:root {
  --bg: #0d1117;
  --surface: #161b22;
  --border: #21262d;
  --accent: #58a6ff;
  --text: #c9d1d9;
  --muted: #6e7681;
  --hover: #1c2128;
  --active: #1f2937;
  --success: #3fb950;
  --topbar-h: 48px;
  --left-w: 300px;
}

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', system-ui, sans-serif;
  font-size: 14px;
  height: 100vh;
  overflow: hidden;
}

.layout {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

/* Topbar */
.topbar {
  height: var(--topbar-h);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 16px;
  gap: 24px;
  flex-shrink: 0;
}

.logo {
  font-weight: 600;
  color: var(--accent);
  font-size: 15px;
  letter-spacing: 0.3px;
}

.tabs {
  display: flex;
  gap: 4px;
}

.tab {
  background: none;
  border: none;
  color: var(--muted);
  cursor: pointer;
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 13px;
  font-weight: 500;
  transition: color 0.15s, background 0.15s;
}

.tab:hover { color: var(--text); background: var(--hover); }
.tab.active { color: var(--accent); background: var(--active); }

/* Main area */
.main {
  display: grid;
  grid-template-columns: var(--left-w) 1fr;
  flex: 1;
  min-height: 0;
  overflow: hidden;
}

/* Panels */
.panel {
  display: flex;
  flex-direction: column;
  min-height: 0;
  overflow: hidden;
}

.panel.left { border-right: 1px solid var(--border); }

.panel.hidden { display: none; }

.panel-header {
  padding: 8px 12px;
  font-size: 11px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.8px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  background: var(--surface);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* Tree */
.tree-container {
  overflow-y: auto;
  flex: 1;
  padding: 6px 0;
}

.tree-item {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 3px 8px;
  cursor: pointer;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  border-radius: 4px;
  margin: 1px 4px;
  font-size: 13px;
  color: var(--text);
  user-select: none;
}

.tree-item:hover { background: var(--hover); }
.tree-item.active { background: var(--active); color: var(--accent); }

.tree-item .icon {
  font-size: 12px;
  flex-shrink: 0;
  color: var(--muted);
}

.tree-item.dir .icon { color: #79c0ff; }
.tree-item.file .icon { color: var(--muted); }

.tree-children {
  padding-left: 16px;
}

.tree-item .toggle {
  font-size: 10px;
  color: var(--muted);
  flex-shrink: 0;
  width: 12px;
  text-align: center;
  transition: transform 0.15s;
}

.tree-item.open .toggle { transform: rotate(90deg); }

/* Content area */
.content-area {
  flex: 1;
  overflow: auto;
  padding: 0;
}

.content-area pre {
  margin: 0;
  padding: 16px;
  font-size: 13px;
  line-height: 1.6;
  background: transparent !important;
}

.content-area pre code {
  background: transparent !important;
  font-family: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
}

.empty-state {
  color: var(--muted);
  padding: 32px 16px;
  font-size: 13px;
}

.binary-notice {
  color: var(--muted);
  padding: 16px;
  font-style: italic;
}

/* Markdown */
.markdown-body {
  padding: 24px 28px;
  line-height: 1.7;
  max-width: 860px;
}

.markdown-body h1 { font-size: 22px; margin-bottom: 16px; color: var(--text); border-bottom: 1px solid var(--border); padding-bottom: 8px; }
.markdown-body h2 { font-size: 17px; margin: 24px 0 10px; color: var(--text); }
.markdown-body h3 { font-size: 15px; margin: 18px 0 8px; color: var(--text); }
.markdown-body p { margin-bottom: 12px; color: var(--text); }
.markdown-body code { background: var(--surface); border: 1px solid var(--border); padding: 1px 5px; border-radius: 3px; font-family: monospace; font-size: 12px; color: #f97583; }
.markdown-body pre { background: var(--surface) !important; border: 1px solid var(--border); border-radius: 6px; padding: 14px; margin: 12px 0; overflow-x: auto; }
.markdown-body pre code { background: none !important; border: none !important; color: var(--text); padding: 0; }
.markdown-body ul, .markdown-body ol { margin: 8px 0 12px 20px; }
.markdown-body li { margin: 4px 0; }
.markdown-body table { border-collapse: collapse; width: 100%; margin: 12px 0; }
.markdown-body th, .markdown-body td { border: 1px solid var(--border); padding: 7px 12px; text-align: left; }
.markdown-body th { background: var(--surface); font-weight: 600; color: var(--muted); font-size: 12px; text-transform: uppercase; letter-spacing: 0.5px; }
.markdown-body blockquote { border-left: 3px solid var(--accent); padding-left: 12px; color: var(--muted); margin: 12px 0; }
.markdown-body a { color: var(--accent); text-decoration: none; }
.markdown-body a:hover { text-decoration: underline; }
.markdown-body hr { border: none; border-top: 1px solid var(--border); margin: 20px 0; }

/* Know-how list */
.knowhow-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  cursor: pointer;
  border-radius: 4px;
  margin: 2px 4px;
  color: var(--text);
  font-size: 13px;
}
.knowhow-item:hover { background: var(--hover); }
.knowhow-item.active { background: var(--active); color: var(--accent); }
.knowhow-item .icon { color: var(--muted); font-size: 14px; }

/* Scrollbar */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--muted); }