/* ============================================================
   Design Tokens
   ============================================================ */
:root {
  /* Colors — Light */
  --c-bg:          #ffffff;
  --c-bg-alt:      #f5f7fb;
  --c-bg-card:     #ffffff;
  --c-text:        #1a1a2e;
  --c-text-sec:    #555770;
  --c-text-muted:  #8888a0;
  --c-accent:      #2563eb;
  --c-accent-hover:#1d4ed8;
  --c-accent-light:#dbeafe;
  --c-highlight:   #fefce8;
  --c-highlight-bd:#eab308;
  --c-border:      #e5e7eb;
  --c-nav-bg:      rgba(255,255,255,0.82);
  --c-shadow:      rgba(0,0,0,0.06);
  --c-badge-new:   #ef4444;
  --c-badge-gold:  #b45309;
  --c-badge-gold-bg:#fef3c7;

  /* Typography */
  --f-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --fs-xs:   0.75rem;
  --fs-sm:   0.875rem;
  --fs-base: 1rem;
  --fs-lg:   1.125rem;
  --fs-xl:   1.25rem;
  --fs-2xl:  1.5rem;
  --fs-3xl:  2rem;
  --fs-hero: 2.75rem;

  /* Spacing */
  --sp-xs:  0.25rem;
  --sp-sm:  0.5rem;
  --sp-md:  1rem;
  --sp-lg:  1.5rem;
  --sp-xl:  2rem;
  --sp-2xl: 3rem;
  --sp-3xl: 4rem;
  --sp-sec: 5rem;

  /* Layout */
  --max-w: 920px;
  --nav-h: 60px;
  --rad-sm: 8px;
  --rad-md: 14px;
  --rad-lg: 18px;

  /* Transitions */
  --t-fast: 150ms ease;
  --t-base: 250ms ease;
  --t-slow: 400ms ease;
}

/* Dark theme */
[data-theme="dark"] {
  --c-bg:          #0f172a;
  --c-bg-alt:      #1e293b;
  --c-bg-card:     #1e293b;
  --c-text:        #f1f5f9;
  --c-text-sec:    #94a3b8;
  --c-text-muted:  #64748b;
  --c-accent:      #60a5fa;
  --c-accent-hover:#93c5fd;
  --c-accent-light:rgba(96,165,250,0.15);
  --c-highlight:   #1c1a00;
  --c-highlight-bd:#ca8a04;
  --c-border:      #334155;
  --c-nav-bg:      rgba(15,23,42,0.82);
  --c-shadow:      rgba(0,0,0,0.25);
}

/* ============================================================
   Reset & Base
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-h) + 24px);
}
body {
  font-family: var(--f-sans);
  font-size: var(--fs-base);
  line-height: 1.7;
  color: var(--c-text);
  background: var(--c-bg);
  -webkit-font-smoothing: antialiased;
  transition: background var(--t-base), color var(--t-base);
}
a {
  color: var(--c-accent);
  text-decoration: none;
  transition: color var(--t-fast);
}
a:hover { color: var(--c-accent-hover); }
img { display: block; max-width: 100%; }

/* Focus */
:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
}

/* Container */
.container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 var(--sp-lg);
}

/* ============================================================
   Navbar
   ============================================================ */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--nav-h);
  background: var(--c-nav-bg);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--c-border);
  transition: box-shadow var(--t-base), background var(--t-base);
}
.navbar--scrolled {
  box-shadow: 0 1px 12px var(--c-shadow);
}
.nav-container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 var(--sp-lg);
  height: 100%;
  display: flex;
  align-items: center;
  gap: var(--sp-lg);
}
.nav-logo {
  font-weight: 700;
  font-size: var(--fs-xl);
  color: var(--c-accent);
  letter-spacing: -0.5px;
  flex-shrink: 0;
}
.nav-logo:hover { color: var(--c-accent-hover); }

.nav-links {
  display: flex;
  list-style: none;
  gap: var(--sp-sm);
  margin-left: auto;
}
.nav-links a {
  display: block;
  padding: var(--sp-xs) var(--sp-sm);
  font-size: var(--fs-sm);
  font-weight: 500;
  color: var(--c-text-sec);
  border-radius: var(--rad-sm);
  transition: color var(--t-fast), background var(--t-fast);
}
.nav-links a:hover,
.nav-links a.active {
  color: var(--c-accent);
  background: var(--c-accent-light);
}

/* Hamburger */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
  margin-left: auto;
}
.nav-toggle-bar {
  width: 22px;
  height: 2px;
  background: var(--c-text);
  border-radius: 2px;
  transition: transform var(--t-base), opacity var(--t-base);
}
.nav-toggle.open .nav-toggle-bar:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.open .nav-toggle-bar:nth-child(2) { opacity: 0; }
.nav-toggle.open .nav-toggle-bar:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* Language toggle */
.lang-toggle {
  display: inline-flex;
  align-items: center;
  gap: 2px;
  background: none;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  padding: 4px 6px;
  cursor: pointer;
  flex-shrink: 0;
  font-family: var(--f-sans);
  transition: border-color var(--t-fast);
}
.lang-toggle:hover { border-color: var(--c-accent); }
.lang-option {
  font-size: var(--fs-xs);
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 999px;
  color: var(--c-text-muted);
  transition: all var(--t-fast);
  line-height: 1.4;
}
.lang-option.active {
  background: var(--c-accent);
  color: #fff;
}
.lang-sep {
  font-size: var(--fs-xs);
  color: var(--c-text-muted);
  user-select: none;
}

/* Theme toggle */
.theme-toggle {
  background: none;
  border: 1px solid var(--c-border);
  border-radius: 50%;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--c-text-sec);
  flex-shrink: 0;
  transition: color var(--t-fast), border-color var(--t-fast), background var(--t-fast);
}
.theme-toggle:hover {
  color: var(--c-accent);
  border-color: var(--c-accent);
  background: var(--c-accent-light);
}
[data-theme="light"] .icon-sun  { display: none; }
[data-theme="light"] .icon-moon { display: block; }
[data-theme="dark"]  .icon-sun  { display: block; }
[data-theme="dark"]  .icon-moon { display: none; }

/* Mobile nav */
@media (max-width: 767px) {
  .nav-toggle { display: flex; }
  .nav-links {
    position: fixed;
    top: var(--nav-h);
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--c-nav-bg);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--c-border);
    padding: var(--sp-md) var(--sp-lg);
    gap: 0;
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: transform var(--t-base), opacity var(--t-base);
  }
  .nav-links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .nav-links a {
    padding: var(--sp-sm) var(--sp-md);
    font-size: var(--fs-base);
  }
}

/* ============================================================
   Hero
   ============================================================ */
.hero {
  padding-top: calc(var(--nav-h) + var(--sp-3xl));
  padding-bottom: var(--sp-3xl);
}
.hero-grid {
  display: grid;
  grid-template-columns: 1fr 240px;
  gap: var(--sp-2xl);
  align-items: center;
}
.hero-name {
  font-size: var(--fs-hero);
  font-weight: 700;
  line-height: 1.15;
  margin-bottom: var(--sp-sm);
  background: linear-gradient(135deg, var(--c-accent), #8b5cf6);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-title {
  font-size: var(--fs-lg);
  color: var(--c-text-sec);
  margin-bottom: var(--sp-lg);
  font-weight: 400;
}
.hero-bio {
  color: var(--c-text-sec);
  font-size: var(--fs-sm);
  line-height: 1.75;
  margin-bottom: var(--sp-sm);
  text-align: justify;
}
.hero-bio a { font-weight: 500; }
.hero-email {
  font-size: var(--fs-sm);
  color: var(--c-text-muted);
  margin-bottom: var(--sp-lg);
}
.hero-links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-sm);
}
.hero-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 16px;
  font-size: var(--fs-sm);
  font-weight: 500;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  color: var(--c-text-sec);
  transition: all var(--t-fast);
}
.hero-link:hover {
  color: var(--c-accent);
  border-color: var(--c-accent);
  background: var(--c-accent-light);
}
.hero-link svg { width: 16px; height: 16px; }

.hero-photo img {
  width: 100%;
  border-radius: var(--rad-lg);
  box-shadow: 0 8px 30px var(--c-shadow);
  transition: transform var(--t-slow);
}
.hero-photo img:hover { transform: scale(1.02); }

@media (max-width: 767px) {
  .hero { padding-top: calc(var(--nav-h) + var(--sp-xl)); padding-bottom: var(--sp-xl); }
  .hero-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }
  .hero-photo { order: -1; justify-self: center; }
  .hero-photo img { width: 180px; }
  .hero-name { font-size: var(--fs-3xl); }
  .hero-links { justify-content: center; }
  .hero-bio { text-align: left; }
}

/* ============================================================
   Sections
   ============================================================ */
.section {
  padding: var(--sp-sec) 0;
}
.section-alt {
  background: var(--c-bg-alt);
}
.section-title {
  font-size: var(--fs-2xl);
  font-weight: 700;
  margin-bottom: var(--sp-2xl);
  position: relative;
  padding-bottom: var(--sp-sm);
}
.section-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 40px;
  height: 3px;
  background: var(--c-accent);
  border-radius: 2px;
}

/* Centered title bar on mobile */
@media (max-width: 767px) {
  .section-title { text-align: center; }
  .section-title::after { left: 50%; transform: translateX(-50%); }
}

/* ============================================================
   Research Interests
   ============================================================ */
.research-text {
  color: var(--c-text-sec);
  line-height: 1.8;
  max-width: 720px;
  text-align: justify;
}
.highlight {
  background: var(--c-highlight);
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 500;
}

/* ============================================================
   News
   ============================================================ */
.news-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-md);
  position: relative;
  padding-left: var(--sp-xl);
}
.news-list::before {
  content: '';
  position: absolute;
  left: 5px;
  top: 4px;
  bottom: 4px;
  width: 2px;
  background: var(--c-border);
  border-radius: 1px;
}
.news-item {
  display: flex;
  align-items: baseline;
  gap: var(--sp-md);
  position: relative;
}
.news-item::before {
  content: '';
  position: absolute;
  left: calc(-1 * var(--sp-xl) + 1px);
  top: 10px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--c-accent);
  border: 2px solid var(--c-bg-alt);
}
.news-date {
  font-weight: 600;
  font-size: var(--fs-sm);
  color: var(--c-accent);
  white-space: nowrap;
  min-width: 90px;
}
.news-content {
  font-size: var(--fs-sm);
  color: var(--c-text-sec);
  line-height: 1.6;
}
.badge-new {
  display: inline-block;
  background: var(--c-badge-new);
  color: #fff;
  font-size: var(--fs-xs);
  font-weight: 700;
  padding: 1px 8px;
  border-radius: 999px;
  margin-right: 6px;
  vertical-align: middle;
  letter-spacing: 0.3px;
}

/* ============================================================
   Publications
   ============================================================ */
.pub-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-lg);
}
.pub-card {
  display: flex;
  gap: var(--sp-lg);
  padding: var(--sp-lg);
  border-radius: var(--rad-md);
  background: var(--c-bg-card);
  border: 1px solid var(--c-border);
  transition: transform var(--t-base), box-shadow var(--t-base);
}
.pub-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px var(--c-shadow);
}
.pub-card--highlighted {
  border-left: 4px solid var(--c-highlight-bd);
  background: var(--c-highlight);
}

/* Image */
.pub-img-wrap {
  width: 200px;
  flex-shrink: 0;
  border-radius: var(--rad-sm);
  overflow: hidden;
  position: relative;
  align-self: center;
}
.pub-img-wrap img {
  width: 100%;
  height: auto;
  display: block;
  transition: transform var(--t-slow);
}
.pub-img-hover {
  position: absolute;
  inset: 0;
  opacity: 0;
  transition: opacity var(--t-base);
}
.pub-card:hover .pub-img-hover { opacity: 1; }
.pub-card:hover .pub-img-wrap img:not(.pub-img-hover img) { transform: scale(1.03); }

/* Content */
.pub-body { flex: 1; min-width: 0; }
.pub-title {
  font-weight: 600;
  font-size: var(--fs-lg);
  color: var(--c-text);
  line-height: 1.4;
  margin-bottom: var(--sp-xs);
}
.pub-authors {
  font-size: var(--fs-sm);
  color: var(--c-text-sec);
  line-height: 1.5;
  margin-bottom: var(--sp-xs);
}
.pub-venue {
  font-size: var(--fs-sm);
  color: var(--c-text-muted);
  font-style: italic;
  margin-bottom: var(--sp-sm);
}
.pub-venue strong { font-style: normal; color: var(--c-text-sec); }
.pub-award {
  display: inline-block;
  background: #fef2f2;
  color: #dc2626;
  font-size: var(--fs-xs);
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 999px;
  margin-bottom: var(--sp-sm);
}
[data-theme="dark"] .pub-award {
  background: rgba(220,38,38,0.15);
}
.pub-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-bottom: var(--sp-sm);
}
.pub-tag {
  font-size: var(--fs-xs);
  background: var(--c-accent-light);
  color: var(--c-accent);
  padding: 2px 10px;
  border-radius: 999px;
  font-weight: 500;
}
.pub-links {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.pub-link {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: var(--fs-xs);
  font-weight: 600;
  padding: 4px 12px;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  color: var(--c-text-sec);
  transition: all var(--t-fast);
}
.pub-link:hover {
  color: var(--c-accent);
  border-color: var(--c-accent);
  background: var(--c-accent-light);
}

@media (max-width: 767px) {
  .pub-card { flex-direction: column; }
  .pub-img-wrap { width: 100%; max-width: 280px; }
}

/* ============================================================
   Competitions
   ============================================================ */
.comp-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-sm);
}
.comp-item {
  display: flex;
  align-items: center;
  gap: var(--sp-md);
  padding: var(--sp-md) var(--sp-lg);
  border-radius: var(--rad-sm);
  background: var(--c-bg-card);
  border: 1px solid var(--c-border);
  transition: transform var(--t-fast), box-shadow var(--t-fast);
}
.comp-item:hover {
  transform: translateX(4px);
  box-shadow: 0 2px 12px var(--c-shadow);
}
.comp-date {
  font-weight: 600;
  font-size: var(--fs-sm);
  color: var(--c-accent);
  white-space: nowrap;
  min-width: 90px;
}
.comp-name {
  flex: 1;
  font-size: var(--fs-sm);
  color: var(--c-text-sec);
}
.comp-name a { color: var(--c-text); font-weight: 500; }
.comp-name a:hover { color: var(--c-accent); }
.comp-badge {
  font-size: var(--fs-xs);
  font-weight: 600;
  padding: 4px 14px;
  border-radius: 999px;
  white-space: nowrap;
  background: var(--c-accent-light);
  color: var(--c-accent);
}
.comp-badge--gold {
  background: var(--c-badge-gold-bg);
  color: var(--c-badge-gold);
}
[data-theme="dark"] .comp-badge--gold {
  background: rgba(180,83,9,0.2);
  color: #fbbf24;
}

@media (max-width: 767px) {
  .comp-item { flex-wrap: wrap; }
  .comp-date { min-width: auto; }
}

/* ============================================================
   Collaborators
   ============================================================ */
.collab-text {
  color: var(--c-text-sec);
  margin-bottom: var(--sp-lg);
}
.collab-chips {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-sm);
}
.collab-chip {
  display: inline-block;
  padding: 6px 18px;
  font-size: var(--fs-sm);
  font-weight: 500;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  color: var(--c-text-sec);
  transition: all var(--t-fast);
}
.collab-chip:hover {
  color: var(--c-accent);
  border-color: var(--c-accent);
  background: var(--c-accent-light);
  transform: translateY(-2px);
}

/* ============================================================
   Footer
   ============================================================ */
.footer {
  padding: var(--sp-xl) 0;
  border-top: 1px solid var(--c-border);
}
.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--sp-md);
}
.footer p {
  font-size: var(--fs-sm);
  color: var(--c-text-muted);
}

/* ============================================================
   Scroll Reveal
   ============================================================ */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}
.reveal.revealed {
  opacity: 1;
  transform: translateY(0);
}
@media (prefers-reduced-motion: reduce) {
  .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
}

/* ============================================================
   Print
   ============================================================ */
@media print {
  .navbar, .theme-toggle, .nav-toggle { display: none !important; }
  .section { padding: 1rem 0; }
  .pub-card { break-inside: avoid; }
  .hero { padding-top: 0; }
}