/* AIVOCA 2.0 - Modern Design System */

:root {
    /* Light Mode Colors */
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary: #ec4899;
    --accent: #14b8a6;
    --success: #22c55e;
    --warning: #f59e0b;
    --danger: #ef4444;
    --info: #3b82f6;

    /* Neutrals */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --border: #e2e8f0;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

    /* Transitions */
    --transition: all 0.2s ease;
    --transition-slow: all 0.3s ease;

    /* Radius */
    --radius-sm: 0.375rem;
    --radius: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    --radius-full: 9999px;
}

/* Dark Mode */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #64748b;
    --border: #334155;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
}

h1 { font-size: 2.25rem; }
h2 { font-size: 1.875rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

/* Container */
.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 1rem;
}

/* Layout */
.app-layout {
    display: flex;
    min-height: 100vh;
}

.sidebar {
    width: 280px;
    background: var(--bg-primary);
    border-right: 1px solid var(--border);
    position: fixed;
    height: 100vh;
    overflow-y: auto;
    z-index: 100;
}

.main-content {
    flex: 1;
    margin-left: 280px;
    padding: 2rem;
}

@media (max-width: 1024px) {
    .sidebar {
        transform: translateX(-100%);
        transition: var(--transition);
    }
    .sidebar.open {
        transform: translateX(0);
    }
    .main-content {
        margin-left: 0;
    }
}

/* Header */
.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border);
    padding: 1rem 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 50;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary);
    text-decoration: none;
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.25rem;
}

/* Navigation */
.nav-menu {
    list-style: none;
    padding: 1rem;
}

.nav-item {
    margin-bottom: 0.25rem;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.875rem 1rem;
    border-radius: var(--radius);
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

.nav-link:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.nav-link.active {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
}

.nav-link i {
    width: 20px;
    text-align: center;
}

/* Cards */
.card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
    overflow: hidden;
    transition: var(--transition);
}

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

.card-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.card-body {
    padding: 1.5rem;
}

.card-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border);
    background: var(--bg-secondary);
}

/* Stats Cards */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    border: 1px solid var(--border);
    transition: var(--transition);
}

.stat-card:hover {
    box-shadow: var(--shadow-md);
}

.stat-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.stat-icon.primary { background: rgba(99, 102, 241, 0.1); color: var(--primary); }
.stat-icon.success { background: rgba(34, 197, 94, 0.1); color: var(--success); }
.stat-icon.warning { background: rgba(245, 158, 11, 0.1); color: var(--warning); }
.stat-icon.danger { background: rgba(239, 68, 68, 0.1); color: var(--danger); }

.stat-value {
    font-size: 2rem;
    font-weight: 800;
    line-height: 1;
    margin-bottom: 0.25rem;
}

.stat-label {
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    font-weight: 600;
    font-size: 0.875rem;
    cursor: pointer;
    transition: var(--transition);
    border: none;
    text-decoration: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
}

.btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.4);
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--border);
}

.btn-success {
    background: linear-gradient(135deg, var(--success), #16a34a);
    color: white;
}

.btn-danger {
    background: linear-gradient(135deg, var(--danger), #dc2626);
    color: white;
}

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

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

.btn-lg {
    padding: 1rem 2rem;
    font-size: 1rem;
    border-radius: var(--radius-md);
}

.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.75rem;
}

.btn-icon {
    width: 40px;
    height: 40px;
    padding: 0;
    border-radius: var(--radius-full);
}

/* Flashcard */
.flashcard-container {
    perspective: 1000px;
    max-width: 600px;
    margin: 0 auto;
}

.flashcard {
    width: 100%;
    aspect-ratio: 16/10;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
}

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

.flashcard-face {
    position: absolute;
    inset: 0;
    backface-visibility: hidden;
    border-radius: var(--radius-xl);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    text-align: center;
}

.flashcard-front {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
}

.flashcard-back {
    background: var(--bg-primary);
    border: 2px solid var(--border);
    transform: rotateY(180deg);
}

.flashcard-word {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 1rem;
}

.flashcard-pronunciation {
    font-size: 1.25rem;
    opacity: 0.9;
    margin-bottom: 1.5rem;
}

.flashcard-meaning {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.flashcard-example {
    font-size: 1rem;
    color: var(--text-secondary);
    max-width: 400px;
}

.flashcard-progress {
    position: absolute;
    bottom: 1.5rem;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    gap: 0.5rem;
}

.progress-dot {
    width: 8px;
    height: 8px;
    border-radius: var(--radius-full);
    background: rgba(255, 255, 255, 0.3);
}

.progress-dot.active {
    background: white;
    width: 24px;
}

/* Learning Controls */
.learning-controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-top: 2rem;
}

.control-btn {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-full);
    border: none;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
}

.control-btn.skip {
    background: var(--bg-tertiary);
    color: var(--text-secondary);
}

.control-btn.wrong {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
}

.control-btn.correct {
    background: rgba(34, 197, 94, 0.1);
    color: var(--success);
}

.control-btn.easy {
    background: rgba(99, 102, 241, 0.1);
    color: var(--primary);
}

.control-btn:hover {
    transform: scale(1.1);
}

/* Lecture Grid */
.lecture-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}

.lecture-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
    overflow: hidden;
    transition: var(--transition);
}

.lecture-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.lecture-card-image {
    height: 160px;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3rem;
    color: white;
}

.lecture-card-body {
    padding: 1.25rem;
}

.lecture-card-title {
    font-size: 1.125rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.lecture-card-meta {
    display: flex;
    gap: 1rem;
    color: var(--text-muted);
    font-size: 0.875rem;
}

.lecture-card-meta span {
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

/* Progress Bar */
.progress-bar {
    height: 8px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    border-radius: var(--radius-full);
    transition: width 0.5s ease;
}

/* Streak */
.streak-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    background: linear-gradient(135deg, #f59e0b, #ea580c);
    color: white;
    border-radius: var(--radius-full);
    font-weight: 700;
}

.streak-badge i {
    animation: flame 0.5s ease infinite alternate;
}

@keyframes flame {
    from { transform: scale(1); }
    to { transform: scale(1.2); }
}

/* XP Bar */
.xp-bar {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 1.25rem;
    border: 1px solid var(--border);
}

.xp-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

.xp-level {
    font-weight: 800;
    color: var(--primary);
}

.xp-progress {
    height: 10px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.xp-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--accent));
    border-radius: var(--radius-full);
    transition: width 0.5s ease;
}

/* Achievement */
.achievement-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: 1rem;
}

.achievement {
    aspect-ratio: 1;
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 0.75rem;
    text-align: center;
    transition: var(--transition);
    cursor: pointer;
}

.achievement.locked {
    background: var(--bg-tertiary);
    opacity: 0.5;
}

.achievement.unlocked {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(236, 72, 153, 0.1));
    border: 2px solid var(--primary);
}

.achievement:hover {
    transform: scale(1.05);
}

.achievement-icon {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.achievement-name {
    font-size: 0.75rem;
    font-weight: 600;
    line-height: 1.2;
}

/* Leaderboard */
.leaderboard {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
    overflow: hidden;
}

.leaderboard-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.25rem;
    border-bottom: 1px solid var(--border);
    transition: var(--transition);
}

.leaderboard-item:last-child {
    border-bottom: none;
}

.leaderboard-item:hover {
    background: var(--bg-secondary);
}

.leaderboard-rank {
    width: 32px;
    height: 32px;
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 800;
    font-size: 0.875rem;
}

.leaderboard-rank.gold {
    background: linear-gradient(135deg, #fcd34d, #f59e0b);
    color: white;
}

.leaderboard-rank.silver {
    background: linear-gradient(135deg, #e2e8f0, #94a3b8);
    color: white;
}

.leaderboard-rank.bronze {
    background: linear-gradient(135deg, #fed7aa, #ea580c);
    color: white;
}

.leaderboard-avatar {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-full);
    background: var(--bg-tertiary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    color: var(--text-secondary);
}

.leaderboard-info {
    flex: 1;
}

.leaderboard-name {
    font-weight: 600;
}

.leaderboard-level {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.leaderboard-score {
    font-weight: 800;
    color: var(--primary);
}

/* Modals */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    max-width: 500px;
    width: 90%;
    max-height: 90vh;
    overflow-y: auto;
    transform: scale(0.9);
    transition: var(--transition);
}

.modal-overlay.active .modal {
    transform: scale(1);
}

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

.modal-body {
    padding: 1.5rem;
}

.modal-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border);
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    z-index: 2000;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.toast {
    background: var(--bg-primary);
    border-radius: var(--radius);
    padding: 1rem 1.25rem;
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    min-width: 300px;
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        transform: translateX(100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

.toast-success { border-left: 4px solid var(--success); }
.toast-error { border-left: 4px solid var(--danger); }
.toast-warning { border-left: 4px solid var(--warning); }
.toast-info { border-left: 4px solid var(--info); }

/* Forms */
.form-group {
    margin-bottom: 1.25rem;
}

.form-label {
    display: block;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.form-input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    font-size: 1rem;
    background: var(--bg-primary);
    color: var(--text-primary);
    transition: var(--transition);
}

.form-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

/* Utilities */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-muted { color: var(--text-muted); }
.text-primary { color: var(--primary); }
.text-success { color: var(--success); }
.text-danger { color: var(--danger); }

.font-bold { font-weight: 700; }
.font-extrabold { font-weight: 800; }

.mt-1 { margin-top: 0.25rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-3 { margin-top: 0.75rem; }
.mt-4 { margin-top: 1rem; }
.mt-6 { margin-top: 1.5rem; }

.mb-1 { margin-bottom: 0.25rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-3 { margin-bottom: 0.75rem; }
.mb-4 { margin-bottom: 1rem; }
.mb-6 { margin-bottom: 1.5rem; }

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: 0.5rem; }
.gap-3 { gap: 0.75rem; }
.gap-4 { gap: 1rem; }

.grid { display: grid; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

.hidden { display: none; }
.block { display: block; }

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

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

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

.animate-fadeIn { animation: fadeIn 0.5s ease; }
.animate-slideUp { animation: slideUp 0.5s ease; }
.animate-pulse { animation: pulse 2s ease infinite; }

/* Quiz Options */
.quiz-options {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin-top: 2rem;
}

.quiz-option {
    padding: 1.25rem;
    border: 2px solid var(--border);
    border-radius: var(--radius-lg);
    background: var(--bg-primary);
    cursor: pointer;
    transition: var(--transition);
    text-align: center;
    font-size: 1.125rem;
    font-weight: 600;
}

.quiz-option:hover {
    border-color: var(--primary);
    background: rgba(99, 102, 241, 0.05);
}

.quiz-option.selected {
    border-color: var(--primary);
    background: rgba(99, 102, 241, 0.1);
}

.quiz-option.correct {
    border-color: var(--success);
    background: rgba(34, 197, 94, 0.1);
    color: var(--success);
}

.quiz-option.wrong {
    border-color: var(--danger);
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
}

/* Timer */
.timer {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--text-primary);
}

.timer.warning {
    color: var(--warning);
    animation: pulse 0.5s ease infinite;
}

.timer.danger {
    color: var(--danger);
    animation: pulse 0.3s ease infinite;
}

/* Audio Button */
.audio-btn {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-full);
    background: var(--bg-tertiary);
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    color: var(--primary);
    transition: var(--transition);
}

.audio-btn:hover {
    background: var(--primary);
    color: white;
    transform: scale(1.1);
}

.audio-btn.playing {
    background: var(--primary);
    color: white;
    animation: pulse 0.5s ease infinite;
}

/* Loading Spinner */
.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem;
}

.empty-state-icon {
    font-size: 4rem;
    margin-bottom: 1rem;
    opacity: 0.5;
}

.empty-state-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.empty-state-text {
    color: var(--text-muted);
    margin-bottom: 1.5rem;
}