/* ==========================================================================
   components.css - UI Components (Header, Cards, Nav, Footer, TOC, etc.)
   luckylinux - Technical Engineering Blog
   ========================================================================== */

/* --- Top Reading Progress Bar --- */
.reading-progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  width: 0%;
  height: 3px;
  background-color: var(--accent);
  z-index: 1000;
  transition: width 60ms linear;
  pointer-events: none;
}

/* --- Site Header --- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 900;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: var(--theme-transition);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
}

/* Brand Wordmark */
.brand {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  text-decoration: none;
  color: var(--text-primary);
}

.brand-wordmark {
  font-family: var(--font-heading);
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  color: var(--text-primary);
}

.brand-wordmark .brand-dot {
  color: var(--accent);
}

.brand-subtitle {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

@media (max-width: 640px) {
  .brand-subtitle {
    display: none;
  }
}

/* Header Navigation */
.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--space-5);
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-link {
  font-family: var(--font-ui);
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  position: relative;
  padding: var(--space-1) 0;
  transition: color var(--transition-fast);
}

.nav-link::after {
  content: "";
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 100%;
  height: 1.5px;
  background-color: var(--accent);
  transform: scaleX(0);
  transform-origin: right;
  transition: transform var(--transition-normal);
}

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

.nav-link:hover::after,
.nav-link.active::after {
  transform: scaleX(1);
  transform-origin: left;
}

.nav-link-external {
  display: inline-flex;
  align-items: center;
  gap: 3px;
  color: var(--text-muted);
}

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

.nav-external-arrow {
  font-size: 0.85em;
  line-height: 1;
  transition: transform var(--transition-fast);
}

.nav-link-external:hover .nav-external-arrow {
  transform: translate(2px, -2px);
}

/* Header Right Actions */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* Theme Toggle Button */
.theme-toggle-btn {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  transition: background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast);
}

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

.theme-toggle-btn svg {
  width: 18px;
  height: 18px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.icon-sun {
  display: none;
}

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

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

/* Mobile Nav Toggle */
.mobile-nav-toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  align-items: center;
  justify-content: center;
  padding: 0;
}

@media (max-width: 768px) {
  .mobile-nav-toggle {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    flex-direction: column;
    align-items: flex-start;
    padding: var(--space-5) var(--space-6);
    gap: var(--space-4);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
    transform: translateY(-120%);
    opacity: 0;
    pointer-events: none;
    transition: transform var(--transition-normal), opacity var(--transition-normal);
  }

  .nav-menu.is-open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
}

/* --- Hero Section (Editorial, Writing-Focused) --- */
.hero-section {
  padding: var(--space-16) 0 var(--space-12) 0;
  border-bottom: 1px solid var(--border-color);
}

.hero-subtitle {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-3);
  font-weight: 600;
}

.hero-title {
  font-size: clamp(2.4rem, 5vw, 3.8rem);
  font-weight: 600;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: var(--space-4);
  max-width: 22ch;
}

.hero-lead {
  font-size: 1.25rem;
  color: var(--text-secondary);
  line-height: 1.6;
  max-width: 58ch;
  margin-bottom: var(--space-5);
}

.hero-byline {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  color: var(--text-muted);
}

.hero-byline-link {
  color: var(--text-primary);
  text-decoration: underline;
  text-underline-offset: 3px;
  font-weight: 500;
}

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

/* --- Section Headers --- */
.section-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-2);
  border-bottom: 1px solid var(--border-color);
}

.section-title {
  font-family: var(--font-heading);
  font-size: 1.6rem;
  font-weight: 600;
  margin-bottom: 0;
}

.section-link {
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.section-link:hover {
  text-decoration: underline;
}

/* --- Post Cards System --- */
.post-cards-grid {
  display: grid;
  gap: var(--space-6);
}

/* Featured Post Card */
.post-card-featured {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-8);
  padding: var(--space-6);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: inherit;
  margin-bottom: var(--space-12);
  transition: transform var(--transition-normal), border-color var(--transition-normal), box-shadow var(--transition-normal);
}

.post-card-featured:hover {
  transform: translateY(-3px);
  border-color: var(--accent-border);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.04);
}

.featured-cover-wrapper {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-sm);
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-subtle);
  aspect-ratio: 16 / 9;
}

.featured-cover-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-normal);
}

.post-card-featured:hover .featured-cover-img {
  transform: scale(1.02);
}

.featured-content {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.featured-badge {
  display: inline-flex;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  background-color: var(--accent-faint);
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  width: fit-content;
  margin-bottom: var(--space-3);
}

@media (max-width: 768px) {
  .post-card-featured {
    grid-template-columns: 1fr;
    gap: var(--space-4);
  }
}

/* Standard Post Card */
.post-card {
  display: block;
  padding: var(--space-6);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: inherit;
  transition: transform var(--transition-normal), border-color var(--transition-normal), background-color var(--transition-fast);
}

.post-card:hover {
  transform: translateY(-2px);
  border-color: var(--accent-border);
  background-color: var(--bg-surface-raised);
}

.post-card-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-3);
  font-family: var(--font-ui);
  font-size: 0.8125rem;
  color: var(--text-muted);
  margin-bottom: var(--space-2);
}

.meta-item {
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.meta-sep {
  opacity: 0.4;
}

.post-card-title {
  font-size: 1.375rem;
  font-weight: 600;
  line-height: 1.3;
  margin-bottom: var(--space-2);
  color: var(--text-primary);
  transition: color var(--transition-fast);
}

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

.post-card-excerpt {
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.post-card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.tag-badge {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-color);
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  white-space: nowrap;
  transition: border-color var(--transition-fast), color var(--transition-fast);
}

.post-card:hover .tag-badge {
  border-color: var(--border-hover);
  color: var(--text-secondary);
}

/* Series Badge */
.series-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-tip-text);
  background-color: var(--color-tip-bg);
  border: 1px solid var(--color-tip-border);
  padding: 2px 6px;
  border-radius: var(--radius-sm);
}

/* --- Search & Filters System (blog.html) --- */
.blog-controls {
  margin: var(--space-8) 0 var(--space-10) 0;
}

.search-box-wrapper {
  position: relative;
  max-width: 580px;
  margin-bottom: var(--space-6);
}

.search-icon {
  position: absolute;
  left: 14px;
  top: 50%;
  transform: translateY(-50%);
  width: 18px;
  height: 18px;
  color: var(--text-muted);
  pointer-events: none;
}

.search-input {
  width: 100%;
  height: 46px;
  padding: 0 46px 0 42px;
  font-family: var(--font-ui);
  font-size: 0.9375rem;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.search-input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-faint);
}

.search-clear-btn {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%);
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px;
  display: none;
}

.search-clear-btn:hover {
  color: var(--text-primary);
}

/* Filter Tag Chips */
.tag-chips-container {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
}

.tag-chip {
  font-family: var(--font-mono);
  font-size: 0.6875rem; /* 11px */
  letter-spacing: 0.02em;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 2px 8px;
  border-radius: 999px;
  cursor: pointer;
  text-decoration: none;
  line-height: 1.35;
  transition: all var(--transition-fast);
}

.tag-chip:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.tag-chip.is-active {
  background-color: var(--accent);
  border-color: var(--accent);
  color: var(--accent-contrast);
}

/* Series Section Grouping */
.series-group {
  margin-bottom: var(--space-12);
}

.series-group-title {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: 1.35rem;
  margin-bottom: var(--space-4);
  padding-bottom: var(--space-2);
  border-bottom: 1px dashed var(--border-color);
}

/* Topic Cloud (index.html) */
.topic-cloud-section {
  padding: var(--space-12) 0;
  border-top: 1px solid var(--border-color);
}

.topic-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.topic-tag-card {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  text-decoration: none;
  transition: all var(--transition-fast);
}

.topic-tag-card:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-1px);
}

.topic-count {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* --- Post Layout & Single Article Page --- */
.post-header {
  padding: var(--space-12) 0 var(--space-6) 0;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: var(--space-8);
}

.post-back-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  color: var(--text-muted);
  text-decoration: none;
  margin-bottom: var(--space-6);
}

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

.post-title {
  font-size: clamp(2.2rem, 4.5vw, 3.2rem);
  line-height: 1.15;
  margin-bottom: var(--space-4);
  max-width: 25ch;
}

.post-meta-bar {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-4);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  color: var(--text-muted);
}

.post-cover-image-container {
  margin: var(--space-8) 0 var(--space-10) 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--border-color);
  background-color: var(--bg-surface);
}

.post-cover-image {
  width: 100%;
  max-height: 440px;
  object-fit: cover;
}

/* Post Two-Column Layout (Content + Sticky TOC) */
.post-body-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 280px;
  gap: var(--space-12);
  align-items: start;
}

@media (max-width: 1024px) {
  .post-body-layout {
    grid-template-columns: 1fr;
    gap: var(--space-6);
  }
}

/* Sticky Table of Contents (Desktop) */
.toc-sidebar {
  position: sticky;
  top: calc(var(--header-height) + var(--space-6));
  max-height: calc(100vh - var(--header-height) - var(--space-12));
  overflow-y: auto;
  padding-left: var(--space-4);
  border-left: 1px solid var(--border-color);
}

.toc-title {
  font-family: var(--font-ui);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: var(--space-3);
}

.toc-nav ol {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc-nav li {
  margin-bottom: var(--space-2);
}

.toc-nav li.toc-h3 {
  padding-left: var(--space-3);
}

.toc-link {
  font-family: var(--font-ui);
  font-size: 0.84375rem;
  line-height: 1.4;
  color: var(--text-muted);
  text-decoration: none;
  display: block;
  transition: color var(--transition-fast);
}

.toc-link:hover {
  color: var(--text-primary);
}

.toc-link.is-active {
  color: var(--accent);
  font-weight: 600;
}

/* Mobile Collapsible TOC */
.mobile-toc-details {
  display: none;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: var(--space-3) var(--space-4);
  margin-bottom: var(--space-6);
}

@media (max-width: 1024px) {
  .toc-sidebar {
    display: none;
  }
  .mobile-toc-details {
    display: block;
  }
}

.mobile-toc-details summary {
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-primary);
  cursor: pointer;
  user-select: none;
}

.mobile-toc-details .toc-nav {
  margin-top: var(--space-3);
  padding-top: var(--space-3);
  border-top: 1px solid var(--border-color);
}

/* Post Bottom Actions & Navigation */
.post-footer-actions {
  margin-top: var(--space-12);
  padding-top: var(--space-6);
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-4);
}

.post-action-buttons {
  display: flex;
  gap: var(--space-3);
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-secondary:hover {
  background-color: var(--bg-surface-raised);
  border-color: var(--border-hover);
  color: var(--text-primary);
}

.prev-next-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-6);
  margin-top: var(--space-8);
  padding-top: var(--space-8);
  border-top: 1px solid var(--border-color);
}

@media (max-width: 640px) {
  .prev-next-nav {
    grid-template-columns: 1fr;
  }
}

.prev-next-card {
  padding: var(--space-4);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: inherit;
  display: flex;
  flex-direction: column;
  transition: border-color var(--transition-fast), transform var(--transition-fast);
}

.prev-next-card:hover {
  border-color: var(--accent-border);
  transform: translateY(-2px);
}

.prev-next-card.next {
  text-align: right;
  align-items: flex-end;
}

.prev-next-label {
  font-family: var(--font-ui);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: var(--space-1);
}

.prev-next-title {
  font-family: var(--font-heading);
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.3;
  color: var(--text-primary);
}

/* Toast Notification (Copy Link Feedback) */
.toast-notice {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background-color: var(--text-primary);
  color: var(--bg-primary);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 500;
  padding: 10px 18px;
  border-radius: var(--radius-md);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.15);
  transform: translateY(100px);
  opacity: 0;
  transition: transform var(--transition-normal), opacity var(--transition-normal);
  z-index: 10000;
  pointer-events: none;
}

.toast-notice.is-visible {
  transform: translateY(0);
  opacity: 1;
}

/* --- Site Footer --- */
.site-footer {
  margin-top: auto;
  border-top: 1px solid var(--border-color);
  padding: var(--space-12) 0 var(--space-8) 0;
  background-color: var(--bg-subtle);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  color: var(--text-muted);
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: var(--space-6);
  margin-bottom: var(--space-8);
}

.footer-brand {
  max-width: 320px;
}

.footer-brand-title {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--space-1);
}

.footer-brand-desc {
  font-size: 0.8125rem;
  line-height: 1.5;
  color: var(--text-muted);
}

.footer-links {
  display: flex;
  gap: var(--space-8);
  list-style: none;
  padding: 0;
  margin: 0;
}

.footer-link-group-title {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: var(--space-3);
}

.footer-links ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.footer-links li {
  margin-bottom: var(--space-2);
}

.footer-link {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-4);
  padding-top: var(--space-6);
  border-top: 1px solid var(--border-subtle);
  font-size: 0.8125rem;
}

.visitor-counter {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--text-muted);
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.counter-dot {
  width: 6px;
  height: 6px;
  background-color: #2F5D50;
  border-radius: 50%;
  display: inline-block;
}

[data-theme="dark"] .counter-dot {
  background-color: #4D8F7D;
}