/* --- CSS 变量与重置 --- */
:root {
    --bnu-blue: #054D91;
    /* 北师大蓝 */
    --bnu-blue-light: #3478B5;
    --wood: #A87853;
    /* 实木色 */
    --wood-light: #EFEAE2;
    /* 实木色浅色/米色背景 */
    --cream: #F6F4EF;
    /* 米白色/书卷色 */
    --text-main: #333333;
    --text-grey: #666666;
    --shadow: 0 4px 12px rgba(5, 77, 145, 0.08);
}

.zimgbox {
    background: url("../img/index.png") no-repeat;
    background-size: cover;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: "PingFang SC", "Microsoft YaHei", sans-serif;
    background-color: var(--cream);
    color: var(--text-main);
    line-height: 1.6;
}

a {
    text-decoration: none;
    color: inherit;
    transition: 0.3s;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    display: inline-block;
}

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

/* --- 头部区域 --- */
.header-top {
    background-color: var(--bnu-blue);
    padding: 15px calc((100vw - 1200px) /2);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    color: #fff;
}

.logo-area {
    display: flex;
    align-items: center;
    gap: 15px;
}

.logo-area h1 {
    font-size: 1.5rem;
    letter-spacing: 2px;
    font-weight: bold;
}

.logo-area .divider {
    width: 1px;
    height: 30px;
    background-color: rgba(255,255,255,0.4);
}

.logo-area h2 {
    font-size: 1.2rem;
    font-weight: 500;
}

.search-bar input {
    background-color: #DDDDDD;
    border: none;
    padding: 8px 15px;
    border-radius: 4px;
    width: 200px;
    outline: none;
    color: #333;
}

/* --- 导航栏 --- */
.nav-area {
    background-color: #fff;
    padding: 0 20px;
    border-bottom: 1px solid #ddd;
}

.nav-list {
    display: flex;
    justify-content: space-around;
    gap: 40px;
    width: 1200px;
    margin: 0 auto;
}

.nav-list > li {
    position: relative;
    padding: 15px 0;
}

.nav-list > li > a {
    color: var(--bnu-blue);
    font-weight: 600;
    font-size: 18px;
}

.nav-list > li:hover > a {
    color: var(--wood);
}

.dropdown .sub-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    background-color: #fff;
    box-shadow: var(--shadow);
    border: 1px solid #eee;
    border-top: 2px solid var(--bnu-blue);
    min-width: 140px;
    z-index: 100;
    padding: 10px 0;
}

.dropdown:hover .sub-menu {
    display: block;
}

.sub-menu li a {
    display: block;
    padding: 10px 20px;
    color: var(--text-grey);
    text-align: center;
}

.sub-menu li a:hover {
    color: var(--bnu-blue);
    background-color: var(--cream);
}

.arrow {
    font-size: 12px;
    margin-left: 5px;
}

.menu-toggle {
    display: none;
    cursor: pointer;
    font-size: 1.5rem;
    color: var(--bnu-blue);
    padding: 10px 0;
}

/* --- 主视觉与快速入口 --- */
.hero-section {
    padding: 30px 20px;
    display: grid;
    grid-template-columns: 2.5fr 1fr;
    gap: 20px;
    background: #fff;
}

.carousel-slider {
    position: relative;
    border: 1px solid #dcdcdc;
    background-color: #fff;
    min-height: 380px;
    overflow: hidden;
    display: flex;
}

.slides-wrapper {
    width: 100%;
    height: 100%;
    position: relative;
}

.slide {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    opacity: 0;
    transition: opacity 0.8s ease-in-out;
    background-color: #fff;
    color: var(--bnu-blue);
}

.slide.active {
    opacity: 1;
    z-index: 1;
}

.slide h2 {
    font-size: 2.8rem;
    letter-spacing: 4px;
    font-weight: 500;
}

.slide p {
    margin-top: 15px;
    font-size: 1.2rem;
    color: var(--wood);
}

.carousel-indicators {
    position: absolute;
    bottom: 15px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 2;
    display: flex;
    gap: 10px;
}

.dot {
    width: 10px;
    height: 10px;
    background-color: #ccc;
    border-radius: 50%;
    cursor: pointer;
    transition: 0.3s;
}

.dot.active {
    background-color: var(--bnu-blue);
    transform: scale(1.2);
}

.arrow-btn {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    background: rgba(0,0,0,0.2);
    color: #fff;
    border: none;
    border-radius: 4px;
    padding: 8px 12px;
    cursor: pointer;
    z-index: 2;
    transition: 0.3s;
}

.arrow-btn:hover {
    background: var(--bnu-blue);
}

.arrow-btn.prev {
    left: 10px;
}

.arrow-btn.next {
    right: 10px;
}

.quick-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    grid-template-rows: 1fr 1fr;
    gap: 15px;
}

.quick-btn {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    font-size: 1.1rem;
    font-weight: 500;
    height: 100%;
    max-height: 182.5px;
    position: relative;
    transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
    cursor: pointer;
    padding: 15px;
    text-align: center;
    overflow: hidden;
}

.bg1 {
    background: url("../img/cgyy.png") center no-repeat;
    background-size: cover;
}
.bg2 {
    background: url("../img/yzt.png") center no-repeat;
    background-size: cover;
}
.bg3 {
    background: url("../img/kfzn.png") center no-repeat;
    background-size: cover;
}
.bg4 {
    background: url("../img/jzzj.png") center no-repeat;
    background-size: cover;
}

.quick-btn .icon {
    font-size: 1.8rem;
    margin-bottom: 6px;
    display: block;
}

.quick-btn:hover {
    transform: translateY(-4px) scale(1.02);
    box-shadow: 0 8px 25px rgba(0,0,0,0.12);
}

.quick-btn.blue-bg {
    /* background-color: var(--bnu-blue); */
    /* color: #fff; */
    border: none;
}

.quick-btn.blue-bg::after {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255,255,255,0.2) 0%, transparent 60%);
    opacity: 0;
    transition: 0.5s;
}

.quick-btn.blue-bg:hover::after {
    opacity: 1;
}

.quick-btn.white-bg {
    background-color: #fff;
    color: var(--bnu-blue);
    border: 1px solid var(--bnu-blue);
    box-shadow: inset 0 0 0 0 var(--bnu-blue);
    transition: 0.4s;
}

.quick-btn.white-bg:hover {
    /* color: #fff; */
    /* background-color: var(--bnu-blue); */
    /* border-color: var(--bnu-blue); */
}

/* --- 模块通用样式 --- */
.module-block {
    padding: 50px 20px;
    /* background-color: #fff; */
}

.module-block.wood-bg {
    /* background: url("../img/bg5.png") no-repeat center; */
    /* background-color: var(--wood-light); */
}

.module-header {
    text-align: center;
    font-size: 1.8rem;
    color: var(--bnu-blue);
    margin-bottom: 40px;
    position: relative;
}

.module-header::after {
    content: '';
    position: absolute;
    bottom: -12px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background-color: var(--wood);
}

/* --- 1. 思政服务 --- */
.sz-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.sz-card {
    background-color: #fff;
    padding: 30px 20px;
    border-radius: 4px;
    text-align: center;
    box-shadow: var(--shadow);
    border-top: 4px solid var(--bnu-blue);
    transition: 0.3s;
}

.sz-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 8px 20px rgba(5, 77, 145, 0.15);
}

.sz-card .icon {
    display: inline-block;
    width: 60px;
    height: 60px;
    background-color: var(--wood-light);
    color: var(--bnu-blue);
    border-radius: 50%;
    line-height: 60px;
    font-size: 1.8rem;
    margin-bottom: 15px;
}

/* --- 2. 专题研究 (为每个卡片增加独立的封面图) --- */
.carousel-wrapper {
    position: relative;
    overflow: hidden;
    padding: 0 40px;
}

.carousel-track {
    display: flex;
    gap: 20px;
    transition: transform 0.4s ease;
    padding: 20px 0px;
}

.research-item {
    flex: 0 0 calc(33.333% - 14px);
    background: #fff;
    border-radius: 4px;
    box-shadow: var(--shadow);
    padding: 15px;
    /* 减少padding，给内部封面图空间 */
}

/* 每张卡片的独立封面图区域 */
.item-cover {
    width: 100%;
    aspect-ratio: 16 / 10;
    /* 按照图片比例设计 */
    overflow: hidden;
    border-radius: 4px;
    margin-bottom: 15px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 4rem;
    color: rgba(255,255,255,0.8);
    transition: transform 0.3s ease;
}

.item-cover:hover {
    transform: scale(1.02);
}

/* 用户在此处可将 background 替换为 `<img>` 标签。此处使用色彩和Emoji模拟4张实体图 */
.cover-1 {
    background: linear-gradient(135deg, #054D91 0%, #2d5f94 100%);
}

/* 对应蓝底金纹钟 */
.cover-2 {
    background: linear-gradient(135deg, #E8DCC6 0%, #C1A782 100%);
}

/* 对应旧纸校歌谱 */
.cover-3 {
    background: linear-gradient(135deg, #9EBF8F 0%, #5D8A47 100%);
}

/* 对应绿色稻穗钟形 */
.cover-4 {
    background: linear-gradient(135deg, #D4C5B0 0%, #8A7560 100%);
}

/* 对应书法旧纸 */
.research-item h4 {
    padding: 0 5px;
    color: var(--bnu-blue);
    font-size: 1.1rem;
    margin-bottom: 8px;
}

.research-item p {
    padding: 0 5px 5px 5px;
    font-size: 0.9rem;
    color: var(--text-grey);
    line-height: 1.5;
}

.research-nav-btn {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 40px;
    height: 40px;
    background: var(--bnu-blue);
    color: #fff;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 1.2rem;
    z-index: 10;
    transition: 0.3s;
}

.research-nav-btn:hover {
    background: var(--wood);
}

.research-nav-btn.prev {
    left: 0px;
}

.research-nav-btn.next {
    right: 0;
}

/* --- 新闻动态 --- */
.news-list {
    display: grid;
    gap: 15px;
    background: #fff;
    padding: 15px;
    border-radius: 4px;
    box-shadow: var(--shadow);
}

.news-item {
    display: flex;
    justify-content: space-between;
    border-bottom: 1px solid #eee;
    padding: 15px 0;
}

.news-item a {
    flex: 1;
    font-weight: 500;
}

.news-item a:hover {
    color: var(--bnu-blue);
}

.news-item span {
    color: var(--text-grey);
    font-size: 0.9rem;
}

/* --- 页脚 --- */
footer {
    background-color: var(--bnu-blue);
    color: rgba(255,255,255,0.85);
    padding: 30px 20px;
    text-align: center;
    font-size: 0.9rem;
}

footer .footer-links {
    margin-bottom: 15px;
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
}

footer .copyright {
    line-height: 1.8;
    margin-top: 10px;
}

/* --- 响应式设计 --- */
@media (max-width: 1024px) {
    .sz-grid {
        grid-template-columns: 1fr 1fr;
    }

    .research-item {
        flex: 0 0 calc(50% - 10px);
    }
}

@media (max-width: 768px) {
    .header-top {
        flex-direction: column;
        align-items: stretch;
        gap: 15px;
    }

    .logo-area {
        justify-content: center;
        flex-wrap: wrap;
    }

    .search-bar input {
        width: 100%;
    }

    .menu-toggle {
        display: block;
        text-align: right;
    }

    .nav-list {
        display: none;
        flex-direction: column;
        gap: 0;
        border-top: 1px solid #eee;
    }

    .nav-list.active {
        display: flex;
    }

    .nav-list li a {
        display: block;
        padding: 12px 0;
        text-align: center;
        border-bottom: 1px solid #f0f0f0;
    }

    .dropdown .sub-menu {
        position: static;
        transform: none;
        box-shadow: none;
        border: none;
        padding: 0;
        background-color: var(--cream);
    }

    .nav-list.active .dropdown .sub-menu {
        display: block;
    }

    .hero-section {
        grid-template-columns: 1fr;
    }

    .carousel-slider {
        min-height: 280px;
    }

    .slide h2 {
        font-size: 2rem;
    }

    .quick-grid {
        grid-template-columns: 1fr 1fr;
    }

    .quick-btn {
        padding: 20px;
        flex-direction: row;
        gap: 10px;
        font-size: 1rem;
    }

    .quick-btn .icon {
        font-size: 1.5rem;
        margin: 0;
    }

    .sz-grid {
        grid-template-columns: 1fr;
    }

    .research-item {
        flex: 0 0 calc(100%);
    }

    .carousel-wrapper {
        padding: 0 30px;
    }
}