/* ============================================================
   CSS Custom Properties
   ============================================================ */
:root {
  /* Colors */
  --color-bg:          #f5f6f7;
  --color-bg-card:     #ffffff;
  --color-bg-section:  #eff1f3;
  --color-border:      #d8dee5;
  --color-text:        #111111;
  --color-text-muted:  #4b5563;
  --color-accent:      #1c4d8d;
  --color-accent-hover:#163f72;

  /* Typography */
  --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont,
               'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  /* Spacing scale */
  --sp-1:  0.25rem;
  --sp-2:  0.5rem;
  --sp-3:  0.75rem;
  --sp-4:  1rem;
  --sp-5:  1.25rem;
  --sp-6:  1.5rem;
  --sp-8:  2rem;
  --sp-12: 3rem;
  --sp-16: 4rem;
  --sp-20: 5rem;
  --sp-24: 6rem;

  /* Layout */
  --container-max: 72rem;
  --prose-max:     48rem;

  /* Transitions */
  --transition: 200ms ease;
}

[data-theme="dark"] {
  --color-bg:          #111111;
  --color-bg-card:     #1a1d21;
  --color-bg-section:  #1a1d21;
  --color-border:      #333333;
  --color-text:        #e0e0e0;
  --color-text-muted:  #9ca3af;
  --color-accent:      #4d9fff;
  --color-accent-hover:#79baff;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--color-bg);
  color: var(--color-text);
  font-size: 1rem;
  line-height: 1.6;
  transition: background-color var(--transition), color var(--transition);
}

img {
  max-width: 100%;
  display: block;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--color-accent-hover);
}

ul {
  list-style: none;
}

/* ============================================================
   Layout Primitives
   ============================================================ */
.container {
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--sp-6);
}

.prose {
  max-width: var(--prose-max);
  margin-inline: auto;
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--sp-8);
}

/* ============================================================
   Navigation
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  transition: background-color var(--transition);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 3.5rem;
}

.nav-logo {
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.nav-logo:hover {
  color: var(--color-accent);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--sp-6);
}

.nav-links a {
  color: var(--color-text-muted);
  font-size: 1rem;
  font-weight: 500;
  transition: color var(--transition);
}

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

/* Download Resume nav button */
.btn-nav {
  background-color: var(--color-accent);
  color: #fff !important;
  padding: 0.55rem 1.1rem;
  border-radius: 6px;
  font-size: 0.95rem;
  font-weight: 500;
  white-space: nowrap;
  transition: background-color var(--transition);
}

.btn-nav:hover {
  background-color: var(--color-accent-hover);
  color: #fff !important;
}

/* Theme toggle */
.theme-toggle {
  background: none;
  border: none;
  border-radius: 8px;
  padding: 6px;
  cursor: pointer;
  color: var(--color-text-muted);
  line-height: 0;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  transition: background-color var(--transition), color var(--transition);
}

.theme-toggle:hover {
  background-color: var(--color-bg-section);
  color: var(--color-text);
}

[data-theme="dark"] .theme-toggle:hover {
  background-color: var(--color-bg-card);
}

/* Mobile hamburger */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--sp-2);
  color: var(--color-text);
  flex-direction: column;
  gap: 5px;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background-color: currentColor;
  transition: transform var(--transition), opacity var(--transition);
}

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

/* ============================================================
   Hero Section
   ============================================================ */
.hero {
  padding-block: var(--sp-20) var(--sp-16);
}

.hero-inner {
  display: flex;
  align-items: center;
  gap: var(--sp-16);
}

.hero-text {
  flex: 1;
  min-width: 0;
}

.hero-label {
  font-size: 0.875rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-4);
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3.75rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.026em;
  color: var(--color-text);
  margin-bottom: var(--sp-4);
}

.hero-divider {
  width: 4.25rem;
  height: 4px;
  background-color: var(--color-accent);
  margin-bottom: var(--sp-6);
  border-radius: 2px;
}

.hero-body {
  max-width: 38rem;
  font-size: 1.125rem;
  color: var(--color-text-muted);
  line-height: 1.67;
  margin-bottom: var(--sp-4);
}

.hero-body strong {
  color: var(--color-text);
  font-weight: 700;
}

/* "Available for new projects" badge */
.hero-status {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--color-text-muted);
  font-size: 1rem;
  margin-bottom: var(--sp-6);
}

.hero-status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: #10b981;
  flex-shrink: 0;
  box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.2);
}

/* Social icon buttons row */
.hero-social-links {
  display: flex;
  gap: 4px;
  align-items: center;
  flex-wrap: wrap;
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  color: var(--color-text-muted);
  flex-shrink: 0;
  transition: background-color var(--transition), color var(--transition);
}

.icon-btn:hover {
  background-color: var(--color-bg-section);
  color: var(--color-text);
}

[data-theme="dark"] .icon-btn:hover {
  background-color: var(--color-bg-card);
}

/* Profile photo */
.hero-photo-wrap {
  flex-shrink: 0;
}

.hero-photo {
  width: 200px;
  height: 200px;
  border-radius: 50%;
  object-fit: cover;
  border: 3.8px solid var(--color-border);
  display: block;
}

/* ============================================================
   Buttons
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
  padding: 0.6rem 1.25rem;
  border-radius: 0.375rem;
  font-weight: 500;
  font-size: 0.95rem;
  transition: all var(--transition);
  cursor: pointer;
  border: 1px solid transparent;
}

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

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

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

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

/* ============================================================
   Section Bands (full-width colored sections)
   ============================================================ */
.section-band {
  padding-block: var(--sp-16);
}

.section-band--alt {
  background-color: var(--color-bg-section);
}

/* ============================================================
   Legacy Section (inner pages)
   ============================================================ */
.section {
  padding-block: var(--sp-16);
  border-top: 1px solid var(--color-border);
}

/* ============================================================
   Section Headings
   ============================================================ */
.section-heading {
  font-size: 1.125rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--color-text);
  margin-bottom: var(--sp-8);
}

.section-more {
  margin-top: var(--sp-6);
  font-size: 0.9rem;
}

.section-more a {
  color: #025acd;
  font-weight: 500;
  display: inline-flex;
  align-items: center;
  gap: 3px;
}

.section-more a:hover {
  color: #0148a3;
}

/* ============================================================
   Project Cards
   ============================================================ */
.project-card {
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: 0.5rem;
  overflow: hidden;
  transition: border-color var(--transition), transform var(--transition);
  display: flex;
  flex-direction: column;
}

.project-card:hover {
  border-color: var(--color-text-muted);
  transform: translateY(-2px);
}

.project-card-img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  background-color: var(--color-border);
}

.project-card-img-placeholder {
  width: 100%;
  aspect-ratio: 16 / 9;
  background-color: var(--color-bg-section);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  font-size: 0.8rem;
  letter-spacing: 0.05em;
}

[data-theme="dark"] .project-card-img-placeholder {
  background-color: var(--color-border);
}

.project-card-body {
  padding: var(--sp-6);
  flex: 1;
  display: flex;
  flex-direction: column;
}

.project-card-title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: var(--sp-3);
  color: var(--color-text);
}

.project-card-desc {
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  line-height: 1.6;
  flex: 1;
  margin-bottom: var(--sp-4);
}

.project-card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-2);
  margin-bottom: var(--sp-4);
}

.tag {
  font-size: 0.75rem;
  font-weight: 400;
  padding: 0.2rem 0.55rem;
  background-color: #ebf4ff;
  border: 1px solid var(--color-border);
  border-radius: 0.25rem;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
}

[data-theme="dark"] .tag {
  background-color: rgba(77, 159, 255, 0.08);
}

.project-card-links {
  display: flex;
  gap: var(--sp-4);
  font-size: 0.875rem;
  margin-top: auto;
}

.project-card-links a {
  color: #025acd;
  font-weight: 500;
  display: inline-flex;
  align-items: center;
  gap: 3px;
}

.project-card-links a:hover {
  color: #0148a3;
}

/* ============================================================
   Writing List (homepage Latest Writing)
   ============================================================ */
.writing-list {
  display: flex;
  flex-direction: column;
  gap: 1.625rem;
  margin-bottom: var(--sp-6);
}

.writing-item {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  border-radius: 4px;
  padding: 12px;
  transition: background-color var(--transition);
}

.writing-item:hover {
  background-color: var(--color-bg-section);
}

[data-theme="dark"] .writing-item:hover {
  background-color: var(--color-bg-card);
}

.writing-thumb {
  width: 90px;
  height: 64px;
  flex-shrink: 0;
  background-color: var(--color-border);
  border-radius: 6px;
}

.writing-meta {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  min-width: 0;
}

.writing-date {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-variant-numeric: tabular-nums;
}

.writing-title {
  font-size: 1rem;
  font-weight: 500;
  color: var(--color-text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  transition: color var(--transition);
}

.writing-title:hover {
  color: var(--color-accent);
}

.writing-arrow {
  flex-shrink: 0;
  color: #025acd;
  display: inline-flex;
  align-items: center;
  padding: 0 4px;
  transition: color var(--transition);
}

.writing-arrow:hover {
  color: #0148a3;
}

/* ============================================================
   Post List (blog index — legacy)
   ============================================================ */
.post-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.post-list-item {
  display: grid;
  grid-template-columns: 7rem 1fr auto;
  align-items: baseline;
  gap: var(--sp-4);
  padding-block: var(--sp-4);
  border-bottom: 1px solid var(--color-border);
  transition: background-color var(--transition);
}

.post-list-item:first-child {
  border-top: 1px solid var(--color-border);
}

.post-list-date {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.post-list-title {
  font-size: 0.95rem;
  color: var(--color-text);
  font-weight: 500;
  transition: color var(--transition);
}

.post-list-title:hover {
  color: var(--color-accent);
}

.post-list-read {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  white-space: nowrap;
}

/* ============================================================
   Page Header (inner pages)
   ============================================================ */
.page-header {
  padding-block: var(--sp-16) var(--sp-8);
}

.page-title {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: var(--sp-3);
}

.page-subtitle {
  font-size: 1.05rem;
  color: var(--color-text-muted);
  max-width: 38rem;
}

/* ============================================================
   About Page
   ============================================================ */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--sp-6);
  margin-bottom: var(--sp-8);
}

.skills-group h3 {
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-3);
}

.skills-group ul {
  display: flex;
  flex-direction: column;
  gap: var(--sp-2);
}

.skills-group li {
  font-size: 0.9rem;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: var(--sp-2);
}

.skills-group li::before {
  content: '·';
  color: var(--color-accent);
  font-weight: 700;
}

.timeline {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.timeline-item {
  display: grid;
  grid-template-columns: 8rem 1fr;
  gap: var(--sp-6);
  padding-block: var(--sp-6);
  border-bottom: 1px solid var(--color-border);
}

.timeline-item:first-child {
  border-top: 1px solid var(--color-border);
}

.timeline-period {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  font-variant-numeric: tabular-nums;
  padding-top: 0.15rem;
  line-height: 1.5;
}

.timeline-role {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: var(--sp-1);
}

.timeline-company {
  font-size: 0.9rem;
  color: var(--color-accent);
  margin-bottom: var(--sp-2);
}

.timeline-desc {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ============================================================
   About Page — Bio prose
   ============================================================ */
.bio p {
  font-size: 1.05rem;
  line-height: 1.8;
  max-width: 44rem;
}

.bio p + p {
  margin-top: var(--sp-5);
}

/* ============================================================
   Contact Page
   ============================================================ */
.contact-links {
  display: flex;
  flex-direction: column;
  gap: var(--sp-4);
}

.contact-link-item {
  display: flex;
  align-items: center;
  gap: var(--sp-4);
  padding: var(--sp-5) var(--sp-6);
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: 0.5rem;
  transition: border-color var(--transition);
  color: var(--color-text);
}

.contact-link-item:hover {
  border-color: var(--color-text-muted);
  color: var(--color-text);
}

.contact-link-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  width: 2rem;
  color: var(--color-text-muted);
}

.contact-link-label {
  font-weight: 500;
  font-size: 0.95rem;
}

.contact-link-value {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-top: 0.1rem;
}

/* ============================================================
   Photography Page
   ============================================================ */
.photo-grid {
  columns: 2;
  column-gap: var(--sp-6);
}

.photo-item {
  break-inside: avoid;
  margin-bottom: var(--sp-6);
  border-radius: 0.375rem;
  overflow: hidden;
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border);
}

.photo-item img {
  width: 100%;
  display: block;
  transition: transform 300ms ease;
}

.photo-item:hover img {
  transform: scale(1.02);
}

.photo-item figcaption {
  padding: var(--sp-3) var(--sp-4);
  font-size: 0.82rem;
  color: var(--color-text-muted);
  line-height: 1.4;
}

/* ============================================================
   Footer
   ============================================================ */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding-block: var(--sp-8);
  margin-top: 0;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-4);
  flex-wrap: wrap;
}

.footer-copy {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.footer-links {
  display: flex;
  gap: var(--sp-6);
}

.footer-links a {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

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

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 640px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 3.5rem;
    left: 0;
    right: 0;
    background-color: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    align-items: flex-start;
    padding: var(--sp-4) var(--sp-6);
    gap: var(--sp-4);
  }

  .nav-links.open {
    display: flex;
  }

  .nav-toggle {
    display: flex;
  }

  .hero {
    padding-block: var(--sp-12) var(--sp-12);
  }

  .hero-inner {
    flex-direction: column-reverse;
    align-items: flex-start;
    gap: var(--sp-8);
  }

  .hero-photo {
    width: 96px;
    height: 96px;
  }

  .hero-body {
    font-size: 1rem;
  }

  .writing-title {
    white-space: normal;
  }

  .post-list-item {
    grid-template-columns: 1fr;
    gap: var(--sp-1);
  }

  .post-list-read {
    display: none;
  }

  .timeline-item {
    grid-template-columns: 1fr;
    gap: var(--sp-2);
  }

  .photo-grid {
    columns: 1;
  }
}

@media (max-width: 1024px) {
  .container {
    padding-inline: var(--sp-4);
  }
}