/* ================================================
   Eugene Nam — Personal Site
   style.css
   ================================================ */

/* ------------------------------------------------
   1. Variables
   ------------------------------------------------ */
:root {
  --navy-900: #0A1628;
  --navy-800: #0D1B35;
  --navy-700: #122040;
  --navy-600: #1A2D52;
  --navy-500: #1E3A6E;
  --navy-400: #2E5491;
  --navy-300: #4A78C4;
  --navy-200: #7AAAE8;
  --navy-100: #C4D8F5;

  --white:    #FFFFFF;
  --gray-50:  #F7F8FC;
  --gray-100: #F0F2F8;
  --gray-200: #E2E6F0;
  --gray-300: #C8D0E0;
  --gray-400: #9AA5BE;
  --gray-500: #6B7A99;
  --gray-600: #4A5568;
  --green:    #22C55E;

  /* Semantic — Light mode */
  --bg:              var(--white);
  --bg-alt:          var(--gray-50);
  --surface:         var(--white);
  --border:          var(--gray-200);
  --text:            var(--navy-800);
  --text-secondary:  var(--gray-600);
  --text-muted:      var(--gray-400);
  --accent:          var(--navy-500);
  --accent-hover:    var(--navy-700);
  --accent-soft:     #EDF2FC;
  --btn-bg:          var(--navy-800);
  --btn-text:        var(--white);
  --btn-border:      var(--navy-800);
  --btn-outline-text: var(--navy-800);
  --nav-bg:          rgba(255, 255, 255, 0.9);
  --nav-border:      var(--gray-200);

  --shadow-sm: 0 1px 3px rgba(10, 22, 40, 0.08);
  --shadow:    0 2px 8px rgba(10, 22, 40, 0.10), 0 1px 3px rgba(10, 22, 40, 0.06);
  --shadow-lg: 0 8px 32px rgba(10, 22, 40, 0.14);

  --max-width:    1080px;
  --section-gap:  clamp(60px, 8vw, 100px);
  --nav-height:   64px;
  --radius:       12px;
  --radius-sm:    8px;
  --radius-full:  9999px;
  --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --t: 0.2s ease;
}

[data-theme="dark"] {
  --bg:              #0A1628;
  --bg-alt:          #0D1E36;
  --surface:         #122040;
  --border:          #1A2D52;
  --text:            #EEF2FA;
  --text-secondary:  #A0B3D0;
  --text-muted:      #5A7099;
  --accent:          var(--navy-200);
  --accent-hover:    var(--white);
  --accent-soft:     #1A2D52;
  --btn-bg:          #1E3A6E;
  --btn-text:        var(--white);
  --btn-border:      #7AAAE8;
  --btn-outline-text: #7AAAE8;
  --nav-bg:          rgba(10, 22, 40, 0.92);
  --nav-border:      #1A2D52;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow:    0 2px 8px rgba(0,0,0,0.4), 0 1px 3px rgba(0,0,0,0.2);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.5);
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background-color: var(--bg);
  transition: background-color 0.3s ease, color 0.3s ease;
}

a            { color: inherit; text-decoration: none; }
ul, ol       { list-style: none; }
img          { display: block; max-width: 100%; }
button       { cursor: pointer; border: none; background: none; font-family: var(--font); }

section[id]  { scroll-margin-top: var(--nav-height); }

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

section { padding: var(--section-gap) 0; }

#about, #projects, #contact { background-color: var(--bg-alt); }

/* ------------------------------------------------
   4. Typography
   ------------------------------------------------ */
h1 {
  font-size: clamp(2.8rem, 6vw, 4.5rem);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.03em;
  color: var(--text);
}

h2 {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h3 {
  font-size: 1.15rem;
  font-weight: 600;
  line-height: 1.3;
}

p { line-height: 1.7; }

/* ------------------------------------------------
   5. Navigation
   ------------------------------------------------ */
#navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  height: var(--nav-height);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  background-color: var(--nav-bg);
  border-bottom: 1px solid transparent;
  transition: border-color var(--t), box-shadow var(--t);
}

#navbar.scrolled {
  border-bottom-color: var(--nav-border);
  box-shadow: var(--shadow-sm);
}

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

.nav-logo {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
  flex-shrink: 0;
}

.nav-links {
  display: flex;
  gap: 28px;
  flex: 1;
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--t);
}

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

.nav-actions {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: auto;
}

/* Theme toggle */
.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  transition: color var(--t), background-color var(--t);
}

.theme-toggle:hover {
  color: var(--text);
  background-color: var(--accent-soft);
}

[data-theme="light"] .icon-moon { display: none; }
[data-theme="light"] .icon-sun  { display: block; }
[data-theme="dark"]  .icon-sun  { display: none; }
[data-theme="dark"]  .icon-moon { display: block; }

/* Hamburger */
.hamburger {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
  color: var(--text);
}

.hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background-color: currentColor;
  border-radius: 1px;
  transition: transform 0.25s ease, opacity 0.25s ease;
}

.hamburger.active span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.hamburger.active span:nth-child(2) { opacity: 0; }
.hamburger.active span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* Mobile menu */
.mobile-menu {
  position: fixed;
  top: var(--nav-height);
  left: 0; right: 0;
  z-index: 99;
  background-color: var(--bg);
  border-bottom: 1px solid var(--border);
  padding: 12px 24px 24px;
  display: none;
  flex-direction: column;
  box-shadow: var(--shadow);
}

.mobile-menu.open { display: flex; }

.mobile-menu a {
  display: block;
  padding: 12px 0;
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border);
  transition: color var(--t);
}

.mobile-menu li:last-child a { border-bottom: none; }
.mobile-menu a:hover          { color: var(--text); }

/* ------------------------------------------------
   6. Buttons
   ------------------------------------------------ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 600;
  transition: all var(--t);
  white-space: nowrap;
  cursor: pointer;
}

.btn-primary {
  background-color: var(--btn-bg);
  color: var(--btn-text);
}

.btn-primary:hover {
  opacity: 0.85;
  transform: translateY(-1px);
}

.btn-outline {
  background-color: transparent;
  color: var(--btn-outline-text);
  border: 1.5px solid var(--btn-border);
}

.btn-outline:hover {
  background-color: var(--accent-soft);
  transform: translateY(-1px);
}

/* ------------------------------------------------
   7. Section Utilities
   ------------------------------------------------ */
.section-header   { margin-bottom: 52px; }
.section-cta      { margin-top: 48px; }

.section-label {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--navy-400);
  margin-bottom: 10px;
}

[data-theme="dark"] .section-label { color: var(--navy-200); }

.section-description {
  margin-top: 12px;
  color: var(--text-secondary);
  font-size: 1.05rem;
  max-width: 560px;
}

/* ------------------------------------------------
   8. Hero
   ------------------------------------------------ */
#hero {
  min-height: 100svh;
  display: flex;
  align-items: center;
  padding-top: var(--nav-height);
  padding-bottom: 80px;
  background-image: radial-gradient(var(--border) 1px, transparent 1px);
  background-size: 28px 28px;
}

.hero-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 64px;
  align-items: center;
}

.hero-text {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.status-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 7px 14px;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  font-size: 0.83rem;
  font-weight: 500;
  color: var(--text-secondary);
  width: fit-content;
  box-shadow: var(--shadow-sm);
}

.status-dot {
  width: 8px;
  height: 8px;
  background-color: var(--green);
  border-radius: 50%;
  flex-shrink: 0;
  animation: pulse 2.4s ease infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50%       { opacity: 0.55; transform: scale(0.8); }
}

.hero-subtitle {
  font-size: clamp(1rem, 2vw, 1.2rem);
  font-weight: 500;
  color: var(--text-secondary);
  margin-top: -6px;
}

.hero-tagline {
  font-size: clamp(1rem, 1.8vw, 1.1rem);
  color: var(--text-secondary);
  line-height: 1.7;
}

.hero-cta {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 4px;
}

.hero-photo {
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-photo img {
  width: 300px;
  height: 300px;
  object-fit: cover;
  border-radius: 50%;
  border: 4px solid var(--border);
  box-shadow: var(--shadow-lg);
}

/* ------------------------------------------------
   9. About
   ------------------------------------------------ */
.about-layout {
  display: grid;
  grid-template-columns: 1fr 240px;
  gap: 56px;
  align-items: start;
}

.about-text {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.about-text p {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.8;
}

.about-stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}

.stat-card {
  padding: 18px 14px;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-align: center;
  box-shadow: var(--shadow-sm);
}

.stat-number {
  font-size: 1.7rem;
  font-weight: 800;
  color: var(--text);
  letter-spacing: -0.03em;
  line-height: 1;
  margin-bottom: 6px;
}

.stat-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  line-height: 1.4;
  font-weight: 500;
}

/* ------------------------------------------------
   10. Experience / Timeline
   ------------------------------------------------ */
.timeline {
  display: flex;
  flex-direction: column;
}

.timeline-item {
  border-left: 2px solid var(--border);
  padding: 0 0 52px 32px;
  position: relative;
}

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

/* Dot on the line */
.timeline-item::before {
  content: '';
  position: absolute;
  left: -5px;
  top: 5px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--navy-400);
  border: 2px solid var(--bg);
  box-shadow: 0 0 0 1px var(--border);
}

[data-theme="dark"] .timeline-item::before {
  background-color: var(--navy-200);
}

.timeline-date {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  letter-spacing: 0.04em;
  margin-bottom: 10px;
}

.timeline-header {
  display: flex;
  align-items: baseline;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 4px;
}

.timeline-company {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
}

.timeline-formerly {
  font-size: 0.83rem;
  color: var(--text-muted);
  font-weight: 400;
}

.timeline-role {
  font-size: 0.92rem;
  color: var(--text-secondary);
  font-weight: 500;
  margin-bottom: 8px;
}

.timeline-progression {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--navy-400);
  background-color: var(--accent-soft);
  padding: 3px 10px;
  border-radius: var(--radius-full);
  margin-bottom: 14px;
  letter-spacing: 0.02em;
}

[data-theme="dark"] .timeline-progression {
  color: var(--navy-200);
  background-color: var(--accent-soft);
}

.timeline-bullets {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.timeline-bullets li {
  font-size: 0.93rem;
  color: var(--text-secondary);
  padding-left: 18px;
  position: relative;
  line-height: 1.65;
}

.timeline-bullets li::before {
  content: '—';
  position: absolute;
  left: 0;
  color: var(--text-muted);
  font-size: 0.8rem;
}

/* ------------------------------------------------
   11. AI Projects
   ------------------------------------------------ */
.projects-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.project-card {
  padding: 32px;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 14px;
  transition: box-shadow var(--t), transform var(--t);
}

.project-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.project-upcoming { opacity: 0.65; }
.project-upcoming:hover { opacity: 1; }

.project-status {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--green);
}

.project-status.muted { color: var(--text-muted); }

.project-card h3 { color: var(--text); }

.project-card p {
  font-size: 0.93rem;
  color: var(--text-secondary);
  line-height: 1.7;
  flex: 1;
}

.project-tools {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tool-tag {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 10px;
  background-color: var(--accent-soft);
  color: var(--navy-400);
  border-radius: var(--radius-full);
}

[data-theme="dark"] .tool-tag { color: var(--navy-200); }

.tool-tag.muted {
  background-color: var(--bg-alt);
  color: var(--text-muted);
}

.project-link {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--navy-400);
  transition: color var(--t);
  margin-top: 4px;
}

[data-theme="dark"] .project-link { color: var(--navy-200); }
.project-link:hover { color: var(--accent-hover); }

/* ------------------------------------------------
   12. Writing
   ------------------------------------------------ */
.posts-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

/* Skeleton */
.post-skeleton {
  height: 220px;
  background: linear-gradient(
    90deg,
    var(--border) 0%,
    var(--bg-alt) 50%,
    var(--border) 100%
  );
  background-size: 200% 100%;
  animation: shimmer 1.6s ease infinite;
  border-radius: var(--radius);
}

@keyframes shimmer {
  0%   { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* Post card (injected by JS) */
.post-card {
  padding: 28px;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 10px;
  color: inherit;
  transition: box-shadow var(--t), transform var(--t);
}

.post-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.post-date {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  letter-spacing: 0.04em;
}

.post-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.4;
  flex: 1;
}

.post-excerpt {
  font-size: 0.86rem;
  color: var(--text-secondary);
  line-height: 1.65;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.post-read-more {
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--navy-400);
  margin-top: 4px;
}

[data-theme="dark"] .post-read-more { color: var(--navy-200); }

.posts-fallback {
  grid-column: 1 / -1;
  text-align: center;
  padding: 48px 0;
  color: var(--text-secondary);
  font-size: 1rem;
}

.posts-fallback a {
  color: var(--navy-400);
  font-weight: 600;
  text-decoration: underline;
}

[data-theme="dark"] .posts-fallback a { color: var(--navy-200); }

/* ------------------------------------------------
   13. Contact
   ------------------------------------------------ */
#contact { text-align: center; }

.contact-inner {
  max-width: 520px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
}

.contact-inner h2 { font-size: clamp(2rem, 5vw, 3.5rem); }

.contact-inner > p {
  font-size: 1rem;
  color: var(--text-secondary);
}

.contact-email {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
  border-bottom: 2px solid var(--border);
  padding-bottom: 2px;
  transition: color var(--t), border-color var(--t);
}

.contact-email:hover {
  color: var(--navy-400);
  border-color: var(--navy-400);
}

[data-theme="dark"] .contact-email:hover {
  color: var(--navy-200);
  border-color: var(--navy-200);
}

.contact-social {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  justify-content: center;
}

.contact-social a {
  font-size: 0.88rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--t);
}

.contact-social a:hover { color: var(--text); }

.contact-social .dot {
  color: var(--border);
  font-size: 1.1rem;
  line-height: 1;
  user-select: none;
}

/* ------------------------------------------------
   14. Footer
   ------------------------------------------------ */
footer {
  padding: 24px 0;
  border-top: 1px solid var(--border);
  background-color: var(--bg);
}

footer p {
  font-size: 0.82rem;
  color: var(--text-muted);
  text-align: center;
}

footer a {
  color: var(--text-secondary);
  transition: color var(--t);
}

footer a:hover { color: var(--text); }

/* ------------------------------------------------
   15. Responsive — Tablet (≤ 900px)
   ------------------------------------------------ */
@media (max-width: 900px) {
  .nav-links  { display: none; }
  .hamburger  { display: flex; }

  .hero-layout {
    grid-template-columns: 1fr;
    gap: 36px;
    text-align: center;
  }

  .hero-photo         { order: -1; }
  .hero-photo img     { width: 200px; height: 200px; }
  .hero-cta           { justify-content: center; }
  .status-badge       { margin: 0 auto; }

  .about-layout       { grid-template-columns: 1fr; }
  .about-stats        { grid-template-columns: repeat(4, 1fr); }

  .projects-grid      { grid-template-columns: 1fr; }
  .posts-grid         { grid-template-columns: 1fr; }
}

/* ------------------------------------------------
   16. Responsive — Mobile (≤ 600px)
   ------------------------------------------------ */
@media (max-width: 600px) {
  .hero-photo img     { width: 160px; height: 160px; }
  .about-stats        { grid-template-columns: 1fr 1fr; }
  .hero-tagline br    { display: none; }
}

/* ------------------------------------------------
   17. Accessibility
   ------------------------------------------------ */
@media (prefers-reduced-motion: reduce) {
  .status-dot    { animation: none; }
  .post-skeleton { animation: none; }
  html           { scroll-behavior: auto; }
}

:focus-visible {
  outline: 2px solid var(--navy-300);
  outline-offset: 3px;
  border-radius: 4px;
}