/* 全局样式 */
:root {
    --primary-color: #4a6bff;
    --secondary-color: #ff6b6b;
    --accent-color: #ffd166;
    --text-color: #333;
    --light-text: #666;
    --bg-color: #fff;
    --light-bg: #f8f9fa;
    --dark-bg: #343a40;
    --border-color: #e1e4e8;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    color: var(--text-color);
    line-height: 1.6;
    background-color: var(--bg-color);
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

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

a:hover {
    color: var(--secondary-color);
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
}

.section-title {
    text-align: center;
    margin-bottom: 40px;
    font-size: 2.5rem;
    color: var(--primary-color);
}



/* 头部导航 */
header {
    background-color: var(--bg-color);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
    padding: 15px 0;
}

header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo img {
    width: 40px;
    height: 40px;
}

.logo h1 {
    font-size: 1.5rem;
    color: var(--primary-color);
}

nav ul {
    display: flex;
    gap: 20px;
}

nav a {
    color: var(--text-color);
    font-weight: 500;
    padding: 5px 10px;
    border-radius: 4px;
}

nav a:hover, nav a.active {
    color: var(--primary-color);
    background-color: rgba(74, 107, 255, 0.1);
}

.mobile-menu-btn {
    display: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--primary-color);
}

/* 英雄区域 */
.hero {
    padding: 80px 0;
    background: linear-gradient(135deg, #f5f7ff 0%, #e8ecff 100%);
}

.hero .container {
    display: flex;
    align-items: center;
    gap: 40px;
}

.hero-content {
    flex: 1;
}

.hero-content h1 {
    font-size: 3rem;
    margin-bottom: 20px;
    color: var(--primary-color);
}

.hero-content p {
    font-size: 1.2rem;
    margin-bottom: 30px;
    color: var(--light-text);
}

.hero-image {
    flex: 1;
    display: flex;
    justify-content: center;
}

.hero-image img {
    max-height: 500px;
    border-radius: 20px;
    /* box-shadow: var(--shadow); */
}

/* 应用下载按钮 */
.app-buttons {
    display: flex;
    gap: 15px;
    margin-top: 30px;
}

.app-button {
    display: flex;
    align-items: center;
    gap: 10px;
    background-color: var(--dark-bg);
    color: white;
    padding: 10px 20px;
    border-radius: 8px;
    transition: var(--transition);
    width: 220px;
    justify-content: center;
}

.app-button:hover {
    background-color: var(--primary-color);
    color: white;
    transform: translateY(-3px);
}

.app-button i {
    font-size: 1.8rem;
}

.app-button span {
    display: flex;
    flex-direction: column;
}

.app-button small {
    font-size: 0.7rem;
    opacity: 0.8;
}

.app-button strong {
    font-size: 1.1rem;
}

/* 特色功能区域 */
.features {
    padding: 80px 0;
    background-color: var(--light-bg);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.feature-card {
    background-color: var(--bg-color);
    border-radius: 10px;
    padding: 30px;
    box-shadow: var(--shadow);
    transition: var(--transition);
    text-align: center;
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

.feature-icon {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 20px;
}

.feature-card h3 {
    margin-bottom: 15px;
    color: var(--primary-color);
}

/* 学习方法区域 */
.how-it-works {
    padding: 80px 0;
}

.steps {
    display: flex;
    flex-direction: column;
    gap: 60px;
}

.step {
    display: flex;
    align-items: center;
    gap: 40px;
}

/* 设置偶数步骤的图片在右边 */
.step:nth-child(2) {
    flex-direction: row-reverse;
}

.step:nth-child(4) {
    flex-direction: row-reverse;
}

.step-image {
    flex: 1;
    display: flex;
    justify-content: center;
}

.step-image img {
    max-height: 500px;
    border-radius: 20px;
    /* box-shadow: var(--shadow); */
}

.step-content {
    flex: 1;
    position: relative;
    padding-top: 40px;
}

.step-number {
    position: absolute;
    top: -30px;
    left: 0;
    width: 60px;
    height: 60px;
    background-color: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    font-weight: bold;
}

.step-content h3 {
    font-size: 1.8rem;
    margin-bottom: 15px;
    color: var(--primary-color);
}

/* 下载区域 */
.download {
    padding: 80px 0;
    background: linear-gradient(135deg, #f5f7ff 0%, #e8ecff 100%);
    text-align: center;
}

.download-subtitle {
    font-size: 1.2rem;
    margin-bottom: 30px;
    color: var(--light-text);
}

.download .app-buttons {
    justify-content: center;
}

/* 页脚 */
footer {
    background-color: var(--dark-bg);
    color: white;
    padding: 60px 0 20px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 40px;
    margin-bottom: 40px;
}

.footer-logo {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
}

.footer-logo img {
    width: 40px;
    height: 40px;
}

.footer-links h4, .footer-contact h4 {
    margin-bottom: 20px;
    font-size: 1.2rem;
}

.footer-links ul {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.footer-links a {
    color: rgba(255, 255, 255, 0.8);
}

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

.footer-contact p {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 10px;
}

.footer-contact a {
    color: rgba(255, 255, 255, 0.8);
}

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

.footer-bottom {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.6);
}

/* 隐私政策页面 */
.privacy-policy {
    padding: 60px 0;
}

.privacy-content {
    background-color: var(--bg-color);
    border-radius: 10px;
    padding: 40px;
    box-shadow: var(--shadow);
}

.last-updated {
    font-style: italic;
    color: var(--light-text);
    margin-bottom: 30px;
}

.policy-section {
    margin-bottom: 30px;
}

.policy-section h2 {
    color: var(--primary-color);
    margin-bottom: 15px;
    font-size: 1.5rem;
}

.policy-section ul {
    margin-left: 20px;
    margin-top: 10px;
}

.policy-section li {
    margin-bottom: 10px;
    position: relative;
    padding-left: 20px;
}

.policy-section li:before {
    content: "•";
    color: var(--primary-color);
    position: absolute;
    left: 0;
}

/* 响应式设计 */
@media (max-width: 992px) {
    .hero .container {
        flex-direction: column;
    }
    
    .step-number {
        left: 50%;
        transform: translateX(-50%);
    }
    
    .step-content {
        text-align: center;
        padding-top: 60px;
    }
}

@media (max-width: 768px) {
    nav {
        display: none;
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background-color: var(--bg-color);
        padding: 20px;
        box-shadow: var(--shadow);
        z-index: 99;
    }

    nav.active {
        display: block;
    }

    nav ul {
        flex-direction: column;
        gap: 15px;
        align-items: center;
    }

    nav a {
        display: block;
        width: 100%;
        text-align: center;
        padding: 10px;
    }

    .mobile-menu-btn {
        display: block;
        font-size: 1.5rem;
        cursor: pointer;
        color: var(--primary-color);
        z-index: 100;
    }



    .hero .container {
        flex-direction: column;
        text-align: center;
    }

    .hero-content {
        order: 2;
    }

    .hero-image {
        order: 1;
        margin-bottom: 30px;
    }

    .hero-content h1 {
        font-size: 2rem;
    }

    .hero-content p {
        font-size: 1rem;
    }

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

    /* 在移动端重新排列步骤内容 */
    .step {
        display: flex;
        flex-direction: column !important;
    }
    
    /* 确保图片始终在上方 */
    .step-image {
        order: 1;
        margin-bottom: 20px;
    }
    
    /* 确保内容始终在下方 */
    .step-content {
        order: 2;
        text-align: center;
        padding-top: 40px;
    }

    .step-number {
        left: 50%;
        transform: translateX(-50%);
    }

    .app-buttons {
        flex-direction: column;
        align-items: center;
        gap: 15px;
    }

    .app-button {
        width: 200px;
    }

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

    .footer-logo {
        align-items: center;
    }
}

@media (max-width: 576px) {

    
    .hero {
        padding: 40px 0;
    }
    
    .features, .how-it-works, .download {
        padding: 40px 0;
    }
    
    .feature-card {
        padding: 20px;
    }
    
    .step-image img {
        max-height: 350px;
    }
    
    .section-title {
        font-size: 1.8rem;
    }
}