:root {
  --pku-red: #8c1515;
  --deep: #10333a;
  --blue: #1d7488;
  --green: #27665d;
  --gold: #c89442;
  --ink: #202a2d;
  --muted: #657275;
  --line: #d9e2e3;
  --bg: #f5f7f5;
  --white: #fff;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--bg);
  font-family: Arial, "Helvetica Neue", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.65;
}

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

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

.w {
  width: min(1200px, calc(100% - 48px));
  margin: 0 auto;
}

.topbar {
  background: var(--deep);
  border-bottom: 0;
}

.topline {
  display: none;
  justify-content: space-between;
  padding: 7px max(24px, calc((100vw - 1180px) / 2));
  color: rgba(255, 255, 255, 0.86);
  background: var(--deep);
  font-size: 13px;
}

.nav-wrap {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 28px;
  max-width: 1180px;
  min-height: 82px;
  margin: 0 auto;
  padding: 16px 24px;
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: 0;
}

.logo-mark {
  display: none;
  width: 50px;
  height: 50px;
  place-items: center;
  border-radius: 4px;
  color: var(--white);
  background: linear-gradient(135deg, var(--pku-red), var(--deep));
  font-weight: 800;
}

.logo strong,
.logo small {
  display: block;
  line-height: 1.2;
}

.logo strong {
  color: var(--white);
  font-size: 22px;
}

.logo small {
  color: rgba(255, 255, 255, 0.76);
  font-size: 13px;
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 2px;
  font-size: 14px;
  font-weight: 700;
}

.main-nav a {
  min-width: 86px;
  padding: 13px 10px;
  border-bottom: 3px solid transparent;
  color: rgba(255, 255, 255, 0.88);
  text-align: center;
  white-space: nowrap;
}

.main-nav a:hover,
.main-nav a.active {
  color: var(--white);
  border-bottom-color: var(--white);
}

.main-nav a.admin-link {
  min-width: auto;
  margin-left: 8px;
  padding: 7px 12px;
  border: 1px solid rgba(255, 255, 255, 0.55);
  border-radius: 4px;
  color: var(--white);
}

.main-nav a.admin-link:hover {
  border-color: var(--white);
  background: rgba(255, 255, 255, 0.12);
}

.lang-toggle {
  width: 64px;
  height: 34px;
  margin-left: 8px;
  border: 1px solid var(--line);
  border-radius: 4px;
  color: var(--white);
  background: transparent;
  font: inherit;
  font-size: 13px;
  font-weight: 800;
  cursor: pointer;
}

.lang-toggle:hover {
  color: var(--deep);
  border-color: var(--white);
  background: var(--white);
}

.nav-toggle {
  display: none;
  width: 42px;
  height: 38px;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--white);
}

.nav-toggle span {
  display: block;
  width: 20px;
  height: 2px;
  margin: 4px auto;
  background: var(--deep);
}

.home-hero {
  position: relative;
  max-width: 1180px;
  height: 430px;
  margin: 24px auto 0;
  overflow: hidden;
  background: var(--deep);
}

.home-hero img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.home-hero::after {
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, rgba(11, 35, 42, 0.78), rgba(11, 35, 42, 0.22), rgba(11, 35, 42, 0));
  content: "";
}

.hero-caption {
  position: absolute;
  z-index: 1;
  left: clamp(28px, 6vw, 70px);
  top: 50%;
  width: min(620px, calc(100% - 56px));
  color: var(--white);
  transform: translateY(-50%);
}

.hero-caption p {
  margin: 0 0 12px;
  color: #cce8ee;
  font-size: 13px;
  font-weight: 700;
}

.hero-caption h1 {
  margin: 0 0 24px;
  font-size: clamp(34px, 4vw, 58px);
  line-height: 1.1;
  letter-spacing: 0;
}

.hero-caption a,
.read-more {
  display: inline-flex;
  align-items: center;
  min-height: 40px;
  padding: 0 17px;
  border-radius: 4px;
  color: var(--white);
  background: var(--pku-red);
  font-weight: 700;
}

.home-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 350px;
  gap: 24px;
  max-width: 1180px;
  margin: 24px auto;
  padding: 0 24px;
}

.home-page {
  padding: 34px 0 46px;
}

.home-about {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(320px, 0.75fr);
  gap: 34px;
  align-items: stretch;
  margin-bottom: 42px;
}

.home-about div {
  padding: 0 12px 0 0;
}

.home-about h2,
.home-news h2,
.home-side h2 {
  width: 100%;
  margin: 0 0 22px;
  padding-bottom: 8px;
  border-bottom: #1a6adc 3px solid;
  color: #1a6adc;
  font-size: 26px;
  line-height: 1.25;
}

.home-about p {
  margin: 0;
  color: #111;
  font-size: 18px;
  line-height: 1.85;
  text-align: justify;
}

.home-about img {
  width: 100%;
  height: 280px;
  object-fit: cover;
  object-position: center 64%;
}

.home-news-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 330px;
  gap: 54px;
  align-items: start;
}

.home-news ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.home-news li {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 96px;
  gap: 24px;
  align-items: center;
  min-height: 76px;
  padding: 13px 18px 13px 0;
  border-bottom: 1px dotted #666;
}

.home-news li:nth-child(2n) {
  background: rgb(240, 240, 240);
}

.home-news a {
  padding-left: 18px;
  color: #000;
  font-size: 18px;
  line-height: 1.5;
}

.home-news a:hover {
  color: #1a6adc;
}

.home-news time {
  color: #a52b2b;
  font-size: 18px;
  line-height: 1.4;
  text-align: center;
}

.home-side {
  display: grid;
  gap: 34px;
}

.home-side p {
  margin: 0 0 10px;
  color: #111;
  font-size: 18px;
  line-height: 1.8;
}

.main-column,
.side-column {
  display: grid;
  gap: 24px;
}

.block,
.quick-about,
.page-head,
.content-list article,
.profile-lead,
.people-grid article,
.pub-list article,
.gallery-grid figure,
.join-panel,
.contact-card {
  border: 1px solid var(--line);
  background: var(--white);
}

.block-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 50px;
  padding: 0 18px;
  border-bottom: 1px solid var(--line);
}

.block-title h2 {
  position: relative;
  margin: 0;
  padding-left: 13px;
  font-size: 20px;
}

.block-title h2::before {
  position: absolute;
  left: 0;
  top: 50%;
  width: 4px;
  height: 20px;
  background: var(--pku-red);
  content: "";
  transform: translateY(-50%);
}

.block-title a {
  color: var(--muted);
  font-size: 13px;
}

.feature-list {
  padding: 4px 18px 12px;
}

.feature-item {
  display: grid;
  grid-template-columns: 70px 1fr 160px;
  gap: 18px;
  padding: 18px 0;
  border-bottom: 1px solid var(--line);
}

.feature-item:last-child {
  border-bottom: 0;
}

.feature-item time,
.content-list span,
.pub-list time {
  color: var(--pku-red);
  font-weight: 800;
}

.feature-item h3 {
  margin: 0;
  font-size: 17px;
  line-height: 1.45;
}

.feature-item p,
.quick-about p,
.content-list p,
.profile-lead p,
.people-grid p,
.pub-list p,
.join-panel p,
.join-panel li,
.contact-card p {
  margin: 0;
  color: var(--muted);
}

.focus-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--line);
}

.focus-grid a {
  min-height: 86px;
  padding: 24px;
  background: #fbfcfc;
  font-weight: 700;
}

.focus-grid a:hover {
  color: var(--pku-red);
  background: #f7eeee;
}

.news-list,
.link-list {
  margin: 0;
  padding: 12px 18px 18px;
  list-style: none;
}

.news-list li,
.link-list li {
  display: flex;
  gap: 10px;
  padding: 10px 0;
  border-bottom: 1px dashed var(--line);
}

.news-list span {
  flex: 0 0 50px;
  color: var(--pku-red);
  font-size: 13px;
  font-weight: 700;
}

.news-list a,
.link-list a {
  color: #28373b;
}

.link-list li::before {
  color: var(--gold);
  content: "•";
}

.quick-about {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 30px;
  max-width: 1132px;
  margin: 0 auto 36px;
  padding: 28px;
}

.quick-about h2 {
  margin: 0 0 8px;
}

.footer {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  padding: 30px max(24px, calc((100vw - 1180px) / 2));
  color: rgba(255, 255, 255, 0.84);
  background: var(--deep);
}

.footer strong {
  color: var(--white);
}

.footer p {
  margin: 6px 0 0;
}

.footer-links {
  display: flex;
  gap: 18px;
  align-items: center;
}

.page {
  max-width: 1180px;
  min-height: 64vh;
  margin: 24px auto 42px;
  padding: 0 24px;
}

.page-head {
  margin-bottom: 24px;
  padding: 34px;
  background:
    linear-gradient(90deg, rgba(16, 51, 58, 0.9), rgba(29, 116, 136, 0.62)),
    url("./assets/cryosphere-river-hero.png") center / cover;
  color: var(--white);
}

.page-head p {
  margin: 0 0 8px;
  color: #cce8ee;
  font-weight: 700;
}

.page-head h1 {
  margin: 0;
  font-size: clamp(34px, 5vw, 54px);
  line-height: 1.15;
}

.content-list,
.pub-list {
  display: grid;
  gap: 16px;
}

.content-list article {
  display: grid;
  grid-template-columns: 70px 1fr;
  gap: 24px;
  padding: 28px;
}

.content-list h2,
.pub-list h2,
.profile-lead h2,
.people-grid h2,
.join-panel h2,
.contact-card h2 {
  margin: 0 0 10px;
  font-size: 22px;
}

.profile-lead {
  display: grid;
  grid-template-columns: 150px 1fr;
  gap: 28px;
  margin-bottom: 24px;
  padding: 28px;
}

.portrait-placeholder {
  display: grid;
  width: 130px;
  height: 160px;
  place-items: center;
  color: var(--white);
  background: linear-gradient(135deg, var(--deep), var(--blue));
  font-size: 46px;
  font-weight: 800;
}

.role {
  margin: 0 0 4px;
  color: var(--pku-red);
  font-size: 13px;
  font-weight: 800;
}

.people-grid,
.gallery-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
}

.people-grid article {
  padding: 24px;
}

.pub-list article {
  display: grid;
  grid-template-columns: 80px 1fr;
  gap: 24px;
  padding: 24px 28px;
}

.news-page-list {
  display: grid;
  gap: 18px;
}

.news-page-list article {
  display: grid;
  grid-template-columns: 110px 1fr;
  gap: 24px;
  padding: 26px 28px;
  border: 1px solid var(--line);
  background: var(--white);
}

.news-page-list time {
  color: var(--pku-red);
  font-weight: 800;
}

.news-page-list h2 {
  margin: 0 0 8px;
  font-size: 22px;
}

.news-page-list p,
.source-note {
  color: var(--muted);
}

.source-note {
  margin-top: 12px;
  font-size: 13px;
}

.people-page {
  margin-top: 30px;
}

.people-page .prof-info {
  overflow: hidden;
  padding: 10px 0 0;
  border: 0;
  background: transparent;
}

.people-page .prof-img {
  float: left;
  width: 256px;
  max-width: calc(100% - 40px);
  height: auto;
  margin-left: 20px;
}

.people-page .prof-txt {
  float: left;
  max-width: 760px;
  padding-top: 20px;
  padding-left: 50px;
  color: #000;
  font-size: 25px;
  line-height: 40px;
}

.people-page .prof-txt b {
  font-size: 30px;
}

.people-page .prof-more {
  margin-top: 30px;
}

.people-page .prof-more h2,
.people-page .student h2 {
  width: 200px;
  margin: 0 0 30px;
  padding-left: 10px;
  border-bottom: #1a6adc 3px solid;
  color: #1a6adc;
  font-size: 25px;
}

.people-page .prof-more div {
  margin: 0 0 30px;
  padding: 0 20px;
  color: #000;
  font-size: 22px;
  line-height: 34px;
  text-align: justify;
}

.people-page .prof-more .indent {
  text-indent: 2em;
}

.people-page .prof-more table {
  width: 100%;
  border-collapse: collapse;
}

.people-page .prof-more td {
  padding-right: 50px;
  border-bottom: #666 1px dotted;
  line-height: 40px;
  vertical-align: top;
}

.people-page .student {
  margin-top: 20px;
}

.people-page .student h3 {
  width: 120px;
  height: 40px;
  margin: 0 0 10px 10px;
  border-radius: 20px;
  background: #1a6adc;
  color: #fff;
  font-size: 24px;
  font-weight: 500;
  line-height: 40px;
  text-align: center;
}

.people-page .student ul {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 34px 18px;
  margin: 0;
  padding: 20px 0 30px 30px;
}

.people-page .student li {
  min-height: 410px;
  padding: 20px 12px 18px;
  border-radius: 10px;
  background-color: rgb(230, 230, 230);
  list-style: none;
  overflow: hidden;
  transition: all 0.4s;
}

.people-page .student .alu li {
  min-height: 330px;
}

.people-page .student li:hover {
  background-color: lightblue;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
  transform: translateY(-10px);
}

.people-page .student li .stu-img {
  width: 100%;
  height: 200px;
  margin-bottom: 20px;
}

.people-page .student li img.stu-img {
  object-fit: cover;
  object-position: center 30%;
}

.people-page .student li img.luo-yingzhong-photo {
  object-position: 38% 48%;
}

.people-page .student li img.chen-shengyue-photo {
  object-position: 58% 46%;
}

.people-page .student li img.yan-yue-photo {
  object-position: 62% 52%;
}

.people-page .student li img.deng-rui-photo {
  object-position: 54% 34%;
}

.people-page .student li img.li-mingyue-photo {
  object-position: 52% 56%;
}

.people-page .student li img.pan-yiru-photo {
  object-position: 58% 48%;
}

.people-page .student li img.xiao-zhaojun-photo {
  object-position: 50% 34%;
}

.people-page .student li img.sha-anmeng-photo {
  object-position: 34% 48%;
}

.people-page .student li img.guo-ziqi-photo {
  object-position: 56% 48%;
}

.empty-person-photo {
  display: block;
  border: 1px dashed #aeb9bd;
  background:
    linear-gradient(135deg, rgba(26, 106, 220, 0.08), rgba(255, 255, 255, 0.5)),
    #f3f5f5;
}

.people-page .student li .stu-info {
  color: #000;
  font-size: 18px;
  font-weight: 400;
  line-height: 28px;
  overflow-wrap: anywhere;
  text-align: center;
}

.people-page .stu-info .stu-research {
  margin-top: 5px;
  padding: 0 4px;
  line-height: 28px;
  text-align: left;
}

.content-box {
  position: relative;
  min-height: 64vh;
  padding: 30px 0 42px;
}

.publication-page .year-nav {
  position: sticky;
  top: 18px;
  float: left;
  width: 82px;
  margin-top: 74px;
}

.publication-page .year-nav a {
  display: block;
  margin-bottom: 10px;
  padding: 6px 0;
  border-left: 3px solid transparent;
  color: #1a6adc;
  font-size: 16px;
  font-weight: 700;
  text-align: center;
}

.publication-page .year-nav a:hover {
  border-left-color: #1a6adc;
  background: rgba(26, 106, 220, 0.08);
}

.publication-page .journal {
  margin-left: 100px;
  padding-bottom: 20px;
}

.publication-page .journal h2 {
  width: 200px;
  margin: 0 0 18px;
  padding-left: 10px;
  border-bottom: #1a6adc 3px solid;
  color: #1a6adc;
  font-size: 25px;
}

.publication-page .journal h3 {
  width: 120px;
  height: 40px;
  margin: 0 0 10px 10px;
  border-radius: 20px;
  background: #1a6adc;
  color: #fff;
  font-size: 24px;
  font-weight: 500;
  line-height: 40px;
  text-align: center;
}

.publication-page .journal ul {
  margin: 0 0 26px;
  padding: 0;
}

.publication-page .journal li {
  position: relative;
  margin: 0 20px;
  padding: 10px 20px;
  border-radius: 10px;
  color: #000;
  font-size: 20px;
  line-height: 1.65;
  list-style: none;
  overflow-wrap: anywhere;
  transition: all 0.4s;
}

.publication-page .journal li:nth-child(2n) {
  background-color: rgb(233, 233, 233);
}

.publication-page .journal li:nth-child(n + 2)::after {
  position: absolute;
  top: 0;
  left: 10px;
  width: calc(100% - 20px);
  border-bottom: 1px dotted #666;
  content: "";
}

.publication-page .journal li:hover {
  background-color: rgba(26, 106, 220, 0.3);
}

.publication-page .journal b {
  color: #000;
}

.publication-page .journal a {
  color: #073f75;
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

.publication-page .journal a:hover {
  color: #1a6adc;
}

.publication-page .journal a.paper-row {
  display: block;
  color: #000;
  text-decoration: none;
}

.publication-page .journal a.paper-row:hover {
  color: #000;
  text-decoration: none;
}

.gallery-grid figure {
  margin: 0;
  overflow: hidden;
}

.gallery-grid img,
.empty-photo {
  height: 230px;
}

.gallery-grid img {
  width: 100%;
  object-fit: cover;
}

.empty-photo {
  display: grid;
  place-items: center;
  color: var(--white);
  background: linear-gradient(135deg, var(--deep), var(--green));
}

.empty-photo span {
  font-size: 22px;
  font-weight: 800;
}

figcaption {
  padding: 12px 14px;
  color: var(--muted);
  background: var(--white);
}

.join-panel {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  padding: 34px;
}

.join-panel ul {
  margin: 0;
  padding-left: 20px;
}

.contact-card {
  padding: 34px;
}

.contact-card a {
  color: var(--pku-red);
}

@media (max-width: 920px) {
  .topline {
    display: none;
  }

  .nav-toggle {
    display: block;
    border-color: rgba(255, 255, 255, 0.5);
    background: transparent;
  }

  .nav-toggle span {
    background: var(--white);
  }

  .main-nav {
    position: absolute;
    top: 82px;
    right: 24px;
    z-index: 10;
    display: none;
    width: min(300px, calc(100vw - 48px));
    padding: 8px;
    border: 1px solid rgba(255, 255, 255, 0.16);
    background: var(--deep);
    box-shadow: 0 16px 36px rgba(15, 35, 40, 0.15);
  }

  .main-nav.is-open {
    display: grid;
  }

  .main-nav a {
    min-width: auto;
    border-bottom: 0;
    text-align: left;
  }

  .lang-toggle {
    width: 100%;
    margin: 6px 0 0;
  }

  .home-layout,
  .home-about,
  .home-news-layout,
  .quick-about,
  .profile-lead,
  .join-panel {
    grid-template-columns: 1fr;
  }

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

  .feature-item {
    grid-template-columns: 64px 1fr;
  }

  .feature-item p {
    grid-column: 2;
  }

  .people-page .prof-img,
  .people-page .prof-txt {
    float: none;
  }

  .people-page .prof-img {
    width: min(256px, 100%);
    margin-left: 0;
  }

  .people-page .prof-txt {
    padding-left: 0;
    font-size: 22px;
  }

  .people-page .student ul {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    padding-left: 0;
  }

  .publication-page .year-nav {
    position: static;
    float: none;
    display: flex;
    flex-wrap: wrap;
    width: auto;
    margin: 0 0 24px;
  }

  .publication-page .year-nav a {
    width: 70px;
    border-left: 0;
    border-bottom: 2px solid transparent;
  }

  .publication-page .year-nav a:hover {
    border-bottom-color: #1a6adc;
  }

  .publication-page .journal {
    margin-left: 0;
  }
}

@media (max-width: 640px) {
  .logo strong {
    font-size: 18px;
  }

  .logo small {
    display: none;
  }

  .home-hero {
    height: 390px;
    margin-top: 0;
  }

  .home-layout,
  .home-page,
  .page {
    padding: 0 14px;
  }

  .home-page {
    padding-top: 24px;
    padding-bottom: 34px;
  }

  .home-about h2,
  .home-news h2,
  .home-side h2 {
    font-size: 24px;
  }

  .home-about p,
  .home-side p {
    font-size: 18px;
    line-height: 1.8;
  }

  .home-about img {
    height: 210px;
  }

  .home-news li {
    grid-template-columns: 1fr;
    gap: 6px;
    padding-right: 0;
  }

  .home-news a,
  .home-news time {
    font-size: 18px;
    text-align: left;
  }

  .home-news time {
    padding-left: 18px;
  }

  .focus-grid,
  .people-grid,
  .gallery-grid,
  .content-list article,
  .pub-list article,
  .news-page-list article {
    grid-template-columns: 1fr;
  }

  .footer {
    display: grid;
  }

  .w {
    width: calc(100% - 28px);
  }

  .people-page .student ul {
    padding-left: 0;
  }

  .people-page .student li {
    min-height: auto;
  }

  .people-page .student ul {
    grid-template-columns: 1fr;
  }

  .publication-page .journal li {
    margin: 0;
    padding: 10px 12px;
    font-size: 16px;
  }

}