/* ============================================================================
   CSS CUSTOM PROPERTIES (DESIGN TOKENS)
   ========================================================================== */

:root {
  /* Color Palette - Light Mode */
  --color-bg: #ffffff;
  --color-bg-alt: #f8f9fa;
  --color-text: #1a1a1a;
  --color-text-muted: #6c757d;
  --color-primary: #0066cc;
  --color-primary-hover: #0052a3;
  --color-secondary: #6c757d;
  --color-secondary-hover: #565e64;
  --color-border: #dee2e6;
  --color-border-light: #e9ecef;
  --color-shadow: rgba(0, 0, 0, 0.1);

  /* Status Colors */
  --color-active: #28a745;
  --color-maintained: #007bff;
  --color-paused: #ffc107;
  --color-archived: #6c757d;

  /* Typography */
  --font-family-base: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-family-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --font-size-base: 1rem;
  --font-size-sm: 0.875rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --line-height-base: 1.6;
  --line-height-heading: 1.2;

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

  /* Layout */
  --container-max-width: 1200px;
  --container-narrow-width: 800px;
  --container-padding: var(--space-lg);

  /* Border Radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;

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

/* Dark Mode */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #1a1a1a;
    --color-bg-alt: #2d2d2d;
    --color-text: #e9ecef;
    --color-text-muted: #adb5bd;
    --color-primary: #4da3ff;
    --color-primary-hover: #80bcff;
    --color-secondary: #adb5bd;
    --color-secondary-hover: #ced4da;
    --color-border: #495057;
    --color-border-light: #343a40;
    --color-shadow: rgba(0, 0, 0, 0.3);

    --color-active: #40c463;
    --color-maintained: #58a6ff;
    --color-paused: #f0ad4e;
    --color-archived: #8b949e;
  }
}

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

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  margin: 0;
  padding: 0;
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  line-height: var(--line-height-base);
  color: var(--color-text);
  background-color: var(--color-bg);
}

/* ============================================================================
   TYPOGRAPHY
   ========================================================================== */

h1, h2, h3, h4, h5, h6 {
  margin: 0 0 var(--space-md);
  font-weight: 700;
  line-height: var(--line-height-heading);
  color: var(--color-text);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.75rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
  margin: 0 0 var(--space-md);
}

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

a:hover {
  color: var(--color-primary-hover);
  text-decoration: underline;
}

code {
  font-family: var(--font-family-mono);
  font-size: 0.875em;
  padding: 0.125rem 0.25rem;
  background-color: var(--color-bg-alt);
  border-radius: var(--radius-sm);
}

pre {
  padding: var(--space-md);
  background-color: var(--color-bg-alt);
  border-radius: var(--radius-md);
  overflow-x: auto;
}

pre code {
  padding: 0;
  background: none;
}

ul, ol {
  margin: 0 0 var(--space-md);
  padding-left: var(--space-xl);
}

/* ============================================================================
   SKIP LINK (Accessibility)
   ========================================================================== */

.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  padding: var(--space-sm) var(--space-md);
  background: var(--color-primary);
  color: white;
  text-decoration: none;
  z-index: 100;
}

.skip-link:focus {
  top: 0;
}

/* ============================================================================
   HEADER & NAVIGATION
   ========================================================================== */

.site-header {
  background-color: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 50;
}

.header-inner {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: var(--space-md) var(--container-padding);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-lg);
}

.site-logo {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
}

.site-logo:hover {
  color: var(--color-primary);
  text-decoration: none;
}

.main-nav ul {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: var(--space-lg);
}

.main-nav a {
  color: var(--color-text);
  text-decoration: none;
  padding: var(--space-sm) 0;
  border-bottom: 2px solid transparent;
  transition: border-color var(--transition-fast), color var(--transition-fast);
}

.main-nav a:hover,
.main-nav a.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
  text-decoration: none;
}

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

.main-content {
  min-height: calc(100vh - 300px);
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: var(--space-2xl) var(--container-padding);
}

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

.hero {
  padding: var(--space-3xl) 0;
  text-align: center;
  border-bottom: 1px solid var(--color-border);
  margin-bottom: var(--space-2xl);
}

.hero-title {
  font-size: 3rem;
  margin-bottom: var(--space-md);
}

.hero-tagline {
  font-size: var(--font-size-xl);
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.hero-bio {
  font-size: var(--font-size-lg);
  max-width: 700px;
  margin: 0 auto var(--space-xl);
  color: var(--color-text-muted);
}

.hero-cta {
  display: flex;
  gap: var(--space-md);
  justify-content: center;
  flex-wrap: wrap;
}

/* ============================================================================
   PAGE LAYOUT
   ========================================================================== */

.page {
  max-width: var(--container-max-width);
  margin: 0 auto;
}

.page-narrow {
  max-width: var(--container-narrow-width);
}

.page-header {
  margin-bottom: var(--space-2xl);
  padding-bottom: var(--space-lg);
  border-bottom: 1px solid var(--color-border);
}

.page-title {
  margin-bottom: var(--space-sm);
}

.page-lead {
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  margin: 0;
}

.page-content {
  margin-bottom: var(--space-2xl);
}

/* ============================================================================
   PROJECTS - CATEGORY ACCORDION (Details/Summary)
   ========================================================================== */

.projects-container {
  margin-bottom: var(--space-2xl);
}

.project-category {
  margin-bottom: var(--space-xl);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.category-header {
  padding: var(--space-lg);
  background-color: var(--color-bg-alt);
  cursor: pointer;
  list-style: none;
  user-select: none;
  transition: background-color var(--transition-fast);
}

.category-header::-webkit-details-marker {
  display: none;
}

.category-header::marker {
  display: none;
}

.category-header:hover {
  background-color: var(--color-border-light);
}

.category-header h2 {
  margin: 0 0 var(--space-xs);
  display: inline-block;
}

.category-header::before {
  content: "▶";
  display: inline-block;
  margin-right: var(--space-sm);
  transition: transform var(--transition-base);
}

.project-category[open] .category-header::before {
  transform: rotate(90deg);
}

.category-description {
  color: var(--color-text-muted);
  margin: var(--space-xs) 0;
  font-size: var(--font-size-sm);
}

.category-count {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-left: var(--space-sm);
}

.category-body {
  padding: var(--space-lg);
  background-color: var(--color-bg);
}

/* ============================================================================
   PROJECT ITEM
   ========================================================================== */

.project-item {
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-bg);
  transition: box-shadow var(--transition-fast);
}

.project-item:hover {
  box-shadow: 0 4px 8px var(--color-shadow);
}

.project-item:last-child {
  margin-bottom: 0;
}

.project-header {
  margin-bottom: var(--space-md);
}

.project-name {
  margin: 0 0 var(--space-xs);
  font-size: 1.5rem;
}

.project-tagline {
  color: var(--color-text-muted);
  margin: 0 0 var(--space-sm);
  font-size: var(--font-size-base);
}

.project-status {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  font-size: var(--font-size-sm);
  font-weight: 600;
  border-radius: var(--radius-lg);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.status-active {
  background-color: rgba(40, 167, 69, 0.1);
  color: var(--color-active);
  border: 1px solid var(--color-active);
}

.status-maintained {
  background-color: rgba(0, 123, 255, 0.1);
  color: var(--color-maintained);
  border: 1px solid var(--color-maintained);
}

.status-paused {
  background-color: rgba(255, 193, 7, 0.1);
  color: var(--color-paused);
  border: 1px solid var(--color-paused);
}

.status-archived {
  background-color: rgba(108, 117, 125, 0.1);
  color: var(--color-archived);
  border: 1px solid var(--color-archived);
}

.project-body {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.project-summary {
  margin: 0;
  line-height: 1.6;
}

.project-links {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

/* ============================================================================
   PROJECT SUBREPOS
   ========================================================================== */

.project-subrepos {
  padding: var(--space-md);
  background-color: var(--color-bg-alt);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--color-primary);
}

.subrepos-title {
  margin: 0 0 var(--space-sm);
  font-size: var(--font-size-base);
  font-weight: 600;
}

.subrepos-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.subrepos-list li {
  padding: var(--space-xs) 0;
}

.subrepos-list a {
  font-weight: 500;
}

.subrepo-note {
  margin-left: var(--space-sm);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

.subrepo-note::before {
  content: "—";
  margin-right: var(--space-xs);
}

/* ============================================================================
   TAGS
   ========================================================================== */

.tag {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  font-size: var(--font-size-sm);
  background-color: var(--color-bg-alt);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  white-space: nowrap;
}

/* ============================================================================
   BUTTONS
   ========================================================================== */

.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  font-size: var(--font-size-base);
  font-weight: 600;
  text-align: center;
  text-decoration: none;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn:hover {
  text-decoration: none;
  transform: translateY(-1px);
  box-shadow: 0 4px 8px var(--color-shadow);
}

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

.btn-primary:hover {
  background-color: var(--color-primary-hover);
  color: white;
}

.btn-secondary {
  background-color: var(--color-secondary);
  color: white;
}

.btn-secondary:hover {
  background-color: var(--color-secondary-hover);
  color: white;
}

.btn-sm {
  padding: 0.5rem 1rem;
  font-size: var(--font-size-sm);
}

/* ============================================================================
   POST STYLES
   ========================================================================== */

.post {
  max-width: var(--container-narrow-width);
  margin: 0 auto;
}

.post-header {
  margin-bottom: var(--space-2xl);
  padding-bottom: var(--space-lg);
  border-bottom: 1px solid var(--color-border);
}

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

.post-meta {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
}

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

.post-content {
  margin-bottom: var(--space-2xl);
}

.post-content img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-md);
}

.post-footer {
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border);
}

/* ============================================================================
   ARTICLE PREVIEW CARDS (Writing Page)
   ========================================================================== */

.writing-note {
  background: var(--color-bg-alt);
  border-left: 3px solid var(--color-primary);
  padding: var(--space-md) var(--space-lg);
  margin-bottom: var(--space-2xl);
  font-size: var(--font-size-sm);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.articles-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2xl);
}

.articles-empty {
  text-align: center;
  padding: var(--space-3xl) 0;
}

.articles-empty p {
  font-size: var(--font-size-xl);
  color: var(--color-text-muted);
}

.article-preview {
  padding: var(--space-xl);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-bg);
  transition: box-shadow var(--transition-fast), border-color var(--transition-fast);
}

.article-preview:hover {
  box-shadow: 0 4px 12px var(--color-shadow);
  border-color: var(--color-primary);
}

.article-preview-header {
  margin-bottom: var(--space-lg);
  padding-bottom: var(--space-md);
  border-bottom: 1px solid var(--color-border-light);
}

.article-preview-title {
  margin: 0 0 var(--space-sm);
  font-size: 1.5rem;
}

.article-preview-title a {
  color: var(--color-text);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.article-preview-title a:hover {
  color: var(--color-primary);
  text-decoration: none;
}

.article-preview-meta {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  flex-wrap: wrap;
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
}

.article-preview-tags {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

.article-preview-excerpt {
  margin-bottom: var(--space-lg);
  line-height: var(--line-height-base);
}

.article-preview-excerpt p {
  margin-bottom: var(--space-md);
}

.article-preview-excerpt p:last-child {
  margin-bottom: 0;
}

.article-preview-footer {
  padding-top: var(--space-md);
  border-top: 1px solid var(--color-border-light);
}

.article-read-more {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  font-weight: 600;
  color: var(--color-primary);
  text-decoration: none;
  transition: gap var(--transition-fast);
}

.article-read-more:hover {
  gap: var(--space-sm);
  text-decoration: none;
}

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

.site-footer {
  background-color: var(--color-bg-alt);
  border-top: 1px solid var(--color-border);
  margin-top: var(--space-3xl);
  padding: var(--space-2xl) 0 var(--space-lg);
}

.footer-inner {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 var(--container-padding);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--space-xl);
  margin-bottom: var(--space-xl);
}

.footer-section h4 {
  margin-bottom: var(--space-md);
  font-size: var(--font-size-base);
}

.footer-section p {
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
}

.social-links {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.social-links a {
  color: var(--color-text);
  font-size: var(--font-size-sm);
}

.footer-bottom {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: var(--space-lg) var(--container-padding) 0;
  border-top: 1px solid var(--color-border);
  text-align: center;
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
}

.footer-bottom p {
  margin: var(--space-sm) 0;
}

/* ============================================================================
   UTILITY CLASSES
   ========================================================================== */

.text-center {
  text-align: center;
}

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

.text-sm {
  font-size: var(--font-size-sm);
}

.mt-1 { margin-top: var(--space-md); }
.mt-2 { margin-top: var(--space-lg); }
.mb-1 { margin-bottom: var(--space-md); }
.mb-2 { margin-bottom: var(--space-lg); }

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

@media (max-width: 768px) {
  .hero-title {
    font-size: 2rem;
  }

  .header-inner {
    flex-direction: column;
    align-items: flex-start;
  }

  .main-nav ul {
    flex-direction: column;
    gap: var(--space-sm);
  }

  .main-nav a {
    display: block;
  }

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

  .main-content {
    padding: var(--space-lg) var(--container-padding);
  }

  h1 { font-size: 2rem; }
  h2 { font-size: 1.75rem; }
  h3 { font-size: 1.5rem; }

  .footer-inner {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  :root {
    --container-padding: var(--space-md);
  }

  .hero-title {
    font-size: 1.75rem;
  }

  .hero-cta {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }
}