:root {
  color-scheme: light;
  --bg: #f6f8fa;
  --surface: #ffffff;
  --border: #d1d9e0;
  --text: #1f2328;
  --muted: #59636e;
  --accent: #0969da;
  --accent-bg: #0969da;
  --accent-text: #ffffff;
  --hover: #eff2f5;
  --overlay: rgba(9, 105, 218, 0.08);
  --toast-bg: #1f2328;
  --toast-text: #ffffff;
  --danger: #d1242f;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans", Helvetica, Arial, sans-serif;
}

@media screen and (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --bg: #010409;
    --surface: #0d1117;
    --border: #3d444d;
    --text: #f0f6fc;
    --muted: #9198a1;
    --accent: #4493f8;
    --accent-bg: #1f6feb;
    --accent-text: #ffffff;
    --hover: #151b23;
    --overlay: rgba(68, 147, 248, 0.12);
    --toast-bg: #f0f6fc;
    --toast-text: #0d1117;
    --danger: #f85149;
  }
}

@media screen {
  :root[data-theme="dark"] {
    color-scheme: dark;
    --bg: #010409;
    --surface: #0d1117;
    --border: #3d444d;
    --text: #f0f6fc;
    --muted: #9198a1;
    --accent: #4493f8;
    --accent-bg: #1f6feb;
    --accent-text: #ffffff;
    --hover: #151b23;
    --overlay: rgba(68, 147, 248, 0.12);
    --toast-bg: #f0f6fc;
    --toast-text: #0d1117;
    --danger: #f85149;
  }
}

*, *::before, *::after { box-sizing: border-box; }

[hidden] { display: none !important; }

html, body { height: 100%; margin: 0; }

body {
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto;
  height: 100vh;
  height: 100dvh;
  background: var(--bg);
  color: var(--text);
  font: 14px/1.4 var(--sans);
}

/* Toolbar */

.toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 12px;
  padding: 8px 16px;
  border-bottom: 1px solid var(--border);
  background: var(--bg);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-right: auto;
  color: var(--text);
  font-size: 15px;
  font-weight: 600;
  text-decoration: none;
}

.brand svg { width: 22px; height: 22px; flex: none; }

.button-group { display: flex; flex-wrap: wrap; gap: 4px; }

.toolbar button {
  padding: 4px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface);
  color: var(--text);
  font: 500 13px/20px var(--sans);
  white-space: nowrap;
  cursor: pointer;
}

.toolbar button:hover { background: var(--hover); }

.toolbar button[aria-pressed="true"] {
  border-color: var(--accent-bg);
  background: var(--accent-bg);
  color: var(--accent-text);
}

.toolbar button:focus-visible, .brand:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

/* Workspace */

.workspace {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  grid-template-rows: minmax(0, 1fr);
  min-height: 0;
}

.workspace[data-view="editor"], .workspace[data-view="preview"] { grid-template-columns: minmax(0, 1fr); }

.workspace[data-view="editor"] .preview-pane, .workspace[data-view="preview"] .editor-pane { display: none; }

.editor-pane {
  position: relative;
  min-height: 0;
  overflow: hidden;
  border-right: 1px solid var(--border);
  background: var(--surface);
}

.workspace[data-view="editor"] .editor-pane { border-right: 0; }

/* The mirror must lay text out exactly like the textarea: scroll sync measures line positions in it. */
.editor, .editor-mirror {
  margin: 0;
  padding: 24px;
  border: 0;
  font: 13.5px/1.65 var(--mono);
  letter-spacing: normal;
  white-space: pre-wrap;
  overflow-wrap: break-word;
  word-break: normal;
  tab-size: 4;
}

.editor {
  display: block;
  width: 100%;
  height: 100%;
  resize: none;
  outline: none;
  overflow-y: auto;
  background: var(--surface);
  color: var(--text);
}

.workspace[data-view="editor"] .editor { padding-inline: max(24px, calc((100% - 900px) / 2)); }

.editor-mirror {
  position: absolute;
  top: 0;
  left: 0;
  height: 0;
  overflow: hidden;
  visibility: hidden;
  pointer-events: none;
}

/* Paint containment makes the pane the containing block for position: fixed, so markup inside a document
   can never cover the toolbar or the editor. */
.preview-pane {
  position: relative;
  min-height: 0;
  overflow-y: auto;
  background: var(--surface);
  contain: paint;
}

.preview-pane .markdown-body {
  max-width: 900px;
  margin: 0 auto;
  padding: 32px;
  background: transparent;
}

.markdown-body pre code.hljs { padding: 0; background: transparent; }

.markdown-body .katex-display { overflow-x: auto; overflow-y: hidden; }

.mermaid-diagram {
  display: flex;
  justify-content: center;
  margin-bottom: 16px;
  overflow-x: auto;
}

.mermaid-diagram svg { max-width: 100%; height: auto; }

/* Mermaid's layout area: off-screen, never display:none (SVG text must stay measurable). Paint containment makes
   it the containing block for position:fixed labels and clips them to its empty box. */
.mermaid-host {
  position: fixed;
  top: 0;
  left: -10000px;
  width: 900px;
  height: 0;
  overflow: hidden;
  visibility: hidden;
  pointer-events: none;
  contain: layout paint style;
}

.diagram-error, .render-error {
  margin: 0 0 16px;
  padding: 12px 16px;
  border: 1px solid var(--danger);
  border-radius: 6px;
  color: var(--danger);
  font: 12px/1.5 var(--mono);
  white-space: pre-wrap;
}

/* Status bar */

.status {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 16px;
  padding: 4px 16px;
  border-top: 1px solid var(--border);
  background: var(--bg);
  color: var(--muted);
  font-size: 12px;
}

.status-note { margin-left: auto; }

/* Overlays */

.drop-overlay {
  position: fixed;
  inset: 12px;
  z-index: 20;
  display: grid;
  place-items: center;
  border: 2px dashed var(--accent);
  border-radius: 12px;
  background: var(--overlay);
  color: var(--text);
  font-size: 18px;
  font-weight: 600;
  pointer-events: none;
}

.toast {
  position: fixed;
  left: 50%;
  bottom: 40px;
  z-index: 30;
  max-width: min(560px, calc(100vw - 32px));
  padding: 10px 16px;
  border-radius: 8px;
  background: var(--toast-bg);
  color: var(--toast-text);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
  transform: translateX(-50%);
}

.noscript { padding: 16px; }

@media (max-width: 760px) {
  .workspace { grid-template-columns: minmax(0, 1fr); grid-template-rows: minmax(0, 1fr) minmax(0, 1fr); }
  .workspace[data-view="editor"], .workspace[data-view="preview"] { grid-template-rows: minmax(0, 1fr); }
  .editor-pane { border-right: 0; border-bottom: 1px solid var(--border); }
  .editor, .editor-mirror, .workspace[data-view="editor"] .editor { padding: 16px; }
  .preview-pane .markdown-body { padding: 16px; }
  .status-note { display: none; }
}

@media print {
  html, body { height: auto; }
  body { display: block; background: #ffffff; }
  .toolbar, .status, .editor-pane, .drop-overlay, .toast { display: none !important; }
  .workspace { display: block; }
  .preview-pane { display: block !important; overflow: visible; contain: none; }
  .preview-pane .markdown-body { max-width: none; padding: 0; }
}