/* ========================================
   CSS Variables for Theming
   ======================================== */
:root {
  /* Light mode colors */
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-code: #f6f8fa;
  --text-primary: #24292f;
  --text-secondary: #57606a;
  --text-link: #0969da;
  --text-link-hover: #0550ae;
  --border-color: #d0d7de;
  --shadow: rgba(0, 0, 0, 0.1);
  --accent: #0969da;

  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans", Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --line-height-base: 1.6;
  --line-height-heading: 1.25;
}

/* Dark mode */
[data-theme="dark"] {
  --bg-primary: #0d1117;
  --bg-secondary: #161b22;
  --bg-code: #161b22;
  --text-primary: #c9d1d9;
  --text-secondary: #8b949e;
  --text-link: #58a6ff;
  --text-link-hover: #79c0ff;
  --border-color: #30363d;
  --shadow: rgba(0, 0, 0, 0.4);
  --accent: #58a6ff;
}

/* Respect user's system preference if no manual selection */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-code: #161b22;
    --text-primary: #c9d1d9;
    --text-secondary: #8b949e;
    --text-link: #58a6ff;
    --text-link-hover: #79c0ff;
    --border-color: #30363d;
    --shadow: rgba(0, 0, 0, 0.4);
    --accent: #58a6ff;
  }
}

/* ========================================
   Base Styles
   ======================================== */
body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-sans);
  line-height: var(--line-height-base);
  transition: background-color 0.3s ease, color 0.3s ease;
}

a {
  color: var(--text-link);
  transition: color 0.2s ease;
}

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

code {
  font-family: var(--font-mono);
  background-color: var(--bg-code);
  padding: 0.2em 0.4em;
  border-radius: 3px;
  font-size: 0.9em;
}

pre {
  background-color: var(--bg-code);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 16px;
  overflow-x: auto;
  line-height: 1.45;
  position: relative;
}

pre code {
  background-color: transparent;
  padding: 0;
  border-radius: 0;
  font-size: 0.85em;
}

.copy-code-button {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 4px 12px;
  font-size: 0.75em;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  cursor: pointer;
  color: var(--text-secondary);
  transition: all 0.2s ease;
  opacity: 0;
}

pre:hover .copy-code-button {
  opacity: 1;
}

.copy-code-button:hover {
  background: var(--accent);
  color: var(--bg-primary);
  border-color: var(--accent);
}

hr {
  margin-top: 30px;
  margin-bottom: 20px;
  border: 0;
  border-top: 1px solid var(--border-color);
}

/* ========================================
   Dark Mode Toggle
   ======================================== */
.theme-toggle {
  position: fixed;
  top: 20px;
  right: 20px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 50%;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  z-index: 1000;
  transition: all 0.3s ease;
  box-shadow: 0 2px 8px var(--shadow);
}

.theme-toggle:hover {
  transform: scale(1.1);
  box-shadow: 0 4px 12px var(--shadow);
}

.theme-toggle svg {
  width: 20px;
  height: 20px;
  fill: var(--text-primary);
}

.theme-toggle .sun-icon {
  display: none;
}

.theme-toggle .moon-icon {
  display: block;
}

[data-theme="dark"] .theme-toggle .sun-icon {
  display: block;
}

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

/* ========================================
   Reading Progress Bar
   ======================================== */
.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  background: var(--bg-secondary);
  z-index: 999;
}

.reading-progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), #7c3aed);
  width: 0%;
  transition: width 0.1s ease;
}

/* ========================================
   Post Meta Enhancements
   ======================================== */
.post-meta {
  color: var(--text-secondary);
  font-size: 0.9em;
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
}

.read-time {
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

/* ========================================
   Table of Contents
   ======================================== */
.toc-wrapper {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 20px;
  margin: 24px 0;
}

.toc-title {
  font-size: 1.1em;
  font-weight: 600;
  margin: 0 0 12px 0;
  color: var(--text-primary);
}

#toc {
  margin: 0;
  padding-left: 20px;
}

#toc li {
  margin: 8px 0;
  line-height: 1.4;
}

#toc a {
  text-decoration: none;
  color: var(--text-secondary);
  transition: color 0.2s ease;
}

#toc a:hover {
  color: var(--text-link);
}

/* Nested TOC levels */
#toc ul {
  padding-left: 20px;
  margin-top: 8px;
}

/* ========================================
   Post Navigation
   ======================================== */
.post_navi {
  display: flex;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
  gap: 16px;
}

.post_navi-label {
  font-size: 0.8em;
  opacity: 0.5;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.post_navi .post_navi-item {
  padding: 0 2.2em;
  width: 50%;
  position: relative;
  color: inherit !important;
  transition: transform 0.2s ease;
}

.post_navi .post_navi-item:hover {
  transform: translateX(4px);
}

.post_navi .nav_prev:hover {
  transform: translateX(-4px);
}

.post_navi .nav_prev {
  text-align: left;
}

.post_navi .nav_next {
  text-align: right;
}

.post_navi .nav_prev .post_navi-arrow {
  left: 0;
}

.post_navi .nav_next .post_navi-arrow {
  right: 0;
}

.post_navi .post_navi-arrow {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  font-size: 2.5em;
  opacity: 0.3;
  transition: opacity 0.2s ease;
}

.post_navi-item:hover .post_navi-arrow {
  opacity: 0.6;
}

/* ========================================
   Tables
   ======================================== */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 24px 0;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  overflow: hidden;
}

thead {
  background: var(--bg-secondary);
}

th, td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}

th {
  font-weight: 600;
  color: var(--text-primary);
}

tbody tr:hover {
  background: var(--bg-secondary);
}

tbody tr:last-child td {
  border-bottom: none;
}

/* ========================================
   Callout Boxes / Admonitions
   ======================================== */
.callout {
  padding: 16px 20px;
  margin: 20px 0;
  border-left: 4px solid var(--accent);
  border-radius: 4px;
  background: var(--bg-secondary);
}

.callout-title {
  font-weight: 600;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.callout.info {
  border-left-color: #0969da;
}

.callout.warning {
  border-left-color: #f85149;
}

.callout.tip {
  border-left-color: #2da44e;
}

.callout.note {
  border-left-color: #bf8700;
}

/* ========================================
   Task Lists
   ======================================== */
.task-list {
  list-style: none;
  padding-left: 0;
}

.task-list-item {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  margin: 8px 0;
}

.task-list-item input[type="checkbox"] {
  margin-top: 4px;
}

/* ========================================
   Series Navigation
   ======================================== */
.series-navigation {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 24px;
  margin: 32px 0;
}

.series-navigation h3 {
  margin: 0 0 16px 0;
  color: var(--text-primary);
  font-size: 1.1em;
}

.series-list {
  list-style: none;
  padding: 0;
  margin: 0;
  counter-reset: series-counter;
}

.series-item {
  margin: 12px 0;
  padding-left: 8px;
}

.series-item a {
  color: var(--text-link);
  text-decoration: none;
  transition: color 0.2s ease;
}

.series-item a:hover {
  color: var(--text-link-hover);
  text-decoration: underline;
}

.series-item.active {
  font-weight: 600;
  color: var(--accent);
  background: var(--bg-primary);
  padding: 8px 12px;
  margin-left: -12px;
  border-radius: 4px;
  border-left: 3px solid var(--accent);
}

.series-item.active .current-part {
  color: var(--text-primary);
}

/* ========================================
   Comments Section
   ======================================== */
.comments-section {
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid var(--border-color);
}

/* ========================================
   Header & Navigation
   ======================================== */
.site-title {
  font-weight: 600 !important;
  color: var(--text-primary) !important;
  font-size: 1.5em !important;
}

.site-nav {
  display: none !important;
}

/* ========================================
   Mobile Responsiveness
   ======================================== */
@media (max-width: 768px) {
  .theme-toggle {
    top: 10px;
    right: 10px;
    width: 40px;
    height: 40px;
  }

  .post_navi {
    flex-direction: column;
    gap: 24px;
  }

  .post_navi .post_navi-item {
    width: 100%;
    padding: 0 2em;
  }

  .post_navi .nav_next {
    text-align: left;
  }

  pre {
    padding: 12px;
    font-size: 0.85em;
  }

  table {
    font-size: 0.9em;
  }

  th, td {
    padding: 8px 12px;
  }

  .toc-wrapper {
    padding: 16px;
  }
}

/* ========================================
   Performance: Reduced Motion
   ======================================== */
@media (prefers-reduced-motion: reduce) {
  * {
    animation: none !important;
    transition: none !important;
  }
}