:root {
  --bg-color: #0b0f19;
  --page-bg: #000;
  --text-primary: #f3f4f6;
  --text-secondary: #9ca3af;
  --accent: #6366f1;
  --accent-violet: #8b5cf6;
  --accent-soft: #a5b4fc;
  --glass-bg: rgba(17, 24, 39, 0.65);
  --glass-bg-strong: rgba(11, 15, 25, 0.72);
  --glass-border: rgba(255, 255, 255, 0.1);
  --glow-border: rgba(129, 140, 248, 0.55);
  --glow-shadow: 0 0 0 1px rgba(129, 140, 248, 0.25), 0 8px 32px rgba(99, 102, 241, 0.25);
  --font-body: "Inter", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-display: "Space Grotesk", "Inter", system-ui, sans-serif;
  --nav-height: 64px;
}

/* =========================================================
   GLOBAL
========================================================= */

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

[hidden] {
  display: none !important;
}

html {
  scroll-behavior: smooth;
  scrollbar-width: none;
  scroll-padding-top: calc(var(--nav-height) + 16px);
}

html::-webkit-scrollbar {
  display: none;
}

body {
  font-family: var(--font-body);

  background-color: var(--page-bg);
  color: var(--text-primary);

  overflow-x: hidden;
  overflow-y: auto;

  min-height: 100vh;

  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: inherit;
}


/* =========================================================
   THREE.JS COSMIC BACKGROUND
========================================================= */

#webgl-canvas {
  position: fixed;

  top: 0;
  left: 0;

  width: 100vw;
  height: 100vh;

  z-index: 0;

  pointer-events: none;
}


/* =========================================================
   STICKY GLASS NAVBAR
========================================================= */

.top-nav {
  position: sticky;
  top: 0;
  z-index: 100;

  background: rgba(8, 10, 22, 0.55);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);

  border-bottom: 1px solid var(--glass-border);
  box-shadow: 0 4px 30px rgba(0, 0, 0, 0.35);
}

.nav-inner {
  max-width: 960px;
  height: var(--nav-height);
  margin: 0 auto;
  padding: 0 1.5rem;

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

.nav-brand {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.01em;
  text-decoration: none;
  white-space: nowrap;

  background: linear-gradient(90deg, #e0e7ff, var(--accent-soft), #c4b5fd);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.nav-links {
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav-links a {
  display: block;
  padding: 0.45rem 0.7rem;
  border-radius: 8px;

  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  font-weight: 500;
  white-space: nowrap;

  transition: color 0.2s ease, background 0.2s ease;
}

.nav-links a:hover,
.nav-links a:focus-visible,
.nav-links a.active {
  color: #ffffff;
  background: rgba(99, 102, 241, 0.18);
}

.menu-toggle {
  display: none;

  width: 44px;
  height: 44px;

  font-size: 1.35rem;
  line-height: 1;
  color: var(--text-primary);

  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--glass-border);
  border-radius: 10px;
  cursor: pointer;

  transition: border-color 0.2s ease, background 0.2s ease;
}

.menu-toggle:hover,
.menu-toggle:focus-visible {
  border-color: var(--glow-border);
  background: rgba(99, 102, 241, 0.15);
}


/* =========================================================
   MAIN CONTENT
========================================================= */

.container {
  position: relative;

  z-index: 2;

  max-width: 960px;

  margin: 0 auto;

  padding: 3rem 1.5rem 4rem;
}


/* =========================================================
   HERO
========================================================= */

.hero {
  padding: 3rem 0 2rem;
}


/* =========================================================
   BADGES
========================================================= */

.badge {
  display: inline-block;

  background: rgba(99, 102, 241, 0.2);

  color: #a5b4fc;

  padding: 0.35rem 0.8rem;

  border-radius: 20px;

  font-size: 0.85rem;

  font-weight: 600;

  border: 1px solid rgba(99, 102, 241, 0.4);
}

.badge a {
  color: #ffffff;

  text-decoration: none;
}


/* =========================================================
   HEADINGS
========================================================= */

h1,
h2,
h3,
h4,
.year-title {
  font-family: var(--font-display);
}

h1 {
  font-size: clamp(2.2rem, 6vw, 3.5rem);

  margin: 1rem 0 0.5rem;

  letter-spacing: -0.02em;

  line-height: 1.1;
}

h2 {
  font-size: clamp(1.3rem, 3vw, 1.6rem);

  margin-bottom: 1rem;

  color: #e0e7ff;
}

p {
  line-height: 1.6;

  color: var(--text-secondary);
}


/* =========================================================
   TAGLINE
========================================================= */

.tagline {
  font-size: clamp(1rem, 2.2vw, 1.25rem);

  color: var(--text-secondary);

  margin-bottom: 2rem;
}


/* =========================================================
   CTA BUTTONS
========================================================= */

.cta-buttons {
  display: flex;

  gap: 1rem;

  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;

  min-height: 44px;

  text-decoration: none;

  padding: 0.75rem 1.5rem;

  border-radius: 8px;

  font-weight: 500;

  transition: all 0.2s ease;
}

.btn.primary {
  background: var(--accent);

  color: white;
}

.btn.secondary {
  background: rgba(255, 255, 255, 0.05);

  color: var(--text-primary);

  border: 1px solid var(--glass-border);
}

.btn:hover {
  transform: translateY(-2px);

  background: rgba(99, 102, 241, 0.2);
}

.btn.secondary:hover {
  border-color: var(--glow-border);
  box-shadow: var(--glow-shadow);
}


/* =========================================================
   GLASS CARDS
========================================================= */

.card {
  position: relative;

  background: var(--glass-bg);

  backdrop-filter: blur(14px);

  -webkit-backdrop-filter: blur(14px);

  border: 1px solid var(--glass-border);

  border-radius: 16px;

  padding: 2rem;

  margin-top: 2rem;

  scroll-margin-top: calc(var(--nav-height) + 16px);
}


/* =========================================================
   SECTION HEADER + ACTION PILLS (About)
========================================================= */

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.75rem 1rem;
  margin-bottom: 1rem;
}

.section-header h2 {
  margin-bottom: 0;
}

.action-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.pill {
  display: inline-flex;
  align-items: center;
  min-height: 38px;
  padding: 0.45rem 1rem;

  font-size: 0.85rem;
  font-weight: 600;
  color: #ffffff;
  text-decoration: none;

  background: linear-gradient(135deg, rgba(99, 102, 241, 0.35), rgba(139, 92, 246, 0.3));
  border: 1px solid rgba(129, 140, 248, 0.45);
  border-radius: 999px;

  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.pill:hover,
.pill:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(196, 181, 253, 0.8);
  box-shadow: var(--glow-shadow);
}


/* =========================================================
   PROJECT / PUBLICATION ITEMS
========================================================= */

.pub-item {
  margin-bottom: 1.2rem;
}

.pub-item h3 {
  font-size: 1.1rem;

  color: var(--text-primary);
}

.meta {
  font-size: 0.875rem;

  color: #818cf8;
}


/* =========================================================
   TIMELINE (Achievements)
========================================================= */

.timeline {
  position: relative;
  padding-left: 2rem;
  margin-top: 0.5rem;
}

.timeline::before {
  content: "";
  position: absolute;
  top: 0.4rem;
  bottom: 0.4rem;
  left: 0.55rem;
  width: 2px;
  background: linear-gradient(180deg, rgba(99, 102, 241, 0.9), rgba(139, 92, 246, 0.5), rgba(99, 102, 241, 0.1));
  border-radius: 2px;
}

.timeline-item {
  position: relative;
  padding: 0 0 1.6rem 0.75rem;
}

.timeline-item:last-child {
  padding-bottom: 0;
}

/* Glowing node */
.timeline-item::before {
  content: "";
  position: absolute;
  left: calc(-2rem + 0.55rem - 6px + 1px);
  top: 0.35rem;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid #c7d2fe;
  box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.18), 0 0 14px rgba(129, 140, 248, 0.9);
}

.timeline-item.current::before {
  background: #22d3ee;
  border-color: #cffafe;
  box-shadow: 0 0 0 4px rgba(34, 211, 238, 0.18), 0 0 16px rgba(34, 211, 238, 0.9);
  animation: node-pulse 2.2s ease-in-out infinite;
}

@keyframes node-pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.25); }
}

.timeline-badge {
  display: inline-block;
  margin-bottom: 0.4rem;
  padding: 0.2rem 0.65rem;

  font-family: var(--font-display);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: #c7d2fe;

  background: rgba(99, 102, 241, 0.15);
  border: 1px solid rgba(129, 140, 248, 0.35);
  border-radius: 999px;
}

.timeline-item h3 {
  font-size: 1.05rem;
  color: var(--text-primary);
  margin-bottom: 0.2rem;
}


/* =========================================================
   PROJECT GRID (Featured Research & Projects)
========================================================= */

.project-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.1rem;
}

.project-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.5rem;

  padding: 1.35rem;

  background: rgba(255, 255, 255, 0.03);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid var(--glass-border);
  border-radius: 14px;

  transition: transform 0.25s ease, border-color 0.25s ease, box-shadow 0.25s ease;
}

.project-card:hover {
  transform: translateY(-4px);
  border-color: var(--glow-border);
  box-shadow: var(--glow-shadow);
}

.project-card.featured {
  background: linear-gradient(145deg, rgba(99, 102, 241, 0.14), rgba(139, 92, 246, 0.07));
  border-color: rgba(129, 140, 248, 0.3);
}

.project-card h3 {
  font-size: 1.08rem;
  color: var(--text-primary);
  line-height: 1.3;
}

.project-tag {
  display: inline-block;
  padding: 0.2rem 0.65rem;

  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: #ddd6fe;

  background: rgba(139, 92, 246, 0.18);
  border: 1px solid rgba(167, 139, 250, 0.4);
  border-radius: 999px;
}

.book-btn {
  margin-top: auto;
  padding: 0.6rem 1.1rem;

  color: #ffffff;
  font-weight: 600;
  font-size: 0.9rem;

  background: linear-gradient(135deg, var(--accent), var(--accent-violet));
  border: 1px solid rgba(196, 181, 253, 0.5);
  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.35);
}

.book-btn:hover {
  background: linear-gradient(135deg, #7c7ff5, #9d74f7);
  box-shadow: 0 10px 28px rgba(139, 92, 246, 0.5);
}

.tech-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.25rem;
}

.tech-tag {
  display: inline-block;
  padding: 0.15rem 0.55rem;
  font-size: 0.72rem;
  font-weight: 500;
  color: #c7d2fe;
  background: rgba(99, 102, 241, 0.12);
  border: 1px solid rgba(129, 140, 248, 0.28);
  border-radius: 6px;
}

:root[data-theme="light"] .tech-tag {
  color: #3730a3;
  background: rgba(99, 102, 241, 0.08);
  border-color: rgba(79, 70, 229, 0.25);
}


/* =========================================================
   CERT GRID (Internships & Certifications)
========================================================= */

.cert-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.cert-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.4rem;

  padding: 1.1rem 1.2rem;

  background: rgba(255, 255, 255, 0.03);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid var(--glass-border);
  border-radius: 12px;

  transition: border-color 0.25s ease, box-shadow 0.25s ease, transform 0.25s ease;
}

.cert-card:hover {
  transform: translateY(-3px);
  border-color: var(--glow-border);
  box-shadow: var(--glow-shadow);
}

.cert-card h3 {
  font-size: 1rem;
  color: var(--text-primary);
  line-height: 1.3;
}

.issuer-badge {
  display: inline-block;
  padding: 0.15rem 0.6rem;

  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  color: #a5f3fc;

  background: rgba(34, 211, 238, 0.12);
  border: 1px solid rgba(34, 211, 238, 0.35);
  border-radius: 6px;
}


/* =========================================================
   CONTACT GRID
========================================================= */

.contact-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.contact-card {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  min-height: 44px;

  padding: 1.1rem 1.2rem;

  text-decoration: none;
  color: var(--text-primary);

  background: rgba(255, 255, 255, 0.03);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid var(--glass-border);
  border-radius: 12px;

  transition: border-color 0.25s ease, box-shadow 0.25s ease, transform 0.25s ease;
}

.contact-card:hover,
.contact-card:focus-within,
a.contact-card:focus-visible {
  transform: translateY(-3px);
  border-color: var(--glow-border);
  box-shadow: var(--glow-shadow);
}

.contact-wide {
  grid-column: 1 / -1;
}

.contact-icon {
  font-size: 1.25rem;
}

.contact-label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--text-secondary);
}

.contact-value {
  font-size: 0.95rem;
  font-weight: 500;
  color: #c7d2fe;
  overflow-wrap: anywhere;
}

.contact-value a {
  color: #c7d2fe;
  text-decoration: none;
  border-bottom: 1px dashed rgba(165, 180, 252, 0.5);
}

.contact-value a:hover {
  color: #ffffff;
  border-bottom-color: #ffffff;
}

.contact-sep {
  margin: 0 0.4rem;
  color: var(--text-secondary);
}


/* =========================================================
   AVATAR
========================================================= */

.avatar-container {
  position: relative;

  display: inline-block;

  margin-bottom: 1.5rem;
}

.avatar-img {
  width: 120px;

  height: 120px;

  object-fit: cover;

  border-radius: 50%;

  border: 3px solid rgba(255, 255, 255, 0.2);

  box-shadow:
    0 0 20px rgba(99, 102, 241, 0.3);

  transition:
    transform 0.3s ease,
    border-color 0.3s ease;

  display: block;
}


/* =========================================================
   PNG FLAG
========================================================= */

.flag-badge {
  position: absolute;

  bottom: -6px;

  /* Start slightly to the right */
  left: 65%;

  transform: translateX(-50%);

  width: 32px;
  height: 22px;

  object-fit: cover;

  border-radius: 4px;

  border: 2px solid var(--bg-color);

  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.5);

  /* Smooth movement */
  transition: left 0.35s ease, transform 0.35s ease;
}

/* Avatar hover */

.avatar-container:hover .flag-badge {
  left: 50%;
  transform: translateX(-50%) scale(1.1);
}


/* =========================================================
   NAVIGATION (legacy back-link style)
========================================================= */

.nav-bar {
  padding: 1.5rem 2rem;

  position: relative;

  z-index: 10;
}

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

  text-decoration: none;

  font-weight: 500;

  transition: opacity 0.2s ease;
}

.nav-link:hover {
  opacity: 0.8;
}


/* =========================================================
   PAGE HEADERS
========================================================= */

.page-header {
  margin-bottom: 2rem;
  padding-top: 1rem;
}


/* =========================================================
   COURSE FILTER CONTROLS
========================================================= */

.course-controls {
  position: relative;
  z-index: 2;

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

  padding: 1rem;

  background: var(--glass-bg);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid var(--glass-border);
  border-radius: 14px;
}

.filter-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.filter-btn {
  min-height: 40px;
  padding: 0.5rem 1rem;

  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);

  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--glass-border);
  border-radius: 999px;
  cursor: pointer;

  transition: color 0.2s ease, background 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
}

.filter-btn:hover,
.filter-btn:focus-visible {
  color: #ffffff;
  border-color: var(--glow-border);
}

.filter-btn.active {
  color: #ffffff;
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.45), rgba(139, 92, 246, 0.4));
  border-color: rgba(196, 181, 253, 0.6);
  box-shadow: var(--glow-shadow);
}

.course-search {
  flex: 1 1 220px;
  max-width: 320px;
  min-height: 42px;
  padding: 0.55rem 1rem;

  font-family: var(--font-body);
  font-size: 0.95rem;
  color: var(--text-primary);

  background: rgba(0, 0, 0, 0.35);
  border: 1px solid var(--glass-border);
  border-radius: 10px;
  outline: none;

  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.course-search::placeholder {
  color: #6b7280;
}

.course-search:focus {
  border-color: var(--glow-border);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.25);
}

.no-results {
  position: relative;
  z-index: 2;
  margin-top: 1.5rem;
  text-align: center;
  color: var(--accent-soft);
}

.course-note h4 {
  font-weight: 500;
  line-height: 1.7;
  color: var(--text-primary);
}


/* =========================================================
   YEAR / SEMESTER
========================================================= */

.year-section {
  margin-top: 3rem;
}

.year-title {
  font-size: 1.75rem;

  color: #a5b4fc;

  margin-bottom: 1rem;

  border-bottom:
    1px solid var(--glass-border);

  padding-bottom: 0.5rem;
}

.semester-grid {
  display: grid;

  grid-template-columns: repeat(2, minmax(0, 1fr));

  gap: 1.5rem;
}

.semester-card {
  margin-top: 0;

  transition: border-color 0.25s ease, box-shadow 0.25s ease;
}

.semester-card:hover {
  border-color: var(--glow-border);
  box-shadow: var(--glow-shadow);
}

.semester-card h3 {
  font-size: 1.2rem;

  color: #ffffff;

  margin-bottom: 1rem;

  display: flex;

  justify-content: space-between;

  align-items: center;

  gap: 0.5rem;
}

.semester-card h6 {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
}


/* =========================================================
   STATUS TAGS
========================================================= */

.upcoming-tag {
  font-size: 0.75rem;

  background: #ffcc00;

  color: #1a1a1a;

  padding: 0.2rem 0.5rem;

  border-radius: 4px;

  font-weight: 600;
}

.current-tag {
  font-size: 0.75rem;

  background: #00ffff;

  color: #000;

  padding: 0.2rem 0.5rem;

  border-radius: 4px;

  font-weight: 600;
}

.done-tag {
  font-size: 0.75rem;

  background: #10b981;

  color: #222222;

  padding: 0.2rem 0.5rem;

  border-radius: 4px;

  font-weight: 600;
}


/* =========================================================
   SUBJECT LIST
========================================================= */

.subject-list {
  list-style: none;

  padding-left: 0;
}

.subject-list li {
  position: relative;

  padding-left: 1.25rem;

  margin-bottom: 0.5rem;

  color: var(--text-secondary);

  font-size: 0.95rem;
}

.subject-list li::before {
  content: "•";

  position: absolute;

  left: 0;

  color: var(--accent);
}

.subject-list li.highlight {
  color: #ffffff;
}

.subject-list li.highlight::before {
  color: #c4b5fd;
  text-shadow: 0 0 8px rgba(196, 181, 253, 0.9);
}


/* =========================================================
   SCROLL REVEAL
========================================================= */

.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition:
    opacity 0.7s ease,
    transform 0.7s cubic-bezier(0.22, 1, 0.36, 1);
  will-change: opacity, transform;
}

.reveal.is-visible {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .timeline-item.current::before {
    animation: none;
  }
}


/* =========================================================
   LAPTOP / DESKTOP (> 1024px)
========================================================= */

@media (min-width: 1025px) {

  .container {
    max-width: 960px;
  }

  .project-grid,
  .cert-grid,
  .semester-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

}


/* =========================================================
   TABLET (768px - 1024px)
========================================================= */

@media (min-width: 768px) and (max-width: 1024px) {

  .nav-inner {
    padding: 0 1.25rem;
  }

  .nav-links a {
    padding: 0.4rem 0.5rem;
    font-size: 0.8rem;
  }

  .container {
    max-width: 100%;
    padding: 2.5rem 2rem 3.5rem;
  }

  .card {
    padding: 1.75rem;
  }

  .project-grid,
  .cert-grid,
  .semester-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

}

/* Tight tablet widths: switch nav links to a scrollable row */
@media (min-width: 768px) and (max-width: 900px) {

  .nav-links {
    overflow-x: auto;
    scrollbar-width: none;
  }

  .nav-links::-webkit-scrollbar {
    display: none;
  }

}


/* =========================================================
   MOBILE (< 768px)
========================================================= */

@media (max-width: 767px) {

  :root {
    --nav-height: 58px;
  }

  .nav-inner {
    padding: 0 1rem;
  }

  .menu-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }

  /* Collapsible hamburger menu */
  .nav-links {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;

    flex-direction: column;
    align-items: stretch;
    gap: 0.25rem;

    padding: 0 1rem;
    max-height: 0;
    overflow: hidden;

    background: var(--glass-bg-strong);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid transparent;

    opacity: 0;
    visibility: hidden;

    transition: max-height 0.35s ease, opacity 0.25s ease, padding 0.35s ease, visibility 0.35s;
  }

  .top-nav.open .nav-links {
    max-height: 480px;
    padding: 0.75rem 1rem 1rem;
    opacity: 1;
    visibility: visible;
    border-bottom-color: var(--glass-border);
  }

  .nav-links a {
    padding: 0.8rem 1rem;
    font-size: 1rem;
    min-height: 44px;
  }

  .container {
    padding: 1.5rem 1rem 3rem;
  }

  .hero {
    padding: 2rem 0 1rem;
    text-align: center;
  }

  .hero .cta-buttons {
    justify-content: center;
  }

  .avatar-img {
    width: 104px;
    height: 104px;
  }

  h1 {
    font-size: clamp(2rem, 9vw, 2.5rem);
  }

  .tagline {
    font-size: clamp(0.95rem, 4vw, 1.05rem);
  }

  .card {
    padding: 1.35rem;
    border-radius: 14px;
  }

  .cta-buttons {
    gap: 0.75rem;
  }

  .btn {
    padding:
      0.7rem 1.1rem;
    min-height: 44px;
  }

  .cta-buttons .btn {
    flex: 1 1 140px;
  }

  .section-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .pill {
    min-height: 44px;
    padding: 0.55rem 1.1rem;
  }

  .project-grid,
  .cert-grid,
  .contact-grid,
  .semester-grid {
    grid-template-columns: 1fr;
  }

  .timeline {
    padding-left: 1.6rem;
  }

  .timeline::before {
    left: 0.4rem;
  }

  .timeline-item {
    padding-left: 0.5rem;
  }

  .timeline-item::before {
    left: calc(-1.6rem + 0.4rem - 6px + 1px);
  }

  .course-controls {
    flex-direction: column;
    align-items: stretch;
  }

  .filter-group {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
  }

  .filter-btn {
    min-height: 44px;
  }

  .course-search {
    max-width: none;
    min-height: 46px;
    font-size: 1rem; /* prevents iOS zoom on focus */
  }

  .year-title {
    font-size: 1.45rem;
  }

}



/* =========================================================
   PRELOADER
========================================================= */

#preloader {
  position: fixed;
  inset: 0;
  z-index: 9999;

  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1.5rem;

  background: radial-gradient(circle at 50% 45%, #14143a 0%, #050510 65%);
  color: #c7d2fe;

  opacity: 1;
  visibility: visible;
}

#preloader.fade-out {
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.8s ease, visibility 0.8s ease;
  pointer-events: none;
}

.preloader-ring {
  width: 72px;
  height: 72px;
  border-radius: 50%;

  border: 3px solid rgba(129, 140, 248, 0.15);
  border-top-color: #818cf8;
  border-right-color: #a78bfa;

  box-shadow: 0 0 24px rgba(129, 140, 248, 0.55), inset 0 0 18px rgba(139, 92, 246, 0.35);
  animation: preloader-spin 1s linear infinite, preloader-pulse 1.8s ease-in-out infinite;
}

.preloader-text {
  font-family: var(--font-display);
  font-size: 1rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: #c7d2fe;
  animation: preloader-fade 1.8s ease-in-out infinite;
}

@keyframes preloader-spin {
  to { transform: rotate(360deg); }
}

@keyframes preloader-pulse {
  0%, 100% { box-shadow: 0 0 18px rgba(129, 140, 248, 0.4), inset 0 0 12px rgba(139, 92, 246, 0.25); }
  50% { box-shadow: 0 0 40px rgba(167, 139, 250, 0.85), inset 0 0 24px rgba(139, 92, 246, 0.5); }
}

@keyframes preloader-fade {
  0%, 100% { opacity: 0.55; }
  50% { opacity: 1; }
}


/* =========================================================
   THEME TOGGLE BUTTON
========================================================= */

.theme-toggle {
  flex-shrink: 0;
  width: 44px;
  height: 44px;

  font-size: 1.2rem;
  line-height: 1;
  color: var(--text-primary);

  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--glass-border);
  border-radius: 10px;
  cursor: pointer;

  transition: border-color 0.2s ease, background 0.2s ease, transform 0.2s ease;
}

.theme-toggle:hover,
.theme-toggle:focus-visible {
  border-color: var(--glow-border);
  background: rgba(99, 102, 241, 0.15);
  transform: rotate(15deg);
}

@media (max-width: 767px) {
  .nav-brand { margin-right: auto; }
  .theme-toggle { order: 2; }
  .menu-toggle { order: 3; }
}


/* =========================================================
   LIGHT THEME (Clean Light)
========================================================= */

:root[data-theme="light"] {
  --bg-color: #f8fafc;
  --page-bg: #f8fafc;
  --text-primary: #1e293b;
  --text-secondary: #475569;
  --accent: #4f46e5;
  --accent-violet: #7c3aed;
  --accent-soft: #4338ca;
  --glass-bg: rgba(255, 255, 255, 0.7);
  --glass-bg-strong: rgba(255, 255, 255, 0.94);
  --glass-border: rgba(15, 23, 42, 0.12);
  --glow-border: rgba(79, 70, 229, 0.55);
  --glow-shadow: 0 0 0 1px rgba(79, 70, 229, 0.2), 0 8px 28px rgba(79, 70, 229, 0.2);
}

/* The dark starfield/black hole is inverted and softened so it blends
   with the light background instead of washing out. */
:root[data-theme="light"] #webgl-canvas {
  filter: invert(1) hue-rotate(180deg);
  opacity: 0.4;
}

:root[data-theme="light"] .top-nav {
  background: rgba(255, 255, 255, 0.65);
  box-shadow: 0 4px 24px rgba(15, 23, 42, 0.08);
}

:root[data-theme="light"] .nav-brand {
  background: linear-gradient(90deg, #4338ca, #6d28d9);
  -webkit-background-clip: text;
  background-clip: text;
}

:root[data-theme="light"] .nav-links a:hover,
:root[data-theme="light"] .nav-links a:focus-visible,
:root[data-theme="light"] .nav-links a.active,
:root[data-theme="light"] .filter-btn:hover,
:root[data-theme="light"] .filter-btn:focus-visible,
:root[data-theme="light"] .contact-value a:hover {
  color: #1e1b4b;
}

:root[data-theme="light"] h2,
:root[data-theme="light"] .semester-card h3,
:root[data-theme="light"] .subject-list li.highlight,
:root[data-theme="light"] .year-title {
  color: #1e1b4b;
}

:root[data-theme="light"] .badge,
:root[data-theme="light"] .timeline-badge,
:root[data-theme="light"] .project-tag,
:root[data-theme="light"] .contact-value,
:root[data-theme="light"] .contact-value a {
  color: #3730a3;
}

:root[data-theme="light"] .badge a,
:root[data-theme="light"] .pill {
  color: #312e81;
}

:root[data-theme="light"] .meta {
  color: #4f46e5;
}

:root[data-theme="light"] .issuer-badge {
  color: #0e7490;
}

:root[data-theme="light"] .project-card,
:root[data-theme="light"] .cert-card,
:root[data-theme="light"] .contact-card {
  background: rgba(255, 255, 255, 0.6);
}

:root[data-theme="light"] .project-card.featured {
  background: linear-gradient(145deg, rgba(99, 102, 241, 0.12), rgba(139, 92, 246, 0.06));
}

:root[data-theme="light"] .btn.secondary,
:root[data-theme="light"] .filter-btn,
:root[data-theme="light"] .menu-toggle,
:root[data-theme="light"] .theme-toggle {
  background: rgba(255, 255, 255, 0.7);
}

:root[data-theme="light"] .filter-btn.active {
  color: #1e1b4b;
}

:root[data-theme="light"] .course-search {
  background: rgba(255, 255, 255, 0.85);
  color: var(--text-primary);
}

:root[data-theme="light"] .course-search::placeholder {
  color: #94a3b8;
}

:root[data-theme="light"] .avatar-img {
  border-color: rgba(15, 23, 42, 0.15);
}

:root[data-theme="light"] .timeline-item::before {
  border-color: #ffffff;
}

:root[data-theme="light"] .book-btn,
:root[data-theme="light"] .book-btn:hover {
  color: #ffffff;
}