
    margin-bottom: var(--space-4);
}

.time-badge {
    background: var(--bg-secondary);
    color: var(--text-secondary);
    padding: var(--space-1) var(--space-3);
    border-radius: 20px;
    font-size: var(--font-size-xs);
    font-weight: 500;
}

.difficulty {
    padding: var(--space-1) var(--space-3);
    border-radius: 20px;
    font-size: var(--font-size-xs);
    font-weight: 600;
}

.difficulty.easy {
    background: var(--success);
    color: white;
}

.difficulty.medium {
    background: var(--warning);
    color: white;
}

.difficulty.hard {
    background: var(--error);
    color: white;
}

.task-button {
    display: inline-flex;
    align-items: center;
    gap: var(--space-2);
    background: var(--accent-primary);
    color: white;
    padding: var(--space-3) var(--space-6);
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: all var(--transition-normal);
}

.task-button:hover {
    background: var(--accent-secondary);
    transform: translateY(-2px);
}

/* Recording Controls */
.record-btn {
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.record-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 25px rgba(239, 68, 68, 0.3);
}

.record-btn.recording {
    background: var(--success) !important;
    animation: pulse 1.5s infinite;
}

.record-btn.recording i::before {
    content: '\f04d'; /* stop icon */
}

@keyframes pulse {
    0% { box-shadow: 0 0 0 0 rgba(16, 185, 129, 0.7); }
    70% { box-shadow: 0 0 0 10px rgba(16, 185, 129, 0); }
    100% { box-shadow: 0 0 0 0 rgba(16, 185, 129, 0); }
}

/* Play Button */
.play-btn {
    transition: all var(--transition-normal);
}

.play-btn:hover {
    background: var(--accent-secondary) !important;
    transform: scale(1.1);
}

.play-btn.playing {
    background: var(--success) !important;
}

.play-btn.playing i::before {
    content: '\f04c'; /* pause icon */
}

/* Navigation */
.lesson-navigation {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: var(--space-6) 0;
    gap: var(--space-4);
    flex-wrap: wrap;
    border-top: 1px solid var(--border-color);
    padding-top: var(--space-4);
}

.nav-button {
    display: inline-block;
    background: var(--accent-primary);
    color: white;
    border: none;
    border-radius: 24px;
    padding: var(--space-3) var(--space-6);
    font-size: var(--font-size-base);
    font-weight: 600;
    text-decoration: none;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
    white-space: nowrap;
}

.nav-button:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    background: var(--accent-secondary);
}

.nav-button.disabled {
    background: var(--text-muted);
    cursor: not-allowed;
    transform: none;
}

.nav-button.disabled:hover {
    transform: none;
    box-shadow: var(--shadow-md);
}

/* Responsive Design */
@media (max-width: 768px) {
    .lesson-container {
        padding: var(--space-2);
    }
    
    .objectives-grid {
        grid-template-columns: 1fr;
        gap: var(--space-4);
    }
    
    .task-grid {
        grid-template-columns: 1fr;
    }
    
    .phrase-grid {
        grid-template-columns: 1fr;
    }
    
    .lesson-title {
        font-size: var(--font-size-3xl);
    }
    
    .fixed-controls {
        position: relative;
        flex-direction: row;
        justify-content: center;
        top: auto;
        right: auto;
        margin-bottom: var(--space-4);
    }
    
    .quick-nav-toggle {
        position: relative;
        left: auto;
        top: auto;
    }
    
    .quick-nav {
        position: relative;
        left: auto;
        top: auto;
        opacity: 1;
        visibility: visible;
        transform: translateX(0);
        margin-bottom: var(--space-4);
        max-width: none;
    }
}

@media (max-width: 480px) {
    .module-title-container {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--space-2);
    }
    
    .module-header {
        padding: var(--space-4);
    }
    
    .module-content {
        padding: var(--space-4);
    }
    
    .lesson-navigation {
        flex-direction: column;
        gap: var(--space-2);
    }
    
    .nav-button {
        width: 100%;
        max-width: 300px;
    }
}

/* Print Styles */
@media print {
    .fixed-controls,
    .quick-nav-toggle,
    .quick-nav,
    .timer-container,
    .record-btn,
    .play-btn,
    .lesson-navigation {
        display: none !important;
    }
    
    .module {
        break-inside: avoid;
        box-shadow: none;
        border: 1px solid #ccc;
    }
    
    .module.collapsed .module-content {
        display: block;
    }
    
    .video-container {
        border: 2px dashed #ccc;
        background: #f9f9f9;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .video-container::after {
        content: 'Video content available in digital version';
        color: #666;
        font-style: italic;
    }
    
    .video-container iframe {
        display: none;
    }
}