:root {
  --bg: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-tertiary: #e9ecef;
  --text: #212529;
  --text-secondary: #6c757d;
  --border: #dee2e6;
  --primary: #0d6efd;
  --primary-hover: #0b5ed7;
  --primary-light: #e7f1ff;
  --sidebar-bg: #f8f9fa;
  --sidebar-width: 280px;
  --header-height: 56px;
  --code-bg: #f1f3f5;
  --blockquote-border: #0d6efd;
  --table-stripe: #f8f9fa;
  --shadow: 0 2px 8px rgba(0,0,0,0.08);
  --scrollbar-thumb: #ced4da;
  --scrollbar-track: #f1f3f5;
  --link-color: #0d6efd;
  --hover-bg: #e9ecef;
}

[data-theme="dark"] {
  --bg: #1a1a2e;
  --bg-secondary: #16213e;
  --bg-tertiary: #0f3460;
  --text: #e4e6eb;
  --text-secondary: #a8b2c1;
  --border: #2d3748;
  --primary: #4facfe;
  --primary-hover: #3d9be8;
  --primary-light: #1a2744;
  --sidebar-bg: #16213e;
  --code-bg: #0f3460;
  --blockquote-border: #4facfe;
  --table-stripe: #16213e;
  --shadow: 0 2px 8px rgba(0,0,0,0.3);
  --scrollbar-thumb: #2d3748;
  --scrollbar-track: #1a1a2e;
  --link-color: #4facfe;
  --hover-bg: #0f3460;
}

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

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-height) + 20px); }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  transition: background 0.3s, color 0.3s;
}

/* Scrollbar */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--scrollbar-track); }
::-webkit-scrollbar-thumb { background: var(--scrollbar-thumb); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-secondary); }

/* Header */
.header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  height: var(--header-height);
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 20px;
  box-shadow: var(--shadow);
  transition: background 0.3s, border-color 0.3s;
}

.header-left { display: flex; align-items: center; gap: 12px; }

.header-title {
  font-size: 18px; font-weight: 700; color: var(--text);
  white-space: nowrap;
}
.header-title span { color: var(--primary); }

.hamburger {
  display: none; background: none; border: none; cursor: pointer;
  padding: 6px; border-radius: 6px; color: var(--text);
  transition: background 0.2s;
}
.hamburger:hover { background: var(--hover-bg); }
.hamburger svg { width: 24px; height: 24px; }

.header-right { display: flex; align-items: center; gap: 10px; }

.lang-select, .search-input {
  padding: 6px 12px; border-radius: 8px;
  border: 1px solid var(--border); background: var(--bg-secondary);
  color: var(--text); font-size: 14px; outline: none;
  transition: border-color 0.2s, background 0.2s;
}
.lang-select:focus, .search-input:focus { border-color: var(--primary); }
.lang-select { max-width: 200px; cursor: pointer; }
.search-input { width: 200px; }
.search-input::placeholder { color: var(--text-secondary); }

.icon-btn {
  background: none; border: none; cursor: pointer;
  padding: 8px; border-radius: 8px; color: var(--text);
  transition: background 0.2s; font-size: 18px; line-height: 1;
}
.icon-btn:hover { background: var(--hover-bg); }
.icon-btn svg { width: 20px; height: 20px; }

/* Sidebar */
.sidebar {
  position: fixed; top: var(--header-height); left: 0; bottom: 0;
  width: var(--sidebar-width); background: var(--sidebar-bg);
  border-right: 1px solid var(--border); overflow-y: auto;
  padding: 16px 0; z-index: 50;
  transition: transform 0.3s ease, background 0.3s, border-color 0.3s;
}

.sidebar-section { margin-bottom: 4px; }

.sidebar-link {
  display: block; padding: 6px 20px; color: var(--text-secondary);
  text-decoration: none; font-size: 13px; line-height: 1.4;
  transition: color 0.2s, background 0.2s, border-left-color 0.2s;
  border-left: 3px solid transparent;
}
.sidebar-link:hover { color: var(--primary); background: var(--primary-light); }
.sidebar-link.active {
  color: var(--primary); font-weight: 600;
  border-left-color: var(--primary); background: var(--primary-light);
}
.sidebar-link.h3 { padding-left: 36px; font-size: 12px; }

.sidebar-search-empty {
  padding: 20px; text-align: center; color: var(--text-secondary); font-size: 13px;
}

/* Main content */
.main {
  margin-left: var(--sidebar-width);
  padding: calc(var(--header-height) + 32px) 32px 60px 32px;
  max-width: calc(var(--sidebar-width) + 800px + 64px);
  min-height: 100vh;
  transition: margin-left 0.3s;
}

.content {
  max-width: 800px; margin: 0 auto;
}

/* Markdown rendered content */
.content h1 { font-size: 2em; margin-bottom: 8px; border-bottom: 2px solid var(--border); padding-bottom: 12px; }
.content h2 {
  font-size: 1.5em; margin-top: 40px; margin-bottom: 16px;
  padding-bottom: 8px; border-bottom: 1px solid var(--border);
  scroll-margin-top: calc(var(--header-height) + 20px);
}
.content h3 { font-size: 1.2em; margin-top: 28px; margin-bottom: 12px; scroll-margin-top: calc(var(--header-height) + 20px); }
.content p { margin-bottom: 14px; }
.content ul, .content ol { margin-bottom: 14px; padding-left: 24px; }
.content li { margin-bottom: 4px; }
.content a { color: var(--link-color); text-decoration: none; }
.content a:hover { text-decoration: underline; }

.content blockquote {
  border-left: 4px solid var(--blockquote-border);
  padding: 12px 20px; margin: 16px 0;
  background: var(--bg-secondary); border-radius: 0 8px 8px 0;
}
.content blockquote p:last-child { margin-bottom: 0; }

.content code {
  background: var(--code-bg); padding: 2px 6px; border-radius: 4px;
  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  font-size: 0.9em;
}
.content pre {
  background: var(--code-bg); padding: 16px; border-radius: 8px;
  overflow-x: auto; margin: 16px 0;
}
.content pre code { background: none; padding: 0; font-size: 0.85em; }

.content table {
  width: 100%; border-collapse: collapse; margin: 16px 0;
  font-size: 0.95em;
}
.content th, .content td {
  border: 1px solid var(--border); padding: 10px 14px; text-align: left;
}
.content th { background: var(--bg-secondary); font-weight: 600; }
.content tr:nth-child(even) { background: var(--table-stripe); }

.content hr { border: none; border-top: 1px solid var(--border); margin: 32px 0; }

.content strong { font-weight: 700; }

.content img { max-width: 100%; height: auto; border-radius: 8px; }

/* Download button */
.download-btn {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 6px 14px; border-radius: 8px;
  background: var(--bg-secondary); border: 1px solid var(--border);
  color: var(--text); font-size: 13px; cursor: pointer;
  transition: background 0.2s, border-color 0.2s;
  text-decoration: none;
}
.download-btn:hover { background: var(--hover-bg); border-color: var(--primary); }

/* Scroll to top */
.scroll-top {
  position: fixed; bottom: 24px; right: 24px; z-index: 90;
  width: 44px; height: 44px; border-radius: 50%;
  background: var(--primary); color: white; border: none;
  cursor: pointer; display: flex; align-items: center; justify-content: center;
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
  opacity: 0; transform: translateY(10px);
  transition: opacity 0.3s, transform 0.3s, background 0.2s;
}
.scroll-top.visible { opacity: 1; transform: translateY(0); }
.scroll-top:hover { background: var(--primary-hover); }

/* Heading alias anchor — invisible, sirve para anchors del MD que quedaron
 * en inglés cuando el heading visible está en otro idioma (ja/zh/ko/ar).
 * Permite que #what-is-esperantai navegue al heading "EsperantAIとは？". */
.heading-alias-anchor {
  display: block;
  height: 0;
  width: 0;
  overflow: hidden;
  scroll-margin-top: var(--header-height);
}
.scroll-top svg { width: 20px; height: 20px; }

/* Overlay for mobile */
.sidebar-overlay {
  display: none; position: fixed; inset: 0; z-index: 40;
  background: rgba(0,0,0,0.4);
}

/* RTL support */
[dir="rtl"] .sidebar { left: auto; right: 0; border-right: none; border-left: 1px solid var(--border); }
[dir="rtl"] .main { margin-left: 0; margin-right: var(--sidebar-width); }
[dir="rtl"] .sidebar-link { border-left: none; border-right: 3px solid transparent; }
[dir="rtl"] .sidebar-link.active { border-right-color: var(--primary); border-left: none; }
[dir="rtl"] .content blockquote { border-left: none; border-right: 4px solid var(--blockquote-border); border-radius: 8px 0 0 8px; }
[dir="rtl"] .content ul, [dir="rtl"] .content ol { padding-left: 0; padding-right: 24px; }

/* Responsive */
@media (max-width: 768px) {
  .hamburger { display: flex; }
  .sidebar {
    transform: translateX(-100%);
    width: 280px;
  }
  [dir="rtl"] .sidebar { transform: translateX(100%); }
  .sidebar.open { transform: translateX(0); }
  .sidebar-overlay.open { display: block; }
  .main { margin-left: 0 !important; margin-right: 0 !important; padding: calc(var(--header-height) + 20px) 16px 60px 16px; }
  .search-input { width: 140px; }
  .lang-select { max-width: 150px; }
  .header-title { font-size: 15px; }
}

@media (max-width: 480px) {
  .search-input { display: none; }
  .header-right { gap: 6px; }
  .content h1 { font-size: 1.6em; }
  .content h2 { font-size: 1.3em; }
}

/* Theme transition */
body, .header, .sidebar, .main, .lang-select, .search-input {
  transition: background 0.3s, color 0.3s, border-color 0.3s;
}

/* Footer */
.footer {
  text-align: center; padding: 32px 0; margin-top: 48px;
  border-top: 1px solid var(--border); color: var(--text-secondary);
  font-size: 13px;
}