/* 
  ===============================
  Theme Variables
  你可以在这里统一修改网页主题
  ===============================
*/
:root {
  --color-bg: #f5f8fb;
  --color-surface: #ffffff;
  --color-surface-soft: #eef4f8;
  --color-primary: #183b56;
  --color-primary-deep: #102c42;
  --color-secondary: #5d7a8c;
  --color-accent: #2f6f8f;
  --color-accent-soft: #d8e8f0;
  --color-text: #1f2d3a;
  --color-text-muted: #5c6b78;
  --color-border: #d7e1e8;
  --color-shadow: 0 12px 32px rgba(16, 44, 66, 0.08);
  --color-shadow-hover: 0 18px 40px rgba(16, 44, 66, 0.12);

  --status-prep: #8b5cf6;
  --status-prep-bg: #f1e9ff;
  --status-accepted: #0f766e;
  --status-accepted-bg: #dff7f2;
  --status-published: #1d4ed8;
  --status-published-bg: #e6efff;

  --font-sans: "Inter", "PingFang SC", "Microsoft YaHei", "Noto Sans SC", Arial, sans-serif;
  --font-serif: "Georgia", "Times New Roman", "Songti SC", "SimSun", serif;

  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --radius-round: 999px;

  --space-1: 8px;
  --space-2: 12px;
  --space-3: 16px;
  --space-4: 20px;
  --space-5: 28px;
  --space-6: 40px;
  --space-7: 64px;
  --space-8: 96px;

  --container-width: 1180px;
  --header-height: 76px;
  --transition: all 0.28s ease;
}

html {
  scroll-behavior: smooth;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  background: linear-gradient(180deg, #f8fbfd 0%, #f4f7fa 100%);
  color: var(--color-text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

a {
  color: var(--color-accent);
  text-decoration: none;
}

a:hover {
  color: var(--color-primary);
}

.container {
  width: min(100% - 32px, var(--container-width));
  margin: 0 auto;
}

.section {
  padding: var(--space-8) 0;
  scroll-margin-top: 92px;
}

.alt-bg {
  background: linear-gradient(180deg, rgba(230, 238, 244, 0.55), rgba(245, 248, 251, 0.92));
}

.section-heading {
  margin-bottom: var(--space-6);
}

.section-kicker {
  margin: 0 0 var(--space-2);
  color: var(--color-accent);
  font-size: 0.92rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-weight: 700;
}

.section-heading h2 {
  margin: 0;
  font-size: clamp(1.8rem, 2.8vw, 2.6rem);
  font-family: var(--font-serif);
  color: var(--color-primary-deep);
}

.card {
  background: rgba(255, 255, 255, 0.9);
  border: 1px solid rgba(215, 225, 232, 0.9);
  border-radius: var(--radius-lg);
  box-shadow: var(--color-shadow);
  transition: var(--transition);
  backdrop-filter: blur(10px);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--color-shadow-hover);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.84);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid rgba(215, 225, 232, 0.75);
}

.nav-container {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.brand {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--color-primary-deep);
  letter-spacing: 0.02em;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 18px;
}

.nav-menu a {
  color: var(--color-text);
  font-size: 0.96rem;
  font-weight: 600;
  position: relative;
}

.nav-menu a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -6px;
  width: 0;
  height: 2px;
  background: var(--color-accent);
  transition: width 0.25s ease;
}

.nav-menu a:hover::after {
  width: 100%;
}

.nav-toggle {
  display: none;
  width: 44px;
  height: 44px;
  border: 1px solid var(--color-border);
  border-radius: 12px;
  background: #fff;
  cursor: pointer;
  padding: 0;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-primary-deep);
  margin: 5px auto;
  border-radius: 2px;
  transition: var(--transition);
}

.hero {
  padding-top: calc(var(--space-8) + 12px);
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.4fr 0.9fr;
  gap: var(--space-6);
  align-items: center;
}

.eyebrow {
  margin: 0 0 var(--space-3);
  color: var(--color-accent);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.9rem;
}

.hero h1 {
  margin: 0;
  font-family: var(--font-serif);
  font-size: clamp(2.6rem, 5vw, 4.4rem);
  line-height: 1.08;
  color: var(--color-primary-deep);
}

.hero-subtitle {
  margin: var(--space-3) 0 var(--space-4);
  font-size: 1.15rem;
  color: var(--color-secondary);
  font-weight: 600;
}

.hero-summary {
  margin: 0 0 var(--space-5);
  max-width: 64ch;
  font-size: 1.02rem;
  color: var(--color-text);
}

.hero-meta {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-3);
  margin-bottom: var(--space-5);
}

.meta-item {
  padding: 16px 18px;
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.72);
  border: 1px solid rgba(215, 225, 232, 0.85);
}

.meta-label {
  display: block;
  margin-bottom: 6px;
  font-size: 0.86rem;
  color: var(--color-text-muted);
  font-weight: 700;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 22px;
  border-radius: var(--radius-round);
  font-weight: 700;
  transition: var(--transition);
  border: 1px solid transparent;
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary) 0%, #245474 100%);
  color: #fff;
  box-shadow: 0 10px 22px rgba(24, 59, 86, 0.16);
}

.btn-primary:hover {
  color: #fff;
  transform: translateY(-2px);
}

.btn-secondary {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-border);
}

.btn-secondary:hover {
  background: #fff;
}

.photo-card {
  position: relative;
  padding: 28px;
  background: linear-gradient(180deg, rgba(255,255,255,0.96), rgba(240,246,250,0.95));
  border-radius: 28px;
  border: 1px solid rgba(215, 225, 232, 0.95);
  box-shadow: var(--color-shadow);
}

.avatar-wrap {
  position: relative;
  width: min(100%, 320px);
  aspect-ratio: 1 / 1;
  margin: 0 auto;
  border-radius: 50%;
  overflow: hidden;
  background: linear-gradient(180deg, #e1e7ec, #cfd9e2);
  display: flex;
  align-items: center;
  justify-content: center;
  border: 8px solid rgba(255, 255, 255, 0.9);
  box-shadow: 0 16px 36px rgba(16, 44, 66, 0.12);
}

.avatar {
  position: relative;
  z-index: 2;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.avatar-fallback {
  position: absolute;
  inset: 0;
  z-index: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  font-weight: 700;
  letter-spacing: 0.04em;
}

.photo-caption {
  margin: 18px 0 0;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.92rem;
}

.about-card,
.interest-card,
.internship-card,
.contact-card,
.education-card,
.skill-card,
.activity-card,
.publication-card,
.research-card {
  padding: 28px;
}

.about-card p,
.interest-card p {
  margin: 0 0 16px;
}

.about-card p:last-child,
.interest-card p:last-child {
  margin-bottom: 0;
}

.education-grid,
.skills-grid,
.activities-grid,
.contact-grid,
.publication-list,
.research-list {
  display: grid;
  gap: 24px;
}

.skills-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.activities-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.contact-grid {
  grid-template-columns: 1.1fr 0.9fr;
}

.publication-list,
.research-list,
.education-grid {
  grid-template-columns: 1fr;
}

.card-top,
.edu-head {
  display: flex;
  justify-content: space-between;
  gap: var(--space-4);
  align-items: flex-start;
  margin-bottom: 18px;
}

.card-top h3,
.edu-head h3,
.skill-card h3,
.activity-card h3,
.contact-card h3,
.publication-card h3 {
  margin: 0;
  color: var(--color-primary-deep);
  font-size: 1.2rem;
  line-height: 1.45;
}

.edu-major,
.mentor {
  margin: 8px 0 0;
  color: var(--color-secondary);
  font-size: 0.95rem;
}

.time-badge {
  flex-shrink: 0;
  display: inline-flex;
  align-items: center;
  height: 36px;
  padding: 0 14px;
  border-radius: var(--radius-round);
  background: var(--color-accent-soft);
  color: var(--color-primary-deep);
  font-weight: 700;
  font-size: 0.92rem;
}

.info-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin-bottom: 18px;
}

.info-item {
  padding: 16px;
  border-radius: var(--radius-md);
  background: var(--color-surface-soft);
  border: 1px solid var(--color-border);
}

.info-label {
  display: block;
  margin-bottom: 6px;
  color: var(--color-text-muted);
  font-size: 0.9rem;
  font-weight: 700;
}

.info-value {
  color: var(--color-primary-deep);
  font-weight: 700;
}

.sub-block {
  margin-top: 18px;
}

.sub-block h4 {
  margin: 0 0 10px;
  color: var(--color-primary);
  font-size: 1rem;
}

.clean-list {
  margin: 0;
  padding-left: 1.2rem;
}

.clean-list li {
  margin-bottom: 10px;
}

.clean-list li:last-child {
  margin-bottom: 0;
}

.project-figure {
  margin: 22px 0 0;
  text-align: center;
}

.project-img {
  width: 100%;
  max-width: 500px;
  margin: 0 auto;
  border-radius: 18px;
  box-shadow: 0 14px 30px rgba(16, 44, 66, 0.12);
  border: 1px solid rgba(215, 225, 232, 0.9);
  object-fit: cover;
  background: linear-gradient(180deg, #e5eaef, #d7dfe7);
}

.project-figure figcaption {
  margin-top: 10px;
  color: var(--color-text-muted);
  font-size: 0.92rem;
}

.publication-top {
  margin-bottom: 14px;
}

.pub-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 34px;
  padding: 0 12px;
  border-radius: var(--radius-round);
  font-size: 0.88rem;
  font-weight: 800;
}

.pub-badge::before {
  content: "";
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: currentColor;
}

.status-prep {
  color: var(--status-prep);
  background: var(--status-prep-bg);
}

.status-accepted {
  color: var(--status-accepted);
  background: var(--status-accepted-bg);
}

.status-published {
  color: var(--status-published);
  background: var(--status-published-bg);
}

.pub-meta {
  margin: 10px 0 0;
  color: var(--color-text-muted);
}

.tag-group {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.tag {
  display: inline-flex;
  align-items: center;
  min-height: 36px;
  padding: 0 14px;
  border-radius: var(--radius-round);
  background: rgba(216, 232, 240, 0.7);
  color: var(--color-primary);
  border: 1px solid rgba(136, 173, 195, 0.26);
  font-size: 0.92rem;
  font-weight: 700;
}

.contact-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.contact-list li {
  margin-bottom: 14px;
  color: var(--color-text);
}

.contact-list li:last-child {
  margin-bottom: 0;
}

.site-footer {
  padding: 28px 0;
  background: var(--color-primary-deep);
  color: rgba(255, 255, 255, 0.88);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 18px;
  flex-wrap: wrap;
}

.site-footer a {
  color: #dcecf8;
}

.back-to-top {
  position: fixed;
  right: 22px;
  bottom: 22px;
  width: 52px;
  height: 52px;
  border: none;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary), #2c6488);
  color: #fff;
  font-size: 1.25rem;
  cursor: pointer;
  box-shadow: 0 12px 24px rgba(16, 44, 66, 0.18);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: var(--transition);
  z-index: 1200;
}

.back-to-top.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.fade-in-up {
  opacity: 0;
  transform: translateY(24px);
  animation: fadeInUp 0.9s ease forwards;
}

.fade-in-up.delay-1 {
  animation-delay: 0.2s;
}

@keyframes fadeInUp {
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* 平板 */
@media (max-width: 1024px) {
  .hero-grid,
  .contact-grid,
  .skills-grid {
    grid-template-columns: 1fr;
  }

  .hero-grid {
    gap: 32px;
  }

  .hero-meta {
    grid-template-columns: 1fr;
  }

  .activities-grid {
    grid-template-columns: 1fr 1fr;
  }
}

/* 手机导航 */
@media (max-width: 860px) {
  .nav-toggle {
    display: inline-block;
  }

  .nav-menu {
    position: absolute;
    top: calc(var(--header-height) - 4px);
    left: 16px;
    right: 16px;
    display: none;
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    background: rgba(255, 255, 255, 0.98);
    border: 1px solid var(--color-border);
    border-radius: 18px;
    box-shadow: var(--color-shadow);
    overflow: hidden;
    padding: 8px 0;
  }

  .nav-menu.active {
    display: flex;
  }

  .nav-menu a {
    width: 100%;
    padding: 14px 18px;
  }

  .nav-menu a::after {
    display: none;
  }
}

/* 手机 */
@media (max-width: 680px) {
  :root {
    --space-8: 72px;
    --space-7: 52px;
    --space-6: 32px;
  }

  .section {
    padding: var(--space-7) 0;
  }

  .hero {
    padding-top: 56px;
  }

  .hero h1 {
    font-size: 2.5rem;
  }

  .hero-subtitle {
    font-size: 1rem;
  }

  .card-top,
  .edu-head,
  .footer-content {
    flex-direction: column;
    align-items: flex-start;
  }

  .activities-grid,
  .info-grid {
    grid-template-columns: 1fr;
  }

  .about-card,
  .interest-card,
  .internship-card,
  .contact-card,
  .education-card,
  .skill-card,
  .activity-card,
  .publication-card,
  .research-card,
  .photo-card {
    padding: 22px;
  }

  .btn {
    width: 100%;
  }

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

  .back-to-top {
    right: 16px;
    bottom: 16px;
    width: 48px;
    height: 48px;
  }
}