/* ============================================================
   VARIABLES & THEME
   ============================================================ */

:root {
  --font-family: 'Work Sans', system-ui, -apple-system, sans-serif;

  /* Spacing */
  --space-xs:  0.25rem;
  --space-sm:  0.5rem;
  --space-md:  1rem;
  --space-lg:  1.5rem;
  --space-xl:  2.5rem;
  --space-2xl: 4rem;
  --space-3xl: 6rem;

  /* Layout */
  --max-width: 680px;
  --header-height: 64px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;

  /* Accent */
  --accent: #6b8cae;
  --accent-hover: #8aadc8;
}

/* DARK THEME (default) */
[data-theme="dark"] {
  --bg:           #1a1a1a;
  --bg-elevated:  #222222;
  --border:       #2e2e2e;
  --text-primary: #e8e8e8;
  --text-secondary: #888888;
  --text-muted:   #555555;
  --tag-bg:       #252525;
  --tag-text:     #999999;
  --hover-bg:     #202020;
}

/* LIGHT THEME */
[data-theme="light"] {
  --bg:           #f5f5f5;
  --bg-elevated:  #efefef;
  --border:       #e0e0e0;
  --text-primary: #2a2a2a;
  --text-secondary: #666666;
  --text-muted:   #aaaaaa;
  --tag-bg:       #e8e8e8;
  --tag-text:     #777777;
  --hover-bg:     #ebebeb;
}

/* ============================================================
   RESET & BASE
   ============================================================ */

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg);
  color: var(--text-primary);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color var(--transition-base), color var(--transition-base);
  min-height: 100vh;
}

a {
  color: inherit;
  text-decoration: none;
}

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

ul, ol {
  list-style: none;
}

button {
  cursor: pointer;
  background: none;
  border: none;
  font-family: inherit;
}

/* ============================================================
   LAYOUT UTILITIES
   ============================================================ */

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

@media (max-width: 600px) {
  .container {
    padding: 0 var(--space-lg);
  }
}

/* ============================================================
   HEADER
   ============================================================ */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-height);
  background-color: var(--bg);
  border-bottom: 1px solid transparent;
  transition: border-color var(--transition-base), background-color var(--transition-base), backdrop-filter var(--transition-base);
}

.site-header.scrolled {
  border-color: var(--border);
  background-color: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

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

@media (max-width: 600px) {
  .header-inner {
    padding: 0 var(--space-lg);
  }
}

.site-logo {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.01em;
  transition: color var(--transition-fast);
}

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

.site-nav {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.nav-link {
  font-size: 0.9rem;
  font-weight: 400;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
  position: relative;
}

.nav-link:hover,
.nav-link.active {
  color: var(--text-primary);
}

/* Theme Toggle */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  color: var(--text-secondary);
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

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

.theme-toggle:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.theme-icon {
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Show moon in dark mode, sun in light mode */
[data-theme="dark"] .theme-icon--sun  { display: none; }
[data-theme="dark"] .theme-icon--moon { display: flex; }
[data-theme="light"] .theme-icon--moon { display: none; }
[data-theme="light"] .theme-icon--sun  { display: flex; }

/* ============================================================
   MAIN CONTENT
   ============================================================ */

.main-content {
  padding-top: var(--space-2xl);
}

/* ============================================================
   SECTIONS
   ============================================================ */

.section {
  padding: var(--space-3xl) 0;
}

.section + .section {
  padding-top: 0;
}

.section--hero {
  padding-top: var(--space-2xl);
  padding-bottom: var(--space-3xl);
}

.section-heading {
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: var(--space-2xl);
}

/* ============================================================
   HERO
   ============================================================ */

.hero-name {
  font-size: clamp(2rem, 6vw, 2.8rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  color: var(--text-primary);
  margin-bottom: var(--space-lg);
}

.hero-bio {
  font-size: 1.05rem;
  font-weight: 400;
  color: var(--text-secondary);
  line-height: 1.75;
  max-width: 560px;
  margin-bottom: var(--space-xl);
}

.social-links {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
  flex-wrap: wrap;
}

.social-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.social-link:hover {
  color: var(--accent);
}

.social-link svg {
  flex-shrink: 0;
}

/* ============================================================
   POST CARDS
   ============================================================ */

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

.post-card {
  display: block;
  padding: var(--space-xl) 0;
  border-bottom: 1px solid var(--border);
  transition: none;
}

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

.post-card-inner {
  transition: opacity var(--transition-fast);
}

.post-card:hover .post-card-inner {
  opacity: 0.72;
}

.post-card-meta {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-sm);
  flex-wrap: wrap;
}

.post-date {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 400;
}

.post-read-time {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 400;
}

.post-read-time::before {
  content: '·';
  margin-right: var(--space-md);
}

.post-tags {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  flex-wrap: wrap;
  margin-left: auto;
}

.post-tag {
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--tag-text);
  background-color: var(--tag-bg);
  padding: 2px 8px;
  border-radius: 4px;
  letter-spacing: 0.02em;
}

.post-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  line-height: 1.35;
  margin-bottom: var(--space-sm);
  transition: color var(--transition-fast);
}

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

.post-excerpt {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

/* View all link */
.view-all-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: var(--space-xl);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--accent);
  transition: color var(--transition-fast), gap var(--transition-fast);
}

.view-all-link:hover {
  color: var(--accent-hover);
  gap: 10px;
}

/* Loading state */
.posts-loading {
  color: var(--text-muted);
  font-size: 0.875rem;
  padding: var(--space-xl) 0;
}

/* ============================================================
   PROJECTS
   ============================================================ */

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

.project-item {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  padding: var(--space-lg) 0;
  border-bottom: 1px solid var(--border);
  gap: var(--space-lg);
  transition: opacity var(--transition-fast);
}

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

.project-left {
  flex: 1;
  min-width: 0;
}

.project-name-wrap {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: 4px;
}

.project-name {
  font-size: 0.975rem;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

.project-link-icon {
  display: inline-flex;
  align-items: center;
  color: var(--text-muted);
  transition: color var(--transition-fast);
  flex-shrink: 0;
}

.project-item-link:hover .project-name {
  color: var(--accent);
}

.project-item-link:hover .project-link-icon {
  color: var(--accent);
}

.project-item-link {
  display: block;
  transition: opacity var(--transition-fast);
}

.project-description {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.55;
}

.project-year {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 400;
  white-space: nowrap;
  flex-shrink: 0;
}

.project-active-badge {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 0.7rem;
  font-weight: 500;
  color: #5a9e7a;
  background: rgba(90, 158, 122, 0.12);
  padding: 2px 8px;
  border-radius: 20px;
  margin-left: var(--space-sm);
  letter-spacing: 0.02em;
}

.project-active-badge::before {
  content: '';
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: #5a9e7a;
  flex-shrink: 0;
}

/* ============================================================
   CONTACT SECTION
   ============================================================ */

.section--contact {
  padding-bottom: var(--space-3xl);
}

.contact-text {
  font-size: 0.975rem;
  color: var(--text-secondary);
  line-height: 1.75;
  max-width: 500px;
  margin-bottom: var(--space-lg);
}

.contact-email {
  font-size: 1rem;
  font-weight: 500;
  color: var(--accent);
  transition: color var(--transition-fast);
}

.contact-email:hover {
  color: var(--accent-hover);
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* ============================================================
   FOOTER
   ============================================================ */

.site-footer {
  border-top: 1px solid var(--border);
  padding: var(--space-xl) 0;
  background-color: var(--bg);
}

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

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

.footer-links {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.footer-link {
  font-size: 0.8rem;
  color: var(--text-muted);
  transition: color var(--transition-fast);
}

.footer-link:hover {
  color: var(--accent);
}

/* ============================================================
   BLOG POST PAGE
   ============================================================ */

.post-header {
  padding-top: var(--space-2xl);
  padding-bottom: var(--space-xl);
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-bottom: var(--space-2xl);
  transition: color var(--transition-fast);
}

.back-link:hover {
  color: var(--accent);
}

.back-link svg {
  transition: transform var(--transition-fast);
}

.back-link:hover svg {
  transform: translateX(-3px);
}

.post-header-title {
  font-size: clamp(1.6rem, 4vw, 2.2rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.2;
  color: var(--text-primary);
  margin-bottom: var(--space-lg);
}

.post-header-meta {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  flex-wrap: wrap;
  color: var(--text-muted);
  font-size: 0.875rem;
}

.post-header-tags {
  display: flex;
  gap: var(--space-xs);
  margin-top: var(--space-md);
  flex-wrap: wrap;
}

/* Post Body */
.post-body {
  padding-bottom: var(--space-3xl);
}

.post-content {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--text-secondary);
}

.post-content p {
  margin-bottom: var(--space-lg);
}

.post-content h2 {
  font-size: 1.35rem;
  font-weight: 650;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  margin-top: var(--space-2xl);
  margin-bottom: var(--space-md);
  line-height: 1.3;
}

.post-content h3 {
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text-primary);
  margin-top: var(--space-xl);
  margin-bottom: var(--space-sm);
  line-height: 1.4;
}

.post-content ul,
.post-content ol {
  margin-bottom: var(--space-lg);
  padding-left: var(--space-xl);
}

.post-content ul { list-style: disc; }
.post-content ol { list-style: decimal; }

.post-content li {
  margin-bottom: var(--space-sm);
}

.post-content strong {
  font-weight: 600;
  color: var(--text-primary);
}

.post-content em {
  font-style: italic;
}

.post-content a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-color: transparent;
  transition: text-decoration-color var(--transition-fast);
}

.post-content a:hover {
  text-decoration-color: var(--accent);
}

.post-content blockquote {
  border-left: 3px solid var(--border);
  padding-left: var(--space-lg);
  margin: var(--space-xl) 0;
  color: var(--text-secondary);
  font-style: italic;
}

.post-content code {
  font-family: 'SF Mono', 'Fira Code', 'Fira Mono', monospace;
  font-size: 0.875em;
  background: var(--tag-bg);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--text-primary);
}

.post-content pre {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: var(--space-lg);
  overflow-x: auto;
  margin: var(--space-xl) 0;
}

.post-content pre code {
  background: none;
  padding: 0;
  font-size: 0.875rem;
}

.post-divider {
  border: none;
  border-top: 1px solid var(--border);
  margin: var(--space-2xl) 0;
}

/* Share buttons */
.post-share {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  flex-wrap: wrap;
  margin-bottom: var(--space-2xl);
}

.post-share-label {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-muted);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.share-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
  background: var(--tag-bg);
  border: 1px solid var(--border);
  padding: 6px 14px;
  border-radius: 6px;
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

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

.share-btn.copied {
  color: #5a9e7a;
}

/* Post navigation */
.post-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
}

.post-nav-item {
  display: block;
  padding: var(--space-lg);
  border: 1px solid var(--border);
  border-radius: 8px;
  transition: border-color var(--transition-fast), background-color var(--transition-fast);
}

.post-nav-item:hover {
  border-color: var(--accent);
  background-color: var(--bg-elevated);
}

.post-nav-item--next {
  text-align: right;
}

.post-nav-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  display: block;
  margin-bottom: 4px;
}

.post-nav-title {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-primary);
  line-height: 1.4;
}

@media (max-width: 500px) {
  .post-nav {
    grid-template-columns: 1fr;
  }
  .post-nav-item--next {
    text-align: left;
  }
}

/* ============================================================
   WRITING ARCHIVE PAGE
   ============================================================ */

.archive-header {
  padding-top: var(--space-2xl);
  padding-bottom: var(--space-xl);
}

.archive-title {
  font-size: clamp(1.6rem, 4vw, 2.2rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  color: var(--text-primary);
  margin-bottom: var(--space-md);
}

.archive-subtitle {
  font-size: 0.975rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

/* Tag filter */
.tag-filter {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  flex-wrap: wrap;
  padding: var(--space-lg) 0;
  border-bottom: 1px solid var(--border);
  margin-bottom: var(--space-xl);
}

.tag-filter-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-right: var(--space-xs);
}

.tag-filter-btn {
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--tag-text);
  background: var(--tag-bg);
  padding: 4px 10px;
  border-radius: 4px;
  transition: color var(--transition-fast), background-color var(--transition-fast);
  letter-spacing: 0.02em;
}

.tag-filter-btn:hover,
.tag-filter-btn.active {
  color: var(--text-primary);
  background: var(--accent);
  color: #ffffff;
}

.archive-posts {
  padding-bottom: var(--space-3xl);
}

/* ============================================================
   FOCUS STYLES (Accessibility)
   ============================================================ */

a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 3px;
}

/* ============================================================
   ANIMATIONS
   ============================================================ */

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

.fade-in {
  animation: fadeInUp 0.4s ease both;
}

.fade-in-delay-1 { animation-delay: 0.05s; }
.fade-in-delay-2 { animation-delay: 0.1s; }
.fade-in-delay-3 { animation-delay: 0.15s; }
.fade-in-delay-4 { animation-delay: 0.2s; }

/* Respect reduced motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

/* ============================================================
   RESPONSIVE
   ============================================================ */

@media (max-width: 640px) {
  .section {
    padding: var(--space-2xl) 0;
  }

  .post-card-meta {
    flex-wrap: wrap;
    gap: var(--space-xs);
  }

  .post-tags {
    margin-left: 0;
    margin-top: var(--space-xs);
    width: 100%;
  }

  .project-item {
    flex-direction: column;
    gap: var(--space-xs);
  }

  .project-year {
    margin-top: 2px;
  }

  .tag-filter {
    gap: var(--space-xs);
  }

  .post-header-meta {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-xs);
  }

  .footer-inner {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-md);
  }
}