/* ================================================================
   Cristián López — Personal Portfolio
   Industrial-luxury design system
   ================================================================ */

/* ----------------------------------------------------------------
   CSS Custom Properties
   ---------------------------------------------------------------- */
:root {
  --navy:        #0A1628;
  --navy-light:  #0D1E38;
  --slate:       #1A2332;
  --slate-light: #233045;
  --teal:        #00BFA6;
  --teal-dark:   #009985;
  --copper:      #D4812A;
  --copper-dark: #B06A1F;
  --text:        #E8ECF1;
  --text-muted:  #8899AA;
  --text-faint:  #4A5568;
  --border:      rgba(255,255,255,0.08);
  --border-teal: rgba(0,191,166,0.25);

  --font-display: 'Playfair Display', Georgia, serif;
  --font-body:    'Outfit', system-ui, sans-serif;
  --font-mono:    'JetBrains Mono', 'Courier New', monospace;

  --nav-h:     68px;
  --radius:    10px;
  --radius-lg: 16px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.6s cubic-bezier(0.4, 0, 0.2, 1);

  --container: 1140px;
  --section-pad: clamp(5rem, 10vw, 8rem);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-h);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  background: var(--navy);
  color: var(--text);
  line-height: 1.7;
  font-size: 1rem;
  overflow-x: hidden;
}

img { display: block; max-width: 100%; }
a { color: var(--teal); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--copper); }
ul { list-style: none; }

.font-mono { font-family: var(--font-mono); }

/* ----------------------------------------------------------------
   Reduced Motion
   ---------------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
  html { scroll-behavior: auto; }
  #particle-canvas { display: none !important; }
}

/* ----------------------------------------------------------------
   Container
   ---------------------------------------------------------------- */
.container {
  width: min(var(--container), 100% - 2rem);
  margin-inline: auto;
}

/* ----------------------------------------------------------------
   Section shared styles
   ---------------------------------------------------------------- */
section {
  padding: var(--section-pad) 0;
  position: relative;
}

.section-header {
  text-align: center;
  margin-bottom: 3.5rem;
}

.section-header h2 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 700;
  color: var(--text);
  margin-bottom: 1rem;
  line-height: 1.15;
}

.section-intro {
  max-width: 660px;
  margin-inline: auto;
  color: var(--text-muted);
  font-size: 1.05rem;
  line-height: 1.75;
}

.eyebrow {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 0.75rem;
}

/* ----------------------------------------------------------------
   AOS (custom scroll animation)
   ---------------------------------------------------------------- */
[data-aos] {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.65s ease, transform 0.65s ease;
}
[data-aos].aos-visible {
  opacity: 1;
  transform: none;
}
[data-aos][data-aos-delay="80"]  { transition-delay: 0.08s; }
[data-aos][data-aos-delay="100"] { transition-delay: 0.10s; }
[data-aos][data-aos-delay="150"] { transition-delay: 0.15s; }
[data-aos][data-aos-delay="160"] { transition-delay: 0.16s; }
[data-aos][data-aos-delay="200"] { transition-delay: 0.20s; }
[data-aos][data-aos-delay="240"] { transition-delay: 0.24s; }
[data-aos][data-aos-delay="300"] { transition-delay: 0.30s; }
[data-aos][data-aos-delay="320"] { transition-delay: 0.32s; }
[data-aos][data-aos-delay="400"] { transition-delay: 0.40s; }

/* ----------------------------------------------------------------
   Navigation
   ---------------------------------------------------------------- */
#navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  height: var(--nav-h);
  transition: background var(--transition), box-shadow var(--transition);
}

#navbar.scrolled {
  background: rgba(10, 22, 40, 0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 1px 0 var(--border);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  width: min(var(--container), 100% - 2rem);
  margin-inline: auto;
}

.nav-brand {
  font-family: var(--font-display);
  font-size: 1.35rem;
  font-weight: 900;
  color: var(--teal);
  letter-spacing: -0.01em;
}
.nav-brand:hover { color: var(--copper); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  padding: 0.4rem 0.75rem;
  border-radius: 6px;
  transition: color var(--transition), background var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--text);
  background: rgba(255,255,255,0.06);
}

.nav-cta {
  background: var(--teal) !important;
  color: var(--navy) !important;
  font-weight: 600 !important;
  padding: 0.4rem 1rem !important;
}
.nav-cta:hover {
  background: var(--copper) !important;
  color: var(--text) !important;
}

.nav-hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
}
.nav-hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}
.nav-hamburger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-hamburger.open span:nth-child(2) { opacity: 0; }
.nav-hamburger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ----------------------------------------------------------------
   Hero
   ---------------------------------------------------------------- */
#hero {
  position: relative;
  height: 100vh;
  min-height: 600px;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  background: var(--navy);
}

#particle-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0.7;
}

.hero-grain {
  position: absolute;
  inset: 0;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='0.04'/%3E%3C/svg%3E");
  pointer-events: none;
  opacity: 0.5;
}

.hero-content {
  position: relative;
  z-index: 2;
  text-align: center;
  padding: 0 1.5rem;
}

.hero-eyebrow {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 1.5rem;
}

.hero-name {
  font-family: var(--font-display);
  font-size: clamp(4rem, 12vw, 9rem);
  font-weight: 900;
  line-height: 0.95;
  color: var(--text);
  margin-bottom: 1.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.1em;
}

.hero-name span:last-child {
  color: transparent;
  -webkit-text-stroke: 1.5px var(--teal);
}

.hero-role {
  font-size: clamp(1rem, 2.5vw, 1.25rem);
  font-weight: 500;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

.hero-tagline {
  font-family: var(--font-mono);
  font-size: clamp(0.75rem, 2vw, 0.9rem);
  letter-spacing: 0.3em;
  color: var(--copper);
  text-transform: uppercase;
  margin-bottom: 3rem;
}

.hero-scroll {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-muted);
  font-size: 0.8rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  transition: color var(--transition), transform var(--transition);
  animation: bounce 2.5s ease-in-out infinite;
}
.hero-scroll:hover { color: var(--teal); transform: translateY(4px); }

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50%       { transform: translateY(6px); }
}

/* ----------------------------------------------------------------
   About
   ---------------------------------------------------------------- */
#about { background: var(--slate); }

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

.about-photo-frame {
  position: sticky;
  top: calc(var(--nav-h) + 2rem);
  border-radius: var(--radius-lg);
  overflow: hidden;
  aspect-ratio: 3/4;
  border: 2px solid var(--copper);
  box-shadow: 0 0 40px rgba(212, 129, 42, 0.15), 0 20px 60px rgba(0,0,0,0.4);
}

.about-photo-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: top;
}

.about-content-col h2 {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3.5vw, 2.4rem);
  font-weight: 700;
  line-height: 1.2;
  color: var(--text);
  margin-bottom: 1.5rem;
}

.about-narrative {
  color: var(--text-muted);
  margin-bottom: 1.25rem;
  font-size: 1.05rem;
  line-height: 1.8;
}

.stat-row {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
  margin-top: 2.5rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}

.stat-item { text-align: left; }

.stat-number {
  display: block;
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 600;
  color: var(--teal);
  line-height: 1;
  margin-bottom: 0.35rem;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

/* ----------------------------------------------------------------
   Skills Visualiser
   ---------------------------------------------------------------- */
#skills { background: var(--navy); }

.skill-tabs {
  display: flex;
  gap: 0.5rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 2.5rem;
}

.skill-tab {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  padding: 0.5rem 1.25rem;
  border-radius: 40px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  transition: all var(--transition);
  letter-spacing: 0.05em;
}
.skill-tab:hover {
  border-color: var(--teal);
  color: var(--teal);
}
.skill-tab.active {
  background: var(--teal);
  border-color: var(--teal);
  color: var(--navy);
  font-weight: 600;
}

.skill-diagram-wrap {
  position: relative;
  max-width: 700px;
  margin: 0 auto 2rem;
}

#skill-svg {
  width: 100%;
  height: 360px;
  display: block;
}

.skill-tooltip {
  position: absolute;
  background: var(--slate);
  border: 1px solid var(--border-teal);
  border-radius: var(--radius);
  padding: 1rem 1.25rem;
  max-width: 260px;
  pointer-events: none;
  z-index: 10;
  box-shadow: 0 8px 32px rgba(0,0,0,0.4);
}

.skill-tooltip h4 {
  font-family: var(--font-display);
  font-size: 0.95rem;
  color: var(--teal);
  margin-bottom: 0.5rem;
}

.skill-tooltip ul {
  list-style: disc;
  padding-left: 1rem;
  color: var(--text-muted);
  font-size: 0.8rem;
  line-height: 1.6;
}

.skill-tooltip[hidden] { display: none; }

.skill-breadth-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
  max-width: 700px;
  margin-inline: auto;
  align-items: center;
}

.breadth-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.tag {
  font-size: 0.78rem;
  padding: 0.3rem 0.75rem;
  background: var(--slate);
  border: 1px solid var(--border);
  border-radius: 40px;
  color: var(--text-muted);
}

/* ----------------------------------------------------------------
   Career Timeline
   ---------------------------------------------------------------- */
#timeline { background: var(--slate); }

.timeline {
  position: relative;
  max-width: 900px;
  margin-inline: auto;
  padding: 2rem 0;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 0; bottom: 0;
  width: 1px;
  background: linear-gradient(to bottom, transparent, var(--teal), transparent);
  transform: translateX(-50%);
}

.timeline-item {
  display: grid;
  grid-template-columns: 1fr 40px 1fr;
  gap: 0 1.5rem;
  margin-bottom: 3rem;
  align-items: start;
}

.timeline-node {
  grid-column: 2;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--navy);
  border: 2px solid var(--teal);
  margin: 1.2rem auto 0;
  position: relative;
  z-index: 2;
  transition: background var(--transition);
}

.timeline-item:hover .timeline-node {
  background: var(--teal);
  box-shadow: 0 0 12px rgba(0, 191, 166, 0.5);
}

.timeline-card {
  background: var(--navy);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.timeline-card:hover {
  border-color: var(--border-teal);
  box-shadow: 0 8px 32px rgba(0,0,0,0.3);
}

.timeline-item[data-side="right"] .timeline-card { grid-column: 3; }
.timeline-item[data-side="left"]  .timeline-card { grid-column: 1; grid-row: 1; }
.timeline-item[data-side="left"]  .timeline-node { grid-column: 2; grid-row: 1; }

.timeline-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  margin-bottom: 0.75rem;
}

.timeline-date {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--teal);
  letter-spacing: 0.04em;
}

.timeline-location {
  font-size: 0.78rem;
  color: var(--text-faint);
}

.timeline-card h3 {
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.25rem;
  line-height: 1.3;
}

.timeline-company {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--copper);
  margin-bottom: 0.75rem;
}

.timeline-achievements {
  padding-left: 1rem;
  list-style: disc;
}

.timeline-achievements li {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 0.35rem;
  padding-left: 0.25rem;
}

/* ----------------------------------------------------------------
   World Map
   ---------------------------------------------------------------- */
#map { background: var(--navy); }

#world-map {
  height: 520px;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border);
  box-shadow: 0 20px 60px rgba(0,0,0,0.4);
}

.map-fallback {
  list-style: none;
  padding: 1.5rem 0 0;
  color: var(--text-muted);
}
.map-fallback li {
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.9rem;
}

/* Leaflet popup overrides */
.leaflet-popup-content-wrapper {
  background: var(--slate) !important;
  border: 1px solid var(--border-teal) !important;
  border-radius: var(--radius) !important;
  box-shadow: 0 8px 32px rgba(0,0,0,0.4) !important;
  color: var(--text) !important;
}
.leaflet-popup-tip { background: var(--slate) !important; }
.leaflet-popup-content { margin: 1rem !important; }
.leaflet-popup-content h4 {
  font-family: var(--font-display);
  color: var(--teal);
  font-size: 0.95rem;
  margin-bottom: 0.35rem;
}
.leaflet-popup-content p {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin: 0;
}
.leaflet-popup-close-button { color: var(--text-muted) !important; top: 6px !important; right: 8px !important; }

/* ----------------------------------------------------------------
   Publications
   ---------------------------------------------------------------- */
#publications { background: var(--slate); }

.pub-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.pub-card {
  background: var(--navy);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  display: grid;
  grid-template-columns: 40px 1fr;
  gap: 1rem;
  align-items: start;
  transition: border-color var(--transition), transform var(--transition);
}

.pub-card:hover {
  border-color: var(--border-teal);
  transform: translateY(-3px);
}

.pub-icon {
  width: 40px;
  height: 40px;
  border-radius: 8px;
  background: rgba(0,191,166,0.1);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--teal);
  flex-shrink: 0;
}

.pub-venue {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--copper);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-bottom: 0.4rem;
}

.pub-content h3 {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.35;
  margin-bottom: 0.6rem;
}

.pub-content p {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.65;
}

/* ----------------------------------------------------------------
   Education
   ---------------------------------------------------------------- */
#education { background: var(--navy); }

.edu-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.25rem;
  margin-bottom: 3rem;
}

.edu-card {
  background: var(--slate);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  border-left: 3px solid var(--teal);
  transition: border-color var(--transition), transform var(--transition);
}

.edu-card:hover { transform: translateY(-3px); }

.edu-degree {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.3;
  margin-bottom: 0.5rem;
}

.edu-institution {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--teal);
  margin-bottom: 0.3rem;
}

.edu-meta {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.04em;
  margin-bottom: 0.4rem;
}

.edu-note {
  font-size: 0.78rem;
  color: var(--copper);
  font-style: italic;
}

.credentials-row { padding-top: 1rem; }

.cred-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.cred-tag {
  font-size: 0.82rem;
  padding: 0.4rem 0.9rem;
  background: var(--slate);
  border: 1px solid var(--border);
  border-radius: 40px;
  color: var(--text-muted);
}

.cred-highlight {
  border-color: var(--copper);
  color: var(--copper);
}

/* ----------------------------------------------------------------
   Values
   ---------------------------------------------------------------- */
#values { background: var(--slate); }

.values-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
}

.value-card {
  background: var(--navy);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem 1.75rem;
  cursor: default;
  transition: border-color var(--transition), transform var(--transition), box-shadow var(--transition);
  position: relative;
  overflow: hidden;
}

.value-card::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(to right, var(--teal), var(--copper));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition-slow);
}

.value-card:hover,
.value-card:focus {
  border-color: var(--border-teal);
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(0,0,0,0.3);
  outline: none;
}

.value-card:hover::after,
.value-card:focus::after { transform: scaleX(1); }

.value-icon {
  font-size: 1.1rem;
  color: var(--teal);
  margin-bottom: 1rem;
  display: block;
}

.value-name {
  font-family: var(--font-display);
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.75rem;
}

.value-desc {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.7;
}

/* ----------------------------------------------------------------
   Contact
   ---------------------------------------------------------------- */
#contact {
  background: var(--navy);
  text-align: center;
}

.contact-inner {
  max-width: 640px;
  margin-inline: auto;
}

.contact-inner h2 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 900;
  color: var(--text);
  line-height: 1.1;
  margin-bottom: 1.25rem;
}

.contact-sub {
  color: var(--text-muted);
  font-size: 1.05rem;
  line-height: 1.7;
  margin-bottom: 2.5rem;
}

.cta-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  background: var(--teal);
  color: var(--navy);
  font-weight: 700;
  font-size: 1rem;
  padding: 0.9rem 2rem;
  border-radius: 50px;
  transition: background var(--transition), transform var(--transition), box-shadow var(--transition);
  margin-bottom: 2.5rem;
}

.cta-btn:hover {
  background: var(--copper);
  color: var(--text);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(212, 129, 42, 0.3);
}

.contact-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1.5rem;
}

.contact-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.9rem;
  color: var(--text-muted);
  transition: color var(--transition);
}

.contact-link:hover { color: var(--teal); }

/* ----------------------------------------------------------------
   Footer
   ---------------------------------------------------------------- */
#footer {
  background: var(--navy);
  border-top: 1px solid var(--border);
  padding: 2rem 0;
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.footer-brand {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
}

.footer-tagline {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--teal);
  letter-spacing: 0.1em;
}

.footer-copy {
  font-size: 0.8rem;
  color: var(--text-faint);
}

/* ----------------------------------------------------------------
   Back to top
   ---------------------------------------------------------------- */
.back-to-top {
  position: fixed;
  right: 1.5rem;
  bottom: 1.5rem;
  z-index: 900;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--teal);
  color: var(--navy);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 16px rgba(0,191,166,0.3);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity var(--transition), transform var(--transition), visibility var(--transition), background var(--transition);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: none;
}

.back-to-top:hover { background: var(--copper); color: var(--text); }

/* ----------------------------------------------------------------
   Responsive: Tablet
   ---------------------------------------------------------------- */
@media (max-width: 900px) {

  .about-grid { grid-template-columns: 1fr; gap: 2.5rem; }
  .about-photo-frame { position: static; max-width: 280px; margin-inline: auto; }

  .timeline::before { left: 20px; }
  .timeline-item {
    grid-template-columns: 40px 1fr;
    grid-template-rows: auto;
  }
  .timeline-node { grid-column: 1; grid-row: 1; margin-top: 1.1rem; }
  .timeline-card { grid-column: 2; grid-row: 1; }
  .timeline-item[data-side="left"] .timeline-card { grid-column: 2; grid-row: 1; }
  .timeline-item[data-side="left"] .timeline-node { grid-column: 1; grid-row: 1; }

}

/* ----------------------------------------------------------------
   Responsive: Mobile
   ---------------------------------------------------------------- */
@media (max-width: 640px) {

  .nav-hamburger { display: flex; }

  .nav-links {
    display: none;
    position: fixed;
    top: var(--nav-h);
    left: 0; right: 0;
    background: rgba(10, 22, 40, 0.97);
    backdrop-filter: blur(12px);
    flex-direction: column;
    padding: 1.5rem 1rem 2rem;
    gap: 0.25rem;
    border-bottom: 1px solid var(--border);
  }

  .nav-links.open { display: flex; }
  .nav-links a { font-size: 1rem; padding: 0.6rem 0.75rem; }
  .nav-cta { margin-top: 0.5rem; }

  .hero-name { font-size: clamp(3rem, 16vw, 5rem); }

  .stat-row { grid-template-columns: 1fr 1fr; gap: 1rem; }

  .footer-inner { flex-direction: column; text-align: center; }

  .contact-links { flex-direction: column; align-items: center; }
}