/* ============================================================
   LUCERNA 秉烛游 — professional light
   ============================================================ */

@font-face {
  font-family: "Noto Sans SC";
  src: url("../fonts/noto-sans-sc-400.woff2") format("woff2");
  font-weight: 400;
  font-display: swap;
}
@font-face {
  font-family: "Noto Sans SC";
  src: url("../fonts/noto-sans-sc-700.woff2") format("woff2");
  font-weight: 700;
  font-display: swap;
}
@font-face {
  font-family: "Manrope";
  src: url("../fonts/manrope-500.woff2") format("woff2");
  font-weight: 500;
  font-display: swap;
}
@font-face {
  font-family: "Manrope";
  src: url("../fonts/manrope-600.woff2") format("woff2");
  font-weight: 600;
  font-display: swap;
}
@font-face {
  font-family: "Manrope";
  src: url("../fonts/manrope-800.woff2") format("woff2");
  font-weight: 800;
  font-display: swap;
}
@font-face {
  font-family: "IBM Plex Mono";
  src: url("../fonts/ibm-plex-mono-500.woff2") format("woff2");
  font-weight: 500;
  font-display: swap;
}

:root {
  --bg: #ffffff;
  --soft: #f5f6f8;
  --ink: #14161a;
  --dim: #555a63;
  --faint: #8a8f99;
  --gold: #b8741f;
  --gold-strong: #9a5f14;
  --link: #1a56db;
  --font-cn: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-en: "Manrope", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, Consolas, monospace;
  --maxw: 1080px;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-cn);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
::selection { background: rgba(184, 116, 31, 0.18); }

/* ---------- Header ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 20px clamp(24px, 5vw, 64px);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}
.nav-logo {
  display: block;
  height: 34px;
  width: auto;
}
.links { display: flex; gap: 28px; }
.links a { font-size: 0.92rem; color: var(--dim); transition: color 0.2s; }
.links a:hover { color: var(--ink); }

/* ---------- Dropdown ---------- */
.dd { position: relative; }
.dd-btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  font-size: 0.92rem;
  color: var(--dim);
  transition: color 0.2s;
  cursor: pointer;
}
.dd-btn:hover, .dd[data-open="true"] .dd-btn { color: var(--ink); }
.dd-btn svg { transition: transform 0.3s cubic-bezier(0.22, 0.61, 0.36, 1); }
.dd[data-open="true"] .dd-btn svg { transform: rotate(180deg); }
.dd-menu {
  position: absolute;
  top: calc(100% + 14px);
  left: 50%;
  transform: translateX(-50%) translateY(-6px) scale(0.97);
  transform-origin: top center;
  min-width: 300px;
  background: #fff;
  border-radius: 10px;
  box-shadow: 0 14px 44px rgba(20, 22, 26, 0.14);
  padding: 8px;
  opacity: 0;
  visibility: hidden;
  transition:
    opacity 0.18s ease,
    transform 0.22s cubic-bezier(0.22, 0.61, 0.36, 1),
    visibility 0.22s;
}
.dd-menu::before {
  content: "";
  position: absolute;
  top: -7px;
  left: 50%;
  transform: translateX(-50%);
  border-left: 7px solid transparent;
  border-right: 7px solid transparent;
  border-bottom: 7px solid #fff;
}
.dd[data-open="true"] .dd-menu {
  opacity: 1;
  visibility: visible;
  animation: ddIn 0.3s cubic-bezier(0.22, 0.61, 0.36, 1) both;
}
@keyframes ddIn {
  from {
    opacity: 0;
    transform: translateX(-50%) translateY(-10px) scale(0.95);
  }
  to {
    opacity: 1;
    transform: translateX(-50%) translateY(0) scale(1);
  }
}
.dd-item {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding: 13px 42px 13px 16px;
  border-radius: 8px;
  transition: background 0.18s cubic-bezier(0.22, 0.61, 0.36, 1), transform 0.18s cubic-bezier(0.22, 0.61, 0.36, 1);
}
.dd-item:hover { background: var(--soft); transform: translateX(3px); }
.dd-title { font-size: 0.95rem; font-weight: 700; color: var(--ink); letter-spacing: 0.02em; }
.dd-en {
  font-family: var(--font-en);
  font-weight: 500;
  font-size: 0.76rem;
  letter-spacing: 0.04em;
  color: var(--faint);
}
.dd-arrow {
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--gold);
  opacity: 0;
  transition: opacity 0.2s, transform 0.2s;
}
.dd-item:hover .dd-arrow { opacity: 1; transform: translate(-3px, -50%); }
.nav-mail {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--link);
  border-bottom: 1px solid rgba(26, 86, 219, 0.35);
  transition: border-color 0.2s;
}
.nav-mail:hover { border-color: var(--link); }

/* ---------- Hero ---------- */
.hero {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: clamp(90px, 13vh, 150px) clamp(24px, 5vw, 64px) 90px;
}
.hero-wordmark {
  font-family: var(--font-en);
  font-weight: 800;
  font-size: clamp(3.6rem, 11vw, 7.4rem);
  letter-spacing: 0.06em;
  line-height: 1;
  color: var(--ink);
}
.hero-title {
  display: flex;
  align-items: baseline;
  gap: 18px;
  margin-top: 34px;
  flex-wrap: wrap;
}
.hero-title h2 { font-size: clamp(1.6rem, 3.4vw, 2.2rem); font-weight: 700; letter-spacing: 0.08em; }
.hero-title .en {
  font-family: var(--font-en);
  font-weight: 500;
  font-size: 1rem;
  letter-spacing: 0.04em;
  color: var(--faint);
}
.hero .zh, .hero .en {
  max-width: 640px;
  margin-top: 22px;
  font-size: 1rem;
  line-height: 2;
  color: var(--dim);
}
.hero .en {
  font-family: var(--font-en);
  font-weight: 500;
  line-height: 1.9;
  color: var(--faint);
  font-size: 0.94rem;
}
.actions { display: flex; gap: 14px; margin-top: 38px; flex-wrap: wrap; align-items: center; }

/* ---------- Buttons & links (affordance) ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  padding: 12px 26px;
  font-size: 0.94rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: #fff;
  background: var(--gold);
  border-radius: 6px;
  transition: background 0.2s, transform 0.2s;
}
.btn:hover { background: var(--gold-strong); transform: translateY(-1px); }
.btn.ghost {
  color: var(--ink);
  background: var(--soft);
}
.btn.ghost:hover { background: #e9ebef; }
.btn.big { padding: 15px 32px; font-size: 1.05rem; }
.link {
  color: var(--link);
  border-bottom: 1px solid rgba(26, 86, 219, 0.35);
  font-size: 0.94rem;
  transition: border-color 0.2s;
}
.link:hover { border-color: var(--link); }

/* ---------- Sections ---------- */
.section {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 96px clamp(24px, 5vw, 64px);
}
.sec-head { margin-bottom: 40px; }
.sec-head h2 {
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 700;
  letter-spacing: 0.06em;
}
.sec-head h2 em {
  font-family: var(--font-en);
  font-style: normal;
  font-weight: 500;
  font-size: 0.72em;
  letter-spacing: 0.08em;
  color: var(--faint);
  margin-left: 12px;
}
.section > .zh {
  max-width: 620px;
  font-size: 1.06rem;
  line-height: 2.05;
  color: var(--ink);
}
.section > .en {
  max-width: 620px;
  margin-top: 10px;
  font-family: var(--font-en);
  font-weight: 500;
  font-size: 0.94rem;
  line-height: 1.9;
  color: var(--faint);
}

/* ---------- Research ---------- */
.grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 22px;
}
.grid article {
  background: var(--soft);
  border-radius: 10px;
  padding: 30px 32px;
  box-shadow: 0 1px 3px rgba(20, 22, 26, 0.05);
}
.grid h3 {
  margin-top: 12px;
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}
.grid h3 em {
  font-family: var(--font-en);
  font-style: normal;
  font-weight: 500;
  font-size: 0.66em;
  color: var(--faint);
  margin-left: 10px;
}
.grid .zh { margin-top: 12px; font-size: 0.94rem; color: var(--dim); }
.grid .en {
  margin-top: 4px;
  font-family: var(--font-en);
  font-weight: 500;
  font-size: 0.82rem;
  color: var(--faint);
}

/* ---------- Members ---------- */
.members {
  list-style: none;
  margin-top: 48px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.member-card {
  background: var(--soft);
  border-radius: 10px;
  padding: 30px 26px 28px;
  text-align: center;
}
.avatar {
  width: 88px;
  height: 88px;
  border-radius: 50%;
  object-fit: cover;
  margin: 0 auto 16px;
  display: block;
}
.member-card h3 { font-size: 1.08rem; font-weight: 700; letter-spacing: 0.02em; }
.member-card .en {
  margin-top: 3px;
  font-family: var(--font-en);
  font-weight: 500;
  font-size: 0.84rem;
  color: var(--faint);
}
.m-links {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 9px;
  margin-top: 16px;
  white-space: nowrap;
}
.m-links a {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--link);
  border-bottom: 1px solid rgba(26, 86, 219, 0.35);
  transition: border-color 0.2s;
}
.m-links a:hover { border-color: var(--link); }

/* ---------- Contact ---------- */
.contact-actions {
  display: flex;
  align-items: center;
  gap: 26px;
  margin-top: 34px;
  flex-wrap: wrap;
}

/* ---------- Footer ---------- */
.footer {
  width: 100%;
  padding: clamp(150px, 20vw, 240px) 24px 14px;
  background: linear-gradient(
    180deg,
    #ffffff 0%,
    #f2f4f6 6%,
    #e2e5ea 16%,
    #c8cdd5 28%,
    #a2a8b4 40%,
    #747b88 52%,
    #434955 64%,
    #1b1e26 76%,
    #07090d 88%,
    #020308 100%
  );
}
.footer-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 14px;
  flex-wrap: wrap;
  font-size: 0.82rem;
  color: #a9aeb9;
}
.footer-inner img { height: 20px; width: auto; }
.footer-inner .lucerna-logo { height: 30px; }
.footer-inner .beian {
  color: #8b919c;
  font-size: 0.78rem;
  transition: color 0.2s;
}
.footer-inner .beian:hover { color: #c7ccd6; }
.footer .en {
  font-family: var(--font-en);
  font-weight: 500;
  font-size: 0.78rem;
}

/* ---------- Responsive ---------- */
@media (max-width: 860px) {
  .links { display: none; }
  .grid { grid-template-columns: 1fr; }
  .members { grid-template-columns: 1fr; max-width: 380px; margin-left: auto; margin-right: auto; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .btn, .btn:hover { transform: none; }
  .dd[data-open="true"] .dd-menu {
    animation: none;
    opacity: 1;
    visibility: visible;
    transform: translateX(-50%);
    transition-duration: 0.2s !important;
  }
}