/* ==========================================================================
   Variables
   ========================================================================== */
:root {
  --bg: #0a0e16;
  --bg-alt: #0d1320;
  --bg-card: #131a28;
  --border: #232c3d;
  --text: #e8edf6;
  --text-muted: #9aa7bd;
  --blue: #3b82f6;
  --blue-light: #60a5fa;
  --blue-dark: #1d4ed8;

  --max-width: 1100px;
  --radius: 10px;
  --gap: 1.5rem;

  --font: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

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

html {
  scroll-behavior: smooth;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

ul {
  list-style: none;
}

a {
  color: inherit;
  text-decoration: none;
}

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

/* ==========================================================================
   Layout helpers
   ========================================================================== */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section {
  padding: 4rem 0;
  border-bottom: 1px solid var(--border);
}

.section__title {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 1.75rem;
  letter-spacing: -0.01em;
}

.section__subtitle {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--blue-light);
  margin: 2rem 0 1rem;
}

.section__title + .section__subtitle,
.leadership-col .section__subtitle {
  margin-top: 0;
}

.section__lead {
  color: var(--text-muted);
  font-size: 1.05rem;
  max-width: 65ch;
}

/* ==========================================================================
   Header / Nav
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 14, 22, 0.85);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 4.25rem;
}

.logo {
  font-weight: 700;
  font-size: 1.1rem;
  letter-spacing: -0.01em;
}

.logo span {
  color: var(--blue-light);
}

.nav {
  display: flex;
  gap: 2rem;
}

.nav a {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-muted);
  transition: color 0.15s ease;
}

.nav a:hover,
.nav a:focus-visible {
  color: var(--blue-light);
}

.nav-toggle,
.nav-toggle-label {
  display: none;
}

/* ==========================================================================
   Buttons
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.7rem 1.4rem;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.95rem;
  border: 1px solid transparent;
  transition: transform 0.15s ease, background 0.15s ease, border-color 0.15s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn--primary {
  background: var(--blue);
  color: #fff;
}

.btn--primary:hover {
  background: var(--blue-dark);
}

.btn--ghost {
  border-color: var(--border);
  color: var(--text);
}

.btn--ghost:hover {
  border-color: var(--blue);
  color: var(--blue-light);
}

/* ==========================================================================
   Hero
   ========================================================================== */
.hero {
  padding: 4.5rem 0 3.5rem;
  background: radial-gradient(circle at 20% 20%, rgba(59, 130, 246, 0.18), transparent 60%),
              var(--bg);
  border-bottom: 1px solid var(--border);
}

.hero__inner {
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
}

@media (min-width: 900px) {
  .hero__inner {
    flex-direction: row;
    align-items: center;
    gap: 3rem;
  }

  .hero__col {
    flex: 1;
    min-width: 0;
  }
}

.eyebrow {
  color: var(--blue-light);
  font-weight: 600;
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 1rem;
}

.hero__name {
  font-size: clamp(2.5rem, 6vw, 3.75rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
}

.hero__tagline {
  color: var(--text-muted);
  font-size: 1.15rem;
  max-width: 60ch;
  margin-bottom: 2rem;
}

.hero__links {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.hero__scroll {
  display: inline-block;
  margin-top: 1.5rem;
  color: var(--text-muted);
  font-size: 0.9rem;
  font-weight: 600;
  transition: color 0.15s ease;
}

.hero__scroll:hover {
  color: var(--blue-light);
}

/* ==========================================================================
   Card grid (Experience / Awards / Leadership / Patents / Teaching)
   ========================================================================== */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 1rem;
}

.experience-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media (min-width: 640px) {
  .experience-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.card-grid--single {
  grid-template-columns: 1fr;
}

.leadership-columns {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

@media (min-width: 640px) {
  .leadership-columns {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* ==========================================================================
   Video embed
   ========================================================================== */
.video-embed__caption {
  color: var(--blue-light);
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 0.75rem;
}

.video-embed {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--bg-card);
}

.video-embed iframe {
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}

/* ==========================================================================
   Education banner
   ========================================================================== */
.education-banner {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  margin-top: 1rem;
  padding: 1.25rem 1.5rem;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.12), transparent);
  border: 1px solid var(--border);
  border-top: 3px solid var(--blue);
  border-radius: var(--radius);
}

.education-banner__icon {
  font-size: 1.75rem;
  flex-shrink: 0;
}

.education-banner__text {
  flex: 1;
}

.education-banner__text h3 {
  font-size: 1rem;
  font-weight: 600;
}

.education-banner__text p {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.education-banner__date {
  color: var(--blue-light);
  font-size: 0.85rem;
  font-weight: 600;
  white-space: nowrap;
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.1rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  transition: border-color 0.15s ease, transform 0.15s ease;
}

.card--accent {
  border-left: 3px solid var(--blue);
}

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

.card__title {
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.4;
}

.card__meta {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.card__date {
  color: var(--blue-light);
  font-size: 0.85rem;
  font-weight: 600;
  margin-top: auto;
}

/* ==========================================================================
   Skills
   ========================================================================== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--gap);
}

.skill-group__title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--blue-light);
  margin-bottom: 1rem;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.4rem 0.9rem;
  font-size: 0.85rem;
  color: var(--text);
}

/* ==========================================================================
   Footer / Contact
   ========================================================================== */
.site-footer {
  padding: 3.25rem 0 2.5rem;
  text-align: center;
}

.site-footer__links {
  display: flex;
  justify-content: center;
  gap: 1.75rem;
  flex-wrap: wrap;
  margin-bottom: 2rem;
  font-weight: 600;
}

.site-footer__links a {
  color: var(--blue-light);
  transition: color 0.15s ease;
}

.site-footer__links a:hover {
  color: var(--text);
}

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

.site-footer .section__title {
  text-align: center;
}

/* ==========================================================================
   Responsive
   ========================================================================== */
@media (max-width: 768px) {
  .section {
    padding: 3.5rem 0;
  }

  .hero {
    padding: 4rem 0 3rem;
  }

  .nav-toggle-label {
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    width: 28px;
    height: 28px;
    cursor: pointer;
    z-index: 110;
  }

  .nav-toggle-label span {
    display: block;
    height: 2px;
    width: 100%;
    background: var(--text);
    border-radius: 2px;
    transition: transform 0.2s ease, opacity 0.2s ease;
  }

  .nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    z-index: 10;
    flex-direction: column;
    gap: 0;
    background: var(--bg-alt);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.35);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s;
  }

  .nav a {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border);
  }

  .nav-toggle:checked ~ .nav {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }

  .nav-toggle:checked ~ .nav-toggle-label span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
  }

  .nav-toggle:checked ~ .nav-toggle-label span:nth-child(2) {
    opacity: 0;
  }

  .nav-toggle:checked ~ .nav-toggle-label span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
  }
}

@media (max-width: 480px) {
  .hero__links {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }

  .education-banner {
    flex-wrap: wrap;
  }
}