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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
  font-size: 16px;
  font-family: "Inter", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;
}

body {
  margin: 0;
  background-color: var(--bg-color);
  color: var(--text-color);
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* CSS Variables for Light/Dark */
:root {
  --bg-color: #0f1724;
  --text-color: #e0e7ff;
  --accent-primary: #7c5cff;
  --accent-secondary: #00d4ff;
  --card-bg: rgba(15, 23, 36, 0.75);
  --btn-bg: #7c5cff;
  --btn-color: #fff;
  --btn-outline-border: #00d4ff;
  --shadow-primary: rgba(124, 92, 255, 0.7);
}

body.light {
  --bg-color: #f0f4ff;
  --text-color: #1e293b;
  --accent-primary: #5b21b6;
  --accent-secondary: #0284c7;
  --card-bg: rgba(240, 244, 255, 0.9);
  --btn-bg: #5b21b6;
  --btn-color: #fff;
  --btn-outline-border: #0284c7;
  --shadow-primary: rgba(91, 33, 182, 0.7);
}

/* Background Canvas fills viewport */
#background-canvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -10;
  pointer-events: none;
  display: block;
}

body.light a {
  color: #1a73e8; /* Light mode link color */
}

body:not(.light) a {
  color: #92b6ee; /* Dark mode link color */
}

body.light a:hover,
body.light a:focus {
  color: #2815b6;
}

body:not(.light) a:hover,
body:not(.light) a:focus {
  color: #e4a1ff;
}

/* Header */
header {
  position: sticky;
  top: 0;
  background: var(--card-bg);
  backdrop-filter: saturate(180%) blur(16px);
  z-index: 1000;
  box-shadow: 0 2px 12px rgb(0 0 0 / 0.25);
}

.nav-container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 1rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-weight: 900;
  font-size: 1.5rem;
  letter-spacing: 0.05em;
  background: linear-gradient(
    135deg,
    var(--accent-primary),
    var(--accent-secondary)
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  user-select: none;
  cursor: default;
}

.logo a {
  text-decoration: none !important;
}

.nav-links {
  list-style: none;
  display: flex;
  gap: 1.5rem;
  margin: 0;
  padding: 0;
  align-items: center;
}

.nav-links a {
  color: var(--text-color);
  text-decoration: none;
  font-weight: 600;
  font-size: 1rem;
  transition: color 0.25s ease;
}

.nav-links a:hover,
.nav-links a:focus-visible {
  color: var(--accent-primary);
  outline-offset: 3px;
}

.nav-links button#theme-toggle {
  background: none;
  border: none;
  color: var(--text-color);
  font-size: 1.4rem;
  cursor: pointer;
  transition: color 0.3s ease;
  /* padding: 0.15rem; */
  display: flex;
  align-items: center;
}

.nav-links button#theme-toggle:hover,
.nav-links button#theme-toggle:focus-visible {
  color: var(--accent-secondary);
  outline-offset: 3px;
}

.nav-links button#theme-toggle span {
  pointer-events: none;
}

/* Hero Section */
.hero {
  max-width: 1080px;
  margin: 3rem auto 5rem auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  gap: 3rem;
  flex-wrap: wrap;
}

.hero-content {
  flex: 1 1 300px;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 900;
  margin-bottom: 0.3rem;
  background: linear-gradient(
    135deg,
    var(--accent-primary),
    var(--accent-secondary)
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero h2 {
  font-weight: 600;
  font-size: 1.5rem;
  margin-top: 0;
  margin-bottom: 1.5rem;
  color: var(--accent-secondary);
}

.hero p {
  font-size: 1.125rem;
  line-height: 1.6;
  margin-bottom: 1rem;
}

.btn-outline {
  background: transparent;
  border: 2.5px solid var(--btn-outline-border);
  color: var(--btn-outline-border);
  line-height: 1;
}

.btn-outline:hover,
.btn-outline:focus-visible {
  background: var(--btn-outline-border);
  color: #fff;
  transform: translateY(-3px);
  outline-offset: 3px;
}

/* Hero photo */
.hero-photo img {
  max-width: 650px;
  border-radius: 20px;
  box-shadow: 0 8px 20px var(--shadow-primary);
}

/* Logos container */
.logos-container {
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}

/* Hide all dark logos by default */
.logo-dark {
  display: none;
  height: 32px;
  width: auto;
}

/* Show light logos by default */
.logo-light {
  display: inline-block;
  height: 32px;
  width: auto;
  transition: transform 0.25s ease;
}

body:not(.light) .logo-light {
  display: none;
}

body:not(.light) .logo-dark {
  display: inline-block;
}

.logos-container a:hover,
.logos-container a:focus-visible {
  transform: scale(1.15);
  outline-offset: 3px;
}

/* Sections */
.section {
  max-width: 1080px;
  margin: 4rem auto;
  padding: 0 1.5rem;
}

.section h2 {
  font-weight: 900;
  font-size: 2.2rem;
  margin-bottom: 2rem;
  background: linear-gradient(
    135deg,
    var(--accent-primary),
    var(--accent-secondary)
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* Research Cards Grid */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
}

.card {
  background: var(--card-bg);
  border-radius: 20px;
  padding: 1.75rem 1.5rem;
  box-shadow: 0 4px 10px rgb(0 0 0 / 0.2);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  cursor: default;
}

.card:hover,
.card:focus-visible {
  transform: translateY(-6px);
  box-shadow: 0 12px 30px var(--shadow-primary);
  outline-offset: 3px;
}

.card h3 {
  margin-top: 0;
  margin-bottom: 0.75rem;
  color: var(--accent-primary);
  font-weight: 700;
  font-size: 1.25rem;
}

.card p {
  font-size: 1rem;
  line-height: 1.5;
  color: var(--text-color);
}

/* Publications */
#pub-search {
  max-width: 400px;
  font-size: 1.125rem;
  padding: 0.5rem 1rem;
  border-radius: 12px;
  border: 2px solid var(--accent-secondary);
  margin-bottom: 1.5rem;
  background: transparent;
  color: var(--text-color);
  transition: border-color 0.3s ease;
}

#pub-search::placeholder {
  color: var(--accent-secondary);
}

#pub-search:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 8px var(--accent-primary);
}

/* Publication list */
.pub-list {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
  max-height: 500px;
  overflow-y: auto;
  padding-right: 1rem;
}

.pub-item {
  background: var(--card-bg);
  padding: 1rem 1.5rem;
  border-radius: 12px;
  cursor: pointer;
  transition: background-color 0.25s ease, box-shadow 0.3s ease;
  box-shadow: 0 3px 8px rgb(0 0 0 / 0.2);
}

.pub-item:hover,
.pub-item:focus-visible {
  background-color: var(--accent-primary);
  color: #fff;
  box-shadow: 0 10px 30px var(--shadow-primary);
  outline-offset: 3px;
}

.pub-item h4 {
  margin: 0 0 0.25rem 0;
  font-weight: 700;
}

.pub-item p {
  margin: 0;
  font-size: 0.9rem;
  color: inherit;
  font-style: italic;
}

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  background-color: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(3px);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  z-index: 2000;
}

.modal[aria-hidden="false"] {
  display: flex;
}

.modal-content {
  background-color: var(--card-bg);
  color: var(--text-color);
  padding: 2rem;
  max-width: 600px;
  border-radius: 20px;
  box-shadow: 0 8px 25px var(--shadow-primary);
  position: relative;
}

.modal-content h3 {
  margin-top: 0;
  margin-bottom: 1rem;
  font-weight: 900;
  background: linear-gradient(
    135deg,
    var(--accent-primary),
    var(--accent-secondary)
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.modal-content p {
  font-size: 1rem;
  line-height: 1.5;
}

.modal-content a.btn {
  margin-top: 1.5rem;
  display: inline-block;
  background: linear-gradient(
    135deg,
    var(--accent-primary),
    var(--accent-secondary)
  );
  color: #fff;
  padding: 0.8rem 2rem;
  font-weight: 700;
  border-radius: 12px;
  text-decoration: none;
  transition: background 0.3s ease;
}

.modal-content a.btn:hover,
.modal-content a.btn:focus-visible {
  background: linear-gradient(
    135deg,
    var(--accent-secondary),
    var(--accent-primary)
  );
  outline-offset: 3px;
}

#modal-close {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: none;
  border: none;
  font-size: 2rem;
  color: var(--text-color);
  cursor: pointer;
  line-height: 1;
  padding: 0;
}

#modal-close:hover,
#modal-close:focus-visible {
  color: var(--accent-primary);
  outline-offset: 3px;
}

/* Experience and Education */
.section-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent-primary);
  margin-bottom: 1.25rem;
  border-bottom: 3px solid var(--accent-primary);
  padding-bottom: 0.3rem;
  max-width: max-content;
}

.experience {
  max-width: 1080px;
  margin: 3rem auto 5rem;
  padding: 0 1.5rem;
  background: var(--card-bg);
  border-radius: 20px;
  box-shadow: 0 8px 25px var(--shadow-primary);
  padding: 2rem 3rem;
}

.entry {
  margin-bottom: 1.75rem;
}

.entry:last-child {
  margin-bottom: 0;
}

.entry h3 {
  font-size: 1.3rem;
  font-weight: 600;
  margin-bottom: 0.3rem;
  color: var(--accent-secondary);
}

.entry span {
  font-weight: 500;
  font-style: italic;
  color: var(--text-color-alt);
  display: block;
  margin-bottom: 0.5rem;
}

.entry p {
  margin: 0;
  font-size: 1.05rem;
  line-height: 1.5;
  color: var(--text-color);
}

/* Responsive */
@media (max-width: 720px) {
  .about-contact {
    flex-direction: column;
    padding: 2rem 1.5rem;
    text-align: center;
  }
  .about-contact-photo {
    margin: 0 auto;
    width: 120px;
    height: 120px;
  }
  .about-contact-content {
    align-items: center;
  }
  .about-contact-contact {
    align-items: center;
  }
}

/* Footer */
footer {
  text-align: center;
  padding: 2rem 1rem;
  font-size: 0.9rem;
  color: var(--accent-secondary);
}

/* Responsive */
@media (max-width: 720px) {
  .hero {
    flex-direction: column;
    text-align: center;
  }
  .hero-photo {
    margin-top: 2rem;
  }
  .about-container {
    flex-direction: column;
    text-align: center;
  }
}

/* Accessibility focus */
a:focus-visible,
button:focus-visible,
input:focus-visible,
.card:focus-visible,
.pub-item:focus-visible {
  outline: 3px solid var(--accent-primary);
  outline-offset: 3px;
  outline-style: solid;
}

/* Tablets: max-width 768px */
@media (max-width: 768px) {
  .hero {
    flex-direction: column;
    align-items: center; /* center children horizontally */
    text-align: center;
    padding: 0.5rem 1rem; /* much less top & bottom padding */
    max-width: 100vw; /* prevent horizontal overflow */
    margin: 0 auto 0rem auto; /* less bottom margin */
    gap: 1rem; /* less gap between items */
  }

  .hero-content {
    width: 100%;
    flex : 1 1 auto; /* allow content to grow */
  }

  .hero h1 {
    margin-top: 0; /* Remove default top margin */
    padding-top: 0; /* Remove any padding if present */
  }

  .hero p {
    font-size: 1.125rem;
    line-height: 1.6;
    margin-bottom: 1rem;
  }

  .hero-content {
    width: 100%;
    padding-bottom: 0.25rem; /* small gap below content */
  }

  .hero p {
    margin-bottom: 0.5rem; /* reduce paragraph bottom margin */
  }

  .hero-photo {
    width: 100%;
    max-width: 650px;
    margin: 0.5rem auto 0.5rem auto; /* tighter vertical margin */
  }

  .hero-photo img {
    width: 100%;
    height: auto;
    display: block;
    border-radius: 20px;
    box-shadow: 0 8px 20px var(--shadow-primary);
  }
}

/* Phones: max-width 480px */
@media (max-width: 480px) {
  /* Further stack hero */
  .hero {
    gap: 1rem;
    margin: 2rem 1rem 4rem 1rem;
  }

  .hero h1 {
    font-size: 2.2rem;
  }

  .hero h2 {
    font-size: 1.1rem;
  }

  .hero p {
    font-size: 1rem;
  }

  .hero-photo img {
    max-width: 90vw;
    box-shadow: 0 4px 14px var(--shadow-primary);
  }

  .nav-links a {
    font-size: 1.1rem;
  }

  .nav-links button#theme-toggle {
    font-size: 1.6rem;
  }

  /* Cards become single column */
  .cards-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  /* Experience container shrinks padding, entries font smaller */
  .experience {
    margin: 2rem 1rem 4rem 1rem;
    padding: 1rem 1.5rem;
  }

  .entry h3 {
    font-size: 1rem;
  }

  .entry p {
    font-size: 0.95rem;
  }

  /* Footer padding tighter */
  footer {
    padding: 1.5rem 1rem;
  }
}