:root {
  --bg: #ffffff;
  --bg-alt: #f6f8fa;
  --fg: #1f2328;
  --muted: #656d76;
  --border: #d0d7de;
  --accent: #0969da;
  --toolbar-h: 48px;
}
[data-theme="dark"] {
  --bg: #0d1117;
  --bg-alt: #161b22;
  --fg: #e6edf3;
  --muted: #8b949e;
  --border: #30363d;
  --accent: #58a6ff;
}

* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--fg);
  background: var(--bg);
  display: flex;
  flex-direction: column;
}

/* Toolbar */
.toolbar {
  height: var(--toolbar-h);
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0 12px;
  background: var(--bg-alt);
  border-bottom: 1px solid var(--border);
  flex: 0 0 auto;
}
.brand { font-weight: 600; }
.spacer { flex: 1; }
.chk { font-size: 13px; color: var(--muted); display: flex; align-items: center; gap: 4px; }
.toolbar button {
  font: inherit;
  font-size: 13px;
  padding: 5px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg);
  color: var(--fg);
  cursor: pointer;
}
.toolbar button:hover { border-color: var(--accent); color: var(--accent); }

/* Split panes — editor | gutter | preview. --split = editor width (%). */
.split {
  flex: 1 1 auto;
  display: grid;
  grid-template-columns: var(--split, 50%) 6px 1fr;
  min-height: 0;
}
#gutter {
  background: var(--border);
  cursor: col-resize;
  transition: background .15s;
}
#gutter:hover, #gutter.dragging { background: var(--accent); }
.split.dragging { user-select: none; cursor: col-resize; }
#editor {
  border: none;
  resize: none;
  padding: 16px;
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  font-size: 14px;
  line-height: 1.6;
  background: var(--bg);
  color: var(--fg);
  outline: none;
  overflow: auto;
}
#preview {
  padding: 16px 24px;
  overflow: auto;
  background: var(--bg);
}
@media (max-width: 720px) {
  .split { grid-template-columns: 1fr; grid-template-rows: 1fr 6px 1fr; }
  #gutter { cursor: row-resize; }
}

/* Toast */
.toast {
  position: fixed;
  bottom: 16px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--fg);
  color: var(--bg);
  padding: 8px 14px;
  border-radius: 6px;
  font-size: 13px;
  z-index: 10;
}

/* Rendered markdown (GitHub-ish) */
.markdown-body { line-height: 1.6; font-size: 16px; }
.markdown-body h1, .markdown-body h2 { border-bottom: 1px solid var(--border); padding-bottom: .3em; }
.markdown-body h1, .markdown-body h2, .markdown-body h3, .markdown-body h4 { margin-top: 1.2em; }
.markdown-body code {
  background: var(--bg-alt);
  padding: .2em .4em;
  border-radius: 6px;
  font-family: ui-monospace, monospace;
  font-size: 85%;
}
.markdown-body pre {
  background: var(--bg-alt);
  padding: 14px;
  border-radius: 8px;
  overflow: auto;
}
.markdown-body pre code { background: none; padding: 0; }
.markdown-body blockquote {
  margin: 0;
  padding: 0 1em;
  color: var(--muted);
  border-left: 4px solid var(--border);
}
.markdown-body table { border-collapse: collapse; }
.markdown-body th, .markdown-body td { border: 1px solid var(--border); padding: 6px 12px; }
.markdown-body tr:nth-child(2n) { background: var(--bg-alt); }
.markdown-body img { max-width: 100%; }
.markdown-body a { color: var(--accent); }

/* Print / PDF: only the preview */
@media print {
  .toolbar, #editor, #gutter { display: none !important; }
  .split { display: block; }
  #preview { overflow: visible; padding: 0; }
}