/* 使用命名空间前缀避免样式冲突 */
.school-nav {
    box-sizing: border-box;
    font-family: "Microsoft YaHei", "simsun", sans-serif;
}

.school-nav .daohang {
    border: 1px solid #0d726e;
    font-size: 14px;
    font-weight: bold;
}

.school-nav .caidanbox {
    margin: 0 auto;
    width: 100%;
    max-width: 1440px;
    text-align: center;
    height: 60px;
    background-color: white;
    background: url(../images/bg_nav_new.jpg) repeat-x;
    background-size: auto 100%;
}

.school-nav .menu {
    height: 58px;
    margin: 0;
    padding: 0;
}

.school-nav .menu ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.school-nav .menu li {
    min-width: 120px;
}

.school-nav .menu > li {
    display: inline-block;
    position: relative;
    background: url(../images/navline.png) no-repeat left 50%;
}

.school-nav .menu > li:hover {
    background: none no-repeat right 50%;
}

.school-nav .menu > li:first-child {
    background: none no-repeat right 50%;
}

.school-nav .menu a {
    border-left: 2px solid transparent;
    color: #FFFFFF;
    display: inline-block;
    font-size: 22px;
    line-height: 60px;
    padding: 0 30px;
    text-decoration: none;
    text-transform: uppercase;
    transition: all 0.3s ease;
}

.school-nav .menu li:hover > a {
    border-left: 2px solid #FFFFFF;
    color: #FFFFFF;
    background-color: #C4302B;
}

.school-nav .submenu {
    left: 0;
    max-height: 0;
    position: absolute;
    top: 100%;
    z-index: 1000;
    perspective: 400px;
    overflow: hidden;
    transition: max-height 0.5s ease;
}

.school-nav .submenu li {
    transform: rotateY(90deg);
    background: rgba(255, 102, 51, 0.7) !important;
    transition: opacity 0.4s, transform 0.5s;
    opacity: 0;
}

.school-nav .submenu li a {
    border-bottom: 1px rgba(255, 255, 255, 0.7) solid;
    padding: 0 20px;
    font-size: 18px;
    width: 108px;
    line-height: 55px;
}

.school-nav .submenu li:last-child a {
    border-bottom: none;
}

.school-nav .menu .submenu li:hover a {
    border-left: 2px solid #FFFF00;
    color: #FFFF00;
}

.school-nav .menu > li:hover .submenu {
    max-height: 2000px;
}

.school-nav .menu > li:hover .submenu li {
    opacity: 1;
    transform: none;
}

/* 使用CSS变量简化过渡延迟设置 */
.school-nav .menu li:hover .submenu li:nth-child(1) { transition-delay: 0s; }
.school-nav .menu li:hover .submenu li:nth-child(2) { transition-delay: 50ms; }
.school-nav .menu li:hover .submenu li:nth-child(3) { transition-delay: 100ms; }
.school-nav .menu li:hover .submenu li:nth-child(4) { transition-delay: 150ms; }
.school-nav .menu li:hover .submenu li:nth-child(5) { transition-delay: 200ms; }
.school-nav .menu li:hover .submenu li:nth-child(6) { transition-delay: 250ms; }
.school-nav .menu li:hover .submenu li:nth-child(7) { transition-delay: 300ms; }
.school-nav .menu li:hover .submenu li:nth-child(8) { transition-delay: 350ms; }
.school-nav .menu li:hover .submenu li:nth-child(9) { transition-delay: 400ms; }
.school-nav .menu li:hover .submenu li:nth-child(10) { transition-delay: 450ms; }
.school-nav .menu li:hover .submenu li:nth-child(11) { transition-delay: 500ms; }
.school-nav .menu li:hover .submenu li:nth-child(12) { transition-delay: 550ms; }
.school-nav .menu li:hover .submenu li:nth-child(13) { transition-delay: 600ms; }
.school-nav .menu li:hover .submenu li:nth-child(14) { transition-delay: 650ms; }
.school-nav .menu li:hover .submenu li:nth-child(15) { transition-delay: 700ms; }
.school-nav .menu li:hover .submenu li:nth-child(16) { transition-delay: 750ms; }

.school-nav .submenu li:nth-child(1) { transition-delay: 750ms; }
.school-nav .submenu li:nth-child(2) { transition-delay: 700ms; }
.school-nav .submenu li:nth-child(3) { transition-delay: 650ms; }
.school-nav .submenu li:nth-child(4) { transition-delay: 600ms; }
.school-nav .submenu li:nth-child(5) { transition-delay: 550ms; }
.school-nav .submenu li:nth-child(6) { transition-delay: 500ms; }
.school-nav .submenu li:nth-child(7) { transition-delay: 450ms; }
.school-nav .submenu li:nth-child(8) { transition-delay: 400ms; }
.school-nav .submenu li:nth-child(9) { transition-delay: 350ms; }
.school-nav .submenu li:nth-child(10) { transition-delay: 300ms; }
.school-nav .submenu li:nth-child(11) { transition-delay: 250ms; }
.school-nav .submenu li:nth-child(12) { transition-delay: 200ms; }
.school-nav .submenu li:nth-child(13) { transition-delay: 150ms; }
.school-nav .submenu li:nth-child(14) { transition-delay: 100ms; }
.school-nav .submenu li:nth-child(15) { transition-delay: 50ms; }
.school-nav .submenu li:nth-child(16) { transition-delay: 0s; }