/* 全局样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Microsoft YaHei', 'Inter', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f7fa;
}

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

/* 顶部导航栏 */
.navbar {
    background-color: #fff;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
}

.logo a {
    color: #3498db;
    font-size: 24px;
    font-weight: bold;
    text-decoration: none;
}

.nav-menu ul {
    display: flex;
    list-style: none;
}

.nav-menu li {
    margin-left: 30px;
}

.nav-menu a {
    color: #555;
    text-decoration: none;
    font-size: 16px;
    transition: all 0.3s ease;
    position: relative;
}

.nav-menu a:hover,
.nav-menu a.active {
    color: #3498db;
}

.nav-menu a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: #3498db;
    transition: width 0.3s ease;
}

.nav-menu a:hover::after,
.nav-menu a.active::after {
    width: 100%;
}

.mobile-menu-btn {
    display: none;
    font-size: 24px;
    color: #555;
    cursor: pointer;
}

/* 中间核心内容区 */
.main-content {
    margin-top: 100px;
    padding: 50px 0;
}

.section-title {
    text-align: center;
    font-size: 36px;
    color: #2c3e50;
    margin-bottom: 50px;
}

.grid-container {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-gap: 30px;
}

.grid-item {
    background-color: #fff;
    border-radius: 10px;
    padding: 30px;
    text-align: center;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    cursor: pointer;
    opacity: 0;
    animation: fadeIn 0.5s ease forwards;
}

.grid-item:nth-child(1) { animation-delay: 0.1s; }
.grid-item:nth-child(2) { animation-delay: 0.2s; }
.grid-item:nth-child(3) { animation-delay: 0.3s; }
.grid-item:nth-child(4) { animation-delay: 0.4s; }
.grid-item:nth-child(5) { animation-delay: 0.5s; }
.grid-item:nth-child(6) { animation-delay: 0.6s; }
.grid-item:nth-child(7) { animation-delay: 0.7s; }
.grid-item:nth-child(8) { animation-delay: 0.8s; }
.grid-item:nth-child(9) { animation-delay: 0.9s; }

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.grid-item:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.2);
}

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

.grid-item h3 {
    font-size: 24px;
    margin-bottom: 15px;
    color: #2c3e50;
}

.grid-item p {
    color: #7f8c8d;
    font-size: 16px;
}

/* 不同分类的颜色 */
.grid-item.frontend {
    border-top: 4px solid #f1c40f;
}

.grid-item.frontend .item-icon {
    color: #f1c40f;
}

.grid-item.backend {
    border-top: 4px solid #2ecc71;
}

.grid-item.backend .item-icon {
    color: #2ecc71;
}

.grid-item.database {
    border-top: 4px solid #e74c3c;
}

.grid-item.database .item-icon {
    color: #e74c3c;
}

.grid-item.devops {
    border-top: 4px solid #9b59b6;
}

.grid-item.devops .item-icon {
    color: #9b59b6;
}

.grid-item.mobile {
    border-top: 4px solid #1abc9c;
}

.grid-item.mobile .item-icon {
    color: #1abc9c;
}

.grid-item.ai {
    border-top: 4px solid #34495e;
}

.grid-item.ai .item-icon {
    color: #34495e;
}

.grid-item.blockchain {
    border-top: 4px solid #f39c12;
}

.grid-item.blockchain .item-icon {
    color: #f39c12;
}

.grid-item.cloud {
    border-top: 4px solid #3498db;
}

.grid-item.cloud .item-icon {
    color: #3498db;
}

.grid-item.security {
    border-top: 4px solid #16a085;
}

.grid-item.security .item-icon {
    color: #16a085;
}

/* 底部版权区 */
.footer {
    background-color: #2c3e50;
    color: #ecf0f1;
    padding: 30px 0;
    text-align: center;
    margin-top: 50px;
}

.footer .container {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.copyright {
    margin-bottom: 10px;
}

.icp {
    font-size: 14px;
    color: #bdc3c7;
}

/* 返回顶部按钮 */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: #3498db;
    color: #fff;
    border: none;
    font-size: 24px;
    cursor: pointer;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
    transition: all 0.3s ease;
    opacity: 0;
    visibility: hidden;
}

.back-to-top.show {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background-color: #2980b9;
    transform: translateY(-5px);
}

/* 响应式设计 */
@media (max-width: 1199px) {
    .grid-container {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (max-width: 768px) {
    .mobile-menu-btn {
        display: block;
    }
    
    .nav-menu {
        position: fixed;
        top: 80px;
        left: 0;
        right: 0;
        background-color: #fff;
        box-shadow: 0 5px 10px rgba(0, 0, 0, 0.1);
        padding: 20px;
        transform: translateY(-150%);
        transition: transform 0.3s ease;
    }
    
    .nav-menu.active {
        transform: translateY(0);
    }
    
    .nav-menu ul {
        flex-direction: column;
    }
    
    .nav-menu li {
        margin: 10px 0;
    }
    
    .grid-container {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 576px) {
    .grid-container {
        grid-template-columns: 1fr;
    }
    
    .section-title {
        font-size: 28px;
    }
    
    .grid-item h3 {
        font-size: 20px;
    }
    
    .back-to-top {
        width: 40px;
        height: 40px;
        font-size: 20px;
        bottom: 20px;
        right: 20px;
    }
}