/* Modern CSS reset */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  line-height: var(--line-height-base);
  color: var(--color-text);
  background-color: var(--color-background);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color var(--transition-smooth), color var(--transition-smooth);
}

img,
picture,
svg {
  display: block;
  max-width: 100%;
  height: auto;
}

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

a:hover,
a:focus {
  color: var(--color-primary-dark);
  text-decoration: underline;
}

a:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 2px;
}

button:focus-visible,
input:focus-visible,
textarea:focus-visible,
select:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  line-height: var(--line-height-heading);
  font-weight: 700;
  margin-bottom: var(--space-3);
  letter-spacing: -0.02em;
}

h1 { font-size: clamp(2rem, 5vw, 3.2rem); }
h2 { font-size: clamp(1.4rem, 3vw, 1.8rem); }
h3 { font-size: 1.25rem; }
h4 { font-size: 1.1rem; }

p {
  margin-bottom: var(--space-3);
}

ul, ol {
  margin-bottom: var(--space-3);
  padding-left: var(--space-4);
}

li {
  margin-bottom: var(--space-1);
}

strong {
  font-weight: 600;
}

/* Skip link for accessibility */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--color-primary);
  color: #fff;
  padding: var(--space-2) var(--space-3);
  z-index: 10000;
  transition: top var(--transition-base);
}

.skip-link:focus {
  top: 0;
}

/* Utility classes */
.container {
  width: 100%;
  max-width: var(--max-content-width);
  margin: 0 auto;
  padding: 0 var(--space-3);
}

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

.section-alt {
  background-color: var(--color-background-alt);
  transition: background-color var(--transition-smooth);
}

.section-header {
  margin-bottom: var(--space-5);
}

.section-header h1,
.section-header h2 {
  margin-bottom: var(--space-2);
}

.section-lead {
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  max-width: 700px;
  margin-bottom: 0;
}

/* Reveal animations */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s cubic-bezier(0.4, 0, 0.2, 1), transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

.reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* Badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-2);
  border-radius: 999px;
  font-size: var(--font-size-sm);
  font-weight: 500;
  background-color: var(--color-background-alt);
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  transition: background-color var(--transition-base), border-color var(--transition-base);
}

.badge-primary {
  background-color: rgba(13, 110, 253, 0.12);
  color: var(--color-primary);
  border-color: rgba(13, 110, 253, 0.25);
}

.badge-success {
  background-color: rgba(25, 135, 84, 0.12);
  color: var(--color-success);
  border-color: rgba(25, 135, 84, 0.25);
}

.badge-muted {
  background-color: var(--color-background-alt);
  color: var(--color-text-muted);
  border-color: var(--color-border);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 0.75rem 1.25rem;
  border: 1px solid transparent;
  border-radius: var(--border-radius-button);
  font-size: var(--font-size-base);
  font-weight: 600;
  line-height: 1.5;
  cursor: pointer;
  text-decoration: none;
  transition: background-color var(--transition-base), border-color var(--transition-base), color var(--transition-base), transform var(--transition-base), box-shadow var(--transition-base);
}

.btn:hover,
.btn:focus {
  text-decoration: none;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  color: #fff;
  border-color: transparent;
}

.btn-primary:hover,
.btn-primary:focus {
  background: linear-gradient(135deg, var(--color-primary-dark) 0%, #004494 100%);
  color: #fff;
}

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

.btn-outline:hover,
.btn-outline:focus {
  background-color: var(--color-primary);
  color: #fff;
}

/* Cards */
.card {
  background-color: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-card);
  padding: var(--space-4);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-smooth), transform var(--transition-smooth), border-color var(--transition-smooth);
}

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

.card-title {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: var(--space-2);
  color: var(--color-text);
}

.card-meta {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
}

.card-text {
  margin-bottom: 0;
  color: var(--color-text);
}

/* Link list */
.link-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.link-list li {
  margin-bottom: var(--space-2);
}

.link-list a {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
}

/* Header & Navigation */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background-color: rgba(var(--color-background-rgb, 255, 255, 255), 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
  transition: background-color var(--transition-smooth), border-color var(--transition-smooth);
}

html.dark .site-header {
  background-color: rgba(15, 23, 42, 0.85);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-weight: 800;
  color: var(--color-text);
  text-decoration: none;
  font-size: 1.15rem;
}

.logo:hover,
.logo:focus {
  color: var(--color-text);
  text-decoration: none;
}

.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  color: #fff;
  font-size: 0.9rem;
  font-weight: 800;
  box-shadow: var(--shadow-sm);
}

.logo-text {
  display: none;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-button);
  background-color: var(--color-background);
  color: var(--color-text);
  cursor: pointer;
  font-size: 1.1rem;
  transition: background-color var(--transition-base), border-color var(--transition-base), transform var(--transition-base);
}

.theme-toggle:hover,
.theme-toggle:focus {
  background-color: var(--color-background-alt);
  border-color: var(--color-primary);
  transform: translateY(-1px);
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  list-style: none;
  padding: 0;
  margin: 0;
}

.nav-menu a {
  display: block;
  padding: var(--space-2) var(--space-3);
  color: var(--color-text);
  font-weight: 500;
  border-radius: var(--border-radius-button);
  transition: background-color var(--transition-base), color var(--transition-base);
}

.nav-menu a:hover,
.nav-menu a:focus {
  background-color: var(--color-background-alt);
  color: var(--color-primary);
  text-decoration: none;
}

.nav-menu a.active {
  background-color: rgba(13, 110, 253, 0.12);
  color: var(--color-primary);
}

.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 44px;
  height: 44px;
  background: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-button);
  cursor: pointer;
  gap: 5px;
}

.hamburger-bar {
  display: block;
  width: 22px;
  height: 2px;
  background-color: var(--color-text);
  border-radius: 2px;
  transition: transform var(--transition-base), opacity var(--transition-base);
}

.hamburger[aria-expanded="true"] .hamburger-bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.hamburger[aria-expanded="true"] .hamburger-bar:nth-child(2) {
  opacity: 0;
}

.hamburger[aria-expanded="true"] .hamburger-bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Main content */
main {
  flex: 1;
}

/* Hero section */
.hero {
  padding: var(--space-8) 0 var(--space-7);
  background: var(--gradient-hero);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(13, 110, 253, 0.08) 0%, transparent 70%);
  border-radius: 50%;
  animation: pulse-glow 8s ease-in-out infinite;
  pointer-events: none;
}

@keyframes pulse-glow {
  0%, 100% { transform: scale(1); opacity: 0.6; }
  50% { transform: scale(1.1); opacity: 1; }
}

.hero-inner {
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: var(--space-6);
  align-items: center;
  position: relative;
  z-index: 1;
}

.hero-visual {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-4);
}

.hero-content {
  max-width: 640px;
}

.hero-eyebrow {
  font-size: var(--font-size-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: var(--space-2);
}

.gradient-text {
  background: var(--gradient-text);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  color: transparent;
  display: inline-block;
}

.hero-subtitle {
  display: none;
}

.hero-badges {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.hero-bio {
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  margin-bottom: var(--space-4);
}

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

/* Profile photo */
.hero-photo,
.about-photo {
  display: flex;
  justify-content: center;
}

.profile-image {
  width: 160px;
  height: 160px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--color-background);
  box-shadow: var(--shadow-md);
  transition: transform var(--transition-smooth), box-shadow var(--transition-smooth);
}

.profile-image:hover {
  transform: scale(1.03);
  box-shadow: var(--shadow-glow);
}

.profile-image-lg {
  width: 240px;
  height: 240px;
  animation: float 6s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-3);
  text-align: center;
  width: 100%;
}

.stat {
  padding: var(--space-3);
  background-color: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-card);
  box-shadow: var(--shadow-sm);
}

.stat-number {
  display: block;
  font-size: var(--font-size-2xl);
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
}

.stat-label {
  display: block;
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-top: var(--space-1);
}

/* Certifications */
.cert-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-3);
}

.cert-card {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  padding: var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-card);
  background-color: var(--color-background);
  color: var(--color-text);
  text-decoration: none;
  transition: border-color var(--transition-base), box-shadow var(--transition-base), transform var(--transition-base);
}

.cert-card:hover,
.cert-card:focus {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-md);
  text-decoration: none;
  color: var(--color-text);
  transform: translateY(-4px);
}

.cert-icon {
  font-size: 1.5rem;
}

.cert-name {
  font-weight: 700;
  line-height: 1.4;
}

.cert-source {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  font-weight: 500;
}

/* Projects */
.project-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-3);
}

.project-card {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  padding: var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-card);
  background-color: var(--color-background);
  color: var(--color-text);
  text-decoration: none;
  transition: border-color var(--transition-base), box-shadow var(--transition-base), transform var(--transition-base);
}

.project-card:hover,
.project-card:focus {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-md);
  text-decoration: none;
  color: var(--color-text);
  transform: translateY(-4px);
}

.project-icon {
  font-size: 1.5rem;
}

.project-name {
  font-weight: 700;
  line-height: 1.4;
}

.project-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  line-height: 1.5;
}

/* Profile / link grid */
.profile-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: var(--space-3);
}

.profile-card {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-card);
  background-color: var(--color-background);
  color: var(--color-text);
  text-decoration: none;
  transition: border-color var(--transition-base), box-shadow var(--transition-base), transform var(--transition-base);
}

.profile-card:hover,
.profile-card:focus {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-md);
  text-decoration: none;
  color: var(--color-text);
  transform: translateY(-4px);
}

.profile-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: var(--border-radius-button);
  background: linear-gradient(135deg, rgba(13, 110, 253, 0.12) 0%, rgba(13, 110, 253, 0.05) 100%);
  color: var(--color-primary);
  font-size: 1.35rem;
  flex-shrink: 0;
}

.profile-info {
  min-width: 0;
}

.profile-name {
  font-weight: 700;
  display: block;
}

.profile-domain {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  display: block;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Publications */
.search-wrapper {
  margin-bottom: var(--space-4);
}

.result-count {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-top: var(--space-2);
  margin-bottom: 0;
}

.publication-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.publication-card {
  background-color: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-card);
  padding: var(--space-4);
  transition: box-shadow var(--transition-smooth), transform var(--transition-smooth), border-color var(--transition-smooth);
}

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

.publication-title {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: var(--space-2);
  color: var(--color-text);
}

.publication-authors {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
}

.publication-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
}

.search-box {
  width: 100%;
  max-width: 420px;
  padding: 0.75rem 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-button);
  font-family: inherit;
  font-size: var(--font-size-base);
  color: var(--color-text);
  background-color: var(--color-background);
}

.search-box::placeholder {
  color: var(--color-text-muted);
}

.search-box:focus {
  border-color: var(--color-primary);
  outline: none;
  box-shadow: 0 0 0 4px rgba(13, 110, 253, 0.12);
}

/* Tags / research interests */
.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  list-style: none;
  padding: 0;
  margin: 0;
}

.tag-list li {
  margin-bottom: 0;
}

.tag {
  display: inline-block;
  padding: var(--space-2) var(--space-3);
  background-color: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-button);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text);
  transition: background-color var(--transition-base), border-color var(--transition-base), color var(--transition-base);
}

.tag:hover {
  background-color: rgba(13, 110, 253, 0.08);
  border-color: var(--color-primary);
  color: var(--color-primary);
}

/* About page */
.about-intro-block {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: var(--space-5);
  align-items: start;
  margin-bottom: var(--space-5);
}

.about-intro {
  font-size: var(--font-size-lg);
  margin-bottom: var(--space-3);
}

.education-list {
  list-style: none;
  padding: 0;
  margin: 0 0 var(--space-5) 0;
}

.education-list li {
  position: relative;
  padding-left: var(--space-4);
  margin-bottom: var(--space-3);
}

.education-list li::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 10px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--color-primary);
}

.education-list li::after {
  content: "";
  position: absolute;
  left: 9px;
  top: 22px;
  bottom: -16px;
  width: 2px;
  background-color: var(--color-border);
}

.education-list li:last-child::after {
  display: none;
}

.education-title {
  font-weight: 700;
  display: block;
}

.education-detail {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* Contact */
.contact-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-3);
  margin-bottom: var(--space-5);
}

.contact-card {
  background-color: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-card);
  padding: var(--space-4);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-smooth), transform var(--transition-smooth);
}

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

.contact-card h2 {
  font-size: 1.1rem;
  margin-bottom: var(--space-2);
}

.contact-email {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  background-color: var(--color-background-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-button);
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: var(--space-2);
  transition: background-color var(--transition-base), border-color var(--transition-base);
}

.contact-email:hover,
.contact-email:focus {
  border-color: var(--color-primary);
  background-color: rgba(13, 110, 253, 0.08);
  text-decoration: none;
}

/* Footer */
.site-footer {
  background-color: var(--color-background-alt);
  border-top: 1px solid var(--color-border);
  padding: var(--space-6) 0 var(--space-5);
  transition: background-color var(--transition-smooth);
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-4);
  margin-bottom: var(--space-4);
}

.footer-brand {
  font-weight: 800;
  margin-bottom: var(--space-2);
}

.footer-text {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

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

.footer-links li {
  margin-bottom: var(--space-1);
}

.footer-links a {
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
}

.footer-links a:hover,
.footer-links a:focus {
  color: var(--color-primary);
}

.footer-bottom {
  border-top: 1px solid var(--color-border);
  padding-top: var(--space-3);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* Utility helpers */
.text-center { text-align: center; }
.mt-0 { margin-top: 0; }
.mt-4 { margin-top: var(--space-4); }
.mb-0 { margin-bottom: 0; }
.mb-2 { margin-bottom: var(--space-2); }
.mb-3 { margin-bottom: var(--space-3); }
.mb-4 { margin-bottom: var(--space-4); }
.hidden { display: none !important; }

/* Visually hidden */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}