:root {
  --xdu-red: #9d1c20;
  --xdu-red-dark: #6f1014;
  --xdu-red-deep: #4d0b0e;
  --xdu-red-soft: #f8e8e9;
  --ink: #1f2937;
  --ink-light: #374151;
  --muted: #667085;
  --line: #e5e7eb;
  --bg: #ffffff;
  --bg-muted: #f8f8f9;
  --card: rgba(255, 255, 255, 0.88);
  --shadow-sm: 0 10px 26px rgba(31, 41, 55, 0.08);
  --shadow-md: 0 20px 46px rgba(31, 41, 55, 0.12);
  --shadow-lg: 0 32px 80px rgba(31, 41, 55, 0.16);
  --radius: 22px;
  --max-width: 1360px;
  --ease: cubic-bezier(0.16, 1, 0.3, 1);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 100px;
}

body {
  margin: 0;
  font-family:
    -apple-system,
    BlinkMacSystemFont,
    "Segoe UI",
    "Microsoft YaHei",
    "PingFang SC",
    "Noto Sans CJK SC",
    Arial,
    sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.7;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -2;
  background:
    radial-gradient(circle at 8% 12%, rgba(157, 28, 32, 0.08), transparent 30%),
    radial-gradient(circle at 88% 16%, rgba(157, 28, 32, 0.11), transparent 30%),
    linear-gradient(180deg, #ffffff 0%, #fffafa 45%, #ffffff 100%);
}

a {
  color: inherit;
  text-decoration: none;
}

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

.container {
  width: min(100% - 40px, var(--max-width));
  margin: 0 auto;
}

/* animation */
[data-animate] {
  opacity: 0;
  transform: translateY(28px);
  transition:
    opacity 0.8s var(--ease),
    transform 0.8s var(--ease);
  transition-delay: var(--delay, 0ms);
}

[data-animate].is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* top bar */
.top-bar {
  background: linear-gradient(90deg, var(--xdu-red-deep), var(--xdu-red-dark));
  color: #fff;
  font-size: 14px;
}

.top-bar-inner {
  min-height: 38px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

/* header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.9);
  border-bottom: 1px solid rgba(229, 231, 235, 0.9);
  backdrop-filter: blur(18px);
  transition:
    box-shadow 0.3s ease,
    background 0.3s ease,
    border-color 0.3s ease;
}

.site-header.is-scrolled {
  background: rgba(255, 255, 255, 0.97);
  border-color: rgba(157, 28, 32, 0.14);
  box-shadow: 0 12px 34px rgba(31, 41, 55, 0.1);
}

.nav-inner {
  min-height: 88px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 28px;
  transition: min-height 0.3s ease;
}

.site-header.is-scrolled .nav-inner {
  min-height: 76px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 18px;
  min-width: max-content;
  flex-shrink: 0;
}

.brand-logo {
    height: 64px;
    width: auto;
    object-fit: contain;
    flex-shrink: 0;
  }
  

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.18;
  min-width: max-content;
}

.brand-text strong {
  font-size: 22px;
  font-weight: 900;
  color: var(--xdu-red-dark);
  letter-spacing: 0.04em;
  white-space: nowrap;
}

.brand-text span {
  margin-top: 5px;
  font-size: 14px;
  color: var(--muted);
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 3px;
  font-size: 15px;
  font-weight: 750;
  flex-shrink: 0;
}

.site-nav a {
  padding: 9px 10px;
  border-radius: 999px;
  color: #344054;
  transition:
    color 0.24s ease,
    background 0.24s ease,
    transform 0.24s ease;
}

.site-nav a:hover {
  color: var(--xdu-red);
  background: var(--xdu-red-soft);
  transform: translateY(-1px);
}

.site-nav a.active {
  color: #fff;
  background: var(--xdu-red);
}

.nav-toggle {
  display: none;
  width: 44px;
  height: 44px;
  border: 0;
  border-radius: 14px;
  background: var(--xdu-red);
  cursor: pointer;
  padding: 11px;
}

.nav-toggle span {
  display: block;
  height: 2px;
  background: #fff;
  margin: 5px 0;
  border-radius: 999px;
}

/* hero */
.hero {
  position: relative;
  overflow: hidden;
  padding: 104px 0 96px;
  background:
    radial-gradient(circle at 78% 16%, rgba(157, 28, 32, 0.18), transparent 31%),
    linear-gradient(135deg, #ffffff, #fff7f7 48%, #f6f6f7);
}

.hero-bg-orb {
  position: absolute;
  border-radius: 999px;
  pointer-events: none;
  background: rgba(157, 28, 32, 0.08);
  animation: floatOrb 10s ease-in-out infinite alternate;
}

.orb-one {
  width: 480px;
  height: 480px;
  right: -190px;
  bottom: -220px;
}

.orb-two {
  width: 220px;
  height: 220px;
  left: -80px;
  top: 70px;
  animation-delay: 1.5s;
}

@keyframes floatOrb {
  from {
    transform: translate3d(0, 0, 0) scale(1);
  }

  to {
    transform: translate3d(22px, -18px, 0) scale(1.06);
  }
}

.hero-grid {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  align-items: center;
  gap: 58px;
}

.eyebrow,
.section-kicker {
  margin: 0 0 12px;
  color: var(--xdu-red);
  text-transform: uppercase;
  letter-spacing: 0.09em;
  font-size: 13px;
  font-weight: 850;
}

.hero h1 {
  margin: 0;
  color: var(--xdu-red-dark);
  font-size: clamp(44px, 6vw, 76px);
  line-height: 1.04;
  letter-spacing: -0.04em;
}

.hero h2 {
  margin: 20px 0 0;
  max-width: 780px;
  color: var(--ink);
  font-size: clamp(23px, 3vw, 36px);
  line-height: 1.25;
  font-weight: 780;
}

.hero-desc {
  margin: 24px 0 0;
  max-width: 760px;
  color: var(--muted);
  font-size: 18px;
}

.hero-actions {
  margin-top: 34px;
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}

.btn {
  position: relative;
  overflow: hidden;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 24px;
  border-radius: 999px;
  font-weight: 800;
  transition:
    transform 0.28s var(--ease),
    box-shadow 0.28s var(--ease),
    background 0.28s ease;
}

.btn:hover {
  transform: translateY(-3px);
}

.btn-primary {
  color: #fff;
  background: linear-gradient(135deg, var(--xdu-red), var(--xdu-red-dark));
  box-shadow: 0 16px 36px rgba(157, 28, 32, 0.28);
}

.btn-primary:hover {
  box-shadow: 0 22px 48px rgba(157, 28, 32, 0.36);
}

.btn-secondary {
  color: var(--xdu-red);
  background: rgba(255, 255, 255, 0.82);
  border: 1px solid rgba(157, 28, 32, 0.22);
  backdrop-filter: blur(12px);
}

/* hero visual */
.hero-visual {
  position: relative;
  min-height: 430px;
}

.image-frame {
  overflow: hidden;
  border-radius: 30px;
  background: #fff;
  border: 1px solid rgba(157, 28, 32, 0.14);
  box-shadow: var(--shadow-lg);
}

.image-frame img {
  width: 100%;
  height: 430px;
  object-fit: cover;
  transition: transform 1.2s var(--ease);
}

.hero-visual:hover .image-frame img {
  transform: scale(1.055);
}

.floating-card {
  position: absolute;
  min-width: 180px;
  padding: 16px 18px;
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.82);
  border: 1px solid rgba(157, 28, 32, 0.16);
  box-shadow: var(--shadow-md);
  backdrop-filter: blur(16px);
}

.floating-card span {
  display: block;
  margin-bottom: 4px;
  color: var(--xdu-red);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 850;
}

.floating-card strong {
  display: block;
  color: var(--ink);
  font-size: 15px;
}

.card-top {
  top: 28px;
  right: -22px;
}

.card-bottom {
  left: -28px;
  bottom: 36px;
}

/* notice */
.notice-strip {
  color: #fff;
  background: linear-gradient(90deg, var(--xdu-red-dark), var(--xdu-red));
}

.notice-inner {
  min-height: 66px;
  display: flex;
  align-items: center;
  gap: 18px;
}

.notice-inner strong {
  padding: 6px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.18);
}

/* sections */
.section {
  padding: 92px 0;
}

.section-muted {
  background:
    radial-gradient(circle at 0 0, rgba(157, 28, 32, 0.06), transparent 34%),
    var(--bg-muted);
}

.split-layout {
  display: grid;
  grid-template-columns: 0.42fr 1fr;
  gap: 64px;
}

.section-title h2,
.section-head h2,
.process-content h2,
.join-card h2 {
  margin: 0;
  color: var(--xdu-red-dark);
  font-size: clamp(31px, 4vw, 46px);
  line-height: 1.12;
  letter-spacing: -0.03em;
}

.section-head {
  max-width: 760px;
  margin-bottom: 36px;
}

.section-head p:last-child,
.about-text p,
.process-content p,
.join-card p {
  color: var(--muted);
  font-size: 17px;
}

.about-text p {
  margin-top: 0;
}

.about-stats {
  margin-top: 28px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}

.about-stats div {
  padding: 20px;
  border-radius: var(--radius);
  background: var(--xdu-red-soft);
  border: 1px solid rgba(157, 28, 32, 0.12);
}

.about-stats strong {
  display: block;
  color: var(--xdu-red-dark);
  font-size: 24px;
}

.about-stats span {
  color: var(--muted);
  font-size: 14px;
}

/* cards */
.card-grid,
.people-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 22px;
}

.research-card,
.person-card,
.publication-item {
  position: relative;
  overflow: hidden;
  background: var(--card);
  border: 1px solid rgba(229, 231, 235, 0.9);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  backdrop-filter: blur(16px);
  transition:
    transform 0.35s var(--ease),
    box-shadow 0.35s var(--ease),
    border-color 0.35s ease;
}

.research-card {
  min-height: 240px;
  padding: 26px;
}

.research-card::before,
.person-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
  background: linear-gradient(90deg, var(--xdu-red), rgba(157, 28, 32, 0.18));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.35s var(--ease);
}

.research-card:hover,
.person-card:hover,
.publication-item:hover {
  transform: translateY(-7px);
  border-color: rgba(157, 28, 32, 0.24);
  box-shadow: var(--shadow-md);
}

.research-card:hover::before,
.person-card:hover::before {
  transform: scaleX(1);
}

.card-number {
  width: 50px;
  height: 50px;
  display: grid;
  place-items: center;
  margin-bottom: 22px;
  border-radius: 16px;
  color: #fff;
  background: linear-gradient(135deg, var(--xdu-red), var(--xdu-red-dark));
  font-weight: 850;
}

.research-card h3,
.person-card h3 {
  margin: 0 0 10px;
  font-size: 21px;
}

.research-card p,
.person-card p {
  margin: 0;
  color: var(--muted);
}

/* process */
.process-grid {
  display: grid;
  grid-template-columns: 0.95fr 1.05fr;
  align-items: center;
  gap: 56px;
}

.process-image {
  overflow: hidden;
  border-radius: 30px;
  box-shadow: var(--shadow-lg);
}

.process-image img {
  width: 100%;
  height: 420px;
  object-fit: cover;
  transition: transform 1s var(--ease);
}

.process-image:hover img {
  transform: scale(1.055);
}

.tag-list {
  margin: 28px 0;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.tag-list span {
  padding: 8px 14px;
  border-radius: 999px;
  color: var(--xdu-red-dark);
  background: var(--xdu-red-soft);
  border: 1px solid rgba(157, 28, 32, 0.14);
  font-size: 14px;
  font-weight: 700;
}

.text-link {
  color: var(--xdu-red);
  font-weight: 850;
}

/* people */
.person-card {
  padding: 26px;
  text-align: center;
}

.person-card.principal {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.92), rgba(255, 248, 248, 0.9));
}

.avatar {
  width: 88px;
  height: 88px;
  display: grid;
  place-items: center;
  margin: 0 auto 18px;
  border-radius: 50%;
  color: var(--xdu-red);
  background: var(--xdu-red-soft);
  font-size: 24px;
  font-weight: 900;
}

.avatar-red {
  color: #fff;
  background: linear-gradient(135deg, var(--xdu-red), var(--xdu-red-dark));
  box-shadow: 0 16px 36px rgba(157, 28, 32, 0.25);
}

.person-card span {
  display: inline-flex;
  margin-top: 12px;
  padding: 6px 12px;
  border-radius: 999px;
  color: var(--xdu-red);
  background: var(--xdu-red-soft);
  font-size: 13px;
  font-weight: 800;
}

/* publications */
.publication-list {
  display: grid;
  gap: 18px;
}

.publication-item {
  display: grid;
  grid-template-columns: 90px 1fr;
  gap: 24px;
  padding: 24px;
}

.publication-item > span {
  width: 70px;
  height: 42px;
  display: grid;
  place-items: center;
  border-radius: 999px;
  color: #fff;
  background: var(--xdu-red);
  font-weight: 850;
}

.publication-item h3 {
  margin: 0 0 8px;
  font-size: 19px;
}

.publication-item p {
  margin: 0;
  color: var(--muted);
}

/* join */
.join-section {
  padding: 90px 0;
  background:
    linear-gradient(135deg, rgba(77, 11, 14, 0.97), rgba(157, 28, 32, 0.93)),
    radial-gradient(circle at right, rgba(255, 255, 255, 0.22), transparent 42%);
}

.join-card {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  gap: 30px;
  color: #fff;
}

.join-card .section-kicker,
.join-card h2 {
  color: #fff;
}

.join-card p {
  max-width: 720px;
  color: rgba(255, 255, 255, 0.84);
}

.join-actions {
  display: flex;
  gap: 12px;
}

.btn-light {
  color: var(--xdu-red-dark);
  background: #fff;
}

.btn-outline-light {
  color: #fff;
  border: 1px solid rgba(255, 255, 255, 0.5);
}

/* footer */
.site-footer {
  padding: 30px 0;
  color: rgba(255, 255, 255, 0.78);
  background: #181b20;
  font-size: 14px;
}

.footer-grid {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
}

.footer-grid strong {
  color: #fff;
  font-size: 16px;
}

.footer-grid p {
  margin: 4px 0;
}

/* back to top */
.back-to-top {
  position: fixed;
  right: 22px;
  bottom: 22px;
  z-index: 90;
  width: 46px;
  height: 46px;
  display: none;
  border: 0;
  border-radius: 50%;
  color: #fff;
  background: var(--xdu-red);
  box-shadow: var(--shadow-md);
  cursor: pointer;
  font-size: 20px;
}

.back-to-top.show {
  display: block;
}

/* responsive */
@media (max-width: 1180px) {
  .brand-logo {
    width: 78px;
    max-height: 48px;
  }

  .brand-text strong {
    font-size: 20px;
  }

  .site-nav {
    font-size: 14px;
  }

  .site-nav a {
    padding: 8px 8px;
  }
}

@media (max-width: 1080px) {
  .hero-grid,
  .split-layout,
  .process-grid,
  .join-card {
    grid-template-columns: 1fr;
  }

  .hero-visual {
    min-height: auto;
  }

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

  .card-top {
    right: 20px;
  }

  .card-bottom {
    left: 20px;
  }
}

@media (max-width: 960px) {
  .nav-toggle {
    display: block;
  }

  .site-nav {
    position: absolute;
    top: 92px;
    left: 20px;
    right: 20px;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0;
    padding: 10px;
    border-radius: 20px;
    background: #fff;
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--line);
    opacity: 0;
    pointer-events: none;
    transform: translateY(-10px);
    transition:
      opacity 0.25s ease,
      transform 0.25s ease;
  }

  .site-nav.is-open {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
  }

  .site-nav a {
    padding: 12px 14px;
  }
}

@media (max-width: 640px) {
  .container {
    width: min(100% - 28px, var(--max-width));
  }

  .top-bar-inner {
    flex-direction: column;
    align-items: flex-start;
    padding: 8px 0;
    gap: 2px;
  }

  .nav-inner {
    min-height: 78px;
  }

  .site-header.is-scrolled .nav-inner {
    min-height: 72px;
  }

  .brand {
    gap: 12px;
  }

  .brand-logo {
    width: 58px;
    max-height: 40px;
  }

  .brand-text strong {
    font-size: 16px;
    letter-spacing: 0;
  }

  .brand-text span {
    font-size: 12px;
  }

  .hero {
    padding: 70px 0;
  }

  .hero h1 {
    font-size: 44px;
  }

  .hero h2 {
    font-size: 24px;
  }

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

  .hero-actions,
  .join-actions {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }

  .image-frame img,
  .process-image img {
    height: 300px;
  }

  .floating-card {
    position: static;
    margin-top: 14px;
  }

  .about-stats,
  .card-grid,
  .people-grid {
    grid-template-columns: 1fr;
  }

  .publication-item {
    grid-template-columns: 1fr;
  }

  .section {
    padding: 68px 0;
  }
}