/* ===== Base ===== */
:root{
  --bg:#f6f8fc;
  --bg-alt:#eef2f9;
  --ink:#16203a;
  --ink-soft:#475069;
  --line:#dce3ef;
  --brand:#13315c;
  --brand-2:#1f6f8b;
  --accent:#f0a500;
  --accent-2:#19c3c3;
  --card:#ffffff;
  --shadow:0 10px 30px rgba(19,49,92,.08);
  --radius:16px;
  --maxw:1120px;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:"Inter","Noto Sans SC",system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;
  color:var(--ink);background:var(--bg);line-height:1.65;
  -webkit-font-smoothing:antialiased;
}
.lang-zh{display:none}
body.zh .lang-en{display:none}
body.zh .lang-zh{display:inline}
a{color:inherit;text-decoration:none}
img{max-width:100%;height:auto}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 22px}

/* ===== Topbar ===== */
.topbar{background:var(--brand);color:#cfe0f5;font-size:.82rem}
.topbar-inner{display:flex;justify-content:space-between;align-items:center;height:40px}
.lang-btn{background:rgba(255,255,255,.12);color:#fff;border:none;padding:5px 14px;border-radius:20px;cursor:pointer;font-weight:600;font-size:.8rem;transition:.2s}
.lang-btn:hover{background:rgba(255,255,255,.22)}

/* ===== Header ===== */
.site-header{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.94);backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
.nav{display:flex;align-items:center;justify-content:space-between;height:64px}
.brand{display:flex;align-items:baseline;gap:6px;font-weight:800}
.brand-mark{font-size:1.35rem;color:var(--brand);letter-spacing:.04em}
.brand-year{color:var(--accent);font-weight:700}
.nav-links{display:flex;gap:20px}
.nav-links a{font-size:.9rem;color:var(--ink-soft);font-weight:500;position:relative;padding:4px 0;transition:.2s}
.nav-links a:hover{color:var(--brand)}
.nav-links a::after{content:"";position:absolute;left:0;bottom:-2px;width:0;height:2px;background:var(--accent);transition:.25s}
.nav-links a:hover::after{width:100%}
.nav-toggle{display:none;flex-direction:column;gap:5px;background:none;border:none;cursor:pointer;padding:6px}
.nav-toggle span{width:24px;height:2px;background:var(--brand);border-radius:2px;transition:.25s}

/* ===== Hero ===== */
.hero{position:relative;display:block;overflow:hidden;background:linear-gradient(180deg,#f2f8f7 0%,#e8f1f2 60%,#e2eef2 100%);color:#0c2233}
.hero-inner{position:relative;z-index:2;width:100%;text-align:center;padding:40px 0 46px}
.hero-bg{position:relative;width:100%;max-width:1000px;margin:0 auto;border-radius:18px;overflow:hidden;box-shadow:0 14px 40px rgba(19,49,92,.16);background:#e8f1f2}
.hero-bg img{display:block;width:100%;height:auto;aspect-ratio:1600/531;object-fit:cover}
.hero-meta{display:flex;flex-wrap:wrap;justify-content:center;gap:14px;margin:30px 0 26px}
.hero-meta-item{background:rgba(255,255,255,.75);border:1px solid rgba(19,49,92,.14);border-radius:12px;padding:10px 18px;min-width:130px;backdrop-filter:blur(6px);box-shadow:0 4px 14px rgba(19,49,92,.08)}
.hm-label{display:block;font-size:.72rem;text-transform:uppercase;letter-spacing:.12em;color:#2b6b7f}
.hm-value{display:block;font-weight:700;font-size:1rem;margin-top:2px;color:#0c2233}
.hero-cta{display:flex;gap:14px;justify-content:center;flex-wrap:wrap}
.btn{display:inline-block;padding:13px 28px;border-radius:30px;font-weight:700;font-size:.95rem;transition:.2s;cursor:pointer}
.btn-primary{background:var(--accent);color:#1a1300}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 10px 24px rgba(240,165,0,.4)}
.btn-ghost{border:1.5px solid rgba(19,49,92,.45);color:#13315c}
.btn-ghost:hover{background:rgba(19,49,92,.08)}

/* ===== Countdown ===== */
.countdown{display:flex;gap:12px;justify-content:center;margin-top:34px}
.cd-box{background:#13315c;border:1px solid rgba(19,49,92,.2);border-radius:12px;padding:12px 16px;min-width:74px;box-shadow:0 6px 16px rgba(19,49,92,.18)}
.cd-num{display:block;font-size:1.7rem;font-weight:800;line-height:1;color:#fff}
.cd-lab{display:block;font-size:.7rem;text-transform:uppercase;letter-spacing:.1em;color:#9fd6e6;margin-top:6px}

/* ===== Sections ===== */
.section{padding:72px 0}
.section-alt{background:var(--bg-alt)}
.section-dark{background:linear-gradient(135deg,#0c1c3a,#13315c);color:#fff}
.sec-head{margin-bottom:34px}
.sec-head.light .sec-tag{color:#9fd6e6}
.sec-tag{display:inline-block;font-size:.78rem;font-weight:700;letter-spacing:.16em;text-transform:uppercase;color:var(--brand-2);margin-bottom:8px}
.sec-head h2{font-size:clamp(1.5rem,3vw,2.2rem);font-weight:800;letter-spacing:-.01em}

/* ===== About ===== */
.about-grid{display:grid;grid-template-columns:1.6fr 1fr;gap:34px;align-items:center}
.about-text p{color:var(--ink-soft);margin-bottom:16px}
.about-text p:last-child{margin-bottom:0}
.about-stats{list-style:none;display:grid;grid-template-columns:1fr 1fr;gap:14px}
.about-stats li{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:18px;text-align:center;box-shadow:var(--shadow)}
.about-stats strong{display:block;font-size:1.9rem;color:var(--brand);font-weight:800}
.about-stats span{font-size:.85rem;color:var(--ink-soft)}

/* ===== Cards ===== */
.cards{display:grid;gap:18px}
.topics-cards{grid-template-columns:repeat(3,1fr)}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:22px;box-shadow:var(--shadow);transition:.2s}
.card:hover{transform:translateY(-4px);border-color:var(--accent-2)}
.card h3{font-size:1.05rem;margin-bottom:8px;color:var(--brand)}
.card p{color:var(--ink-soft);font-size:.92rem}

/* ===== Speakers ===== */
.spk-group-title{margin:0 0 16px;font-size:1.05rem;color:var(--brand-2);text-transform:uppercase;letter-spacing:.1em;font-weight:700}
.spk-group-title + .cards{margin-bottom:34px}
.spk-grid{grid-template-columns:repeat(4,1fr)}
.spk-card{text-align:center}
.spk-avatar{width:72px;height:72px;margin:0 auto 14px;border-radius:50%;background:linear-gradient(135deg,var(--brand),var(--brand-2));color:#fff;display:flex;align-items:center;justify-content:center;font-size:1.3rem;font-weight:800;letter-spacing:.02em}
.spk-avatar.muted{background:linear-gradient(135deg,#8fa3bf,#b6c4d8)}
.spk-card h3{font-size:1rem;margin-bottom:0}
.spk-pending .card{border-style:dashed;box-shadow:none;opacity:.85}
.speakers-note{margin-top:26px;color:var(--ink-soft);font-size:.92rem}

/* ===== Program ===== */
.program{display:grid;grid-template-columns:repeat(4,1fr);gap:18px}
.day{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow)}
.day-head{background:linear-gradient(135deg,var(--brand),var(--brand-2));color:#fff;padding:14px 18px}
.day-date{display:block;font-weight:800;font-size:1.15rem}
.day-theme{display:block;font-size:.82rem;color:#cfe0f5;margin-top:2px}
.day-list{list-style:none;padding:14px 18px}
.day-list li{display:flex;gap:12px;padding:8px 0;border-bottom:1px dashed var(--line);font-size:.9rem}
.day-list li:last-child{border-bottom:none}
.day-list .t{color:var(--brand-2);font-weight:600;white-space:nowrap}
.day-list .e{color:var(--ink-soft)}

/* ===== Abstract ===== */
.abs-grid{display:grid;grid-template-columns:1fr 1.4fr;gap:22px;align-items:stretch}
.abs-dates{display:flex;flex-direction:column;gap:16px}
.abs-date-card{background:var(--card);border:1px solid var(--line);border-left:5px solid var(--accent-2);border-radius:12px;padding:18px 20px;box-shadow:var(--shadow)}
.abs-label{display:block;font-size:.78rem;text-transform:uppercase;letter-spacing:.12em;color:var(--ink-soft)}
.abs-value{display:block;font-size:1.35rem;font-weight:800;color:var(--brand);margin-top:4px}
.req-list{list-style:none;margin:6px 0 18px}
.req-list li{position:relative;padding:7px 0 7px 24px;color:var(--ink-soft);font-size:.95rem;border-bottom:1px dashed var(--line)}
.req-list li:last-child{border-bottom:none}
.req-list li::before{content:"✓";position:absolute;left:0;color:var(--accent-2);font-weight:800}
.btn-mail{display:inline-block;background:var(--brand);color:#fff;padding:13px 26px;border-radius:12px;font-weight:700;transition:.2s}
.btn-mail:hover{background:var(--brand-2);transform:translateY(-2px);box-shadow:0 10px 24px rgba(19,49,92,.25)}

/* ===== Registration ===== */
.reg-grid{display:grid;grid-template-columns:1fr;gap:34px;max-width:680px;margin:0 auto}
.fee-title{font-size:1rem;color:var(--brand-2);text-transform:uppercase;letter-spacing:.08em;margin-bottom:14px;font-weight:700}
.reg-table{width:100%;border-collapse:collapse;background:var(--card);border-radius:12px;overflow:hidden;box-shadow:var(--shadow)}
.reg-table th{background:var(--brand);color:#fff;text-align:left;padding:12px 16px;font-size:.88rem;font-weight:600}
.reg-table td{padding:13px 16px;border-bottom:1px solid var(--line);font-size:.95rem}
.reg-table tr:last-child td{border-bottom:none}
.reg-table tr:nth-child(even) td{background:#fafcff}
.fee-note{margin-top:14px;font-size:.88rem;color:var(--ink-soft);background:rgba(240,165,0,.1);border-left:4px solid var(--accent);border-radius:8px;padding:12px 14px}
.usd{display:block;font-size:.78rem;font-weight:600;color:#0c6b6b;margin-top:3px}

/* ===== Contact ===== */
.contact-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:22px}
.contact-card{background:rgba(255,255,255,.06);border:1px solid rgba(255,255,255,.14);border-radius:var(--radius);padding:26px}
.contact-card h3{font-size:1.2rem;margin-bottom:6px}
.contact-card p{color:#c3d3ea;font-size:.95rem}
.contact-meta{margin-top:6px}
.contact-card a:hover{color:var(--accent)}

/* ===== Footer ===== */
.site-footer{background:#081228;color:#8fa3c2;padding:28px 0;text-align:center;font-size:.88rem}
.footer-sub{margin-top:4px;font-size:.8rem;color:#5d6f92}

/* ===== To top ===== */
.to-top{position:fixed;right:22px;bottom:22px;width:44px;height:44px;border-radius:50%;border:none;background:var(--brand);color:#fff;font-size:1.2rem;cursor:pointer;opacity:0;pointer-events:none;transition:.25s;z-index:60;box-shadow:0 8px 20px rgba(19,49,92,.3)}
.to-top.show{opacity:1;pointer-events:auto}
.to-top:hover{background:var(--brand-2)}

/* ===== Responsive ===== */
@media (max-width:960px){
  .topics-cards{grid-template-columns:repeat(2,1fr)}
  .spk-grid{grid-template-columns:repeat(3,1fr)}
  .program{grid-template-columns:repeat(2,1fr)}
  .about-grid,.abs-grid,.reg-grid,.contact-grid{grid-template-columns:1fr}
}
@media (max-width:760px){
  .nav-toggle{display:flex}
  .hero-inner{padding:24px 0 36px}
  .hero-bg{border-radius:12px}
  .nav-links{position:absolute;top:64px;left:0;right:0;background:#fff;flex-direction:column;gap:0;padding:8px 22px 16px;border-bottom:1px solid var(--line);display:none}
  .nav-links.open{display:flex}
  .nav-links a{padding:12px 0;border-bottom:1px solid var(--line)}
  .nav-links a:last-child{border-bottom:none}
  
  .spk-grid{grid-template-columns:repeat(2,1fr)}
  .topics-cards,.program{grid-template-columns:1fr}
  .countdown{flex-wrap:wrap}
  .section{padding:56px 0}
}