:root {
    --bg: #faf9f7;
    --surface: #ffffff;
    --text: #1a1a1a;
    --muted: #5c5c5c;
    --accent: #0d4f6c;
    --accent-soft: #e8f2f6;
    --border: #e6e2dc;
    --hero-overlay: rgba(13, 40, 55, 0.72);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    margin: 0;
    font-family: "Inter", system-ui, sans-serif;
    font-size: 16px;
    line-height: 1.65;
    color: var(--text);
    background: var(--bg);
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Header */
#header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(8px);
    border-bottom: 1px solid var(--border);
}
#header .inner {
    max-width: 1120px;
    margin: 0 auto;
    padding: 0.75rem 1.25rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}
.brand {
    display: flex;
    flex-direction: column;
    gap: 0.1rem;
}
.brand a {
    text-decoration: none;
    color: inherit;
}
.brand a:hover { text-decoration: none; }
.brand strong {
    font-family: "Playfair Display", Georgia, serif;
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--accent);
    letter-spacing: 0.02em;
}
.main-nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-wrap: wrap;
    gap: 0.25rem 1rem;
    align-items: center;
}
.main-nav a {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text);
    text-decoration: none;
    padding: 0.35rem 0;
}
.main-nav a:hover { color: var(--accent); text-decoration: none; }
.main-nav a.active {
    color: var(--accent);
    font-weight: 600;
    border-bottom: 2px solid var(--accent);
    padding-bottom: 0.15rem;
}
.mobile-toggle {
    display: none;
    background: #ffffff;
    border: 1px solid rgba(0, 0, 0, 0.18);
    padding: 0.5rem 0.85rem;
    border-radius: 8px;
    cursor: pointer;
    color: #111111;
    font-size: 1.6rem;
    line-height: 1;
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.12);
    -webkit-tap-highlight-color: transparent;
}
/* 内联 SVG 三点，不依赖 Font Awesome 字体（移动端 CDN 失败时仍可见） */
.mobile-toggle-icon {
    display: block;
    flex-shrink: 0;
}
@media (max-width: 900px) {
    .main-nav { display: none; width: 100%; }
    .main-nav.open { display: block; }
    .main-nav ul { flex-direction: column; align-items: flex-start; padding: 0.5rem 0; }
    .mobile-toggle { display: inline-flex; align-items: center; justify-content: center; }
    #header .inner { flex-wrap: wrap; }
}

/* Hero */
#hero {
    position: relative;
    min-height: 420px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: #fff;
    background: #1a3a4a url("https://yinlaetitia.github.io/isbdai2026/img/page/polyu.jpg") center/cover no-repeat;
}
#hero::before {
    content: "";
    position: absolute;
    inset: 0;
    background: var(--hero-overlay);
}
.hero-inner {
    position: relative;
    z-index: 1;
    max-width: 900px;
    padding: 3rem 1.25rem 3.5rem;
}
.hero-kicker {
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    opacity: 0.92;
    margin-bottom: 0.75rem;
}
.hero-inner h1 {
    font-family: "Playfair Display", Georgia, serif;
    font-weight: 600;
    font-size: clamp(1.5rem, 4vw, 2.25rem);
    line-height: 1.25;
    margin: 0 0 1rem;
}
.hero-badges {
    display: flex;
    flex-wrap: wrap;
    gap: 0.65rem;
    justify-content: center;
    margin-top: 1.25rem;
}
.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.9rem;
    padding: 0.45rem 0.85rem;
    background: rgba(255, 255, 255, 0.12);
    border: 1px solid rgba(255, 255, 255, 0.35);
    border-radius: 999px;
}

/* Sections */
main { padding-bottom: 3rem; }
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 1.25rem;
}
section {
    padding: 2.75rem 0;
    border-bottom: 1px solid var(--border);
}
main > .main-layout > .main-primary > section:last-child { border-bottom: none; }

/* Two-column layout */
.main-layout {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(260px, 300px);
    gap: 2rem 2.5rem;
    max-width: 1180px;
    margin: 0 auto;
    padding: 0 1.25rem;
    align-items: start;
}
.main-primary {
    min-width: 0;
}
.main-primary section .container {
    max-width: none;
    margin: 0;
    padding-left: 0;
    padding-right: 0;
}
.main-sidebar {
    position: sticky;
    top: 4rem;
    align-self: start;
}
.main-sidebar .container {
    max-width: none;
    margin: 0;
    padding-left: 0;
    padding-right: 0;
}
.main-sidebar .dates-sidebar-section {
    padding: 2.75rem 0;
    border-bottom: none;
}
.main-sidebar .dates-sidebar-section h2 {
    font-size: 1.35rem;
    margin-bottom: 0.65rem;
}
.main-sidebar .dates-sidebar-section .lead {
    font-size: 0.95rem;
    margin-bottom: 0.75rem;
}
.main-sidebar .dates-grid {
    grid-template-columns: 1fr;
    margin-top: 0.5rem;
}
.main-sidebar .date-item {
    padding: 0.85rem 1rem;
}
@media (max-width: 960px) {
    .main-layout {
        grid-template-columns: 1fr;
        gap: 0;
    }
    .main-sidebar {
        position: static;
        border-top: 1px solid var(--border);
    }
    .main-sidebar .dates-sidebar-section {
        padding: 2.75rem 0;
    }
    .main-primary section .container {
        padding-left: 0;
        padding-right: 0;
    }
}
h2 {
    font-family: "Playfair Display", Georgia, serif;
    font-size: 1.65rem;
    font-weight: 600;
    color: var(--accent);
    margin: 0 0 1rem;
}
h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 1.5rem 0 0.6rem;
    color: var(--text);
}
.lead {
    font-size: 1.05rem;
    color: var(--muted);
}
ul.clean {
    margin: 0.5rem 0 0;
    padding-left: 1.2rem;
}
ul.clean li { margin: 0.35rem 0; }

.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1.25rem 1.35rem;
    margin: 1rem 0;
}
.dates-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 0.75rem;
    margin-top: 1rem;
}
.date-item {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1rem 1.1rem;
}
.date-item strong {
    display: block;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--muted);
    margin-bottom: 0.35rem;
}
.track {
    margin: 1.25rem 0;
}
.track h3 {
    font-family: "Playfair Display", Georgia, serif;
    font-size: 1.15rem;
    color: var(--accent);
    margin-top: 0;
}
.people-grid {
    display: grid;
    gap: 1rem;
    margin-top: 1rem;
}
.person {
    padding: 1rem 1.1rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
}
.person-name {
    display: block;
    margin-bottom: 0.2rem;
    font-weight: 600;
    color: #1565c0;
    text-decoration: none;
}
.person-name:hover { text-decoration: underline; }
.person .meta { font-size: 0.9rem; color: var(--muted); }
.pc-list {
    columns: 2;
    column-gap: 2rem;
    margin: 0.5rem 0 0;
    padding-left: 1.2rem;
}
@media (max-width: 640px) {
    .pc-list { columns: 1; }
}
footer {
    background: #1e2a30;
    color: #c8d0d4;
    padding: 2rem 1.25rem;
    font-size: 0.9rem;
    text-align: center;
}
footer .container { max-width: 900px; }
footer a { color: #9ec9dd; }
footer p { margin: 0.4rem 0; }