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

:root {
    --primary-color: #0071e3;
    --primary-hover: #0077ed;
    --text-primary: #1d1d1f;
    --text-secondary: #6e6e73;
    --bg-white: #ffffff;
    --bg-gray: #f5f5f7;
    --border-color: #d2d2d7;
    --success-color: #34c759;
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 12px 30px rgba(0, 0, 0, 0.12);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    color: var(--text-primary);
    line-height: 1.6;
    background: var(--bg-white);
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 40px;
}

@media (max-width: 768px) {
    .container {
        padding: 0 20px;
    }
}

/* ===== 导航栏 ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
    z-index: 1000;
    transition: var(--transition);
}

.navbar.scrolled {
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 40px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 48px;
}

.nav-logo {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
}

.nav-logo:hover {
    opacity: 0.7;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 32px;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-primary);
    font-size: 12px;
    font-weight: 400;
    transition: var(--transition);
    opacity: 0.8;
}

.nav-links a:hover {
    opacity: 1;
    color: var(--primary-color);
}

.buy-button {
    display: inline-block;
    padding: 4px 12px;
    background: var(--primary-color);
    color: white;
    text-decoration: none;
    font-size: 12px;
    border-radius: 4px;
    transition: var(--transition);
}

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

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
}

/* ===== 主视觉区域 ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 120px 40px 80px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 100%;
    height: 200%;
    background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, transparent 70%);
    animation: rotate 20s linear infinite;
}

@keyframes rotate {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.hero-content {
    text-align: center;
    color: white;
    z-index: 1;
}

.hero-title {
    font-size: 96px;
    font-weight: 700;
    margin-bottom: 20px;
    letter-spacing: -2px;
    animation: fadeInUp 1s ease;
}

.hero-subtitle {
    font-size: 28px;
    font-weight: 400;
    margin-bottom: 40px;
    opacity: 0.95;
    animation: fadeInUp 1s ease 0.2s both;
}

.hero-cta {
    display: flex;
    gap: 20px;
    justify-content: center;
    animation: fadeInUp 1s ease 0.4s both;
}

.cta-button {
    display: inline-block;
    padding: 14px 36px;
    background: var(--bg-white);
    color: var(--primary-color);
    text-decoration: none;
    font-size: 17px;
    font-weight: 600;
    border-radius: 30px;
    transition: var(--transition);
    box-shadow: var(--shadow-lg);
}

.cta-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 16px 40px rgba(0, 0, 0, 0.15);
}

.learn-more {
    display: inline-flex;
    align-items: center;
    padding: 14px 24px;
    color: white;
    text-decoration: none;
    font-size: 17px;
    font-weight: 500;
    border: 2px solid rgba(255, 255, 255, 0.5);
    border-radius: 30px;
    transition: var(--transition);
}

.learn-more:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: white;
}

.hero-image {
    position: absolute;
    right: 10%;
    top: 50%;
    transform: translateY(-50%);
    z-index: 1;
}

/* ===== 3D网球球体 ===== */
.tennis-ball-wrapper {
    position: relative;
    animation: bounce 3s ease-in-out infinite;
}

.tennis-ball-image {
    width: 320px;
    height: 320px;
    object-fit: contain;
    filter: drop-shadow(0 20px 40px rgba(0, 0, 0, 0.3));
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-20px); }
}

/* 阴影效果 */
.ball-shadow {
    position: absolute;
    width: 180px;
    height: 25px;
    background: radial-gradient(ellipse, rgba(0, 0, 0, 0.35) 0%, transparent 70%);
    bottom: -40px;
    left: 50%;
    transform: translateX(-50%);
    border-radius: 50%;
    animation: shadow-bounce 3s ease-in-out infinite;
}

@keyframes shadow-bounce {
    0%, 100% {
        transform: translateX(-50%) scale(1);
        opacity: 0.35;
    }
    50% {
        transform: translateX(-50%) scale(0.85);
        opacity: 0.2;
    }
}

@media (max-width: 768px) {
    .hero-title {
        font-size: 56px;
    }

    .hero-subtitle {
        font-size: 20px;
    }

    .hero-cta {
        flex-direction: column;
    }

    .hero-image {
        display: none;
    }
}

/* ===== 动画关键帧 ===== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===== 通用section样式 ===== */
section {
    padding: 120px 0;
}

.section-title {
    font-size: 56px;
    font-weight: 700;
    text-align: center;
    margin-bottom: 16px;
    letter-spacing: -1px;
}

.section-subtitle {
    font-size: 24px;
    font-weight: 400;
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 80px;
}

@media (max-width: 768px) {
    .section-title {
        font-size: 40px;
    }

    .section-subtitle {
        font-size: 20px;
        margin-bottom: 60px;
    }

    section {
        padding: 80px 0;
    }
}

/* ===== 产品概览 ===== */
.overview {
    background: var(--bg-white);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 32px;
}

.feature-card {
    padding: 40px;
    background: var(--bg-gray);
    border-radius: 20px;
    transition: var(--transition);
    cursor: default;
}

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

.feature-icon {
    font-size: 48px;
    margin-bottom: 24px;
}

.feature-card h3 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 16px;
}

.feature-card p {
    font-size: 17px;
    line-height: 1.6;
    color: var(--text-secondary);
}

@media (max-width: 1024px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .features-grid {
        grid-template-columns: 1fr;
    }
}

/* ===== 核心功能 ===== */
.features {
    background: var(--bg-gray);
}

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

.tab-btn {
    padding: 12px 32px;
    background: white;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 16px;
    font-weight: 500;
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
}

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

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

.tab-content {
    background: white;
    border-radius: 20px;
    padding: 60px;
    box-shadow: var(--shadow-sm);
}

.tab-pane {
    display: none;
}

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

.feature-detail {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
}

.feature-text h3 {
    font-size: 40px;
    font-weight: 700;
    margin-bottom: 24px;
}

.feature-desc {
    font-size: 19px;
    line-height: 1.6;
    color: var(--text-secondary);
    margin-bottom: 32px;
}

.spec-list {
    list-style: none;
}

.spec-list li {
    padding: 12px 0;
    border-bottom: 1px solid var(--bg-gray);
    font-size: 17px;
}

.spec-label {
    font-weight: 600;
    color: var(--text-primary);
    margin-right: 8px;
}

.feature-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.feature-image {
    width: 100%;
    max-width: 400px;
    height: auto;
    border-radius: 20px;
    box-shadow: var(--shadow-lg);
    transition: var(--transition);
}

.feature-image:hover {
    transform: scale(1.05);
}

.cloud-image {
    max-width: 500px;
}

/* 下载按钮样式 */
.download-buttons {
    display: flex;
    gap: 16px;
    margin-top: 32px;
    flex-wrap: wrap;
}

.download-btn {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 24px;
    background: var(--text-primary);
    color: white;
    text-decoration: none;
    border-radius: 12px;
    transition: var(--transition);
    min-width: 200px;
    box-shadow: var(--shadow-sm);
}

.download-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    background: #000;
}

.download-btn.ios {
    background: #000;
}

.download-btn.android {
    background: linear-gradient(135deg, #4CAF50 0%, #388E3C 100%);
}

.btn-icon {
    font-size: 28px;
    font-weight: 300;
    display: flex;
    align-items: center;
}

.btn-icon svg {
    width: 28px;
    height: 28px;
    fill: currentColor;
}

.btn-text {
    display: flex;
    flex-direction: column;
    line-height: 1.2;
}

.btn-small {
    font-size: 10px;
    opacity: 0.8;
    text-transform: uppercase;
}

.btn-large {
    font-size: 18px;
    font-weight: 600;
}

.phone-frame {
    width: 280px;
    height: 560px;
    background: linear-gradient(145deg, #2d2d2d 0%, #1a1a1a 100%);
    border-radius: 40px;
    padding: 12px;
    box-shadow: var(--shadow-lg);
    position: relative;
}

.phone-frame::before {
    content: '';
    position: absolute;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 24px;
    background: #000;
    border-radius: 12px;
    z-index: 2;
}

.phone-screen-image {
    width: 100%;
    height: 100%;
    object-fit: cover;
    border-radius: 30px;
    border: 2px solid #333;
}

/* 保留原有的动画类，用于其他可能需要的地方 */

@media (max-width: 768px) {
    .feature-tabs {
        flex-wrap: wrap;
    }

    .tab-content {
        padding: 40px 20px;
    }

    .feature-detail {
        grid-template-columns: 1fr;
        gap: 40px;
    }

    .feature-text h3 {
        font-size: 32px;
    }
}

/* ===== 技术规格 ===== */
.specs {
    background: var(--bg-white);
}

.specs-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}

.spec-category {
    background: var(--bg-gray);
    padding: 40px;
    border-radius: 20px;
}

.spec-category h3 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 24px;
    padding-bottom: 16px;
    border-bottom: 2px solid var(--primary-color);
}

.spec-table {
    width: 100%;
    border-collapse: collapse;
}

.spec-table td {
    padding: 12px 0;
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
}

.spec-table td:first-child {
    font-weight: 500;
    color: var(--text-secondary);
    width: 30%;
    white-space: nowrap;
}

.spec-table td:last-child {
    font-weight: 600;
    color: var(--text-primary);
    text-align: right;
    white-space: nowrap;
}

@media (max-width: 1024px) {
    .specs-grid {
        grid-template-columns: 1fr;
    }
}

/* ===== APP展示 ===== */
.app-showcase {
    background: var(--bg-gray);
}

.app-modules {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}

.module-card {
    background: white;
    padding: 32px;
    border-radius: 20px;
    transition: var(--transition);
}

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

.module-icon {
    font-size: 48px;
    margin-bottom: 20px;
}

.module-card h3 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 12px;
}

.module-card p {
    font-size: 15px;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 20px;
}

.module-tags {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.module-tags span {
    padding: 4px 12px;
    background: var(--bg-gray);
    border-radius: 4px;
    font-size: 12px;
    font-weight: 500;
    color: var(--primary-color);
}

.app-download-section {
    margin-top: 5px;
    margin-bottom: 30px;
    text-align: center;
    padding: 5px 0;
}

.download-buttons-center {
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
}

@media (max-width: 1024px) {
    .app-modules {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .app-modules {
        grid-template-columns: 1fr;
    }
}

/* ===== 对比优势 ===== */
.comparison {
    background: var(--bg-white);
}

.comparison-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.compare-card {
    background: var(--bg-gray);
    padding: 40px;
    border-radius: 20px;
    text-align: center;
    transition: var(--transition);
}

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

.compare-card.popular {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    position: relative;
}

.compare-card.popular .compare-features li,
.compare-card.popular .compare-features .check,
.compare-card.popular .compare-features .cross {
    color: white;
}

.compare-card.competitor {
    opacity: 0.7;
}

.compare-price {
    font-size: 48px;
    font-weight: 700;
    margin-bottom: 24px;
    color: var(--primary-color);
}

.compare-card.popular .compare-price {
    color: white;
}

.compare-card h3 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 24px;
}

.compare-features {
    list-style: none;
    text-align: left;
    margin-bottom: 32px;
}

.compare-features li {
    padding: 12px 0;
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
}

.check {
    color: var(--success-color);
}

.cross {
    color: #ff3b30;
}

.compare-btn {
    display: block;
    width: 100%;
    padding: 14px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.compare-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
}

.compare-btn.disabled {
    background: var(--border-color);
    cursor: not-allowed;
}

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

.compare-btn.primary:hover {
    background: var(--bg-white);
}

@media (max-width: 1024px) {
    .comparison-grid {
        grid-template-columns: 1fr;
    }
}

/* ===== 用户场景 ===== */
.scenarios {
    background: var(--bg-gray);
}

.scenario-list {
    display: grid;
    gap: 24px;
}

.scenario-item {
    background: white;
    padding: 40px;
    border-radius: 20px;
    display: flex;
    align-items: flex-start;
    gap: 32px;
    transition: var(--transition);
}

.scenario-item:hover {
    transform: translateX(16px);
    box-shadow: var(--shadow-lg);
}

.scenario-age {
    flex-shrink: 0;
    width: 100px;
    height: 100px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    font-size: 24px;
    font-weight: 700;
}

.scenario-item h3 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 12px;
}

.scenario-item p {
    color: var(--text-secondary);
    line-height: 1.6;
}

@media (max-width: 768px) {
    .scenario-item {
        flex-direction: column;
        text-align: center;
    }

    .scenario-item:hover {
        transform: translateY(-8px);
    }
}

/* ===== 购买区域 ===== */
.buy {
    background: var(--bg-white);
}

.buy-options {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.buy-card {
    background: var(--bg-gray);
    padding: 40px;
    border-radius: 20px;
    position: relative;
    transition: var(--transition);
}

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

.buy-card.popular {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.buy-card.popular .buy-name,
.buy-card.popular .buy-desc,
.buy-card.popular .buy-features li {
    color: white;
}

.popular-tag {
    position: absolute;
    top: -12px;
    left: 50%;
    transform: translateX(-50%);
    padding: 6px 20px;
    background: var(--success-color);
    color: white;
    border-radius: 20px;
    font-size: 14px;
    font-weight: 600;
}

.buy-name {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 16px;
}

.buy-price {
    margin-bottom: 16px;
}

.price-symbol {
    font-size: 24px;
    vertical-align: super;
}

.price-number {
    font-size: 56px;
    font-weight: 700;
    color: var(--primary-color);
}

.buy-card.popular .price-number {
    color: white;
}

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

.buy-desc {
    color: var(--text-secondary);
    margin-bottom: 24px;
    padding-bottom: 24px;
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
}

.buy-features {
    list-style: none;
    margin-bottom: 32px;
}

.buy-features li {
    padding: 10px 0;
    color: var(--text-secondary);
}

.buy-btn {
    width: 100%;
    padding: 14px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.buy-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
}

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

.buy-btn.primary:hover {
    background: var(--bg-white);
}

@media (max-width: 1024px) {
    .buy-options {
        grid-template-columns: 1fr;
    }
}

/* ===== 常见问题 ===== */
.faq {
    background: var(--bg-gray);
}

.faq-list {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    background: white;
    border-radius: 12px;
    margin-bottom: 16px;
    overflow: hidden;
    transition: var(--transition);
}

.faq-item:hover {
    box-shadow: var(--shadow-sm);
}

.faq-question {
    padding: 24px 32px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition);
}

.faq-question:hover {
    background: var(--bg-gray);
}

.faq-question h3 {
    font-size: 19px;
    font-weight: 600;
    flex: 1;
    margin: 0;
}

.faq-toggle {
    width: 32px;
    height: 32px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 24px;
    font-weight: 600;
    color: var(--primary-color);
    transition: var(--transition);
}

.faq-item.active .faq-toggle {
    transform: rotate(45deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
}

.faq-answer p {
    padding: 0 32px 24px;
    color: var(--text-secondary);
    line-height: 1.7;
}

.faq-item.active .faq-answer {
    max-height: 200px;
}

/* ===== 页脚 ===== */
.footer {
    background: var(--bg-gray);
    padding: 60px 0 32px;
    border-top: 1px solid var(--border-color);
}

.footer-content {
    display: grid;
    grid-template-columns: 1fr 3fr;
    gap: 60px;
    margin-bottom: 40px;
}

.footer-brand {
    display: flex;
    flex-direction: column;
}

.footer-logo {
    font-size: 24px;
    font-weight: 700;
    margin-bottom: 12px;
}

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

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 40px;
}

.footer-column h4 {
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 16px;
    color: var(--text-secondary);
}

.footer-column a {
    display: block;
    text-decoration: none;
    color: var(--text-primary);
    font-size: 14px;
    margin-bottom: 12px;
    transition: var(--transition);
}

.footer-column a:hover {
    color: var(--primary-color);
}

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

.footer-bottom p {
    font-size: 12px;
    color: var(--text-secondary);
}

.footer-legal {
    display: flex;
    gap: 24px;
}

.footer-legal a {
    text-decoration: none;
    color: var(--text-secondary);
    font-size: 12px;
    transition: var(--transition);
}

.footer-legal a:hover {
    color: var(--text-primary);
}

@media (max-width: 768px) {
    .footer-content {
        grid-template-columns: 1fr;
        gap: 40px;
    }

    .footer-links {
        grid-template-columns: 1fr;
        gap: 32px;
    }

    .footer-bottom {
        flex-direction: column;
        gap: 16px;
        text-align: center;
    }

    .footer-legal {
        flex-direction: column;
        gap: 12px;
    }
}

/* ===== 回到顶部按钮 ===== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 56px;
    height: 56px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 999;
    box-shadow: 0 8px 25px rgba(0, 113, 227, 0.3);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0;
    overflow: hidden;
}

.back-to-top::before {
    content: '';
    width: 20px;
    height: 20px;
    border-top: 3px solid white;
    border-left: 3px solid white;
    transform: rotate(45deg);
    margin-top: 6px;
    transition: all 0.3s ease;
}

.back-to-top.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    transform: scale(1.15) translateY(-2px);
    box-shadow: 0 12px 35px rgba(0, 113, 227, 0.4);
}

.back-to-top:hover::before {
    transform: rotate(45deg) translateY(-2px);
}

.back-to-top:active {
    transform: scale(1.05);
}

@media (max-width: 768px) {
    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 50px;
        height: 50px;
    }
    
    .back-to-top::before {
        width: 18px;
        height: 18px;
        border-top-width: 2px;
        border-left-width: 2px;
    }
}

/* ===== 平滑滚动 ===== */
html {
    scroll-behavior: smooth;
}

/* ===== 选择高亮 ===== */
::selection {
    background: var(--primary-color);
    color: white;
}

/* ===== 滚动条样式 ===== */
::-webkit-scrollbar {
    width: 10px;
}

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

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 5px;
}

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