/* 全局重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-color: #e6f0fa;   /* 淡蓝色背景 */
    font-family: 'Segoe UI', 'Noto Sans', system-ui, sans-serif;
    padding-top: 80px;           /* 为固定顶栏留出空间 */
}

/* ========== 顶栏样式 ========== */
.aias-topbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: #1a3e60;
    color: white;
    padding: 10px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.aias-logo {
    display: flex;
    align-items: center;
    gap: 12px;
    cursor: pointer;
}

.aias-logo img {
    height: 45px;
    width: auto;
}

.aias-logo span {
    font-size: 1.4rem;
    font-weight: bold;
    letter-spacing: 1px;
}

.aias-nav {
    display: flex;
    gap: 20px;
    align-items: center;
}

.aias-nav > a, .dropbtn {
    color: white;
    text-decoration: none;
    font-size: 1rem;
    font-weight: 500;
    padding: 8px 16px;
    border-radius: 30px;
    transition: background 0.2s;
    cursor: pointer;
    background: none;
    border: none;
    font-family: inherit;
}

.aias-nav > a:hover, .dropbtn:hover {
    background-color: #2c5a7a;
}

/* 下拉菜单 */
.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #1a3e60;
    min-width: 140px;
    box-shadow: 0 8px 16px rgba(0,0,0,0.2);
    border-radius: 12px;
    z-index: 1;
    top: 100%;
    left: 0;
    margin-top: 5px;
}

.dropdown-content a {
    color: white;
    padding: 10px 16px;
    text-decoration: none;
    display: block;
    font-size: 0.95rem;
    border-radius: 8px;
}

.dropdown-content a:hover {
    background-color: #2c5a7a;
}

/* 点击后显示（JS控制） */
.dropdown-content.show {
    display: block;
}

/* ========== 主内容容器 ========== */
.container {
    max-width: 1100px;
    margin: 0 auto;
    background: rgba(255, 255, 255, 0.85);
    border-radius: 20px;
    padding: 30px 40px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
}

/* 中心页轮播图样式 */
.carousel {
    width: 100%;
    aspect-ratio: 3 / 2;          /* 强制宽高比 3:2 */
    overflow: hidden;
    border-radius: 16px;
    margin-bottom: 30px;
    position: relative;
    background-color: #c0d4e8;
}

.carousel img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: none;
    border-radius: 16px;
}

.carousel img.active {
    display: block;
}

/* 目录列表样式 */
.catalog {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-top: 20px;
}

.catalog-item {
    border-left: 4px solid #2c5a7a;
    padding: 12px 20px;
    background: rgba(255,255,255,0.6);
    border-radius: 12px;
    transition: transform 0.2s;
}

.catalog-item:hover {
    transform: translateX(4px);
    background: rgba(255,255,255,0.9);
}

.catalog-item a {
    text-decoration: none;
    color: #1a3e60;
    font-size: 1.1rem;
    font-weight: 500;
    display: block;
}

/* 通用标题样式 */
h1 {
    color: #1a3e60;
    border-bottom: 2px solid #c0d4e8;
    padding-bottom: 12px;
    margin-bottom: 24px;
}

h2 {
    color: #1a3e60;
    margin: 20px 0 12px;
}

p {
    line-height: 1.6;
    color: #1e2f3c;
    margin-bottom: 16px;
}

/* 响应式 */
@media (max-width: 700px) {
    body {
        padding-top: 100px;
    }
    .aias-topbar {
        flex-direction: column;
        gap: 10px;
        padding: 12px;
    }
    .container {
        padding: 20px;
    }
    .carousel {
        height: 200px;
    }
}