/* CSS Custom Properties */
:root {
  --color-bg: #ffffff;
  --color-bg-secondary: #f7f7f7;
  --color-text: #1a1a1a;
  --color-text-secondary: #666666;
  --color-text-muted: #999999;
  --color-border: #e5e5e5;
  --color-accent: #0085ff;
  --color-accent-hover: #0066cc;
  --color-connector: #ddd;
  --color-error: #dc3545;
  --color-error-bg: #fee2e5;

  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, 'SF Mono', Monaco, 'Cascadia Code', monospace;

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.08);

  --indent-size: 24px;
  --avatar-size: 42px;
  --avatar-size-sm: 24px;
}

/* Dark mode */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #16181c;
    --color-bg-secondary: #1e2128;
    --color-text: #f1f3f5;
    --color-text-secondary: #adb5bd;
    --color-text-muted: #6c757d;
    --color-border: #2d3139;
    --color-accent: #1d9bf0;
    --color-accent-hover: #1a8cd8;
    --color-connector: #3a3f47;
    --color-error: #f87171;
    --color-error-bg: #3b1d1d;
  }
}

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

body {
  margin: 0;
  padding: 0;
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.5;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

/* Layout */
.container {
  max-width: 680px;
  margin: 0 auto;
  padding: 20px;
}

/* Header */
.site-header {
  text-align: center;
  padding: 40px 0 30px;
  border-bottom: 1px solid var(--color-border);
  margin-bottom: 30px;
}

.site-title {
  font-size: 28px;
  font-weight: 700;
  margin: 0 0 8px;
  color: var(--color-text);
}

.site-tagline {
  font-size: 16px;
  color: var(--color-text-secondary);
  margin: 0;
}

/* Input Form */
.input-section {
  margin-bottom: 30px;
}

.input-form {
  display: flex;
  gap: 12px;
}

.url-input {
  flex: 1;
  padding: 12px 16px;
  font-size: 15px;
  font-family: var(--font-sans);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg);
  color: var(--color-text);
  transition: border-color 0.15s, box-shadow 0.15s;
}

.url-input:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(0, 133, 255, 0.15);
}

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

.submit-btn {
  padding: 12px 24px;
  font-size: 15px;
  font-weight: 600;
  font-family: var(--font-sans);
  color: #fff;
  background: var(--color-accent);
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background 0.15s;
  white-space: nowrap;
}

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

.submit-btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

/* Error Message */
.error-message {
  display: none;
  padding: 12px 16px;
  margin-bottom: 20px;
  background: var(--color-error-bg);
  color: var(--color-error);
  border-radius: var(--radius-md);
  font-size: 14px;
}

.error-message.visible {
  display: block;
}

/* Thread Container */
.thread-container {
  display: none;
}

.thread-container.visible {
  display: block;
}

/* Thread Controls */
.thread-controls {
  display: flex;
  gap: 12px;
  margin-bottom: 16px;
  align-items: center;
  flex-wrap: wrap;
}

.op-filter-btn {
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 500;
  font-family: var(--font-sans);
  color: var(--color-text-secondary);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.15s;
}

.op-filter-btn:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.op-filter-btn:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 2px rgba(0, 133, 255, 0.15);
}

.op-filter-btn.is-active {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: #fff;
}

.op-filter-btn.is-active:hover {
  background: var(--color-accent-hover);
  border-color: var(--color-accent-hover);
}

/* Search Container */
.search-container {
  flex: 1;
  min-width: 200px;
  max-width: 300px;
  position: relative;
  display: flex;
  align-items: center;
}

.thread-search-input {
  width: 100%;
  padding: 8px 60px 8px 12px;
  font-size: 14px;
  font-family: var(--font-sans);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg);
  color: var(--color-text);
  transition: border-color 0.15s, box-shadow 0.15s;
}

.thread-search-input:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 2px rgba(0, 133, 255, 0.15);
}

.thread-search-input::placeholder {
  color: var(--color-text-muted);
}

.search-count {
  position: absolute;
  right: 32px;
  font-size: 12px;
  color: var(--color-text-muted);
  pointer-events: none;
}

.search-clear {
  position: absolute;
  right: 8px;
  width: 20px;
  height: 20px;
  padding: 0;
  display: none;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  font-family: var(--font-sans);
  color: var(--color-text-muted);
  background: transparent;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  transition: color 0.15s, background 0.15s;
}

.search-clear.visible {
  display: flex;
}

.search-clear:hover {
  color: var(--color-text);
  background: var(--color-bg-secondary);
}

/* Media Toggle */
.media-toggle {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 10px;
  font-size: 13px;
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg);
  cursor: pointer;
  user-select: none;
}

.media-toggle input {
  margin: 0;
  accent-color: var(--color-accent);
}

.media-toggle:focus-within {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 2px rgba(0, 133, 255, 0.15);
}

/* Search Highlight */
.search-highlight {
  background: rgba(255, 230, 0, 0.4);
  color: inherit;
  border-radius: 2px;
  padding: 0 1px;
}

@media (prefers-color-scheme: dark) {
  .search-highlight {
    background: rgba(255, 200, 0, 0.3);
  }
}

/* Thread Header */
.thread-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 20px;
  background: var(--color-bg-secondary);
  border-radius: var(--radius-lg);
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 12px;
}

.thread-author {
  display: flex;
  align-items: center;
  gap: 12px;
}

.thread-author-avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  object-fit: cover;
}

.thread-author-info {
  display: flex;
  flex-direction: column;
}

.thread-label {
  font-size: 12px;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.thread-author-name {
  font-weight: 600;
  color: var(--color-text);
}

.thread-stats {
  display: flex;
  gap: 16px;
  font-size: 14px;
  color: var(--color-text-secondary);
}

.thread-stats .stat-deleted {
  color: var(--color-error);
}

/* Post Wrapper (handles nesting) */
.post-wrapper {
  --depth: 0;
  position: relative;
  padding-left: calc(var(--depth) * var(--indent-size));
  margin-bottom: 2px;
}

.post-wrapper.is-reply::before {
  content: '';
  position: absolute;
  left: calc((var(--depth) - 1) * var(--indent-size) + 20px);
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--color-connector);
}

.post-wrapper.is-reply::after {
  content: '';
  position: absolute;
  left: calc((var(--depth) - 1) * var(--indent-size) + 20px);
  top: 24px;
  width: calc(var(--indent-size) - 8px);
  height: 2px;
  background: var(--color-connector);
}

/* Branch Color Coding */
.post-wrapper.has-branch-color .post {
  border-left: 3px solid var(--branch-color);
}

/* OP posts keep accent border - higher specificity overrides branch color */
.post-wrapper.has-branch-color .post.post-op {
  border-left: 3px solid var(--color-accent);
}

/* Post */
.post {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 16px;
  position: relative;
}

/* OP Post Highlighting */
.post-op {
  border-left: 3px solid var(--color-accent);
}

.op-badge {
  display: inline-flex;
  align-items: center;
  padding: 1px 6px;
  font-size: 11px;
  font-weight: 600;
  color: var(--color-accent);
  background: rgba(0, 133, 255, 0.1);
  border-radius: 4px;
  text-transform: uppercase;
  letter-spacing: 0.3px;
}

@media (prefers-color-scheme: dark) {
  .op-badge {
    background: rgba(29, 155, 240, 0.15);
  }
}

.post-deleted,
.post-blocked {
  background: var(--color-bg-secondary);
}

.post-placeholder {
  font-style: italic;
  color: var(--color-text-muted);
  padding: 8px 0;
}

/* Post Header */
.post-header {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  margin-bottom: 12px;
}

.post-avatar {
  width: var(--avatar-size);
  height: var(--avatar-size);
  border-radius: 50%;
  object-fit: cover;
  flex-shrink: 0;
}

.post-author-info {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 4px 8px;
  min-width: 0;
}

.post-display-name {
  font-weight: 600;
  color: var(--color-text);
}

.post-handle {
  color: var(--color-text-muted);
  font-size: 14px;
}

.post-timestamp {
  color: var(--color-text-muted);
  font-size: 14px;
}

/* Post Content */
.post-content {
  margin-bottom: 12px;
}

.post-text {
  white-space: pre-wrap;
  word-wrap: break-word;
}

.post-text a {
  color: var(--color-accent);
  text-decoration: none;
}

.post-text a:hover {
  text-decoration: underline;
}

.post-text .mention {
  color: var(--color-accent);
}

.post-text .hashtag {
  color: var(--color-accent);
}

/* Post Embeds */
.post-embed {
  margin-top: 12px;
}

/* Media Blocked */
.embed-media-blocked {
  border: 1px dashed var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg-secondary);
  color: var(--color-text-muted);
  padding: 12px;
  font-size: 13px;
}

/* Image Embed */
.embed-images {
  display: grid;
  gap: 4px;
  border-radius: var(--radius-md);
  overflow: hidden;
}

.embed-images.image-count-1 {
  grid-template-columns: 1fr;
}

.embed-images.image-count-2 {
  grid-template-columns: 1fr 1fr;
}

.embed-images.image-count-3 {
  grid-template-columns: 1fr 1fr;
}

.embed-images.image-count-3 .embed-image-wrapper:first-child {
  grid-row: span 2;
}

.embed-images.image-count-4 {
  grid-template-columns: 1fr 1fr;
}

.embed-image-wrapper {
  position: relative;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: var(--color-bg-secondary);
}

.embed-image-wrapper img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* External Link Card */
.embed-external {
  margin-top: 12px;
}

.external-card {
  display: flex;
  flex-direction: column;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s;
}

.external-card:hover {
  border-color: var(--color-accent);
}

.external-thumb {
  width: 100%;
  aspect-ratio: 2 / 1;
  object-fit: cover;
  background: var(--color-bg-secondary);
}

.external-info {
  padding: 12px;
}

.external-title {
  font-weight: 600;
  margin-bottom: 4px;
  color: var(--color-text);
}

.external-description {
  font-size: 14px;
  color: var(--color-text-secondary);
  margin-bottom: 4px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.external-domain {
  font-size: 13px;
  color: var(--color-text-muted);
}

/* Quote Post Embed */
.embed-quote {
  margin-top: 12px;
}

.quote-card {
  display: block;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 12px;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s;
}

.quote-card:hover {
  border-color: var(--color-accent);
}

.quote-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
}

.quote-avatar {
  width: var(--avatar-size-sm);
  height: var(--avatar-size-sm);
  border-radius: 50%;
  object-fit: cover;
}

.quote-name {
  font-weight: 600;
  font-size: 14px;
}

.quote-handle {
  font-size: 13px;
  color: var(--color-text-muted);
}

.quote-text {
  font-size: 14px;
  color: var(--color-text-secondary);
  white-space: pre-wrap;
  word-wrap: break-word;
}

.quote-unavailable .quote-placeholder {
  font-style: italic;
  color: var(--color-text-muted);
  font-size: 14px;
}

/* Post Footer */
.post-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--color-border);
}

.post-stats {
  display: flex;
  gap: 16px;
}

.stat {
  font-size: 13px;
  color: var(--color-text-muted);
}

.post-view-link {
  display: flex;
  align-items: center;
  color: var(--color-text-muted);
  text-decoration: none;
  padding: 4px;
  border-radius: var(--radius-sm);
  transition: color 0.15s, background-color 0.15s;
}

.post-view-link:hover {
  color: var(--color-accent);
  background-color: rgba(0, 133, 255, 0.08);
}

.post-view-link[aria-disabled="true"] {
  opacity: 0.4;
  pointer-events: none;
}

.external-link-icon {
  width: 14px;
  height: 14px;
}

/* Branch Indicator (Collapsible Button) */
.branch-indicator {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  width: 100%;
  margin-top: 12px;
  padding: 8px 12px;
  background: var(--color-bg-secondary);
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-family: var(--font-sans);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}

.branch-indicator:hover {
  border-color: var(--color-border);
  background: var(--color-bg);
}

.branch-indicator:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 2px rgba(0, 133, 255, 0.15);
}

.branch-indicator-text {
  flex: 1;
  text-align: left;
}

.branch-indicator-hint {
  font-size: 12px;
  color: var(--color-text-muted);
  opacity: 0;
  transition: opacity 0.15s;
}

.branch-indicator:hover .branch-indicator-hint,
.branch-indicator:focus .branch-indicator-hint {
  opacity: 1;
}

.branch-indicator.is-collapsed {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

.branch-indicator.is-collapsed .branch-indicator-hint {
  color: rgba(255, 255, 255, 0.8);
  opacity: 1;
}

.branch-indicator.is-collapsed:hover {
  background: var(--color-accent-hover);
  border-color: var(--color-accent-hover);
}

/* Hidden Post Wrapper */
.post-wrapper.is-hidden {
  display: none;
}

/* Loading Overlay */
.loading-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: var(--color-bg);
  justify-content: center;
  align-items: flex-start;
  padding-top: 120px;
  z-index: 1000;
  opacity: 0;
  transition: opacity 0.2s ease-out;
}

.loading-overlay.visible {
  display: flex;
  opacity: 1;
}

/* Loading Skeleton */
.loading-skeleton {
  width: 100%;
  max-width: 680px;
  padding: 0 20px;
}

.skeleton-container {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.post-skeleton {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 16px;
  animation-delay: calc(var(--skeleton-index) * 0.1s);
}

.skeleton-header {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  margin-bottom: 12px;
}

.skeleton-avatar {
  width: var(--avatar-size);
  height: var(--avatar-size);
  border-radius: 50%;
  background: var(--color-bg-secondary);
  flex-shrink: 0;
}

.skeleton-author-info {
  display: flex;
  flex-direction: column;
  gap: 6px;
  flex: 1;
}

.skeleton-name {
  height: 14px;
  width: 120px;
  background: var(--color-bg-secondary);
  border-radius: var(--radius-sm);
}

.skeleton-handle {
  height: 12px;
  width: 80px;
  background: var(--color-bg-secondary);
  border-radius: var(--radius-sm);
}

.skeleton-content {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.skeleton-line {
  height: 14px;
  background: var(--color-bg-secondary);
  border-radius: var(--radius-sm);
}

.skeleton-line-full {
  width: 100%;
}

.skeleton-line-medium {
  width: 70%;
}

/* Shimmer Animation */
.skeleton-shimmer {
  position: relative;
  overflow: hidden;
}

.skeleton-shimmer::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(
    90deg,
    transparent 0%,
    rgba(255, 255, 255, 0.08) 50%,
    transparent 100%
  );
  animation: shimmer 1.5s infinite;
  animation-delay: calc(var(--skeleton-index, 0) * 0.1s);
}

@keyframes shimmer {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  .skeleton-shimmer::after {
    animation: none;
  }
}

/* Dark mode shimmer adjustment */
@media (prefers-color-scheme: dark) {
  .skeleton-shimmer::after {
    background: linear-gradient(
      90deg,
      transparent 0%,
      rgba(255, 255, 255, 0.03) 50%,
      transparent 100%
    );
  }
}

/* Footer */
.site-footer {
  text-align: center;
  padding: 30px 0;
  margin-top: 40px;
  border-top: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font-size: 14px;
}

.site-footer a {
  color: var(--color-accent);
  text-decoration: none;
}

.site-footer a:hover {
  text-decoration: underline;
}

/* Floating Action Button (Back to Top) */
.fab-back-to-top {
  position: fixed;
  bottom: 32px;
  left: 50%;
  transform: translateX(-50%) translateY(16px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 14px 24px;
  font-family: var(--font-sans);
  font-size: 16px;
  font-weight: 600;
  color: var(--color-text);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 28px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15), 0 2px 8px rgba(0, 0, 0, 0.1);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.2s, visibility 0.2s, transform 0.2s, background-color 0.15s, border-color 0.15s;
  z-index: 100;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.fab-back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}

.fab-back-to-top:hover {
  background: var(--color-bg-secondary);
  border-color: var(--color-accent);
}

.fab-back-to-top:active {
  transform: translateX(-50%) scale(0.96);
}

.fab-content {
  display: flex;
  align-items: center;
  gap: 6px;
  white-space: nowrap;
}

.fab-icon {
  font-size: 14px;
}

@media (prefers-color-scheme: dark) {
  .fab-back-to-top {
    background: rgba(30, 33, 40, 0.9);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.3);
  }

  .fab-back-to-top:hover {
    background: var(--color-bg-secondary);
  }
}

/* Responsive */
@media (max-width: 600px) {
  .container {
    padding: 16px;
  }

  .site-header {
    padding: 24px 0 20px;
  }

  .site-title {
    font-size: 22px;
  }

  .input-form {
    flex-direction: column;
  }

  .submit-btn {
    width: 100%;
  }

  :root {
    --indent-size: 16px;
    --avatar-size: 36px;
  }

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

  .post {
    padding: 12px;
  }

  .post-header {
    gap: 10px;
  }

  .thread-controls {
    flex-direction: column;
    align-items: stretch;
  }

  .search-container {
    max-width: none;
  }
}