/* ============================================================
   CSS Variables & Reset
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:          #0d1117;
  --bg-2:        #161b22;
  --bg-3:        #21262d;
  --border:      #30363d;
  --text:        #e6edf3;
  --text-2:      #8b949e;
  --text-3:      #6e7681;
  --accent:      #3fb950;
  --accent-h:    #2ea043;
  --accent-glow: rgba(63, 185, 80, 0.12);
  --accent-glow2:rgba(63, 185, 80, 0.28);
  --radius:      8px;
  --radius-lg:   14px;
  --shadow:      0 8px 32px rgba(0,0,0,0.45);
  --shadow-lg:   0 16px 48px rgba(0,0,0,0.6);
  --nav-h:       64px;
  --max-w:       1200px;
  --t:           0.2s ease;
}

html { scroll-behavior: smooth; }

.skip-link {
  position: absolute;
  left: 1rem;
  top: -120px;
  z-index: 10000;
  padding: 0.65rem 1rem;
  background: var(--accent);
  color: var(--bg);
  font-weight: 600;
  font-size: 0.9rem;
  border-radius: var(--radius);
  transition: top 0.2s ease;
}
.skip-link:focus {
  top: calc(var(--nav-h) + 0.5rem);
  outline: 2px solid var(--text);
  outline-offset: 3px;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 16px;
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }
a  { color: var(--accent); text-decoration: none; transition: color var(--t); }
a:hover { color: var(--accent-h); }

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

.section-title {
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  color: var(--text);
  margin-bottom: 0.4rem;
}
.section-subtitle {
  color: var(--text-2);
  font-size: 1rem;
  margin-bottom: 3rem;
}
.section-header { margin-bottom: 3rem; }

/* ============================================================
   Layout
   ============================================================ */
.container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 1.5rem;
}
section { padding: 6rem 0; }

/* ============================================================
   Navigation
   ============================================================ */
nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-h);
  background: rgba(13,17,23,0.88);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 1.5rem;
}

.nav-logo {
  font-size: 1.2rem;
  font-weight: 800;
  color: var(--text);
  letter-spacing: -0.03em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2rem;
  list-style: none;
}
.nav-links a {
  color: var(--text-2);
  font-size: 0.9rem;
  font-weight: 500;
  transition: color var(--t);
}
.nav-links a:hover,
.nav-links a.active { color: var(--text); }

.nav-right { display: flex; align-items: center; gap: 1rem; }

.lang-toggle {
  background: var(--bg-3);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.28rem 0.7rem;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-2);
  cursor: pointer;
  transition: all var(--t);
  letter-spacing: 0.06em;
}
.lang-toggle:hover { border-color: var(--accent); color: var(--accent); }

.nav-hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 0.4rem;
  background: none;
  border: none;
}
.nav-hamburger span {
  display: block;
  width: 22px; height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: all var(--t);
}

/* Mobile nav */
.nav-mobile {
  display: none;
  position: fixed;
  top: var(--nav-h); left: 0; right: 0;
  background: var(--bg-2);
  border-bottom: 1px solid var(--border);
  padding: 1.25rem 1.5rem 1.5rem;
  z-index: 99;
}
.nav-mobile.open { display: block; }
.nav-mobile ul { list-style: none; display: flex; flex-direction: column; gap: 1rem; }
.nav-mobile a { color: var(--text-2); font-size: 1rem; font-weight: 500; }
.nav-mobile a:hover { color: var(--text); }
.nav-mobile .lang-toggle { margin-top: 1.25rem; }

/* ============================================================
   Hero
   ============================================================ */
#hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: var(--nav-h);
  position: relative;
  overflow: hidden;
}

.hero-bg {
  position: absolute; inset: 0;
  background:
    radial-gradient(ellipse 80% 50% at 50% -5%, rgba(63,185,80,0.09) 0%, transparent 60%),
    radial-gradient(ellipse 50% 60% at 85% 85%, rgba(56,139,253,0.05) 0%, transparent 50%);
  pointer-events: none;
}

.hero-grid {
  position: absolute; inset: 0;
  background-image:
    linear-gradient(var(--border) 1px, transparent 1px),
    linear-gradient(90deg, var(--border) 1px, transparent 1px);
  background-size: 60px 60px;
  opacity: 0.25;
  pointer-events: none;
  mask-image: radial-gradient(ellipse 90% 80% at 50% 40%, black 0%, transparent 100%);
  -webkit-mask-image: radial-gradient(ellipse 90% 80% at 50% 40%, black 0%, transparent 100%);
}

.hero-content {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 4rem;
  align-items: center;
  width: 100%;
}

.hero-text { max-width: 680px; }

.hero-greeting {
  display: block;
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

.hero-name {
  font-size: clamp(2.4rem, 6vw, 3.8rem);
  font-weight: 800;
  line-height: 1.1;
  margin-bottom: 1rem;
  letter-spacing: -0.03em;
}

.hero-tagline {
  font-size: clamp(0.95rem, 1.8vw, 1.1rem);
  color: var(--text-2);
  margin-bottom: 2rem;
  line-height: 1.7;
}
.hero-tagline .dot { color: var(--accent); margin: 0 0.35rem; }

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

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.7rem 1.6rem;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--t);
  border: none;
  font-family: inherit;
}
.btn-primary {
  background: var(--accent);
  color: #0d1117;
}
.btn-primary:hover {
  background: var(--accent-h);
  color: #0d1117;
  transform: translateY(-2px);
  box-shadow: 0 4px 20px var(--accent-glow2);
}
.btn-secondary {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}
.btn-secondary:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}

/* Profile photo */
.hero-photo-wrap { flex-shrink: 0; }
.hero-photo {
  width: 260px; height: 260px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid var(--border);
  box-shadow: 0 0 0 7px var(--accent-glow), var(--shadow);
  transition: box-shadow var(--t);
}
.hero-photo:hover { box-shadow: 0 0 0 10px var(--accent-glow2), var(--shadow-lg); }

/* Accent highlight — used in hero name (J, L) */
.hl { color: var(--accent); }

/* Scroll indicator */
.hero-scroll {
  position: absolute;
  bottom: 2rem; left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.4rem;
  color: var(--text-3);
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  animation: bounce 2.2s ease-in-out infinite;
}
.hero-scroll svg { opacity: 0.45; }

@keyframes bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50%       { transform: translateX(-50%) translateY(7px); }
}

/* ============================================================
   About
   ============================================================ */
#about { background: var(--bg-2); }

.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4.5rem;
  align-items: start;
}

.about-bio p {
  color: var(--text-2);
  margin-bottom: 1.2rem;
  font-size: 0.97rem;
  line-height: 1.78;
}
.about-bio p:last-of-type { margin-bottom: 0; }
.about-bio strong { color: var(--text); font-weight: 600; }

.about-location {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-3);
  font-size: 0.875rem;
  margin-top: 1.5rem;
}
.about-location svg { color: var(--accent); flex-shrink: 0; }

/* Publication badge */
.publication-card {
  margin-top: 1.75rem;
  background: var(--bg-3);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
  padding: 1rem 1.25rem;
}
.pub-label {
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.4rem;
}
.pub-title {
  font-size: 0.875rem;
  color: var(--text);
  font-weight: 500;
  line-height: 1.5;
}
.publication-card a {
  font-size: 0.8rem;
  color: var(--text-3);
  margin-top: 0.45rem;
  display: inline-block;
}
.publication-card a:hover { color: var(--accent); }

/* Skills */
.skills-section { }
.skill-group { margin-bottom: 1.5rem; }
.skill-group:last-child { margin-bottom: 0; }
.skill-group-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 0.65rem;
}
.skills-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
}
.skill-tag {
  background: var(--bg-3);
  border: 1px solid var(--border);
  color: var(--text-2);
  padding: 0.28rem 0.7rem;
  border-radius: 20px;
  font-size: 0.78rem;
  font-weight: 500;
  transition: all var(--t);
  cursor: default;
}
.skill-tag:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-glow);
}
.skill-tag.hi {
  background: var(--accent-glow);
  border-color: rgba(63,185,80,0.3);
  color: var(--accent);
}

/* ============================================================
   Projects
   ============================================================ */
#projects { background: var(--bg); }

.project-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-bottom: 2.5rem;
}
.filter-btn {
  padding: 0.4rem 1rem;
  border-radius: 20px;
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  background: var(--bg-2);
  border: 1px solid var(--border);
  color: var(--text-2);
  transition: all var(--t);
  font-family: inherit;
}
.filter-btn:hover { border-color: var(--accent); color: var(--accent); }
.filter-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #0d1117;
  font-weight: 700;
}

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
  gap: 1.5rem;
}

/* Card */
.project-card {
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform var(--t), border-color var(--t), box-shadow var(--t);
  display: flex;
  flex-direction: column;
  animation: fadeInUp 0.4s ease both;
}
.project-card:hover {
  border-color: rgba(63,185,80,0.35);
  transform: translateY(-3px);
  box-shadow: var(--shadow);
}
.project-card.hidden { display: none; }

@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* Carousel */
.carousel {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 9;
  background: var(--bg-3);
}
.carousel-track {
  display: flex;
  height: 100%;
  transition: transform 0.4s cubic-bezier(0.4,0,0.2,1);
}
.carousel-slide {
  min-width: 100%;
  height: 100%;
}
.carousel-slide img {
  width: 100%; height: 100%;
  object-fit: cover;
}
.carousel-btn {
  position: absolute;
  top: 50%; transform: translateY(-50%);
  background: rgba(13,17,23,0.75);
  border: 1px solid rgba(255,255,255,0.1);
  color: var(--text);
  width: 30px; height: 30px;
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  cursor: pointer;
  transition: all var(--t);
  z-index: 2;
  font-size: 1rem;
  line-height: 1;
}
.carousel-btn:hover { background: var(--bg-3); border-color: var(--accent); color: var(--accent); }
.carousel-btn.prev { left: 0.6rem; }
.carousel-btn.next { right: 0.6rem; }
.carousel-dots {
  position: absolute;
  bottom: 0.6rem; left: 50%;
  transform: translateX(-50%);
  display: flex; gap: 0.35rem;
}
.carousel-dot {
  width: 6px; height: 6px;
  border-radius: 50%;
  background: rgba(255,255,255,0.3);
  cursor: pointer;
  transition: all var(--t);
}
.carousel-dot.active {
  background: var(--accent);
  width: 16px;
  border-radius: 3px;
}

/* Card body */
.card-body {
  padding: 1.4rem;
  flex: 1;
  display: flex;
  flex-direction: column;
}
.card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.65rem;
}
.card-category {
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 0.18rem 0.55rem;
  border-radius: 4px;
  background: var(--accent-glow);
  color: var(--accent);
  border: 1px solid rgba(63,185,80,0.25);
}
.card-link {
  color: var(--text-3);
  font-size: 0.8rem;
  display: flex;
  align-items: center;
  gap: 0.2rem;
  transition: color var(--t);
}
.card-link:hover { color: var(--accent); }
.card-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.55rem;
}
.card-desc {
  font-size: 0.855rem;
  color: var(--text-2);
  line-height: 1.65;
  margin-bottom: 1.1rem;
  flex: 1;
}
.card-tech {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}
.tech-tag {
  font-size: 0.7rem;
  padding: 0.18rem 0.5rem;
  background: var(--bg-3);
  border: 1px solid var(--border);
  color: var(--text-3);
  border-radius: 4px;
  font-weight: 500;
}
.card-publication {
  margin-top: 0.9rem;
  padding-top: 0.9rem;
  border-top: 1px solid var(--border);
  font-size: 0.78rem;
  color: var(--text-3);
}
.card-publication a {
  color: var(--accent);
  font-weight: 500;
}
.card-publication a:hover { text-decoration: underline; }

/* ============================================================
   Contact
   ============================================================ */
#contact { background: var(--bg-2); }

.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1.6fr;
  gap: 4rem;
  align-items: start;
}

.contact-info > p {
  color: var(--text-2);
  font-size: 0.94rem;
  line-height: 1.7;
  margin-bottom: 2rem;
}
.contact-links {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}
.contact-link {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  color: var(--text-2);
  font-size: 0.88rem;
  padding: 0.75rem 1rem;
  background: var(--bg-3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: all var(--t);
}
.contact-link:hover {
  color: var(--accent);
  border-color: rgba(63,185,80,0.3);
  background: var(--bg);
}
.contact-link .icon {
  width: 34px; height: 34px;
  border-radius: 7px;
  background: var(--bg);
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
  color: var(--accent);
}
.contact-link-static { cursor: default; }
.contact-link-static:hover {
  color: var(--text-2);
  border-color: var(--border);
  background: var(--bg-3);
}

/* Form */
.form-group { margin-bottom: 1.15rem; }
.form-group label {
  display: block;
  font-size: 0.83rem;
  font-weight: 500;
  color: var(--text-2);
  margin-bottom: 0.45rem;
}
.form-group input,
.form-group textarea {
  width: 100%;
  background: var(--bg-3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.7rem 0.95rem;
  color: var(--text);
  font-family: inherit;
  font-size: 0.9rem;
  transition: border-color var(--t), box-shadow var(--t);
  outline: none;
  resize: vertical;
}
.form-group input::placeholder,
.form-group textarea::placeholder { color: var(--text-3); }
.form-group input:focus,
.form-group textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}
.form-group textarea { min-height: 130px; }

.form-status {
  padding: 0.7rem 1rem;
  border-radius: var(--radius);
  font-size: 0.855rem;
  margin-top: 0.75rem;
  display: none;
}
.form-status.success {
  display: block;
  background: rgba(63,185,80,0.1);
  border: 1px solid rgba(63,185,80,0.3);
  color: var(--accent);
}
.form-status.error {
  display: block;
  background: rgba(248,81,73,0.1);
  border: 1px solid rgba(248,81,73,0.3);
  color: #f85149;
}

/* ============================================================
   Footer
   ============================================================ */
footer {
  background: var(--bg);
  border-top: 1px solid var(--border);
  padding: 1.75rem 0;
  text-align: center;
  color: var(--text-3);
  font-size: 0.82rem;
}
footer a { color: var(--text-3); }
footer a:hover { color: var(--accent); }

/* ============================================================
   Scroll Animations
   ============================================================ */
.fade-in {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 0.65s ease, transform 0.65s ease;
}
.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 960px) {
  .hero-content {
    grid-template-columns: 1fr;
    text-align: center;
    gap: 2.5rem;
  }
  .hero-photo-wrap {
    display: flex;
    justify-content: center;
    order: -1;
  }
  .hero-photo { width: 200px; height: 200px; }
  .hero-ctas { justify-content: center; }
  .about-grid { grid-template-columns: 1fr; gap: 3rem; }
  .contact-grid { grid-template-columns: 1fr; gap: 3rem; }
  .projects-grid { grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); }
}

@media (max-width: 640px) {
  :root { --nav-h: 60px; }
  section { padding: 4rem 0; }
  .nav-links { display: none; }
  .nav-hamburger { display: flex; }
  .projects-grid { grid-template-columns: 1fr; }
  .hero-photo { width: 160px; height: 160px; }
  .hero-name { font-size: 2.2rem; }
}