/* 基础样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* CSS 变量定义 */
:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --secondary-color: #64748b;
    --accent-color: #06d6a0;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --background-color: #f8fafc;
    --surface-color: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --border-radius: 12px;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --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);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* 暗色主题 */
@media (prefers-color-scheme: dark) {
    :root {
        --background-color: #0f172a;
        --surface-color: #1e293b;
        --text-primary: #f1f5f9;
        --text-secondary: #94a3b8;
        --border-color: #334155;
    }
}

/* 基础样式 */
body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    line-height: 1.6;
    font-size: 16px;
    overflow-x: hidden;
}

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* 头部样式 */
.header {
    background: var(--surface-color);
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo i {
    font-size: 1.8rem;
}

.nav-menu {
    display: flex;
    gap: 0.5rem;
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    border-radius: var(--border-radius);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.9rem;
}

.nav-btn:hover {
    background: var(--background-color);
    color: var(--text-primary);
}

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

/* 主要内容区域 */
.main-content {
    flex: 1;
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
    width: 100%;
}

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

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

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

/* 学习页面样式 */
.learning-container {
    max-width: 600px;
    margin: 0 auto;
}

.progress-section {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    margin-bottom: 2rem;
}

.progress-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.progress-text {
    font-weight: 500;
    color: var(--text-primary);
}

.progress-numbers {
    font-weight: 600;
    color: var(--primary-color);
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--border-color);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    border-radius: 4px;
    transition: width 0.5s ease;
    width: 0%;
}

/* 单词卡片样式 */
.word-card {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    transition: var(--transition);
}

.word-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
}

.card-content {
    padding: 2rem;
}

.word-display {
    text-align: center;
    margin-bottom: 2rem;
    position: relative;
}

.word-text {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
}

.phonetic-container {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 1.5rem;
}

.phonetic-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.phonetic-label {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--primary-color);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.word-phonetic {
    font-size: 1.1rem;
    color: var(--text-secondary);
    font-style: italic;
    min-height: 1.5rem;
    display: flex;
    align-items: center;
}

.audio-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 50%;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.9rem;
    position: relative;
}

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

.audio-btn:active {
    transform: scale(0.95);
}

.audio-btn.playing {
    background: var(--accent-color);
    animation: pulse 1s infinite;
}

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.1); }
    100% { transform: scale(1); }
}

.audio-btn:active {
    transform: scale(0.95);
}

/* 释义区域 */
.word-meaning {
    background: var(--background-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    margin-bottom: 1.5rem;
}

.meaning-content h3 {
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-weight: 600;
}

.definitions {
    margin-bottom: 1rem;
}

.definition-item {
    margin-bottom: 0.75rem;
    padding: 0.75rem;
    background: var(--surface-color);
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

.definition-type {
    font-weight: 600;
    color: var(--primary-color);
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.definition-text {
    color: var(--text-primary);
    margin-top: 0.25rem;
}

.example-sentences {
    margin-top: 1rem;
}

.example-item {
    margin-bottom: 0.5rem;
    padding: 0.5rem;
    background: var(--surface-color);
    border-radius: 6px;
    font-style: italic;
    color: var(--text-secondary);
    border-left: 3px solid var(--accent-color);
}

/* 拼写练习区域 */
.spelling-section {
    background: var(--background-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    margin-bottom: 1.5rem;
}

.spelling-section h3 {
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-weight: 600;
}

.spelling-input-area {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.spelling-input {
    flex: 1;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--surface-color);
    color: var(--text-primary);
    font-size: 1rem;
    transition: var(--transition);
}

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

.check-spelling-btn {
    padding: 0.75rem 1rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.check-spelling-btn:hover {
    background: var(--primary-dark);
}

.spelling-result {
    padding: 0.75rem;
    border-radius: var(--border-radius);
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.spelling-result.correct {
    background: rgb(16 185 129 / 0.1);
    color: var(--success-color);
    border: 1px solid rgb(16 185 129 / 0.2);
}

.spelling-result.incorrect {
    background: rgb(239 68 68 / 0.1);
    color: var(--danger-color);
    border: 1px solid rgb(239 68 68 / 0.2);
}

.spelling-hint {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-style: italic;
}

/* 按钮样式 */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    font-size: 0.9rem;
    justify-content: center;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
}

.btn-secondary {
    background: var(--background-color);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

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

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

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

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

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

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

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

.action-btn {
    width: 100%;
    padding: 1rem 2rem;
    font-size: 1.1rem;
    font-weight: 600;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
}

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

.learning-buttons {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.learning-buttons .btn {
    flex: 1;
}

.difficulty-buttons {
    display: flex;
    gap: 1rem;
}

.difficulty-buttons .btn {
    flex: 1;
}

/* 复习页面样式 */
.review-container {
    max-width: 800px;
    margin: 0 auto;
}

.review-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.review-header h2 {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--text-primary);
    font-size: 1.8rem;
}

.review-stats {
    display: flex;
    gap: 2rem;
}

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

.stat-number {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.review-list {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
}

.review-item {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.review-item:hover {
    background: var(--background-color);
}

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

.review-word {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 1.1rem;
}

.review-progress {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.progress-dots {
    display: flex;
    gap: 0.25rem;
}

.progress-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--border-color);
}

.progress-dot.filled {
    background: var(--primary-color);
}

.empty-state {
    text-align: center;
    padding: 3rem 1.5rem;
    color: var(--text-secondary);
}

.empty-state i {
    font-size: 3rem;
    margin-bottom: 1rem;
    color: var(--accent-color);
}

/* 统计页面样式 */
.stats-container {
    max-width: 900px;
    margin: 0 auto;
}

.stats-container h2 {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 2rem;
    color: var(--text-primary);
    font-size: 1.8rem;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-bottom: 3rem;
}

.stat-card {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    display: flex;
    align-items: center;
    gap: 1rem;
    transition: var(--transition);
}

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

.stat-icon {
    width: 50px;
    height: 50px;
    border-radius: 10px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.25rem;
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

.stat-title {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.chart-section {
    background: var(--surface-color);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
}

.chart-section h3 {
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    font-weight: 600;
}

.chart-container {
    height: 300px;
    position: relative;
}

/* 设置页面样式 */
.settings-container {
    max-width: 600px;
    margin: 0 auto;
}

.settings-container h2 {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 2rem;
    color: var(--text-primary);
    font-size: 1.8rem;
}

.settings-section {
    background: var(--surface-color);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    margin-bottom: 2rem;
}

.settings-section h3 {
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    font-weight: 600;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border-color);
}

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

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

.setting-item label {
    font-weight: 500;
    color: var(--text-primary);
}

.setting-item input[type="number"] {
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    background: var(--background-color);
    color: var(--text-primary);
    width: 100px;
}

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

.setting-item select {
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    background: var(--background-color);
    color: var(--text-primary);
    min-width: 120px;
    cursor: pointer;
}

.setting-item select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgb(99 102 241 / 0.1);
}

.setting-actions {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.setting-actions .btn {
    flex: 1;
    min-width: 120px;
}

.import-help {
    margin-top: 1rem;
    padding: 1rem;
    background: var(--background-color);
    border-radius: 8px;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.import-help p {
    margin: 0.25rem 0;
}

/* 模态框样式 */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal-content {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    max-width: 90vw;
    max-height: 80vh;
    width: 600px;
    overflow: hidden;
}

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

.modal-header h3 {
    margin: 0;
    color: var(--text-primary);
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-secondary);
    cursor: pointer;
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: var(--transition);
}

.modal-close:hover {
    background: var(--background-color);
    color: var(--text-primary);
}

.modal-body {
    padding: 1.5rem;
    max-height: 50vh;
    overflow-y: auto;
}

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

.words-stats {
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: var(--background-color);
    border-radius: 8px;
}

.words-stats p {
    margin: 0.25rem 0;
    font-weight: 500;
}

.words-list {
    max-height: 300px;
    overflow-y: auto;
}

.word-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
}

.word-item:hover {
    background: var(--background-color);
}

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

.word-info {
    flex: 1;
}

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

.word-info .phonetic {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-style: italic;
}

.word-status {
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-size: 0.8rem;
    font-weight: 500;
}

.word-status.learned {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success-color);
}

.word-status.new {
    background: rgba(99, 102, 241, 0.1);
    color: var(--primary-color);
}

/* Toast 消息样式 */
.toast {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 1rem 1.5rem;
    border-radius: var(--border-radius);
    color: white;
    font-weight: 500;
    z-index: 1001;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    min-width: 250px;
    box-shadow: var(--shadow-lg);
    transform: translateX(100%);
    opacity: 0;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.toast.show {
    transform: translateX(0);
    opacity: 1;
}

.toast-success {
    background: var(--success-color);
}

.toast-error {
    background: var(--danger-color);
}

.toast-info {
    background: var(--primary-color);
}

.toast i {
    font-size: 1.2rem;
    flex-shrink: 0;
}

.toast span {
    flex: 1;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .header-content {
        padding: 0 1rem;
        height: 60px;
        flex-direction: column;
        gap: 1rem;
        height: auto;
        padding: 1rem;
    }

    .nav-menu {
        width: 100%;
        justify-content: center;
    }

    .nav-btn {
        padding: 0.5rem 0.75rem;
        font-size: 0.8rem;
    }

    .main-content {
        padding: 1rem;
    }

    .word-text {
        font-size: 2rem;
    }

    .phonetic-container {
        flex-direction: column;
        gap: 1rem;
    }

    .card-content {
        padding: 1.5rem;
    }

    .learning-buttons {
        flex-direction: column;
    }

    .difficulty-buttons {
        flex-direction: column;
    }

    .review-header {
        flex-direction: column;
        text-align: center;
    }

    .review-stats {
        gap: 1rem;
    }

    .stats-grid {
        grid-template-columns: 1fr;
    }

    .spelling-input-area {
        flex-direction: column;
    }

    .setting-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }

    .setting-actions {
        flex-direction: column;
    }
}

@media (max-width: 480px) {
    .word-text {
        font-size: 1.75rem;
    }

    .card-content {
        padding: 1rem;
    }

    .progress-section {
        padding: 1rem;
    }

    .chart-container {
        height: 250px;
    }
}

/* 动画和过渡效果 */
.fade-in {
    animation: fadeIn 0.3s ease-in-out;
}

.slide-up {
    animation: slideUp 0.3s ease-out;
}

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

.bounce {
    animation: bounce 0.6s ease-in-out;
}

@keyframes bounce {
    0%, 20%, 53%, 80%, 100% {
        transform: translateY(0);
    }
    40%, 43% {
        transform: translateY(-10px);
    }
    70% {
        transform: translateY(-5px);
    }
    90% {
        transform: translateY(-2px);
    }
}

/* 加载状态 */
.loading {
    opacity: 0.6;
    pointer-events: none;
    position: relative;
}

.loading::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    margin: -10px 0 0 -10px;
    border: 2px solid var(--border-color);
    border-top: 2px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* 滚动条样式 */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--background-color);
}

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}