:root {
  --primary-color: #1a1a1a;
  --secondary-color: #666;
  --accent-color: #06c;
  --light-bg: #fff;
  --light-border: #e0e0e0;
  --light-text: #333;
}

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

html {
  font-size: 16px;
}

body {
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", sans-serif;
  background-color: var(--light-bg);
  color: var(--light-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 20px;
}

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

.navbar {
  padding: 2rem 0;
}

.navbar .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-brand h1 {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -1px;
}

.nav-brand h1 a {
  color: var(--primary-color);
  text-decoration: none;
  transition: color 0.3s ease;
}

.nav-brand h1 a:hover {
  color: var(--accent-color);
}

.tagline {
  font-size: 0.875rem;
  color: var(--secondary-color);
  margin-top: 0.25rem;
  font-weight: 400;
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: 2rem;
}

.nav-menu a {
  color: var(--secondary-color);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  transition: color 0.3s ease;
  cursor: pointer;
}

.nav-menu a:hover,
.nav-menu a.active {
  color: var(--accent-color);
}

.nav-social {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  position: relative;
}

.social-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  background: none;
  border: none;
  padding: 0.25rem;
  cursor: pointer;
  color: var(--secondary-color);
  transition: color 0.2s ease;
  line-height: 0;
}

.social-icon:hover {
  color: var(--primary-color);
}

.social-icon--unset {
  opacity: 0.35;
  cursor: default;
}

.social-tooltip {
  position: fixed;
  background: var(--primary-color);
  color: #fff;
  font-size: 0.78rem;
  padding: 0.3rem 0.65rem;
  border-radius: 4px;
  white-space: nowrap;
  pointer-events: none;
  opacity: 0;
  transform: translateX(-50%);
  transition: opacity 0.15s ease;
  z-index: 300;
}

.social-tooltip.visible {
  opacity: 1;
}

/* Main Content */
main {
  padding: 3rem 0;
  min-height: calc(100vh - 300px);
}

.posts-section {
  width: 100%;
  margin-top: 2rem;
}

.posts-list {
  display: grid;
  gap: 2rem;
}

.post-item {
  padding: 1.5rem;
  border: 1px solid var(--light-border);
  border-radius: 4px;
  cursor: pointer;
  transition: all 0.3s ease;
  background-color: var(--light-bg);
}

.post-item:hover {
  border-color: var(--accent-color);
  box-shadow: 0 2px 8px rgb(0 102 204 / 10%);
}

.post-item-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
  margin-bottom: 0.75rem;
}

.post-item-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--primary-color);
  margin-bottom: 0.5rem;
}

.post-item-date {
  font-size: 0.875rem;
  color: var(--secondary-color);
  white-space: nowrap;
}

.post-item-category {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  background-color: #f5f5f5;
  color: var(--secondary-color);
  font-size: 0.8rem;
  border-radius: 3px;
  text-transform: capitalize;
}

.post-item-excerpt {
  color: var(--secondary-color);
  font-size: 0.95rem;
  line-height: 1.5;
}

.post-item-tags {
  display: flex;
  gap: 0.5rem;
  margin-top: 0.75rem;
  flex-wrap: wrap;
}

.post-tag {
  font-size: 0.8rem;
  color: var(--accent-color);
  padding: 0.25rem 0.5rem;
  background-color: #f0f6ff;
  border-radius: 3px;
}

/* Series — 목록 카드 배지 */
.post-item-series {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.series-badge-name {
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  color: var(--accent-color);
  padding: 0.2rem 0.55rem;
  background-color: #f0f6ff;
  border-radius: 3px;
}

.series-badge-count {
  font-size: 0.78rem;
  font-variant-numeric: tabular-nums;
  color: var(--secondary-color);
}

/* Series — 상세 뷰 목차 */
.series-toc {
  border: 1px solid var(--light-border);
  border-left: 3px solid var(--accent-color);
  border-radius: 4px;
  background-color: #fafbfc;
  padding: 1rem 1.25rem;
  margin-bottom: 2.5rem;
}

.series-toc-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 1rem;
  padding-bottom: 0.6rem;
  border-bottom: 1px solid var(--light-border);
}

.series-toc-name {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--primary-color);
}

.series-toc-progress {
  font-size: 0.85rem;
  font-variant-numeric: tabular-nums;
  color: var(--secondary-color);
  white-space: nowrap;
}

.series-toc-list {
  list-style: none;
  margin: 0.6rem 0 0;
  padding: 0;
}

.series-toc-item {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  padding: 0.3rem 0;
  font-size: 0.92rem;
  line-height: 1.45;
}

.series-toc-num {
  flex-shrink: 0;
  width: 1.4rem;
  font-size: 0.8rem;
  font-variant-numeric: tabular-nums;
  text-align: right;
  color: var(--secondary-color);
}

.series-toc-item.current .series-toc-num {
  font-weight: 700;
  color: var(--accent-color);
}

a.series-toc-title {
  color: var(--light-text);
  text-decoration: none;
  border-bottom: 1px solid transparent;
}

a.series-toc-title:hover {
  color: var(--accent-color);
  border-bottom-color: var(--accent-color);
}

.series-toc-item.current .series-toc-title {
  font-weight: 600;
  color: var(--primary-color);
}

.series-toc-here {
  display: inline-block;
  margin-left: 0.5rem;
  padding: 0.1rem 0.4rem;
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--accent-color);
  background-color: #f0f6ff;
  border-radius: 3px;
  white-space: nowrap;
}

.series-toc-repo {
  margin-top: 0.8rem;
  padding-top: 0.7rem;
  border-top: 1px solid var(--light-border);
  font-size: 0.83rem;
  color: var(--secondary-color);
}

.series-toc-repo a {
  color: var(--accent-color);
}

/* Post Detail View */
.post-detail-view {
  display: none;
}

.post-detail-view.active {
  display: block;
}

.posts-section.hidden {
  display: none;
}

.back-btn {
  display: inline-block;
  margin: 1.5rem 0 0;
  background: none;
  border: none;
  cursor: pointer;
  font-size: 0.9rem;
  color: var(--secondary-color);
  padding: 0;
}

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

.post-content {
  padding: 1.5rem 0 3rem;
}

/* Post Content Styles */
.post-content h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 1rem;
  line-height: 1.2;
}

.post-content h2 {
  font-size: 1.75rem;
  font-weight: 600;
  margin: 2rem 0 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--light-border);
}

.post-content h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 1.5rem 0 0.75rem;
}

.post-content p {
  margin-bottom: 1rem;
  line-height: 1.8;
}

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

.post-content em {
  font-style: italic;
  color: var(--secondary-color);
}

.post-content ul,
.post-content ol {
  margin: 1rem 0 1rem 2rem;
  line-height: 1.8;
}

.post-content li {
  margin-bottom: 0.5rem;
}

.post-content blockquote {
  margin: 1.5rem 0;
  padding-left: 1.5rem;
  border-left: 3px solid var(--accent-color);
  color: var(--secondary-color);
  font-style: italic;
}

.post-content code {
  background-color: #f5f5f5;
  padding: 0.2rem 0.4rem;
  border-radius: 3px;
  font-family: Monaco, Menlo, "Ubuntu Mono", monospace;
  font-size: 0.9rem;
  color: #d63384;
}

.post-content pre {
  background-color: #f5f5f5;
  border: 1px solid var(--light-border);
  border-radius: 4px;
  padding: 1rem;
  margin: 1.5rem 0;
  overflow-x: auto;
}

.post-content pre code {
  background-color: transparent;
  padding: 0;
  color: inherit;
  font-size: 0.9rem;
}

.post-content a {
  color: var(--accent-color);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s ease;
}

.post-content a:hover {
  border-bottom-color: var(--accent-color);
}

.post-content img {
  max-width: 100%;
  height: auto;
  margin: 1.5rem 0;
  border-radius: 4px;
  border: 1px solid var(--light-border);
}

/* Table styles */
.post-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 0.9rem;
  overflow-x: auto;
  display: block;
}

.post-content th,
.post-content td {
  border: 1px solid var(--light-border);
  padding: 0.6rem 1rem;
  text-align: left;
  white-space: nowrap;
}

.post-content th {
  background-color: #f5f5f5;
  font-weight: 600;
  color: var(--primary-color);
}

.post-content tr:nth-child(even) td {
  background-color: #fafafa;
}

/* Demo Block (html-demo tabs) */
.demo-block {
  border: 1px solid var(--light-border);
  border-radius: 4px;
  margin: 1.5rem 0;
  overflow: hidden;
}

.demo-tabs {
  display: flex;
  border-bottom: 1px solid var(--light-border);
  background-color: #f9f9f9;
}

.demo-tab {
  padding: 0.5rem 1.25rem;
  border: none;
  background: none;
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--secondary-color);
  border-bottom: 2px solid transparent;
  transition:
    color 0.2s,
    border-color 0.2s;
}

.demo-tab:hover {
  color: var(--primary-color);
}

.demo-tab.active {
  color: var(--accent-color);
  border-bottom-color: var(--accent-color);
}

.demo-panel {
  display: none;
}

.demo-panel.active {
  display: block;
}

.demo-panel-code pre {
  margin: 0;
  border: none;
  border-radius: 0;
}

.demo-panel-result iframe {
  width: 100%;
  min-height: 200px;
  border: none;
  display: block;
}

/* KaTeX 수식 */
.katex {
  font-size: 1.1em;
}

.katex-display {
  margin: 1.5rem 0;
  padding: 1rem;
  background-color: #f9f9f9;
  border-radius: 4px;
}

/* Footer */
.footer {
  border-top: 1px solid var(--light-border);
  padding: 2rem 0;
  text-align: center;
  color: var(--secondary-color);
  font-size: 0.875rem;
  margin-top: 3rem;
}

/* Responsive Design */
@media (width <= 768px) {
  .navbar .container {
    flex-direction: column;
    gap: 1.5rem;
    align-items: flex-start;
  }

  .nav-menu {
    gap: 1rem;
    font-size: 0.9rem;
  }

  .post-item-header {
    flex-direction: column;
  }

  .post-item-title {
    font-size: 1.1rem;
  }

  .post-content h1 {
    font-size: 1.75rem;
  }

  .post-content h2 {
    font-size: 1.25rem;
  }

  .post-item-tags {
    gap: 0.25rem;
  }

  .series-toc {
    padding: 0.9rem 1rem;
  }

  .series-toc-head {
    flex-direction: column;
    gap: 0.15rem;
  }

  .series-toc-item {
    font-size: 0.88rem;
  }
}

/* Empty state */
.empty-state {
  text-align: center;
  padding: 3rem;
  color: var(--secondary-color);
}

.empty-state p {
  font-size: 1.1rem;
}

/* Loading Spinner */
.loading-spinner {
  width: 36px;
  height: 36px;
  border: 3px solid #eef0ff;
  border-top-color: var(--accent-color);
  border-radius: 50%;
  animation: spin 0.75s linear infinite;
  margin: 2.5rem auto 1.5rem;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

/* Skeleton Loading */
.skeleton-card {
  padding: 1.5rem;
  border: 1px solid var(--light-border);
  border-radius: 4px;
  background: var(--light-bg);
}

.skeleton-line {
  background: linear-gradient(90deg, #f0f0f0 25%, #e8e8e8 50%, #f0f0f0 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s ease-in-out infinite;
  border-radius: 3px;
}

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

  100% {
    background-position: -200% 0;
  }
}