:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --panel: #f7f7f8;
  --border: #d8d8dd;
  --text: #222222;
  --muted: #666;
  --accent: #4f46e5;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #151519;
    --panel: #1f1f26;
    --border: #32323d;
    --text: #efeff5;
    --muted: #a0a0b2;
    --accent: #7c82ff;
  }
}

* { box-sizing: border-box; }

html,
body {
  height: 100%;
}

body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  background: var(--bg);
  color: var(--text);
  min-height: 100dvh;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

header {
  padding: 0.9rem 1rem;
  border-bottom: 1px solid var(--border);
  background: var(--panel);
}

h1 {
  margin: 0;
  font-size: 1rem;
  font-weight: 700;
}

.layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  flex: 1;
  min-height: 0;
}

.pane {
  display: flex;
  flex-direction: column;
  min-width: 0;
  min-height: 0;
}

.pane + .pane {
  border-left: 1px solid var(--border);
}

.pane-label {
  margin: 0;
  padding: 0.6rem 0.8rem;
  font-size: 0.85rem;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
  background: color-mix(in srgb, var(--panel) 92%, transparent);
}

textarea {
  width: 100%;
  flex: 1;
  min-height: 0;
  padding: 1rem;
  border: 0;
  resize: none;
  background: transparent;
  color: var(--text);
  font-size: 0.95rem;
  line-height: 1.6;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
}

textarea:focus { outline: 2px solid var(--accent); outline-offset: -2px; }

.preview {
  flex: 1;
  overflow: auto;
  padding: 1rem;
  line-height: 1.7;
}

.preview pre {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.75rem;
  overflow: auto;
}

.preview code {
  background: color-mix(in srgb, var(--panel) 85%, transparent);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.1rem 0.3rem;
}

.preview blockquote {
  margin: 1rem 0;
  padding-left: 0.9rem;
  border-left: 4px solid var(--border);
  color: var(--muted);
}

.preview table {
  border-collapse: collapse;
}

.preview th,
.preview td {
  border: 1px solid var(--border);
  padding: 0.35rem 0.5rem;
}

@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr 1fr;
  }

  .pane + .pane {
    border-left: 0;
    border-top: 1px solid var(--border);
  }
}