/* 全局样式 */
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
    font-family: "Microsoft YaHei", sans-serif;
    line-height: 1.6;
    padding-top: 60px; /* 为固定导航栏留出空间，防止内容被遮挡 */
}
.container { width: 1200px; margin: 0 auto; }

/* 导航样式 */
nav {
    background: #ff5f0f;
    position: fixed; /* 新增：固定定位 */
    top: 0;          /* 固定在顶部 */
    left: 0;         /* 从左侧开始 */
    width: 100%;     /* 全宽度 */
    z-index: 1000;   /* 确保导航栏在其他内容之上 */
}
.navbar { display: flex; position: relative; }
.nav-item { position: relative; }
.nav-link {
    color: white;
    padding: 20px 25px;
    display: block;
    text-decoration: none;
    font-size: 16px;
    transition: background 0.3s;
}
.nav-link:hover,
.nav-item:hover > .nav-link { background: #fa864b; }
ul {
    list-style: none;
}
.dropdown-menu {
    position: absolute;
    background: white;
    min-width: 220px;
    box-shadow: 0 8px 16px rgba(0,0,0,0.2);
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    z-index: 1000;
}
.nav-item:hover > .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}
.dropdown-item { display: block; }
.dropdown-link {
    padding: 12px 20px;
    color: #333;
    text-decoration: none;
    display: block;
    transition: background 0.2s;
}
.dropdown-link:hover {
    background: #eef4fc;
    color: #ff5f0f;
}