:root {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f1f5f9;
  --bg-card: #ffffff;
  --bg-card-hover: #ffffff;
  --border-color: #e2e8f0;
  --border-hover: #cbd5e1;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  --accent-primary: #0284c7;
  --accent-primary-hover: #0369a1;
  --accent-secondary: #2563eb;
  --accent-glow: rgba(2, 132, 199, 0.12);
  --badge-bg: #e0f2fe;
  --badge-text: #0369a1;
  --badge-border: #bae6fd;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --header-height: 64px;
}

[data-theme="dark"] {
  --bg-primary: #0b0f19;
  --bg-secondary: #111827;
  --bg-tertiary: #1f2937;
  --bg-card: #111827;
  --bg-card-hover: #17223b;
  --border-color: #1f293d;
  --border-hover: #334155;
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --accent-primary: #38bdf8;
  --accent-primary-hover: #7dd3fc;
  --accent-secondary: #60a5fa;
  --accent-glow: rgba(56, 189, 248, 0.15);
  --badge-bg: rgba(56, 189, 248, 0.12);
  --badge-text: #38bdf8;
  --badge-border: rgba(56, 189, 248, 0.25);
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.4);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.2);
  --shadow-lg: 0 10px 20px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.2);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  transition: background-color 0.25s ease, color 0.25s ease;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* Header & Navigation */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(248, 250, 252, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  transition: background-color 0.25s ease, border-color 0.25s ease;
}

[data-theme="dark"] header {
  background-color: rgba(11, 15, 25, 0.85);
}

.nav-container {
  max-width: 1040px;
  margin: 0 auto;
  height: var(--header-height);
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--text-primary);
  text-decoration: none;
  letter-spacing: -0.01em;
}

.brand-icon {
  width: 28px;
  height: 28px;
}

.brand-accent {
  color: var(--accent-primary);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  list-style: none;
}

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  transition: color 0.2s ease;
  padding: 0.35rem 0.5rem;
  border-radius: var(--radius-sm);
}

.nav-link:hover {
  color: var(--accent-primary);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.theme-toggle {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s ease;
}

.theme-toggle:hover {
  color: var(--accent-primary);
  border-color: var(--accent-primary);
  transform: rotate(15deg);
}

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
}

/* Container & Layout */
.container {
  max-width: 1040px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

section {
  padding: 4.5rem 0;
  border-bottom: 1px solid var(--border-color);
}

section:last-of-type {
  border-bottom: none;
}

/* Hero Section */
.hero {
  padding: 5.5rem 0 4.5rem 0;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  align-items: center;
}

.hero-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--badge-bg);
  color: var(--badge-text);
  border: 1px solid var(--badge-border);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.35rem 0.85rem;
  border-radius: 9999px;
  margin-bottom: 1.25rem;
}

.hero-pill .dot {
  width: 8px;
  height: 8px;
  background: var(--accent-primary);
  border-radius: 50%;
  box-shadow: 0 0 8px var(--accent-primary);
  display: inline-block;
}

.hero-title {
  font-size: 2.75rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 1rem;
}

.hero-subtitle {
  font-size: 1.35rem;
  color: var(--text-secondary);
  font-weight: 500;
  line-height: 1.45;
  margin-bottom: 1.25rem;
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 1.25rem;
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-bottom: 1.75rem;
}

.meta-item {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}

.hero-desc {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 720px;
  margin-bottom: 2rem;
  line-height: 1.7;
}

.hero-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: center;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.65rem 1.25rem;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  border-radius: var(--radius-sm);
  transition: all 0.2s ease;
  cursor: pointer;
  border: 1px solid transparent;
}

.btn-primary {
  background: var(--accent-primary);
  color: #ffffff;
  box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
  background: var(--accent-primary-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px var(--accent-glow);
}

.btn-outline {
  background: var(--bg-card);
  color: var(--text-primary);
  border-color: var(--border-color);
}

.btn-outline:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  transform: translateY(-1px);
  background: var(--bg-tertiary);
}

/* Section Header */
.section-header {
  margin-bottom: 2.5rem;
}

.section-label {
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent-primary);
  margin-bottom: 0.4rem;
}

.section-title {
  font-size: 1.95rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

.section-desc {
  font-size: 1.05rem;
  color: var(--text-muted);
  margin-top: 0.5rem;
  max-width: 680px;
}

/* Cards & Grid */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  transition: all 0.25s ease;
  display: flex;
  flex-direction: column;
}

.card:hover {
  border-color: var(--border-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.card-icon {
  width: 42px;
  height: 42px;
  border-radius: var(--radius-sm);
  background: var(--badge-bg);
  color: var(--accent-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1rem;
}

.card-title {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.card-desc {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
  margin-bottom: 1.25rem;
  flex-grow: 1;
}

.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: auto;
}

.tag {
  font-size: 0.75rem;
  font-family: var(--font-mono);
  background: var(--bg-tertiary);
  color: var(--text-muted);
  border: 1px solid var(--border-color);
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
}

.card-link {
  text-decoration: none;
  color: inherit;
}

.repo-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.75rem;
}

.repo-name {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.repo-name:hover {
  color: var(--accent-primary);
}

/* About Grid */
.about-grid {
  display: grid;
  grid-template-columns: 3fr 2fr;
  gap: 2.5rem;
  align-items: start;
}

.about-text p {
  font-size: 1.05rem;
  color: var(--text-secondary);
  margin-bottom: 1.25rem;
  line-height: 1.7;
}

.info-box {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.info-box-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 1rem;
  color: var(--text-primary);
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 0.5rem;
}

.info-list {
  list-style: none;
}

.info-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.55rem 0;
  font-size: 0.95rem;
  border-bottom: 1px solid var(--border-color);
}

.info-item:last-child {
  border-bottom: none;
}

.info-label {
  color: var(--text-muted);
}

.info-value {
  color: var(--text-primary);
  font-weight: 500;
}

.info-value a {
  color: var(--accent-primary);
  text-decoration: none;
}

.info-value a:hover {
  text-decoration: underline;
}

/* Academic Profiles / Connect */
.connect-card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: inherit;
  transition: all 0.2s ease;
}

.connect-card:hover {
  border-color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}

.connect-left {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.connect-icon {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--bg-tertiary);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-primary);
  transition: all 0.2s ease;
}

.connect-card:hover .connect-icon {
  background: var(--accent-primary);
  color: #ffffff;
}

.connect-title {
  font-weight: 600;
  font-size: 1rem;
  color: var(--text-primary);
}

.connect-subtitle {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Copy email block */
.email-box {
  margin-top: 2rem;
  padding: 1.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.email-info {
  display: flex;
  flex-direction: column;
}

.email-label {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.email-address {
  font-family: var(--font-mono);
  font-size: 1.05rem;
  color: var(--accent-primary);
  font-weight: 600;
}

/* Footer */
footer {
  padding: 3rem 0;
  border-top: 1px solid var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-muted);
  font-size: 0.9rem;
}

.footer-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
}

.footer-links {
  display: flex;
  gap: 1.25rem;
  list-style: none;
}

.footer-link {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s ease;
}

.footer-link:hover {
  color: var(--accent-primary);
}

/* Responsive */
@media (max-width: 860px) {
  .about-grid {
    grid-template-columns: 1fr;
  }
  .grid-3 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 640px) {
  .hero-title {
    font-size: 2.15rem;
  }
  .hero-subtitle {
    font-size: 1.15rem;
  }
  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }
  .nav-links {
    display: none;
  }
  .mobile-menu-btn {
    display: block;
  }
  .nav-links.active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    padding: 1.5rem;
    box-shadow: var(--shadow-lg);
  }
  .footer-content {
    flex-direction: column;
    align-items: flex-start;
  }
}