:root {
  /* Colors - Light Theme (Default) */
  --bg-color: #f8f9fa;
  --text-color: #212529;
  --card-bg: #ffffff;
  --header-bg: rgba(255, 255, 255, 0.95);
  --border-color: #dee2e6;
  --primary-color: #0d6efd;
  --accent-color: #6610f2;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  
  /* Link Color */
  --link-color: #0056b3;

  /* Spacing */
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;

  /* Modal Z-Index */
  --z-modal: 2000;

  /* Scrollbar color scheme */
  color-scheme: light dark;
}

[data-theme="dark"] {
  --bg-color: #121212;
  --text-color: #e0e0e0;
  --card-bg: #1e1e1e;
  --header-bg: rgba(30, 30, 30, 0.95);
  --border-color: #333;
  --link-color: #6ea8fe;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.5), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.5;
  /* No transition on background-color to prevent flicker */
}

a {
  color: var(--link-color);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* Language Switching (i18n) */
.lang-en {
  display: none;
}

html[lang="en"] .lang-ja {
  display: none;
}

html[lang="en"] .lang-en {
  display: inline;
}

/* For block-level elements */
html[lang="en"] p.lang-ja,
html[lang="en"] div.lang-ja,
html[lang="en"] h1.lang-ja,
html[lang="en"] h2.lang-ja,
html[lang="en"] h3.lang-ja {
  display: none;
}

html[lang="en"] p.lang-en,
html[lang="en"] div.lang-en,
html[lang="en"] h1.lang-en,
html[lang="en"] h2.lang-en,
html[lang="en"] h3.lang-en {
  display: block;
}

/* Custom Scrollbar for Dark Mode Support */
::-webkit-scrollbar {
  width: 12px;
  height: 12px;
}

::-webkit-scrollbar-track {
  background: var(--bg-color);
}

::-webkit-scrollbar-thumb {
  background-color: var(--border-color);
  border: 3px solid var(--bg-color);
  border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
  background-color: #888;
}

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background-color: var(--header-bg);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-color);
  padding: var(--space-sm) 0;
}

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

.brand {
  font-weight: bold;
  font-size: 1.25rem;
  color: var(--text-color);
  text-decoration: none;
}

.header-controls {
  display: flex;
  gap: var(--space-md);
  align-items: center;
}

.header-controls select,
.header-controls button {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-color);
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 0.9rem;
  cursor: pointer;
}

.header-controls select option {
  background-color: var(--card-bg);
  color: var(--text-color);
}

/* Footer */
.site-footer {
  margin-top: var(--space-lg);
  padding: var(--space-lg) 0;
  border-top: 1px solid var(--border-color);
  font-size: 0.9rem;
  color: #6c757d;
}

[data-theme="dark"] .site-footer {
  color: #adb5bd;
}

.site-footer p {
  margin: var(--space-sm) 0;
}

/* Utilities */
.text-center {
  text-align: center;
}

.mb-1 {
  margin-bottom: var(--space-sm);
}

.mb-2 {
  margin-bottom: var(--space-md);
}

.mb-3 {
  margin-bottom: var(--space-lg);
}

/* Card Styles (used in Index) */
.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-lg);
}

.tool-card {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: var(--space-lg);
  box-shadow: var(--shadow);
  transition: transform 0.2s, box-shadow 0.2s;
  display: flex;
  flex-direction: column;
  position: relative;
}

.tool-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

/* Make entire card clickable */
.tool-card h3 a::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1;
}

.tool-card h3 {
  margin-top: 0;
  margin-bottom: var(--space-sm);
}

.tool-card h3 a {
  color: var(--text-color);
}

.tool-desc {
  font-size: 0.95rem;
  margin-bottom: var(--space-md);
  flex-grow: 1;
}

/* Markdown/Common Tool Content Wrapper */
.tool-content {
  padding: var(--space-lg) 0;
}

/* Hide elements based on lang */
html[lang="ja"] .lang-en {
  display: none !important;
}

html[lang="en"] .lang-ja {
  display: none !important;
}

/* --- Footer Links & Modal --- */

.footer-links {
  display: flex;
  gap: var(--space-md);
  justify-content: center;
  margin-bottom: var(--space-md);
  flex-wrap: wrap;
}

.footer-icon-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-color);
  font-weight: 500;
  opacity: 0.8;
  transition: opacity 0.2s;
}

.footer-icon-link:hover {
  opacity: 1;
  text-decoration: none;
}

.footer-sep {
  color: var(--border-color);
}

/* Privacy Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(2px);
  z-index: var(--z-modal);
  display: none;
  justify-content: center;
  align-items: center;
  padding: 20px;
  opacity: 0;
  transition: opacity 0.3s;
}

.modal-overlay.open {
  display: flex;
  opacity: 1;
}

.modal-content {
  background: var(--card-bg);
  width: 100%;
  max-width: 600px;
  max-height: 85vh;
  border-radius: 16px;
  box-shadow: var(--shadow);
  position: relative;
  border: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
}

.modal-header {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.modal-title {
  font-weight: bold;
  font-size: 1.1rem;
  margin: 0;
}

.modal-close-btn {
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: 50%;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--text-color);
  transition: background 0.2s;
  flex-shrink: 0;
}

.modal-close-btn:hover {
  background: rgba(0, 0, 0, 0.05);
}

[data-theme="dark"] .modal-close-btn:hover {
  background: rgba(255, 255, 255, 0.1);
}

.modal-body {
  padding: 24px;
  overflow-y: auto;
  font-size: 0.95rem;
  line-height: 1.7;
}

.modal-body h3 {
  font-size: 1rem;
  margin-top: 1.5em;
  margin-bottom: 0.5em;
  color: var(--primary-color);
}

.modal-body h3:first-child {
  margin-top: 0;
}