:root {
  --bg: #f7f8fa;
  --panel: #ffffff;
  --border: #e3e6eb;
  --text: #1f2328;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-soft: #dbeafe;
  --code-bg: #f3f4f6;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  height: 100%;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.app {
  display: grid;
  grid-template-columns: 280px 1fr 220px;
  height: 100vh;
}

.sidebar {
  background: var(--panel);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.brand {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border);
  font-size: 18px;
}
.brand a { color: var(--text); }

.search {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
}
.search input {
  width: 100%;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13px;
  outline: none;
}
.search input:focus { border-color: var(--accent); }

.docs-nav {
  overflow-y: auto;
  flex: 1;
  padding: 8px 0;
}

.docs-nav ul { list-style: none; margin: 0; padding: 0; }

.doc-item a {
  display: block;
  padding: 8px 20px;
  font-size: 14px;
  color: var(--text);
  border-left: 3px solid transparent;
}
.doc-item a:hover {
  background: var(--accent-soft);
  text-decoration: none;
}
.doc-item.active a {
  background: var(--accent-soft);
  border-left-color: var(--accent);
  font-weight: 600;
}

.empty { color: var(--muted); padding: 16px 20px; font-size: 14px; }

.folder-item details { margin: 0; }
.folder-item summary {
  padding: 8px 20px 8px 16px;
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  user-select: none;
}
.folder-item summary::-webkit-details-marker { display: none; }
.folder-item summary::before {
  content: '\203A';
  display: inline-block;
  margin-right: 4px;
  font-size: 16px;
  transition: transform 0.15s ease;
}
.folder-item details[open] > summary::before {
  transform: rotate(90deg);
}
.folder-item summary:hover { color: var(--accent); }
.folder-item details > ul {
  padding-left: 14px;
  border-left: 1px solid var(--border);
  margin-left: 20px;
}
.folder-item .doc-item a { padding-left: 24px; font-size: 13.5px; }
.folder-item .doc-item.active a { padding-left: 24px; }

.content {
  background: var(--bg);
  overflow-y: auto;
  padding: 32px 48px;
  line-height: 1.65;
  font-size: 15px;
}

.doc {
  max-width: 820px;
  margin: 0 auto;
  background: var(--panel);
  padding: 32px 40px;
  border-radius: 8px;
  border: 1px solid var(--border);
}

.doc-placeholder, .error-box {
  max-width: 820px;
  margin: 80px auto;
  background: var(--panel);
  padding: 32px 40px;
  border-radius: 8px;
  border: 1px solid var(--border);
  text-align: center;
}

.doc h1, .doc h2, .doc h3, .doc h4 {
  margin-top: 1.6em;
  margin-bottom: 0.6em;
  line-height: 1.3;
}
.doc h1 { font-size: 1.9em; border-bottom: 1px solid var(--border); padding-bottom: 0.3em; }
.doc h2 { font-size: 1.45em; border-bottom: 1px solid var(--border); padding-bottom: 0.25em; }
.doc h3 { font-size: 1.2em; }
.doc p { margin: 0.8em 0; }
.doc ul, .doc ol { padding-left: 1.6em; }
.doc li { margin: 0.3em 0; }
.doc code {
  background: var(--code-bg);
  padding: 2px 5px;
  border-radius: 4px;
  font-size: 0.9em;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
}
.doc pre {
  background: #0f172a;
  color: #e2e8f0;
  padding: 16px;
  border-radius: 8px;
  overflow-x: auto;
  font-size: 0.85em;
}
.doc pre code {
  background: transparent;
  color: inherit;
  padding: 0;
}
.doc blockquote {
  border-left: 4px solid var(--accent);
  margin: 1em 0;
  padding: 0.4em 1em;
  color: var(--muted);
  background: var(--accent-soft);
  border-radius: 0 6px 6px 0;
}
.doc table {
  border-collapse: collapse;
  width: 100%;
  margin: 1em 0;
}
.doc th, .doc td {
  border: 1px solid var(--border);
  padding: 8px 12px;
  text-align: left;
}
.doc th { background: var(--code-bg); }
.doc a { color: var(--accent); }

.toc {
  background: var(--panel);
  border-left: 1px solid var(--border);
  overflow-y: auto;
  padding: 24px 18px;
  font-size: 13px;
}
.toc h4 {
  margin: 0 0 12px 0;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
}
.toc ul { list-style: none; margin: 0; padding: 0; }
.toc li { margin: 4px 0; }
.toc li.toc-empty { color: var(--muted); font-style: italic; }
.toc li.lvl-3 { padding-left: 14px; font-size: 12px; }
.toc a { color: var(--text); }
.toc a:hover { color: var(--accent); }

.loading { color: var(--muted); padding: 20px 0; text-align: center; }
.hint { color: var(--muted); font-size: 14px; }

@media (max-width: 900px) {
  .app { grid-template-columns: 240px 1fr; }
  .toc { display: none; }
}
@media (max-width: 600px) {
  .app { grid-template-columns: 1fr; }
  .sidebar { display: none; }
  .content { padding: 16px; }
}