*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
    line-height: 1.5;
    color: #1b2733;
    background-color: #f4f6f8;
}

h1,
h2,
h3,
h4 {
    margin-top: 0;
    font-weight: 600;
    color: #12212f;
}

p {
    margin-top: 0;
    margin-bottom: 1em;
}

a {
    color: #0055aa;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* =========================
   Layout helpers
   ========================= */

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

.section {
    padding: 60px 0;
    background-color: #ffffff;
}

.section-light {
    background-color: #f9fbfd;
}

.section-alt {
    background-color: #ffffff;
}

.section-block {
    /* 预留给区块间距等扩展用 */
}

.section-accent {
    background: linear-gradient(135deg, #0b2341, #243b64);
    color: #e5e9f0;
    /* 略带灰的白色，避免太刺眼 */
}

.section-accent h2 {
    color: #f3f5fb;
}

.section-dark {
    background: linear-gradient(135deg, #0b2341, #243b64);
    color: #e5e9f0;
}

.section-dark h2,
.section-dark h3 {
    color: #f3f5fb;
}

.section-dark p,
.section-dark li {
    color: #e5e9f0;
}

.section-intro {
    max-width: 720px;
}

/* 联系方式区块可以稍微突出一点 */
.section-contact {
    background-color: #f0f4fa;
}

/* =========================
   Header & navigation
   ========================= */

.site-header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background-color: #0b2341;
    color: #ffffff;
    transition: transform 0.2s ease;
}

/* 向下滚动时隐藏导航栏，向上滚动显示 */
.site-header.header-hidden {
    transform: translateY(-100%);
}

/* 内部左右布局容器（桌面端） */
.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 24px;
    max-width: 1100px;
    margin: 0 auto;
}

/* 品牌区 */
.brand-title {
    font-size: 20px;
    font-weight: 700;
    color: #ffffff;
}

.brand-subtitle {
    font-size: 12px;
    color: rgba(255, 255, 255, 0.8);
}

/* 顶部导航（桌面端） */
.nav-desktop {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 10px;
}

.nav-link {
    font-size: 14px;
    padding: 6px 10px;
    border-radius: 4px;
    color: #ffffff;
    text-decoration: none;
}

.nav-link:hover {
    background-color: rgba(255, 255, 255, 0.12);
    text-decoration: none;
}

.nav-link.active {
    background-color: #ffffff;
    color: #0b2341;
}

/* 汉堡按钮（移动端） */
.menu-toggle {
    display: none;
    /* 默认桌面端隐藏 */
    position: relative;
    width: 30px;
    height: 22px;
    border: none;
    background-color: transparent;
    padding: 0;
    cursor: pointer;
}

.menu-line {
    position: absolute;
    left: 0;
    right: 0;
    height: 3px;
    border-radius: 999px;
    background-color: #ffffff;
    transition: transform 0.2s ease, opacity 0.2s ease, top 0.2s ease, bottom 0.2s ease;
}

.menu-line:nth-child(1) {
    top: 0;
}

.menu-line:nth-child(2) {
    top: 9.5px;
}

.menu-line:nth-child(3) {
    bottom: 0;
}

/* 汉堡按钮展开成 X 的动画 */
.menu-toggle.open .menu-line:nth-child(1) {
    top: 9.5px;
    transform: rotate(45deg);
}

.menu-toggle.open .menu-line:nth-child(2) {
    opacity: 0;
}

.menu-toggle.open .menu-line:nth-child(3) {
    bottom: auto;
    top: 9.5px;
    transform: rotate(-45deg);
}

/* 抽屉导航（移动端） */
.nav-drawer {
    position: fixed;
    top: 0;
    right: 0;
    width: 240px;
    height: 100vh;
    background-color: #0b2341;
    padding: 70px 24px 24px;
    transform: translateX(100%);
    transition: transform 0.2s ease;
    z-index: 90;
}

.nav-drawer.open {
    transform: translateX(0);
}

.nav-drawer .nav-link {
    display: block;
    margin-bottom: 12px;
    color: #ffffff;
}

.nav-drawer .nav-link.active {
    background-color: #ffffff;
    color: #0b2341 !important;  /* 强制覆盖通用颜色 */
    border-radius: 999px;
    padding-left: 18px;
    padding-right: 18px;
}



/* 兼容旧写法：如果 HTML 里还在用 .site-nav，当成桌面导航的一种 */
.site-nav {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 10px;
}

/* 抽屉导航遮罩层 */
.nav-overlay {
    position: fixed;
    inset: 0;
    background-color: rgba(0, 0, 0, 0.35);
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.2s ease;
    z-index: 80;
}

.nav-overlay.open {
    opacity: 1;
    visibility: visible;
}

/* =========================
   Hero
   ========================= */

.hero {
    position: relative;
    width: 100%;
    /* 4:1 长宽比：高度 = 宽度的 1/4 */
    padding-top: 25%;
    background-image: url("../images/conference.png");
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
}
/* 小屏（手机）时拉高头图区域，防止文字被裁掉 */
@media (max-width: 768px) {
    .hero {
        padding-top: 60%;       /* 从 25% 提高到 60%，高度明显增加 */
        min-height: 60vh;       /* 至少占 60% 的视口高度，保证文字有空间 */
    }

    .hero h1 {
        font-size: 24px;
        line-height: 1.25;
    }

    .hero-tagline {
        font-size: 16px;
    }

    .hero-meta {
        font-size: 14px;
    }
}


.hero-inner {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: #ffffff;
    padding: 0 20px;
    z-index: 1;
}

.hero h1 {
    font-size: 32px;
    margin-bottom: 12px;
}

.hero-tagline {
    font-size: 18px;
    margin-bottom: 10px;
}

.hero-meta {
    font-size: 15px;
    opacity: 0.9;
}

/* =========================
   Buttons
   ========================= */

.btn {
    display: inline-block;
    padding: 10px 20px;
    border-radius: 20px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    border: 1px solid transparent;
    text-decoration: none;
}

.btn-primary {
    background-color: #ffb547;
    color: #12212f;
    border-color: #ffb547;
}

.btn-primary:hover {
    background-color: #ff9f0f;
}

.btn-outline {
    background-color: transparent;
    color: #ffffff;
    border-color: #ffffff;
}

.btn-outline:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

/* =========================
   Grids
   ========================= */

.grid {
    display: grid;
    gap: 24px;
}

.grid-2 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

/* Important dates grid */
.dates-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 16px;
}

.date-card {
    padding: 16px;
    border-radius: 8px;
    background-color: rgba(0, 0, 0, 0.12);
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.section:not(.section-accent) .date-card {
    background-color: #ffffff;
    border-color: #d0d7e2;
}

.date-title {
    font-size: 14px;
    opacity: 0.9;
    margin-bottom: 4px;
}

.date-value {
    font-size: 16px;
    font-weight: 600;
}

/* =========================
   Lists & tables
   ========================= */

.bullet-list {
    padding-left: 20px;
}

.bullet-list li {
    margin-bottom: 6px;
}

.fee-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 10px;
}

.fee-table th,
.fee-table td {
    border: 1px solid #d0d7e2;
    padding: 8px 12px;
    text-align: left;
}

.fee-table th {
    background-color: #f0f4fa;
}

/* =========================
   Committees & Sponsors
   ========================= */

.committee-list {
    list-style: none;
    padding-left: 0;
    margin-top: 4px;
    margin-bottom: 12px;
}

.committee-list li {
    padding: 2px 0;
}

/* 备注类文字 */
.note {
    font-size: 13px;
    color: #6b7685;
}

/* =========================
   Footer
   ========================= */

.site-footer {
    background-color: #0b2341;
    color: #ffffff;
    padding: 20px 0;
    margin-top: 0;
}

.footer-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    font-size: 13px;
}

.footer-title {
    font-weight: 600;
}

.footer-subtitle {
    font-size: 12px;
    opacity: 0.8;
}

.footer-meta {
    opacity: 0.85;
}

/* =========================
   Committees 折叠样式
   ========================= */

.committee-collapse {
    margin-top: 8px;
    margin-bottom: 16px;
}

.committee-collapse-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 8px;
}

.committee-collapse-title {
    font-size: 14px;
}

/* 折叠按钮 */
.collapse-toggle {
    padding: 4px 12px;
    font-size: 13px;
    border-radius: 999px;
    border: 1px solid #d0d7e2;
    background-color: transparent;
    cursor: pointer;
}

/* 深色底下按钮的颜色调整 */
.section-dark .collapse-toggle {
    color: #e5e9f0;
    border-color: rgba(229, 233, 240, 0.5);
}

.section-dark .collapse-toggle:hover {
    background-color: rgba(255, 255, 255, 0.08);
}

.section-dark .collapse-toggle.open {
    background-color: rgba(255, 255, 255, 0.15);
}

/* 折叠内容区域 */
.collapsible {
    display: none;
    margin-top: 8px;
}

.collapsible.open {
    display: block;
}

/* =========================
   Responsive
   ========================= */

@media (max-width: 900px) {

    /* 头部布局：减小左右 padding */
    .header-inner {
        padding: 10px 16px;
    }

    /* 桌面导航隐藏，显示汉堡按钮 */
    .nav-desktop {
        display: none;
    }

    .menu-toggle {
        display: block;
    }

    .hero h1 {
        font-size: 24px;
    }

    .hero-tagline {
        font-size: 16px;
    }

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

    .grid-2 {
        grid-template-columns: 1fr;
    }

    .footer-inner {
        flex-direction: column;
        align-items: flex-start;
    }
}

@media (max-width: 600px) {
    .hero-inner {
        padding: 0 12px;
    }

    .hero h1 {
        font-size: 20px;
    }

    .hero-tagline {
        font-size: 14px;
    }

    .hero-meta {
        font-size: 13px;
    }
}