/* 全局重置与基础样式 */
:root {
    --primary-color: #0056b3;
    --secondary-color: #333;
    --light-bg: #f8f9fa;
    --text-color: #555;
    --white: #ffffff;
    --border-color: #ddd;
    --max-width: 1200px;
}

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

body {
    font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--white);
}

a {
    text-decoration: none;
    color: inherit;
    transition: color 0.3s;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    display: block;
}

/* 容器工具类 */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
}

.section-padding {
    padding: 60px 0;
}

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

/* 按钮样式 */
.btn {
    display: inline-block;
    padding: 10px 24px;
    background-color: var(--primary-color);
    color: var(--white);
    border-radius: 4px;
    font-weight: 500;
}

.btn:hover {
    background-color: #004494;
    color: var(--white);
}

/* 头部导航 */
header {
    background-color: var(--white);
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

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

.nav-links {
    display: flex;
    gap: 30px;
}

.nav-links a {
    color: var(--secondary-color);
    font-weight: 500;
}

.nav-links a:hover, .nav-links a.active {
    color: var(--primary-color);
}

.mobile-menu-btn {
    display: none;
    font-size: 24px;
    cursor: pointer;
}

/* Hero 区域 */
.hero {
    background-color: var(--light-bg);
    padding: 100px 0;
    text-align: center;
}

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

.hero p {
    font-size: 1.2rem;
    margin-bottom: 30px;
    color: #666;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

/* 产品卡片网格 */
.products-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.product-card {
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
    transition: transform 0.3s, box-shadow 0.3s;
    background: var(--white);
}

.product-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

.product-image {
    height: 200px;
    background-color: #eee;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #999;
}

.product-info {
    padding: 20px;
}

.product-info h3 {
    margin-bottom: 10px;
    color: var(--secondary-color);
}

.product-info p {
    font-size: 0.9rem;
    margin-bottom: 15px;
    color: #777;
}

/* 关于我们简述 */
.about-preview {
    background-color: var(--light-bg);
}

.features {
    display: flex;
    flex-wrap: wrap;
    gap: 30px;
    margin-top: 40px;
}

.feature-item {
    flex: 1;
    min-width: 250px;
    background: var(--white);
    padding: 30px;
    border-radius: 8px;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0,0,0,0.03);
}

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

/* 页脚 */
footer {
    background-color: #222;
    color: #ccc;
    padding: 50px 0 20px;
}

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

.footer-col h4 {
    color: var(--white);
    margin-bottom: 20px;
    font-size: 1.1rem;
}

.footer-col ul li {
    margin-bottom: 10px;
}

.footer-col a:hover {
    color: var(--white);
}

.copyright {
    text-align: center;
    border-top: 1px solid #444;
    padding-top: 20px;
    font-size: 0.9rem;
}

/* 响应式适配 */
@media (max-width: 768px) {
    .navbar {
        position: relative;
    }

    .mobile-menu-btn {
        display: block;
    }

    .nav-links {
        display: none;
        position: absolute;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--white);
        flex-direction: column;
        padding: 20px;
        box-shadow: 0 5px 10px rgba(0,0,0,0.1);
        text-align: center;
    }

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

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