/* ============================================
   QIXIN HU — Personal Website Stylesheet
   Clean White Theme with Modern Accents
   ============================================ */

/* ---- Google Fonts ---- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

/* ---- CSS Custom Properties ---- */
:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fc;
  --bg-card: #ffffff;
  --bg-card-hover: #ffffff;
  --border-card: #e8eaef;
  --border-card-hover: rgba(99, 102, 241, 0.35);

  --text-primary: #1a1a2e;
  --text-secondary: #4a4a68;
  --text-muted: #8888a0;

  --accent: #4f46e5;
  --accent-light: #6366f1;
  --accent-glow: rgba(99, 102, 241, 0.15);
  --accent-gradient: linear-gradient(135deg, #4f46e5 0%, #7c3aed 100%);

  --tag-bg: #f0efff;
  --tag-border: #dddaff;
  --tag-text: #4f46e5;

  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --radius: 16px;
  --radius-sm: 10px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --max-width: 900px;
  --nav-height: 60px;

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.08);
}

/* ---- Reset & Base ---- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-height) + 24px);
}

body {
  font-family: var(--font-main);
  background: var(--bg-secondary);
  color: var(--text-primary);
  line-height: 1.7;
  font-size: 15px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

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

::selection {
  background: var(--accent);
  color: #fff;
}

/* ---- Navigation ---- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-card);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
}

.nav-inner {
  width: 100%;
  max-width: var(--max-width);
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}
.nav-logo span {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-links {
  display: flex;
  gap: 4px;
  list-style: none;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: 0.82rem;
  font-weight: 500;
  padding: 6px 14px;
  border-radius: 8px;
  transition: all var(--transition);
  letter-spacing: 0.01em;
}
.nav-links a:hover {
  color: var(--accent);
  background: var(--tag-bg);
}

/* ---- Main Container ---- */
.container {
  position: relative;
  z-index: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: calc(var(--nav-height) + 40px) 24px 60px;
}

/* ---- Section Styles ---- */
section {
  margin-bottom: 48px;
}

.section-title {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 20px;
  display: flex;
  align-items: center;
  gap: 10px;
  letter-spacing: -0.02em;
}
.section-title .emoji {
  font-size: 1.25rem;
}
.section-title::after {
  content: '';
  flex: 1;
  height: 1px;
  background: linear-gradient(to right, var(--border-card), transparent);
  margin-left: 12px;
}

/* ---- Glass Card ---- */
.glass-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
}
.glass-card:hover {
  border-color: var(--border-card-hover);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

/* ---- Hero Section ---- */
.hero {
  display: flex;
  align-items: center;
  gap: 44px;
  margin-bottom: 40px;
  padding: 32px;
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: 20px;
  box-shadow: var(--shadow-sm);
}

.hero-photo-wrapper {
  flex-shrink: 0;
  position: relative;
}

.hero-photo {
  width: 170px;
  height: 170px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid var(--border-card);
  transition: all var(--transition);
}
.hero-photo-wrapper::after {
  content: '';
  position: absolute;
  inset: -4px;
  border-radius: 50%;
  background: var(--accent-gradient);
  opacity: 0;
  z-index: -1;
  transition: opacity var(--transition);
}
.hero-photo-wrapper:hover::after {
  opacity: 0.4;
}
.hero-photo-wrapper:hover .hero-photo {
  border-color: transparent;
}

.hero-info {
  flex: 1;
}

.hero-name {
  font-size: 2.2rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 4px;
  color: var(--text-primary);
}
.hero-name-cn {
  font-size: 1.05rem;
  color: var(--text-muted);
  font-weight: 400;
  margin-left: 4px;
}

.hero-title {
  font-size: 1.02rem;
  color: var(--text-secondary);
  margin-top: 6px;
  font-weight: 400;
}
.hero-title a {
  font-weight: 600;
  color: var(--accent);
}

.hero-affiliation {
  color: var(--text-muted);
  font-size: 0.88rem;
  margin-top: 4px;
}

.hero-email {
  color: var(--text-secondary);
  font-size: 0.88rem;
  margin-top: 8px;
}
.hero-email a {
  color: var(--text-secondary);
  border-bottom: 1px dashed var(--text-muted);
  padding-bottom: 1px;
}
.hero-email a:hover {
  color: var(--accent);
  border-color: var(--accent);
}

/* Social Icons */
.social-links {
  display: flex;
  gap: 10px;
  margin-top: 14px;
}
.social-links a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: 10px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-card);
  color: var(--text-secondary);
  font-size: 1.05rem;
  transition: all var(--transition);
}
.social-links a:hover {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px var(--accent-glow);
}

/* ---- About Section ---- */
.about-text {
  color: var(--text-secondary);
  line-height: 1.85;
  font-size: 0.93rem;
}
.about-text strong,
.about-text b {
  color: var(--text-primary);
  font-weight: 600;
}
.about-text a {
  font-weight: 500;
}

.collaboration-note {
  margin-top: 18px;
  padding: 12px 16px;
  border-left: 3px solid var(--accent);
  background: var(--tag-bg);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--accent);
  font-size: 0.88rem;
  font-weight: 500;
}

/* ---- News Section ---- */
.news-list {
  max-height: 320px;
  overflow-y: auto;
  padding-right: 8px;
}
.news-list::-webkit-scrollbar {
  width: 4px;
}
.news-list::-webkit-scrollbar-track {
  background: transparent;
}
.news-list::-webkit-scrollbar-thumb {
  background: var(--border-card);
  border-radius: 4px;
}

.news-item {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  padding: 11px 0;
  border-bottom: 1px solid #f1f2f5;
}
.news-item:last-child {
  border-bottom: none;
}

.news-date {
  flex-shrink: 0;
  font-size: 0.76rem;
  font-weight: 600;
  color: var(--tag-text);
  background: var(--tag-bg);
  padding: 3px 10px;
  border-radius: 6px;
  border: 1px solid var(--tag-border);
  min-width: 72px;
  text-align: center;
  white-space: nowrap;
}

.news-content {
  color: var(--text-secondary);
  font-size: 0.88rem;
  line-height: 1.6;
}
.news-content strong {
  color: var(--text-primary);
}

/* ---- Publications Section ---- */
.pub-grid {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.pub-card {
  display: flex;
  gap: 22px;
  align-items: flex-start;
}

.pub-image-wrapper {
  flex-shrink: 0;
  width: 170px;
  height: 110px;
  border-radius: var(--radius-sm);
  overflow: hidden;
  border: 1px solid var(--border-card);
  background: var(--bg-secondary);
}
.pub-image-wrapper img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition);
}
.glass-card:hover .pub-image-wrapper img {
  transform: scale(1.05);
}

.pub-info {
  flex: 1;
  min-width: 0;
}

.pub-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.4;
  margin-bottom: 4px;
}

.pub-venue {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 4px;
}

.pub-authors {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin-bottom: 8px;
}

.pub-links {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  align-items: center;
}

.pub-link {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--tag-text);
  padding: 3px 10px;
  border-radius: 6px;
  background: var(--tag-bg);
  border: 1px solid var(--tag-border);
  transition: all var(--transition);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.pub-link:hover {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.pub-stars {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.pub-stars img {
  height: 20px;
  display: inline;
  vertical-align: middle;
}

/* ---- Open Source Section ---- */
.oss-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
}

.oss-card {
  padding: 20px;
}

.oss-header {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 10px;
}

.oss-name {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
}

.oss-repo {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 500;
}
.oss-repo a {
  color: var(--text-muted);
}
.oss-repo a:hover {
  color: var(--accent);
}

.oss-desc {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

.oss-icon {
  font-size: 1.3rem;
  color: var(--accent);
}

/* ---- Experience Section ---- */
.exp-grid {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.exp-card {
  display: flex;
  gap: 20px;
  align-items: center;
}

.exp-logo {
  flex-shrink: 0;
  width: 58px;
  height: 58px;
  border-radius: 14px;
  background: var(--bg-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  border: 1px solid var(--border-card);
}
.exp-logo img {
  max-width: 44px;
  max-height: 44px;
  object-fit: contain;
}

.exp-info {
  flex: 1;
}

.exp-institution {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.4;
}
.exp-institution a {
  color: var(--text-primary);
}
.exp-institution a:hover {
  color: var(--accent);
}

.exp-details {
  list-style: none;
  margin-top: 4px;
}
.exp-details li {
  font-size: 0.83rem;
  color: var(--text-secondary);
  line-height: 1.6;
  position: relative;
  padding-left: 14px;
}
.exp-details li::before {
  content: '›';
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: 700;
}

/* ---- Honors Section ---- */
.honors-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.honors-list li {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.88rem;
  color: var(--text-secondary);
  padding: 10px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
}
.honors-list li:hover {
  border-color: var(--border-card-hover);
  box-shadow: var(--shadow-md);
}

.honor-year {
  font-weight: 700;
  color: var(--accent);
  font-size: 0.8rem;
  flex-shrink: 0;
  min-width: 42px;
}

/* ---- Academic Service Section ---- */
.service-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.service-tag {
  display: inline-block;
  font-size: 0.8rem;
  color: var(--text-secondary);
  padding: 7px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: 20px;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
  line-height: 1.4;
}
.service-tag:hover {
  border-color: var(--border-card-hover);
  color: var(--accent);
  box-shadow: var(--shadow-md);
}

/* ---- Footer ---- */
.footer {
  text-align: center;
  padding: 28px 0 8px;
  border-top: 1px solid var(--border-card);
  margin-top: 40px;
}
.footer p {
  font-size: 0.78rem;
  color: var(--text-muted);
}

/* ---- Animations ---- */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}
.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Staggered children */
.stagger > * {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 0.5s ease-out, transform 0.5s ease-out;
}
.stagger.visible > *:nth-child(1) { transition-delay: 0s; }
.stagger.visible > *:nth-child(2) { transition-delay: 0.05s; }
.stagger.visible > *:nth-child(3) { transition-delay: 0.1s; }
.stagger.visible > *:nth-child(4) { transition-delay: 0.15s; }
.stagger.visible > *:nth-child(5) { transition-delay: 0.2s; }
.stagger.visible > *:nth-child(6) { transition-delay: 0.25s; }
.stagger.visible > *:nth-child(7) { transition-delay: 0.3s; }
.stagger.visible > *:nth-child(8) { transition-delay: 0.35s; }
.stagger.visible > *:nth-child(9) { transition-delay: 0.4s; }
.stagger.visible > *:nth-child(10) { transition-delay: 0.45s; }
.stagger.visible > *:nth-child(11) { transition-delay: 0.5s; }
.stagger.visible > * {
  opacity: 1;
  transform: translateY(0);
}

/* ---- Responsive ---- */
@media (max-width: 768px) {
  .hero {
    flex-direction: column;
    text-align: center;
    gap: 24px;
    padding: 24px;
  }
  .hero-photo {
    width: 130px;
    height: 130px;
  }
  .hero-name {
    font-size: 1.7rem;
  }
  .social-links {
    justify-content: center;
  }
  .pub-card {
    flex-direction: column;
    gap: 12px;
  }
  .pub-image-wrapper {
    width: 100%;
    height: 170px;
  }
  .exp-card {
    flex-direction: column;
    align-items: flex-start;
    gap: 12px;
  }
  .oss-grid {
    grid-template-columns: 1fr;
  }
  .nav-links {
    gap: 2px;
  }
  .nav-links a {
    font-size: 0.72rem;
    padding: 5px 8px;
  }
  .container {
    padding-left: 16px;
    padding-right: 16px;
  }
}

@media (max-width: 480px) {
  .nav-logo {
    font-size: 0.95rem;
  }
  .nav-links a {
    font-size: 0.68rem;
    padding: 4px 5px;
  }
  .hero-name {
    font-size: 1.4rem;
  }
  .section-title {
    font-size: 1.1rem;
  }
}