/* =============================================================================
   Design Tokens
   ============================================================================= */
:root {
  --c-bg:         #ffffff;
  --c-bg-alt:     #f8fafc;
  --c-border:     #e2e8f0;
  --c-text:       #0f172a;
  --c-muted:      #64748b;
  --c-accent:     #2563eb;
  --c-accent-h:   #1d4ed8;

  --nav-h:        64px;
  --max-w:        860px;
  --r:            6px;
  --ease:         cubic-bezier(0.4, 0, 0.2, 1);
  --dur:          150ms;
}

[data-theme="dark"] {
  --c-bg:         #0c0c0c;
  --c-bg-alt:     #161616;
  --c-border:     #3a3a3a;
  --c-text:       #f1f5f9;
  --c-muted:      #a1a1aa;
  --c-accent:     #3b82f6;
  --c-accent-h:   #60a5fa;
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  font-size: 15px;
  line-height: 1.7;
  background: var(--c-bg);
  color: var(--c-text);
  transition: background 200ms var(--ease), color 200ms var(--ease);
}

img    { display: block; max-width: 100%; }
a      { color: inherit; text-decoration: none; }
ul     { list-style: none; }
button { font-family: inherit; }

/* =============================================================================
   Layout
   ============================================================================= */
.container {
  width: 100%;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 24px;
}

section {
  padding: 96px 0;
}

#hero {
  padding-top: calc(var(--nav-h) + 96px);
}

/* =============================================================================
   Navigation
   ============================================================================= */
#nav {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  height: var(--nav-h);
  border-bottom: 1px solid transparent;
  transition:
    background var(--dur) var(--ease),
    border-color var(--dur) var(--ease);
}

#nav.scrolled,
#nav.menu-open {
  background: var(--c-bg);
  border-bottom-color: var(--c-border);
}

.nav-inner {
  display: flex;
  align-items: center;
  gap: 32px;
  height: 100%;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 24px;
}

.nav-logo {
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--c-text);
  margin-right: auto;
  transition: opacity var(--dur);
}
.nav-logo:hover { opacity: 0.65; }

.nav-links {
  display: flex;
  gap: 28px;
}
.nav-links a {
  font-size: 14px;
  color: var(--c-muted);
  transition: color var(--dur);
}
.nav-links a:hover,
.nav-links a.active { color: var(--c-text); }

.nav-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.theme-toggle,
.nav-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: transparent;
  border: 1px solid var(--c-border);
  border-radius: var(--r);
  color: var(--c-muted);
  cursor: pointer;
  transition: color var(--dur), border-color var(--dur);
}
.theme-toggle:hover,
.nav-toggle:hover {
  color: var(--c-text);
  border-color: var(--c-muted);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
}
.nav-toggle span {
  display: block;
  width: 18px;
  height: 1.5px;
  background: currentColor;
  border-radius: 2px;
  transform-origin: center;
  transition: transform 200ms var(--ease), opacity 200ms;
}

#nav.menu-open .nav-toggle span:nth-child(1) { transform: translateY(6.5px) rotate(45deg);  }
#nav.menu-open .nav-toggle span:nth-child(2) { opacity: 0; transform: scaleX(0); }
#nav.menu-open .nav-toggle span:nth-child(3) { transform: translateY(-6.5px) rotate(-45deg); }

/* =============================================================================
   Section Label
   ============================================================================= */
.section-label {
  font-size: 18px;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--c-text);
  margin-bottom: 48px;
}

/* =============================================================================
   Hero
   ============================================================================= */
#hero .container { max-width: 720px; }

.hero-label {
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--c-accent);
  margin-bottom: 20px;
  animation: fadeUp 500ms var(--ease) both;
}

#hero h1 {
  font-size: clamp(2.8rem, 7vw, 4.5rem);
  font-weight: 600;
  letter-spacing: -0.04em;
  line-height: 1.0;
  margin-bottom: 24px;
  animation: fadeUp 500ms var(--ease) 80ms both;
}

.hero-desc {
  font-size: 17px;
  line-height: 1.6;
  color: var(--c-muted);
  max-width: 520px;
  margin-bottom: 36px;
  animation: fadeUp 500ms var(--ease) 160ms both;
}

.hero-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 40px;
  animation: fadeUp 500ms var(--ease) 240ms both;
}

.hero-socials {
  display: flex;
  gap: 18px;
  animation: fadeUp 500ms var(--ease) 320ms both;
}
.hero-socials a {
  font-size: 19px;
  color: var(--c-muted);
  transition: color var(--dur);
}
.hero-socials a:hover { color: var(--c-text); }

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(18px); }
  to   { opacity: 1; transform: none; }
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 9px 18px;
  border-radius: var(--r);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  border: 1px solid transparent;
  transition:
    background var(--dur),
    border-color var(--dur),
    color var(--dur),
    opacity var(--dur);
}

.btn-primary {
  background: var(--c-accent);
  color: #fff;
}
.btn-primary:hover { background: var(--c-accent-h); }

.btn-outline {
  background: transparent;
  border-color: var(--c-border);
  color: var(--c-text);
}
.btn-outline:hover { border-color: var(--c-muted); }

/* =============================================================================
   About
   ============================================================================= */
.about-grid {
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 48px;
  align-items: start;
}

.about-photo img {
  width: 260px;
  height: 260px;
  object-fit: cover;
  border-radius: var(--r);
  border: 1px solid var(--c-border);
}

.about-text p {
  color: var(--c-muted);
  margin-bottom: 16px;
  font-size: 15px;
}
.about-text p:last-of-type { margin-bottom: 0; }

.about-details {
  margin-top: 28px;
  padding-top: 28px;
  border-top: 1px solid var(--c-border);
  display: flex;
  flex-direction: column;
  gap: 10px;
  font-size: 14px;
  color: var(--c-muted);
}

.detail-label {
  display: inline-block;
  min-width: 82px;
  font-weight: 500;
  color: var(--c-text);
  margin-right: 8px;
}

/* =============================================================================
   Timeline
   ============================================================================= */
.timeline {
  position: relative;
  padding-left: 20px;
  border-left: 1px solid var(--c-border);
}

.timeline-item {
  position: relative;
  padding: 0 0 56px 36px;
}
.timeline-item:last-child { padding-bottom: 0; }

.timeline-item::before {
  content: '';
  position: absolute;
  top: 7px;
  left: -4px;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--c-accent);
  border: 2px solid var(--c-bg);
  box-shadow: 0 0 0 1px var(--c-accent);
}

.timeline-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}

.timeline-period {
  font-size: 13px;
  font-weight: 500;
  color: var(--c-muted);
}

.timeline-loc {
  font-size: 12px;
  color: var(--c-muted);
  padding: 2px 9px;
  border: 1px solid var(--c-border);
  border-radius: 100px;
}

.timeline-body h3 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 4px;
}

.timeline-org {
  font-size: 14px;
  color: var(--c-accent);
  margin-bottom: 14px;
}

.timeline-body ul {
  display: flex;
  flex-direction: column;
  gap: 7px;
  margin-bottom: 16px;
}

.timeline-body li {
  font-size: 14px;
  color: var(--c-muted);
  padding-left: 14px;
  position: relative;
}
.timeline-body li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 11px;
  width: 5px;
  height: 1px;
  background: var(--c-muted);
  opacity: 0.5;
}

.timeline-note {
  font-size: 14px;
  color: var(--c-muted);
  margin-bottom: 12px;
}

/* =============================================================================
   Tag Row — shared component
   ============================================================================= */
.tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.tag-row span {
  font-size: 12px;
  padding: 3px 9px;
  border: 1px solid var(--c-border);
  border-radius: 100px;
  color: var(--c-muted);
  transition: border-color var(--dur), color var(--dur);
}

/* =============================================================================
   Skills
   ============================================================================= */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(190px, 1fr));
  gap: 36px;
}

.skill-group h3 {
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--c-muted);
  margin-bottom: 12px;
}

.skill-group .tag-row span:hover {
  border-color: var(--c-accent);
  color: var(--c-accent);
}

/* =============================================================================
   Projects
   ============================================================================= */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
}

.project-card {
  padding: 24px;
  border: 1px solid var(--c-border);
  border-radius: var(--r);
  transition: border-color var(--dur);
}
.project-card:hover { border-color: var(--c-muted); }

.project-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: 10px;
}
.project-top h3 {
  font-size: 15px;
  font-weight: 600;
}

.project-links {
  display: flex;
  gap: 12px;
  flex-shrink: 0;
}
.project-links a {
  font-size: 15px;
  color: var(--c-muted);
  transition: color var(--dur);
}
.project-links a:hover { color: var(--c-text); }

.project-card > p {
  font-size: 14px;
  color: var(--c-muted);
  line-height: 1.6;
  margin-bottom: 16px;
}

/* =============================================================================
   Additional Info
   ============================================================================= */
.additional-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
}

.sub-label {
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--c-muted);
  margin-bottom: 20px;
}

.link-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.link-list a {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 14px;
  color: var(--c-muted);
  transition: color var(--dur);
}
.link-list a:hover { color: var(--c-accent); }
.link-list a i { font-size: 11px; }

.lang-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.lang-list li {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 14px;
}
.lang-badge {
  font-size: 12px;
  padding: 2px 9px;
  border: 1px solid var(--c-border);
  border-radius: 100px;
  color: var(--c-muted);
}

/* =============================================================================
   Contact
   ============================================================================= */
.contact-intro {
  font-size: 16px;
  color: var(--c-muted);
  margin-bottom: 40px;
}

.contact-grid {
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 48px;
  align-items: start;
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.contact-link {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 14px;
  color: var(--c-muted);
  transition: color var(--dur);
}
.contact-link:hover { color: var(--c-text); }
.contact-link i {
  width: 16px;
  text-align: center;
}

#contact-form {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

#contact-form input,
#contact-form textarea {
  width: 100%;
  padding: 10px 13px;
  background: var(--c-bg-alt);
  border: 1px solid var(--c-border);
  border-radius: var(--r);
  color: var(--c-text);
  font-family: inherit;
  font-size: 14px;
  outline: none;
  resize: none;
  transition: border-color var(--dur);
  -webkit-appearance: none;
}
#contact-form input:focus,
#contact-form textarea:focus { border-color: var(--c-accent); }

#contact-form input::placeholder,
#contact-form textarea::placeholder {
  color: var(--c-muted);
  opacity: 0.5;
}

#submit-btn {
  align-self: flex-start;
  padding: 10px 22px;
  background: var(--c-accent);
  color: #fff;
  border: none;
  border-radius: var(--r);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--dur), opacity var(--dur);
}
#submit-btn:hover    { background: var(--c-accent-h); }
#submit-btn:disabled { opacity: 0.55; cursor: not-allowed; }
#submit-btn.success  { background: #16a34a; }
#submit-btn.error    { background: #dc2626; }

/* =============================================================================
   Footer
   ============================================================================= */
footer {
  padding: 32px 0;
  border-top: 1px solid var(--c-border);
}

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

.footer-name {
  font-size: 13px;
  color: var(--c-muted);
}

.footer-socials {
  display: flex;
  gap: 16px;
}
.footer-socials a {
  font-size: 16px;
  color: var(--c-muted);
  transition: color var(--dur);
}
.footer-socials a:hover { color: var(--c-text); }

/* =============================================================================
   Scroll Reveal
   ============================================================================= */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 500ms var(--ease), transform 500ms var(--ease);
}

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

/* =============================================================================
   Responsive
   ============================================================================= */
@media (max-width: 680px) {
  .nav-toggle { display: flex; }

  /* Fullscreen overlay */
  .nav-links {
    display: flex;
    position: fixed;
    inset: var(--nav-h) 0 0 0;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 8px;
    background: var(--c-bg);
    opacity: 0;
    pointer-events: none;
    transition: opacity 300ms var(--ease);
    z-index: 99;
  }

  .nav-links li {
    transform: translateY(16px);
    opacity: 0;
    transition:
      transform 350ms var(--ease),
      opacity 350ms var(--ease);
  }

  .nav-links a {
    font-size: 26px;
    font-weight: 600;
    letter-spacing: -0.02em;
    color: var(--c-muted);
    padding: 12px 24px;
    display: block;
    transition: color var(--dur);
  }
  .nav-links a:hover,
  .nav-links a.active { color: var(--c-text); }

  #nav.menu-open .nav-links {
    opacity: 1;
    pointer-events: auto;
  }

  #nav.menu-open .nav-links li {
    opacity: 1;
    transform: none;
  }

  /* Stagger link entrance */
  #nav.menu-open .nav-links li:nth-child(1) { transition-delay: 60ms;  }
  #nav.menu-open .nav-links li:nth-child(2) { transition-delay: 120ms; }
  #nav.menu-open .nav-links li:nth-child(3) { transition-delay: 180ms; }
  #nav.menu-open .nav-links li:nth-child(4) { transition-delay: 240ms; }
  #nav.menu-open .nav-links li:nth-child(5) { transition-delay: 300ms; }

  section { padding: 72px 0; }
  #hero   { padding-top: calc(var(--nav-h) + 72px); }

  .about-grid {
    grid-template-columns: 1fr;
    gap: 28px;
  }
  .about-photo { display: block; }
  .about-photo img { width: 160px; height: 160px; margin-left: 0; margin-right: auto; }

  .projects-grid   { grid-template-columns: 1fr; }
  .additional-grid { grid-template-columns: 1fr; gap: 36px; }

  .contact-grid { grid-template-columns: 1fr; gap: 32px; }
  .form-row     { grid-template-columns: 1fr; }
}

@media (max-width: 400px) {
  .container { padding: 0 16px; }
  section    { padding: 56px 0; }
  #hero h1   { font-size: 2.4rem; }
}