/* CSS Variables */
:root {
  --color-primary: #4f46e5;
  --color-primary-dark: #4338ca;
  --color-text: #1f2937;
  --color-text-muted: #6b7280;
  --color-background: #ffffff;
  --color-surface: #f9fafb;
  --color-border: #e5e7eb;
  --color-error: #dc2626;
  --color-error-bg: #fef2f2;
  --font-sans:
    system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial,
    sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --border-radius: 0.5rem;
  --max-width: 42rem;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);

  /* z-index scale */
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-overlay: 300;
  --z-modal: 400;
  --z-toast: 500;

  /* focus ring */
  --focus-ring: 0 0 0 3px rgb(79 70 229 / 0.2);
  --focus-ring-error: 0 0 0 3px rgb(220 38 38 / 0.2);
}

/* Dark Mode */
@media (prefers-color-scheme: dark) {
  :root {
    --color-primary: #818cf8;
    --color-primary-dark: #6366f1;
    --color-text: #f9fafb;
    --color-text-muted: #9ca3af;
    --color-background: #111827;
    --color-surface: #1f2937;
    --color-border: #374151;
    --color-error: #f87171;
    --color-error-bg: #450a0a;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.2);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.3), 0 2px 4px -2px rgb(0 0 0 / 0.3);
  }
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* Reset */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* Base */
html {
  font-size: 16px;
  line-height: 1.6;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background-color: var(--color-background);
}

/* Layout */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--spacing-sm) var(--spacing-lg);
}

/* Header */
.header {
  text-align: center;
  padding-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-2xl);
}

.header h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.025em;
  margin-bottom: var(--spacing-sm);
}

.header .subtitle {
  margin-bottom: var(--spacing-lg);
}

.header .locale-switcher {
  opacity: 0.7;
  transition: opacity 0.2s ease-out;
}

.header .locale-switcher:hover,
.header .locale-switcher:focus-within {
  opacity: 1;
}

/* Compact Header (for read page) */
.header--compact {
  display: flex;
  justify-content: space-between;
  align-items: center;
  text-align: left;
  padding-top: 0;
  margin-bottom: var(--spacing-sm);
  padding-bottom: var(--spacing-xs);
  border-bottom: 1px solid var(--color-border);
}

.header--compact .header__title {
  font-size: 1rem;
  font-weight: 600;
  margin: 0;
  color: var(--color-text-muted);
}

.header__title-link,
.header__title-link:hover,
.header__title-link:focus,
.header__title-link:active {
  text-decoration: none;
  color: inherit;
}

.header__title-link {
  transition: color 0.2s ease-out;
}

@media (hover: hover) {
  .header__title-link:hover .header__title {
    color: var(--color-text);
  }
}

.subtitle {
  color: var(--color-text-muted);
  font-size: 1.125rem;
}

/* Navigation */
.nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-lg);
}

.back-link {
  color: var(--color-text-muted);
  text-decoration: none;
  font-weight: 400;
  font-size: 0.875rem;
}

@media (hover: hover) {
  .back-link:hover {
    text-decoration: underline;
  }
}

/* URL Form */
.url-form {
  margin-bottom: var(--spacing-2xl);
}

.input-group {
  display: flex;
  gap: var(--spacing-sm);
}

.url-input {
  flex: 1;
  padding: var(--spacing-sm) var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  font-size: 1rem;
  transition:
    border-color 0.2s ease-out,
    box-shadow 0.2s ease-out;
}

.url-input:focus-visible {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--focus-ring);
}

.url-input--error {
  border-color: var(--color-error);
}

.url-input--error:focus-visible {
  border-color: var(--color-error);
  box-shadow: var(--focus-ring-error);
}

.submit-button {
  padding: var(--spacing-sm) var(--spacing-lg);
  background-color: var(--color-primary);
  color: white;
  border: none;
  border-radius: var(--border-radius);
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition:
    background-color 0.2s ease-out,
    transform 0.1s ease-out,
    box-shadow 0.2s ease-out;
}

.submit-button:active:not(:disabled) {
  transform: scale(0.98);
}

@media (hover: hover) {
  .submit-button:hover:not(:disabled) {
    background-color: var(--color-primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
  }
}

.submit-button:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

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

/* Error Messages */
.error-message {
  display: flex;
  align-items: flex-start;
  gap: var(--spacing-xs);
  color: var(--color-error);
  font-size: 0.875rem;
  margin-top: var(--spacing-sm);
}

.error-message::before {
  content: "⚠";
  flex-shrink: 0;
}

.error-container {
  background-color: var(--color-error-bg);
  border: 1px solid var(--color-error);
  border-radius: var(--border-radius);
  padding: var(--spacing-lg);
  text-align: center;
  margin-bottom: var(--spacing-lg);
}

.retry-link {
  color: var(--color-primary);
  text-decoration: underline;
  margin-top: var(--spacing-sm);
  display: inline-block;
}

/* Instructions */
.instructions {
  background-color: var(--color-surface);
  border-radius: var(--border-radius);
  padding: var(--spacing-lg);
}

.instructions h2 {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: var(--spacing-md);
}

.instructions ol {
  padding-left: var(--spacing-lg);
}

.instructions li {
  margin-bottom: var(--spacing-sm);
}

/* Thread */
.thread {
  margin-bottom: var(--spacing-2xl);
}

.thread-meta {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-lg);
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.author-link {
  color: var(--color-text);
  text-decoration: none;
  font-weight: 500;
}

@media (hover: hover) {
  .author-link:hover {
    text-decoration: underline;
  }
}

.author-name {
  color: var(--color-text);
  font-weight: 500;
}

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

.original-link {
  color: var(--color-primary);
  text-decoration: none;
  font-size: 0.875rem;
}

@media (hover: hover) {
  .original-link:hover {
    text-decoration: underline;
  }
}

.thread-empty {
  text-align: center;
  padding: var(--spacing-2xl);
  color: var(--color-text-muted);
}

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

.thread-loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-md);
  padding: var(--spacing-2xl);
  min-height: 200px;
}

.loading-spinner {
  width: 2rem;
  height: 2rem;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

/* Page Transitions */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.home-content,
.thread-content {
  animation: fadeIn 0.3s ease-out;
}

/* Post */
.post {
  padding-bottom: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
  border-bottom: 1px solid var(--color-border);
  animation: fadeIn 0.4s ease-out backwards;
}

.post:nth-child(1) { animation-delay: 0ms; }
.post:nth-child(2) { animation-delay: 50ms; }
.post:nth-child(3) { animation-delay: 100ms; }
.post:nth-child(4) { animation-delay: 150ms; }
.post:nth-child(5) { animation-delay: 200ms; }
.post:nth-child(n+6) { animation-delay: 250ms; }

.post:last-child {
  border-bottom: none;
  margin-bottom: 0;
  padding-bottom: 0;
}

.post-content {
  font-size: 1.0625rem;
  line-height: 1.75;
}

.post-content p {
  margin-bottom: var(--spacing-md);
}

.post-content p:last-child {
  margin-bottom: 0;
}

.post-content a {
  color: var(--color-primary);
  text-decoration: underline;
}

.post-content code {
  font-family: var(--font-mono);
  background-color: var(--color-surface);
  padding: 0.125rem 0.375rem;
  border-radius: 0.25rem;
  font-size: 0.875em;
}

.post-content pre {
  background-color: var(--color-surface);
  padding: var(--spacing-md);
  border-radius: var(--border-radius);
  overflow-x: auto;
  margin: var(--spacing-md) 0;
}

.post-content pre code {
  background: none;
  padding: 0;
}

.post-content blockquote {
  border-left: 3px solid var(--color-border);
  padding-left: var(--spacing-md);
  margin: var(--spacing-md) 0;
  color: var(--color-text-muted);
}

.post-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: var(--spacing-md);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.post-time {
  color: inherit;
}

.post-time-link {
  color: var(--color-text-muted);
  text-decoration: none;
}

@media (hover: hover) {
  .post-time-link:hover {
    text-decoration: underline;
  }
}

.post-link {
  color: var(--color-primary);
  text-decoration: none;
}

@media (hover: hover) {
  .post-link:hover {
    text-decoration: underline;
  }
}

/* Locale Switcher */
.locale-switcher {
  display: inline-block;
}

.locale-select {
  padding: var(--spacing-xs) var(--spacing-sm);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  background-color: var(--color-background);
  color: var(--color-text);
  font-size: 0.875rem;
  cursor: pointer;
}

.locale-select:focus-visible {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--focus-ring);
}

.locale-select option {
  background-color: var(--color-background);
  color: var(--color-text);
}

/* Screen reader only */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* Skip Link */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--spacing-md);
  padding: var(--spacing-sm) var(--spacing-md);
  background-color: var(--color-primary);
  color: white;
  text-decoration: none;
  border-radius: var(--border-radius);
  z-index: var(--z-toast);
  transition: top 0.2s ease-out;
}

.skip-link:focus {
  top: var(--spacing-md);
}

/* Responsive */
@media (max-width: 640px) {
  .container {
    padding: var(--spacing-md);
  }

  .header h1 {
    font-size: 1.5rem;
  }

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

  .submit-button {
    width: 100%;
  }

  .nav {
    flex-direction: column;
    gap: var(--spacing-sm);
    text-align: center;
  }

  .header--compact {
    flex-wrap: wrap;
    gap: var(--spacing-xs);
  }

  .header--compact .header__title-link {
    order: -1;
    width: 100%;
    text-align: center;
    margin-bottom: var(--spacing-xs);
  }

  .thread-meta {
    flex-direction: column;
    gap: var(--spacing-sm);
    text-align: center;
  }
}

/* Touch Targets */
@media (pointer: coarse) {
  .back-link,
  .original-link,
  .post-link,
  .retry-link {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
    padding: var(--spacing-sm);
  }

  .locale-select {
    min-height: 44px;
    padding: var(--spacing-sm) var(--spacing-md);
  }
}

/* Print Styles */
@media print {
  /* Hide navigation and interactive elements */
  .nav,
  .url-form,
  .locale-switcher,
  .skip-link,
  .retry-link {
    display: none !important;
  }

  /* Reset colors for print */
  :root {
    --color-text: #000;
    --color-text-muted: #333;
    --color-background: #fff;
    --color-surface: #f5f5f5;
    --color-border: #ccc;
    --color-primary: #000;
  }

  /* Remove animations */
  *,
  *::before,
  *::after {
    animation: none !important;
    transition: none !important;
  }

  /* Show link URLs */
  .post-content a[href]::after {
    content: " (" attr(href) ")";
    font-size: 0.75em;
    color: #666;
  }

  /* Optimize page breaks */
  .post {
    page-break-inside: avoid;
  }

  .thread-meta {
    page-break-after: avoid;
  }

  /* Adjust spacing for print */
  .container {
    max-width: 100%;
    padding: 0;
  }

  .header {
    margin-bottom: 1rem;
  }
}