/* ==============================
   Design System & Variables
============================== */
:root {
  --bg-primary: #070c18;
  --bg-secondary: #0f1829;
  --bg-card: #111e35;
  --text-primary: #f0f4ff;
  --text-secondary: #8899bb;
  --accent-sky: #38bdf8;
  --accent-orange: #fb923c;
  --accent-teal: #2dd4bf;
  --gradient-primary: linear-gradient(135deg, #38bdf8, #818cf8);
  --gradient-fire: linear-gradient(135deg, #fb923c, #f43f5e);
  --gradient-mixed: linear-gradient(135deg, #38bdf8, #fb923c);
  --glass-bg: rgba(7, 12, 24, 0.8);
  --glass-border: rgba(56, 189, 248, 0.1);
  --glass-shadow: 0 8px 40px rgba(0, 0, 0, 0.6);
  --max-width: 1000px;
  --border-radius: 18px;
  --transition-fast: 0.2s ease;
  --transition-normal: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ==============================
   Fire Canvas Background
============================== */
#fire-bg {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  pointer-events: none;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
  /* NO background-attachment:fixed — breaks iOS Safari */
  background-image:
    radial-gradient(ellipse at 0% 50%,  rgba(56, 189, 248, 0.08) 0%, transparent 60%),
    radial-gradient(ellipse at 100% 10%, rgba(251, 146, 60, 0.08) 0%, transparent 60%),
    radial-gradient(ellipse at 60% 90%,  rgba(129, 140, 248, 0.06) 0%, transparent 50%);
}

/* Subtle dot grid — scroll with page on mobile */
body::before {
  content: '';
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  background-image: radial-gradient(rgba(56,189,248,0.06) 1px, transparent 1px);
  background-size: 32px 32px;
  z-index: 0;
  pointer-events: none;
}

a {
  color: var(--accent-sky);
  text-decoration: none;
  transition: color var(--transition-fast);
}
a:hover { color: var(--accent-orange); }

/* ==============================
   Typography
============================== */
h1, h2, h3, h4 {
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 1rem;
}

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

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

/* ==============================
   Navigation
============================== */
nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  background: #070c18;
  background: rgba(7, 12, 24, 0.97);
  border-bottom: 1px solid rgba(56, 189, 248, 0.12);
  padding: 0.85rem 0;
}

@supports (backdrop-filter: blur(1px)) {
  nav {
    background: rgba(7, 12, 24, 0.92);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
  }
}

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

.nav-logo {
  font-size: 1.3rem;
  font-weight: 900;
  letter-spacing: 3px;
  flex-shrink: 0;
}

.nav-logo a {
  background: var(--gradient-mixed);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Right-side group */
.nav-right {
  display: flex;
  align-items: center;
  gap: 1rem;
}

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

nav ul li a {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 1.2px;
  position: relative;
  padding: 0.4rem 0;
  transition: color var(--transition-fast);
  white-space: nowrap;
}

nav ul li a::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0;
  width: 0; height: 2px;
  background: var(--gradient-mixed);
  transition: width var(--transition-normal);
  border-radius: 2px;
}

nav ul li a:hover { color: var(--text-primary); }
nav ul li a:hover::after { width: 100%; }

/* ==============================
   Layout
============================== */
main {
  max-width: var(--max-width);
  margin: 100px auto 40px;
  padding: 2rem;
  min-height: calc(100vh - 200px);
  position: relative;
  z-index: 1;
}

section {
  background: #0f1829; /* solid fallback for browsers without backdrop-filter */
  background: var(--bg-secondary);
  border: 1px solid rgba(56, 189, 248, 0.1);
  border-radius: var(--border-radius);
  padding: 3rem;
  box-shadow: 0 8px 40px rgba(0, 0, 0, 0.5);
  margin-bottom: 2.5rem;
  position: relative;
  z-index: 1;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal), border-color var(--transition-normal);
}

/* Glassy effect only where supported */
@supports (backdrop-filter: blur(1px)) {
  section {
    background: rgba(15, 24, 41, 0.85);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
  }
}

section:hover {
  transform: translateY(-4px);
  border-color: rgba(56, 189, 248, 0.22);
  box-shadow: 0 20px 60px rgba(0,0,0,0.6);
}

/* ==============================
   Hero Profile
============================== */
.hero-wrapper {
  display: flex;
  align-items: center;
  gap: 3.5rem;
  flex-wrap: wrap;
}

.profile-image-container {
  flex: 0 0 200px;
  position: relative;
}

/* Animated halo */
.profile-image-container::before {
  content: '';
  position: absolute;
  inset: -8px;
  border-radius: 50%;
  background: var(--gradient-mixed);
  z-index: -1;
  filter: blur(16px);
  opacity: 0.65;
  animation: halo-pulse 4s ease-in-out infinite;
}

@keyframes halo-pulse {
  0%, 100% { opacity: 0.55; filter: blur(16px); transform: scale(1);   }
  50%       { opacity: 0.85; filter: blur(22px); transform: scale(1.05); }
}

.profile-image {
  width: 200px;
  height: 200px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid rgba(56, 189, 248, 0.3);
  box-shadow: 0 0 40px rgba(0,0,0,0.7);
  transition: transform var(--transition-normal);
}

.profile-image:hover { transform: scale(1.04); }

.hero-content { flex: 1; min-width: 280px; }

.hero-title {
  font-size: 2.8rem;
  margin-bottom: 0.4rem;
  letter-spacing: -0.5px;
}

.hero-subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
  font-weight: 400;
  margin-bottom: 1.5rem;
  line-height: 1.6;
}

.hero-bio {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
  line-height: 1.8;
}

/* ==============================
   Social Buttons
============================== */
.social-links {
  display: flex;
  gap: 0.75rem;
  align-items: center;
  flex-wrap: wrap;
  margin-top: 2rem;
}

.social-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 12px;
  background: rgba(56, 189, 248, 0.07);
  border: 1px solid rgba(56, 189, 248, 0.15);
  color: var(--text-primary);
  font-size: 1.1rem;
  transition: all var(--transition-normal);
  cursor: pointer;
  font-family: inherit;
}

.social-icon:hover {
  background: var(--gradient-primary);
  border-color: transparent;
  transform: translateY(-4px);
  box-shadow: 0 10px 24px rgba(56, 189, 248, 0.35);
  color: white;
}

/* CV badge button */
.cv-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: rgba(251, 146, 60, 0.1);
  border: 1px solid rgba(251, 146, 60, 0.25);
  color: var(--accent-orange);
  padding: 0 1rem;
  height: 44px;
  border-radius: 12px;
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  cursor: pointer;
  font-family: inherit;
  transition: all var(--transition-normal);
}

.cv-badge:hover {
  background: var(--gradient-fire);
  border-color: transparent;
  color: white;
  transform: translateY(-4px);
  box-shadow: 0 10px 24px rgba(251, 146, 60, 0.35);
}

.contact-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--gradient-primary);
  color: white !important;
  padding: 0 1.5rem;
  height: 44px;
  border-radius: 12px;
  font-weight: 600;
  font-size: 0.9rem;
  transition: all var(--transition-normal);
  box-shadow: 0 4px 16px rgba(56, 189, 248, 0.25);
}

.contact-btn:hover {
  transform: translateY(-4px);
  box-shadow: 0 10px 28px rgba(56, 189, 248, 0.45);
}

/* ==============================
   CV Modal
============================== */
.cv-modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.85);
  backdrop-filter: blur(6px);
  z-index: 9999;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  animation: fadeIn 0.25s ease;
}

.cv-modal-overlay.open {
  display: flex;
}

@keyframes fadeIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}

.cv-modal-box {
  background: var(--bg-secondary);
  border: 1px solid rgba(56, 189, 248, 0.2);
  border-radius: 18px;
  width: 100%;
  max-width: 860px;
  max-height: 90vh;
  display: flex;
  flex-direction: column;
  box-shadow: 0 30px 80px rgba(0,0,0,0.8);
  animation: slideUp 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  overflow: hidden;
}

@keyframes slideUp {
  from { transform: translateY(30px); opacity: 0; }
  to   { transform: translateY(0);    opacity: 1; }
}

.cv-modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.2rem 1.8rem;
  border-bottom: 1px solid rgba(56, 189, 248, 0.1);
  flex-shrink: 0;
}

.cv-modal-header h3 {
  margin: 0;
  font-size: 1rem;
  letter-spacing: 1px;
}

.cv-modal-actions {
  display: flex;
  gap: 0.8rem;
  align-items: center;
}

.cv-btn-download {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--gradient-fire);
  color: white;
  padding: 0.5rem 1.1rem;
  border-radius: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  transition: all var(--transition-fast);
}

.cv-btn-download:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(251, 146, 60, 0.4);
  color: white;
}

.cv-btn-close {
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.1);
  color: var(--text-secondary);
  width: 36px;
  height: 36px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.cv-btn-close:hover {
  background: rgba(255,255,255,0.12);
  color: var(--text-primary);
}

.cv-modal-body {
  flex: 1;
  overflow: hidden;
}

.cv-modal-body iframe {
  width: 100%;
  height: 100%;
  min-height: 600px;
  border: none;
  display: block;
}

/* ==============================
   Research Interest Tags
============================== */
.tag {
  display: inline-block;
  background: rgba(56, 189, 248, 0.08);
  border: 1px solid rgba(56, 189, 248, 0.18);
  color: var(--accent-sky);
  padding: 5px 14px;
  border-radius: 20px;
  font-size: 0.82rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.tag:hover {
  background: rgba(56, 189, 248, 0.18);
  transform: translateY(-2px);
}

/* ==============================
   Education Timeline (about page)
============================== */
.edu-item {
  padding: 1rem 1.5rem;
  border-left: 3px solid;
  margin-bottom: 1rem;
  background: rgba(255,255,255,0.02);
  border-radius: 0 10px 10px 0;
}

/* ==============================
   Cards (publications, talks, etc.)
============================== */
.pub-card {
  background: var(--bg-card);
  padding: 2rem;
  border-radius: 14px;
  border: 1px solid rgba(56, 189, 248, 0.08);
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.pub-card::after {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: var(--gradient-primary);
  opacity: 0;
  transition: opacity var(--transition-normal);
}

.pub-card:hover {
  transform: translateY(-4px);
  border-color: rgba(56, 189, 248, 0.2);
  box-shadow: 0 12px 32px rgba(0,0,0,0.4);
}

.pub-card:hover::after { opacity: 1; }

/* ==============================
   Experiment Cards
============================== */
.experiment-card {
  background: var(--glass-bg);
  border-radius: 16px;
  border: 1px solid var(--glass-border);
  overflow: hidden;
  transition: all var(--transition-normal);
}

.experiment-card:hover {
  transform: translateY(-8px);
  border-color: rgba(56, 189, 248, 0.3);
  box-shadow: 0 20px 50px rgba(0,0,0,0.5);
}

/* ==============================
   Footer
============================== */
footer {
  text-align: center;
  padding: 3rem 2rem;
  background: rgba(7, 12, 24, 0.95);
  border-top: 1px solid rgba(56, 189, 248, 0.08);
  color: var(--text-secondary);
  position: relative;
  z-index: 10;
}

footer p { margin-bottom: 0.5rem; }

footer a {
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}
footer a:hover { color: var(--accent-sky); }

.copyright {
  margin-top: 2rem;
  font-size: 0.8rem;
  opacity: 0.4;
}

/* ==============================
   Scroll-to-top
============================== */
#scroll-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  background: var(--gradient-primary);
  color: white;
  border: none;
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  z-index: 998;
  box-shadow: 0 4px 16px rgba(56, 189, 248, 0.35);
  transition: all var(--transition-normal);
}

#scroll-top:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 24px rgba(56, 189, 248, 0.5);
}

#scroll-top.visible { display: flex; }

/* ==============================
   Hamburger Button
============================== */
.nav-hamburger {
  display: none;
  flex-direction: column;
  justify-content: space-between;
  width: 38px;
  height: 38px;
  background: rgba(56,189,248,0.06);
  border: 1px solid rgba(56,189,248,0.2);
  border-radius: 10px;
  cursor: pointer;
  padding: 10px 9px;
  flex-shrink: 0;
  transition: background var(--transition-fast), border-color var(--transition-fast);
}

.nav-hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all 0.28s ease;
  transform-origin: center;
}

.nav-hamburger:hover {
  background: rgba(56,189,248,0.12);
  border-color: var(--accent-sky);
}

/* ≡ → ✕ */
.nav-hamburger.active span:nth-child(1) { transform: translateY(6px) rotate(45deg);  }
.nav-hamburger.active span:nth-child(2) { opacity: 0; transform: scaleX(0);          }
.nav-hamburger.active span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

/* ==============================
   Language Switcher
============================== */
.lang-switcher {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-shrink: 0;
}

.lang-btn {
  background: none;
  border: 2px solid transparent;
  border-radius: 5px;
  cursor: pointer;
  opacity: 0.45;
  padding: 2px;
  display: flex;
  align-items: center;
  transition: opacity var(--transition-fast), transform var(--transition-fast), border-color var(--transition-fast);
}

.lang-btn img {
  display: block;
  border-radius: 3px;
}

.lang-btn:hover  { opacity: 0.8;  transform: scale(1.08); }
.lang-btn.active { opacity: 1;    transform: scale(1.1);  border-color: rgba(56,189,248,0.4); }

/* ==============================
   Responsive — Mobile
============================== */
@media (max-width: 768px) {

  /* Show hamburger */
  .nav-hamburger { display: flex; }

  /* Hide nav links inline, show as dropdown */
  nav ul {
    display: none;
    position: fixed;
    top: 58px; /* height of nav bar */
    left: 0;
    right: 0;
    flex-direction: column;
    background: rgba(7, 12, 24, 0.98);
    backdrop-filter: blur(24px);
    -webkit-backdrop-filter: blur(24px);
    border-bottom: 1px solid rgba(56,189,248,0.15);
    padding: 0.5rem 0 1rem;
    gap: 0;
    z-index: 999;
  }

  nav ul.open { display: flex; }

  nav ul li a {
    display: block;
    padding: 1rem 2rem;
    font-size: 0.95rem;
    letter-spacing: 1px;
    border-bottom: 1px solid rgba(255,255,255,0.04);
    color: var(--text-secondary);
  }

  nav ul li a:hover { color: var(--text-primary); background: rgba(56,189,248,0.04); }
  nav ul li:last-child a { border-bottom: none; }
  nav ul li a::after { display: none; }

  /* Reduce nav padding */
  nav { padding: 0.7rem 0; }
  .nav-container { padding: 0 1rem; gap: 0.6rem; }

  /* Hero */
  .hero-wrapper {
    flex-direction: column;
    text-align: center;
    gap: 2rem;
  }

  .hero-title    { font-size: 1.9rem; }
  .hero-subtitle { font-size: 0.95rem; }
  .hero-bio      { font-size: 0.95rem; }

  .profile-image-container { flex: 0 0 150px; }
  .profile-image { width: 150px; height: 150px; }

  .social-links { justify-content: center; }

  /* Sections */
  section { padding: 1.6rem 1.1rem; }
  main    { padding: 0.8rem; margin-top: 75px; }

  /* CV Modal — slide up from bottom on mobile */
  .cv-modal-overlay {
    padding: 0;
    align-items: flex-end;
  }

  .cv-modal-box {
    border-radius: 20px 20px 0 0;
    max-height: 90vh;
  }

  .cv-modal-body iframe { min-height: 60vh; }

  /* Footer */
  footer { padding: 2rem 1rem; font-size: 0.9rem; }

  /* Scroll to top — avoid overlap with content */
  #scroll-top { bottom: 1.2rem; right: 1.2rem; }
}