/* ==========================================
   CET-4 Pro - 苹果风格现代化设计
   ========================================== */

/* CSS Variables */
:root {
    --primary-color: #007AFF;
    --primary-dark: #0056CC;
    --secondary-color: #5856D6;
    --success-color: #34C759;
    --warning-color: #FF9500;
    --danger-color: #FF3B30;
    --text-primary: #1D1D1F;
    --text-secondary: #86868B;
    --text-tertiary: #AEAEB2;
    --bg-primary: #FFFFFF;
    --bg-secondary: #F5F5F7;
    --bg-tertiary: #E8E8ED;
    --border-color: rgba(0, 0, 0, 0.1);
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.12);
    --shadow-xl: 0 20px 60px rgba(0, 0, 0, 0.16);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-xl: 28px;
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    --font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    color: var(--text-primary);
    background-color: var(--bg-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    letter-spacing: -0.02em;
}

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

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 28px;
    font-size: 16px;
    font-weight: 500;
    border-radius: var(--radius-xl);
    border: none;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(0, 122, 255, 0.3);
}

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

.btn-secondary:hover {
    background: var(--border-color);
    transform: translateY(-2px);
}

/* ==========================================
   Navigation
   ========================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.72);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid var(--border-color);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 60px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
}

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

.nav-menu {
    display: flex;
    list-style: none;
    gap: 8px;
}

.nav-link {
    padding: 8px 16px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

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

.nav-toggle {
    display: none;
    font-size: 24px;
    cursor: pointer;
}

/* ==========================================
   Hero Section
   ========================================== */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 120px 24px 80px;
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    opacity: 0.05;
    z-index: -1;
}

.hero-content {
    text-align: center;
    max-width: 800px;
}

.hero-title {
    font-size: clamp(48px, 8vw, 80px);
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: 24px;
    letter-spacing: -0.03em;
}

.gradient-text {
    background: linear-gradient(135deg, #007AFF, #5856D6, #AF52DE);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 21px;
    color: var(--text-secondary);
    margin-bottom: 40px;
    line-height: 1.5;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    justify-content: center;
    margin-bottom: 60px;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 60px;
}

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

.stat-number {
    display: block;
    font-size: 40px;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

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

/* ==========================================
   Features Section
   ========================================== */
.features {
    padding: 100px 0;
    background: var(--bg-secondary);
}

.section-title {
    text-align: center;
    font-size: 40px;
    font-weight: 700;
    margin-bottom: 60px;
    letter-spacing: -0.02em;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 24px;
}

.feature-card {
    background: var(--bg-primary);
    padding: 40px 32px;
    border-radius: var(--radius-lg);
    text-align: center;
    transition: all var(--transition-normal);
    border: 1px solid transparent;
}

.feature-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: var(--border-color);
}

.feature-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    border-radius: var(--radius-md);
    font-size: 28px;
    color: white;
}

.feature-card h3 {
    font-size: 20px;
    margin-bottom: 12px;
}

.feature-card p {
    font-size: 15px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ==========================================
   Vocabulary Section
   ========================================== */
.vocabulary-section {
    padding: 100px 0;
}

.vocab-controls {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 20px;
    margin-bottom: 40px;
}

.vocab-select {
    padding: 12px 20px;
    font-size: 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-primary);
    cursor: pointer;
    min-width: 160px;
}

.vocab-mode-toggle {
    display: flex;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    padding: 4px;
}

.mode-btn {
    padding: 10px 20px;
    font-size: 14px;
    font-weight: 500;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.mode-btn.active {
    background: var(--bg-primary);
    color: var(--text-primary);
    box-shadow: var(--shadow-sm);
}

/* Word Card */
.word-card {
    max-width: 600px;
    margin: 0 auto 40px;
    perspective: 1000px;
}

.card-inner {
    position: relative;
    width: 100%;
    min-height: 300px;
    transition: transform 0.6s;
    transform-style: preserve-3d;
    cursor: pointer;
}

.word-card.flipped .card-inner {
    transform: rotateY(180deg);
}

.card-front,
.card-back {
    position: absolute;
    width: 100%;
    min-height: 300px;
    backface-visibility: hidden;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px;
}

.card-back {
    transform: rotateY(180deg);
}

.word {
    font-size: 48px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 16px;
}

.phonetic {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 16px;
}

.phonetic-uk {
    font-size: 18px;
    color: var(--text-secondary);
}

.sound-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 14px;
    font-size: 13px;
    font-weight: 500;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--bg-secondary);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.sound-btn:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.hint {
    font-size: 14px;
    color: var(--text-tertiary);
}

.word-meaning {
    text-align: center;
    margin-bottom: 24px;
}

.pos {
    font-size: 14px;
    color: var(--primary-color);
    font-weight: 600;
    margin-bottom: 8px;
}

.definition {
    font-size: 24px;
    font-weight: 600;
    color: var(--text-primary);
}

.word-example {
    text-align: center;
    padding: 20px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    width: 100%;
}

.example-sentence {
    font-size: 16px;
    color: var(--text-primary);
    margin-bottom: 8px;
    font-style: italic;
}

.example-translation {
    font-size: 14px;
    color: var(--text-secondary);
}

/* Card Controls */
.card-controls {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 40px;
    margin-bottom: 32px;
}

.control-btn {
    width: 56px;
    height: 56px;
    border: none;
    background: var(--bg-secondary);
    border-radius: 50%;
    font-size: 20px;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.progress-info {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
}

/* Card Actions */
.card-actions {
    display: flex;
    justify-content: center;
    gap: 16px;
}

.action-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    font-size: 15px;
    font-weight: 500;
    border: none;
    border-radius: var(--radius-xl);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.action-btn.forget {
    background: rgba(255, 59, 48, 0.1);
    color: var(--danger-color);
}

.action-btn.forget:hover {
    background: var(--danger-color);
    color: white;
}

.action-btn.known {
    background: rgba(52, 199, 89, 0.1);
    color: var(--success-color);
}

.action-btn.known:hover {
    background: var(--success-color);
    color: white;
}

.action-btn.favorite {
    background: rgba(255, 149, 0, 0.1);
    color: var(--warning-color);
}

.action-btn.favorite:hover {
    background: var(--warning-color);
    color: white;
}

/* Word List Mode */
.word-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 16px;
}

.word-list-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 20px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.word-list-item:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-sm);
}

.word-list-item .word-info {
    flex: 1;
}

.word-list-item .word-text {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.word-list-item .word-trans {
    font-size: 14px;
    color: var(--text-secondary);
}

.word-list-item .word-actions {
    display: flex;
    gap: 8px;
}

.word-list-item .word-actions button {
    width: 36px;
    height: 36px;
    border: none;
    background: var(--bg-secondary);
    border-radius: 50%;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.word-list-item .word-actions button:hover {
    background: var(--primary-color);
    color: white;
}

/* Test Mode */
.test-container {
    max-width: 600px;
    margin: 0 auto;
}

.test-progress {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 40px;
}

.test-progress-bar {
    flex: 1;
    height: 8px;
    background: var(--bg-tertiary);
    border-radius: 4px;
    overflow: hidden;
}

.test-progress-fill {
    height: 100%;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    border-radius: 4px;
    transition: width var(--transition-normal);
}

.test-question {
    text-align: center;
    padding: 40px;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.test-question h3 {
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 32px;
}

.test-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.test-option {
    padding: 16px 24px;
    background: var(--bg-secondary);
    border: 2px solid transparent;
    border-radius: var(--radius-md);
    font-size: 16px;
    text-align: left;
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.test-option.correct {
    background: rgba(52, 199, 89, 0.1);
    border-color: var(--success-color);
}

.test-option.wrong {
    background: rgba(255, 59, 48, 0.1);
    border-color: var(--danger-color);
}

.test-result {
    text-align: center;
    padding: 40px;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.result-score {
    margin-bottom: 24px;
}

.score-number {
    font-size: 72px;
    font-weight: 700;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.score-total {
    font-size: 36px;
    color: var(--text-secondary);
}

.result-message {
    font-size: 18px;
    color: var(--text-secondary);
    margin-bottom: 24px;
}

/* ==========================================
   Exam Section
   ========================================== */
.exam-section {
    padding: 100px 0;
    background: var(--bg-secondary);
}

.exam-tabs {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-bottom: 32px;
    flex-wrap: wrap;
}

.exam-tab {
    padding: 12px 24px;
    font-size: 15px;
    font-weight: 500;
    border: none;
    background: var(--bg-primary);
    color: var(--text-secondary);
    border-radius: var(--radius-xl);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.exam-tab:hover,
.exam-tab.active {
    background: var(--primary-color);
    color: white;
}

.exam-filter {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-bottom: 40px;
}

.exam-select {
    padding: 12px 20px;
    font-size: 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-primary);
    cursor: pointer;
}

/* Exam Paper */
.exam-paper {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 40px;
    box-shadow: var(--shadow-md);
}

.paper-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 32px;
    padding-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
}

.paper-header h3 {
    font-size: 24px;
    font-weight: 600;
}

.timer {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 18px;
    font-weight: 600;
    color: var(--primary-color);
}

.passage {
    margin-bottom: 40px;
    padding: 24px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.passage p {
    margin-bottom: 16px;
    line-height: 1.8;
    font-size: 16px;
}

.passage p:last-child {
    margin-bottom: 0;
}

.questions {
    margin-bottom: 32px;
}

.question-item {
    margin-bottom: 32px;
}

.question-text {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 16px;
}

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

.option {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 20px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.option input[type="radio"] {
    width: 20px;
    height: 20px;
    accent-color: var(--primary-color);
}

.paper-actions {
    display: flex;
    justify-content: center;
    gap: 16px;
}

/* ==========================================
   Writing Section
   ========================================== */
.writing-section {
    padding: 100px 0;
}

.writing-filter {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-bottom: 40px;
}

.writing-select {
    padding: 12px 20px;
    font-size: 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-primary);
    cursor: pointer;
}

/* Writing List */
.writing-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 24px;
}

.writing-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
    transition: all var(--transition-normal);
    cursor: pointer;
}

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

.writing-card-header {
    padding: 20px 24px;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    color: white;
}

.writing-card-header .year-tag {
    display: inline-block;
    padding: 4px 12px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-sm);
    font-size: 13px;
    margin-bottom: 8px;
}

.writing-card-header h3 {
    font-size: 18px;
    font-weight: 600;
}

.writing-card-body {
    padding: 20px 24px;
}

.writing-card-body p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.6;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.writing-card-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.writing-type-tag {
    padding: 4px 12px;
    background: var(--bg-secondary);
    border-radius: var(--radius-sm);
    font-size: 13px;
    color: var(--text-secondary);
}

.writing-progress {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 13px;
    color: var(--text-secondary);
}

.writing-progress i {
    color: var(--success-color);
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(8px);
    z-index: 2000;
    align-items: center;
    justify-content: center;
    padding: 24px;
}

.modal.active {
    display: flex;
}

.modal-content {
    width: 100%;
    max-width: 900px;
    max-height: 90vh;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 24px;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h3 {
    font-size: 20px;
    font-weight: 600;
}

.modal-close {
    width: 36px;
    height: 36px;
    border: none;
    background: var(--bg-secondary);
    border-radius: 50%;
    font-size: 16px;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: var(--danger-color);
    color: white;
}

.modal-body {
    flex: 1;
    overflow-y: auto;
    padding: 24px;
}

/* Writing Tabs */
.writing-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    flex-wrap: wrap;
}

.writing-tab {
    padding: 10px 20px;
    font-size: 14px;
    font-weight: 500;
    border: none;
    background: var(--bg-secondary);
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.writing-tab:hover,
.writing-tab.active {
    background: var(--primary-color);
    color: white;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

/* Topic Box */
.topic-box {
    padding: 24px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.topic-box h4 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--primary-color);
}

.topic-box p {
    line-height: 1.8;
}

/* Sample Essay */
.sample-essay {
    padding: 24px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.essay-controls {
    display: flex;
    gap: 12px;
    margin-bottom: 20px;
}

.essay-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 16px;
    font-size: 14px;
    font-weight: 500;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.essay-btn:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* Essay text with line-by-line translation */
.essay-text-with-translation {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.essay-paragraph {
    line-height: 2;
    font-size: 16px;
    padding: 16px 20px;
    border-radius: var(--radius-md);
    white-space: pre-wrap;
}

.essay-paragraph.original {
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-weight: 500;
}

.essay-paragraph.translation {
    background: transparent;
    color: var(--text-secondary);
    font-size: 15px;
    line-height: 1.8;
    padding-left: 32px;
    padding-right: 32px;
    border-left: 3px solid var(--primary-color);
    margin-bottom: 8px;
}

/* Analysis Box */
.analysis-box {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.analysis-section {
    padding: 20px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.analysis-section h4 {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--primary-color);
}

.highlight-words {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.highlight-word {
    padding: 8px 16px;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    font-size: 14px;
}

.highlight-word .word {
    font-weight: 600;
    color: var(--primary-color);
}

.highlight-word .meaning {
    color: var(--text-secondary);
    margin-left: 8px;
}

.highlight-sentences {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.highlight-sentence {
    padding: 16px;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    border-left: 4px solid var(--primary-color);
}

.highlight-sentence .sentence {
    font-size: 15px;
    font-weight: 500;
    margin-bottom: 8px;
}

.highlight-sentence .translation {
    font-size: 14px;
    color: var(--text-secondary);
}

/* Recite Box */
.recite-box {
    padding: 24px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.recite-progress {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 24px;
}

.recite-progress-bar {
    flex: 1;
    height: 8px;
    background: var(--bg-tertiary);
    border-radius: 4px;
    overflow: hidden;
}

.recite-progress-fill {
    height: 100%;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    border-radius: 4px;
    transition: width var(--transition-normal);
}

.recite-mode-select {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    flex-wrap: wrap;
}

.recite-mode-btn {
    padding: 10px 16px;
    font-size: 14px;
    font-weight: 500;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.recite-mode-btn:hover,
.recite-mode-btn.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.recite-area {
    padding: 20px;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    margin-bottom: 24px;
    min-height: 200px;
    line-height: 2;
    font-size: 16px;
}

.recite-area .blank {
    display: inline-block;
    min-width: 80px;
    border-bottom: 2px solid var(--primary-color);
    margin: 0 4px;
}

.recite-area .first-letter {
    color: var(--primary-color);
    font-weight: 600;
}

.recite-input {
    display: flex;
    gap: 16px;
    margin-bottom: 24px;
}

.recite-input textarea {
    flex: 1;
    min-height: 120px;
    padding: 16px;
    font-size: 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    resize: vertical;
    font-family: inherit;
}

.recite-input textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.1);
}

.recite-result {
    padding: 20px;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
}

.accuracy {
    text-align: center;
    margin-bottom: 20px;
}

.accuracy-label {
    font-size: 16px;
    color: var(--text-secondary);
}

.accuracy-value {
    font-size: 36px;
    font-weight: 700;
    color: var(--success-color);
}

.diff-view {
    line-height: 2;
    font-size: 15px;
}

.diff-view .correct {
    color: var(--success-color);
}

.diff-view .wrong {
    color: var(--danger-color);
    text-decoration: line-through;
}

.diff-view .missing {
    color: var(--warning-color);
    background: rgba(255, 149, 0, 0.1);
    padding: 2px 4px;
    border-radius: 4px;
}

/* ==========================================
   Progress Section
   ========================================== */
.progress-section {
    padding: 100px 0;
    background: var(--bg-secondary);
}

.progress-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 24px;
    margin-bottom: 40px;
}

.progress-card {
    display: flex;
    align-items: center;
    gap: 20px;
    padding: 24px;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
}

.progress-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    border-radius: var(--radius-md);
    font-size: 24px;
    color: white;
}

.progress-info {
    flex: 1;
}

.progress-info h3 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 12px;
}

.progress-bar-container {
    display: flex;
    align-items: center;
    gap: 12px;
}

.progress-bar {
    flex: 1;
    height: 8px;
    background: var(--bg-tertiary);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    border-radius: 4px;
    transition: width var(--transition-normal);
}

.progress-text {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap;
}

.streak-info {
    display: flex;
    align-items: baseline;
    gap: 4px;
}

.streak-number {
    font-size: 40px;
    font-weight: 700;
    background: linear-gradient(135deg, #FF9500, #FF3B30);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.streak-label {
    font-size: 16px;
    color: var(--text-secondary);
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
}

.stat-card {
    padding: 24px;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
}

.stat-card h4 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 20px;
}

.stat-details {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.stat-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 0;
    border-bottom: 1px solid var(--border-color);
}

.stat-row:last-child {
    border-bottom: none;
}

.stat-row span:first-child {
    color: var(--text-secondary);
}

.stat-value {
    font-weight: 600;
    color: var(--primary-color);
}

/* Week Chart */
.week-chart {
    display: flex;
    align-items: flex-end;
    justify-content: space-around;
    height: 150px;
    padding-top: 20px;
}

.chart-bar {
    width: 32px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm) var(--radius-sm) 0 0;
    position: relative;
    transition: all var(--transition-normal);
}

.chart-bar:hover {
    background: var(--primary-color);
}

.chart-bar.active {
    background: linear-gradient(135deg, #007AFF, #5856D6);
}

.chart-bar span {
    position: absolute;
    bottom: -28px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 13px;
    color: var(--text-secondary);
}

/* ==========================================
   Footer
   ========================================== */
.footer {
    padding: 60px 0 30px;
    background: var(--text-primary);
    color: white;
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 40px;
}

.footer-brand .logo {
    color: white;
    margin-bottom: 12px;
}

.footer-brand .logo i {
    color: var(--primary-color);
}

.footer-brand p {
    color: var(--text-tertiary);
}

.footer-links h4,
.footer-contact h4 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 20px;
}

.footer-links ul {
    list-style: none;
}

.footer-links li {
    margin-bottom: 12px;
}

.footer-links a {
    color: var(--text-tertiary);
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: white;
}

.footer-contact p {
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--text-tertiary);
}

.footer-bottom {
    padding-top: 30px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
}

.footer-bottom p {
    font-size: 14px;
    color: var(--text-tertiary);
}

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

.vocab-mode {
    display: none;
}

.vocab-mode.active {
    display: block;
}

/* Page Content */
.page-content {
    padding-top: 100px;
    padding-bottom: 60px;
    min-height: calc(100vh - 200px);
}

.page-header {
    text-align: center;
    margin-bottom: 48px;
}

.page-title {
    font-size: 40px;
    font-weight: 700;
    margin-bottom: 12px;
    background: linear-gradient(135deg, #007AFF, #5856D6);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.page-subtitle {
    font-size: 18px;
    color: var(--text-secondary);
}

/* Card Inner Flip */
.card-inner {
    position: relative;
    width: 100%;
    min-height: 300px;
    transition: transform 0.6s;
    transform-style: preserve-3d;
    cursor: pointer;
}

.card-inner.flipped {
    transform: rotateY(180deg);
}

/* ==========================================
   Responsive Design
   ========================================== */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
        position: absolute;
        top: 60px;
        left: 0;
        right: 0;
        background: var(--bg-primary);
        flex-direction: column;
        padding: 20px;
        border-bottom: 1px solid var(--border-color);
    }

    .nav-menu.active {
        display: flex;
    }

    .nav-toggle {
        display: block;
    }

    .hero-title {
        font-size: 40px;
    }

    .hero-subtitle {
        font-size: 18px;
    }

    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }

    .hero-stats {
        flex-wrap: wrap;
        gap: 30px;
    }

    .vocab-controls {
        flex-direction: column;
        align-items: stretch;
    }

    .vocab-mode-toggle {
        justify-content: center;
    }

    .word {
        font-size: 36px;
    }

    .card-actions {
        flex-wrap: wrap;
    }

    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .footer-brand,
    .footer-links,
    .footer-contact {
        text-align: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }

    .section-title {
        font-size: 28px;
    }

    .hero-title {
        font-size: 32px;
    }

    .word-card {
        min-height: auto;
    }

    .card-front,
    .card-back {
        min-height: 280px;
        padding: 24px;
    }

    .writing-list {
        grid-template-columns: 1fr;
    }

    .modal-content {
        max-height: 95vh;
    }
}