/* 全局基础 */
body {
    margin: 0;
    font-family: "Segoe UI", Helvetica, Arial, sans-serif;
    background: #fff;
    color: #111;
    line-height: 1.6;
}

/* 顶部导航 */
header {
    width: 100%;
    background: #fff;
    padding: 15px 50px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid #f0f0f0;
    position: fixed;
    top: 0;
    z-index: 1000;
}
.top-nav a {
    margin-left: 25px;
    text-decoration: none;
    color: #0d47a1;
    font-weight: 600;
    font-size: 16px;
    transition: color 0.3s ease;
}
.top-nav a:hover {
    color: #1976d2;
}

/* 主体居中区块 */
.center-section {
    max-width: 1000px;
    margin: 120px auto 60px;
    text-align: center;
    padding: 0 20px;
}

/* 首页主标题 */
.main-title {
    font-size: 48px;
    font-weight: 700;
    margin-bottom: 25px;
    letter-spacing: 1px;
    color: #0d47a1;
}

/* 副标题和段落 */
.intro {
    font-size: 18px;
    line-height: 1.8;
    margin-bottom: 50px;
    color: #333;
}

/* 功能模块卡片 */
.features {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 30px;
}
.feature {
    flex: 1 1 280px;
    background: rgba(13,71,161,0.05);
    padding: 25px 20px;
    border-radius: 12px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.08);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    text-align: left;
}
.feature:hover {
    transform: translateY(-10px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.15);
}
.feature h3 {
    font-size: 20px;
    color: #0d47a1;
    margin-bottom: 12px;
}
.feature p {
    font-size: 16px;
    color: #333;
}

/* 业务页产品卡片 */
.business-items {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 25px;
    margin: 40px 0;
}
.business-item {
    width: 260px;
    padding: 15px;
    border-radius: 12px;
    box-shadow: 0 8px 20px rgba(0,0,0,0.1);
    cursor: pointer;
    background: #f9f9f9;
    transition: transform 0.3s;
    text-align: center;
}
.business-item:hover {
    transform: translateY(-5px);
}
.business-item img {
    width: 100%;
    border-radius: 8px;
    margin-bottom: 10px;
}
.business-item h3 {
    font-size: 18px;
    font-weight: 600;
    color: #0d47a1;
    margin-bottom: 8px;
}
.business-item p {
    font-size: 15px;
    color: #555;
}

/* 产品详情页缩略图导航 */
#thumbnailNav img {
    width: 100px;
    margin: 5px;
    cursor: pointer;
    border-radius: 8px;
    transition: transform 0.2s ease;
}
#thumbnailNav img:hover {
    transform: scale(1.1);
}

/* 页脚 */
footer {
    text-align: center;
    padding: 25px 0;
    font-size: 14px;
    color: #999;
    border-top: 1px solid #eee;
}