/* ===== 基础样式 ===== */
:root {
    --primary-color: #2196F3;
    --primary-dark: #1976D2;
    --primary-light: #BBDEFB;
    --secondary-color: #4CAF50;
    --secondary-dark: #388E3C;
    --accent-color: #FF9800;
    --danger-color: #f44336;
    --success-color: #4CAF50;
    --warning-color: #FF9800;
    --info-color: #2196F3;
    --text-primary: #212121;
    --text-secondary: #757575;
    --background: #f5f7fa;
    --surface: #ffffff;
    --border-color: #e0e0e0;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.15);
    --radius: 8px;
    --radius-lg: 12px;
    --transition: all 0.3s ease;
}

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

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

/* ===== 导航栏 ===== */
.navbar {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    padding: 0 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
    height: 64px;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo {
    font-size: 1.8rem;
    color: white;
}

.logo i {
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.2));
}

.logo-img {
    width: 36px;
    height: 36px;
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.2));
}

.brand-text {
    color: white;
    font-size: 1.25rem;
    font-weight: 700;
}

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

.nav-link {
    color: rgba(255, 255, 255, 0.85);
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: var(--radius);
    transition: var(--transition);
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.nav-link i {
    font-size: 0.95rem;
}

.nav-link:hover {
    background: rgba(255, 255, 255, 0.15);
    color: white;
}

.nav-link.active {
    background: rgba(255, 255, 255, 0.25);
    color: white;
}

/* ===== 主内容区 ===== */
.main-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
    min-height: calc(100vh - 64px - 60px);
}

.page {
    display: none;
    animation: fadeIn 0.3s ease;
}

.page.active {
    display: block;
}

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

/* ===== 按钮样式 ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
}

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

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

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

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

.btn-info {
    background: linear-gradient(135deg, var(--info-color), #1565C0);
    color: white;
}

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

.btn-danger {
    background: linear-gradient(135deg, var(--danger-color), #c62828);
    color: white;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.btn i {
    font-size: 0.95rem;
}

/* ===== 图标样式 ===== */
.section-icon {
    margin-right: 0.5rem;
    color: var(--primary-color);
}

h2 .section-icon {
    font-size: 1.3rem;
}

h3 i {
    margin-right: 0.4rem;
    color: var(--primary-color);
}

.input-hint i {
    margin-right: 0.3rem;
    color: var(--info-color);
}

.mode-icon {
    font-size: 2.5rem;
    margin-bottom: 0.75rem;
    color: var(--primary-color);
}

.mode-icon i {
    transition: var(--transition);
}

.mode-card:hover .mode-icon i {
    transform: scale(1.1);
    color: var(--primary-dark);
}

.status-icon i {
    color: var(--success-color);
}

.error-icon i {
    color: var(--danger-color);
    font-size: 1.5rem;
}

.detail-label i {
    width: 20px;
    text-align: center;
    margin-right: 0.3rem;
    color: var(--primary-color);
}

.calc-tab i {
    margin-right: 0.4rem;
}

.method-btn i {
    margin-right: 0.3rem;
}

/* ===== 配平页面 ===== */
.balance-container {
    max-width: 900px;
    margin: 0 auto;
}

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

.input-section h2 {
    margin-bottom: 1.5rem;
    color: var(--primary-dark);
}

.equation-input-wrapper {
    margin-bottom: 1rem;
}

#equation-input {
    width: 100%;
    padding: 1rem 1.25rem;
    font-size: 1.25rem;
    font-family: 'Consolas', 'Monaco', monospace;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
    transition: var(--transition);
}

#equation-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.input-hint {
    margin-top: 0.5rem;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.symbol-keyboard {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.symbol-btn {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    background: var(--background);
    border-radius: var(--radius);
    font-size: 1.1rem;
    cursor: pointer;
    transition: var(--transition);
}

.symbol-btn:hover {
    background: var(--primary-light);
    border-color: var(--primary-color);
}

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

/* ===== 结果区域 ===== */
.result-section {
    background: var(--surface);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
}

.result-section h2 {
    margin-bottom: 1.5rem;
    color: var(--secondary-dark);
}

.result-card {
    background: linear-gradient(135deg, #e8f5e9, #c8e6c9);
    padding: 1.5rem;
    border-radius: var(--radius);
    margin-bottom: 1.5rem;
}

.original-equation,
.balanced-equation {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.75rem 0;
}

.original-equation {
    border-bottom: 1px dashed rgba(0, 0, 0, 0.1);
    margin-bottom: 0.5rem;
}

.label {
    font-weight: 500;
    color: var(--text-secondary);
    min-width: 80px;
}

.equation-display {
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 1.25rem;
    flex: 1;
}

.equation-display.success {
    color: var(--secondary-dark);
    font-weight: 600;
}

.status-icon {
    font-size: 1.5rem;
    color: var(--success-color);
}

/* ===== 验证表格 ===== */
.verification-section {
    margin-bottom: 1.5rem;
}

.verification-section h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.verification-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--surface);
    border-radius: var(--radius);
    overflow: hidden;
}

.verification-table th,
.verification-table td {
    padding: 0.75rem 1rem;
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

.verification-table th {
    background: var(--primary-color);
    color: white;
    font-weight: 500;
}

.verification-table tr:last-child td {
    border-bottom: none;
}

.verification-table tr:hover {
    background: var(--background);
}

/* ===== 步骤展示 ===== */
.steps-section {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.steps-content {
    background: var(--background);
    padding: 1.5rem;
    border-radius: var(--radius);
    font-family: 'Consolas', 'Monaco', monospace;
}

.step-item {
    padding: 1rem;
    margin-bottom: 1rem;
    background: var(--surface);
    border-radius: var(--radius);
    border-left: 4px solid var(--primary-color);
}

.step-item:last-child {
    margin-bottom: 0;
}

.step-number {
    display: inline-block;
    width: 28px;
    height: 28px;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    text-align: center;
    line-height: 28px;
    font-weight: 600;
    margin-right: 0.75rem;
}

.step-title {
    font-weight: 600;
    color: var(--primary-dark);
    margin-bottom: 0.5rem;
}

.step-content {
    color: var(--text-secondary);
    margin-left: 2.5rem;
}

.step-equation {
    font-size: 1.1rem;
    color: var(--text-primary);
    margin-top: 0.5rem;
    padding: 0.5rem;
    background: var(--background);
    border-radius: 4px;
}

/* ===== 错误提示 ===== */
.error-section {
    margin-bottom: 1.5rem;
}

.error-card {
    background: linear-gradient(135deg, #ffebee, #ffcdd2);
    padding: 1.5rem;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    gap: 1rem;
    color: #c62828;
}

.error-icon {
    font-size: 1.5rem;
}

/* ===== 教学页面 ===== */
.teaching-container {
    max-width: 1000px;
    margin: 0 auto;
}

.teaching-container h2 {
    margin-bottom: 1.5rem;
    color: var(--primary-dark);
}

.method-selector {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.method-btn {
    padding: 0.75rem 1.25rem;
    border: 2px solid var(--border-color);
    background: var(--surface);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
    font-weight: 500;
}

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

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

.teaching-content {
    background: var(--surface);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
}

.method-intro {
    padding: 1.5rem;
    background: linear-gradient(135deg, var(--primary-light), #e3f2fd);
    border-radius: var(--radius);
    margin-bottom: 2rem;
}

.method-intro h3 {
    color: var(--primary-dark);
    margin-bottom: 0.75rem;
}

.demo-section {
    margin-bottom: 2rem;
}

.demo-section h3 {
    margin-bottom: 1rem;
}

.demo-equation-select {
    margin-bottom: 1rem;
}

.demo-equation-select select {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 1rem;
    min-width: 300px;
}

.demo-content {
    background: var(--background);
    padding: 1.5rem;
    border-radius: var(--radius);
    min-height: 200px;
    margin-bottom: 1rem;
}

.demo-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
    justify-content: center;
}

#demo-progress {
    color: var(--text-secondary);
    min-width: 100px;
    text-align: center;
}

.theory-section {
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.theory-section h3 {
    margin-bottom: 1rem;
}

.theory-content {
    line-height: 1.8;
    color: var(--text-secondary);
}

.theory-content h4 {
    color: var(--text-primary);
    margin: 1rem 0 0.5rem;
}

.theory-content ul {
    margin-left: 1.5rem;
}

/* ===== 练习页面 ===== */
.practice-container {
    max-width: 900px;
    margin: 0 auto;
}

.practice-container h2 {
    margin-bottom: 1.5rem;
    color: var(--primary-dark);
}

.practice-modes {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.mode-card {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
}

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

.mode-card.selected {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.mode-icon {
    font-size: 2.5rem;
    margin-bottom: 0.75rem;
}

.mode-card h3 {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.mode-card p {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.practice-settings {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.settings-row {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.settings-row:last-child {
    margin-bottom: 0;
}

.settings-row label {
    min-width: 60px;
    font-weight: 500;
}

.settings-row select {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 1rem;
    flex: 1;
    max-width: 200px;
}

.practice-area {
    background: var(--surface);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
}

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

.practice-header-right {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.btn-sm {
    padding: 0.4rem 0.8rem;
    font-size: 0.875rem;
}

.practice-info {
    display: flex;
    gap: 2rem;
}

#question-num {
    font-weight: 600;
    color: var(--primary-dark);
}

#timer-display {
    font-weight: 600;
    color: var(--danger-color);
}

.practice-score {
    color: var(--text-secondary);
}

#correct-count {
    color: var(--success-color);
    font-weight: 600;
}

#wrong-count {
    color: var(--danger-color);
    font-weight: 600;
}

.question-card {
    position: relative;
    padding: 1.5rem;
    background: var(--background);
    border-radius: var(--radius);
    margin-bottom: 1rem;
}

.difficulty-badge {
    position: absolute;
    top: 1rem;
    right: 1rem;
    padding: 0.25rem 0.75rem;
    background: var(--accent-color);
    color: white;
    border-radius: 20px;
    font-size: 0.875rem;
}

.question-text {
    margin-bottom: 1.5rem;
}

.question-equation {
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 1.5rem;
    padding: 1rem;
    background: var(--surface);
    border-radius: var(--radius);
    margin-top: 0.75rem;
    text-align: center;
}

.answer-input {
    margin-bottom: 1rem;
}

.answer-input label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

#practice-answer {
    width: 100%;
    padding: 0.75rem 1rem;
    font-size: 1.1rem;
    font-family: 'Consolas', 'Monaco', monospace;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
}

#practice-answer:focus {
    outline: none;
    border-color: var(--primary-color);
}

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

.feedback-card {
    padding: 1.5rem;
    border-radius: var(--radius);
    margin-bottom: 1rem;
}

.feedback-card.correct {
    background: linear-gradient(135deg, #e8f5e9, #c8e6c9);
}

.feedback-card.wrong {
    background: linear-gradient(135deg, #ffebee, #ffcdd2);
}

#feedback-content {
    margin-bottom: 1rem;
}

.practice-result {
    background: var(--surface);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    text-align: center;
}

.practice-result h3 {
    color: var(--secondary-dark);
    margin-bottom: 1.5rem;
}

.result-stats {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-bottom: 2rem;
}

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

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.stat-label {
    color: var(--text-secondary);
}

/* ===== 化学计算器 ===== */
.calculator-container {
    max-width: 800px;
    margin: 0 auto;
}

.calculator-container h2 {
    margin-bottom: 1.5rem;
    color: var(--primary-dark);
}

.calc-tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.calc-tab {
    padding: 0.75rem 1.25rem;
    border: none;
    background: var(--surface);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
    font-weight: 500;
    box-shadow: var(--shadow);
}

.calc-tab:hover {
    background: var(--primary-light);
}

.calc-tab.active {
    background: var(--primary-color);
    color: white;
}

.calc-content {
    background: var(--surface);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
}

.calc-panel {
    display: none;
}

.calc-panel.active {
    display: block;
}

.calc-panel h3 {
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.calc-input-group {
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.calc-input-group label {
    min-width: 100px;
    font-weight: 500;
}

.calc-input-group input,
.calc-input-group select {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 1rem;
    flex: 1;
    min-width: 150px;
}

.calc-input-group input:focus,
.calc-input-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.calc-result {
    margin-top: 1.5rem;
    padding: 1.5rem;
    background: linear-gradient(135deg, #e8f5e9, #c8e6c9);
    border-radius: var(--radius);
    font-size: 1.1rem;
}

.calc-result .result-row {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px dashed rgba(0, 0, 0, 0.1);
}

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

/* ===== 示例库 ===== */
.examples-container {
    max-width: 1200px;
    margin: 0 auto;
}

.examples-container h2 {
    margin-bottom: 1.5rem;
    color: var(--primary-dark);
}

.examples-filter {
    display: flex;
    gap: 1.5rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
    align-items: center;
}

.filter-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.filter-group label {
    font-weight: 500;
    color: var(--text-secondary);
}

.filter-group select,
.filter-group input {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.9rem;
}

.examples-stats {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

.examples-list {
    display: grid;
    gap: 1rem;
}

.example-item {
    background: var(--surface);
    padding: 1.25rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    gap: 1rem;
    transition: var(--transition);
    cursor: pointer;
}

.example-item:hover {
    transform: translateX(4px);
    box-shadow: var(--shadow-lg);
}

.example-id {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius);
    font-size: 0.875rem;
    font-weight: 500;
    min-width: 60px;
    text-align: center;
}

.example-equation {
    flex: 1;
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 1.1rem;
}

.example-meta {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.example-difficulty {
    font-size: 0.875rem;
}

.example-type {
    padding: 0.25rem 0.5rem;
    background: var(--background);
    border-radius: 4px;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.example-actions {
    display: flex;
    gap: 0.5rem;
}

.example-actions button {
    padding: 0.4rem 0.75rem;
    border: none;
    background: var(--background);
    border-radius: var(--radius);
    cursor: pointer;
    font-size: 0.875rem;
    transition: var(--transition);
}

.example-actions button:hover {
    background: var(--primary-light);
}

.examples-pagination {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    margin-top: 1.5rem;
}

.page-btn {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    background: var(--surface);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
}

.page-btn:hover {
    background: var(--primary-light);
}

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

/* ===== 页脚 ===== */
.footer {
    background: var(--text-primary);
    color: rgba(255, 255, 255, 0.7);
    text-align: center;
    padding: 1.5rem;
    margin-top: auto;
}

.friend-links {
    margin-top: 0.75rem;
    font-size: 0.85rem;
}

.friend-links span {
    margin-right: 0.5rem;
}

.friend-links a {
    color: rgba(255, 255, 255, 0.6);
    text-decoration: none;
    margin: 0 0.5rem;
    transition: color 0.2s;
}

.friend-links a:hover {
    color: #fff;
    text-decoration: underline;
}

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

    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
        margin-top: 0.75rem;
    }

    .nav-link {
        padding: 0.4rem 0.75rem;
        font-size: 0.9rem;
    }

    .main-content {
        padding: 1rem;
    }

    .input-section,
    .result-section {
        padding: 1.25rem;
    }

    #equation-input {
        font-size: 1rem;
    }

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

    .btn {
        width: 100%;
    }

    .practice-modes {
        grid-template-columns: 1fr 1fr;
    }

    .result-stats {
        flex-direction: column;
        gap: 1.5rem;
    }

    .calc-input-group {
        flex-direction: column;
        align-items: stretch;
    }

    .calc-input-group label {
        min-width: auto;
    }

    .example-item {
        flex-direction: column;
        align-items: flex-start;
    }

    .example-meta {
        width: 100%;
        justify-content: space-between;
    }
}

/* ===== 动画效果 ===== */
@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.05); }
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}

.pulse {
    animation: pulse 0.5s ease;
}

.shake {
    animation: shake 0.3s ease;
}

/* ===== 化学式显示美化 ===== */
.chem-formula {
    font-family: 'Times New Roman', serif;
}

.chem-sub {
    font-size: 0.75em;
    vertical-align: sub;
}

.chem-sup {
    font-size: 0.75em;
    vertical-align: super;
}

.chem-arrow {
    margin: 0 0.5rem;
    color: var(--text-secondary);
}

/* ===== 工具提示 ===== */
.tooltip {
    position: relative;
}

.tooltip::after {
    content: attr(data-tooltip);
    position: absolute;
    bottom: 100%;
    left: 50%;
    transform: translateX(-50%);
    padding: 0.5rem 0.75rem;
    background: var(--text-primary);
    color: white;
    font-size: 0.8rem;
    border-radius: 4px;
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s;
}

.tooltip:hover::after {
    opacity: 1;
}

/* ===== 加载状态 ===== */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 2px solid var(--primary-light);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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