diff --git a/README.md b/README.md
index 7bac394..45ca7a7 100644
--- a/README.md
+++ b/README.md
@@ -58,6 +58,7 @@ Also online at [p10node.github.io/office-engine](https://p10node.github.io/offic
 
 - [Features](docs/features.md): format coverage, editing, saving, limitations
 - [API](docs/api.md): props, custom views, `mount()`, `<office-viewer>`, core API, CSP
+- [Theming](docs/theming.md): design tokens, light / dark, loading the stylesheet yourself
 - [Real-time collaboration](docs/collaboration.md)
 - [Development](docs/development.md): playground, architecture, demo deploy, release
 
@@ -75,7 +76,7 @@ Also online at [p10node.github.io/office-engine](https://p10node.github.io/offic
 - **File menu**: new, open (also DOC / XLS / PPT / RTF / OpenDocument / Pages / Keynote / Numbers / CSV / text / Markdown / HTML / SVG / diagrams), import CSV, rename, download as PDF / HTML / text / CSV, document details, print
 - **Comments**: threads with replies, resolve, edit / delete, @mentions; on DOCX text, XLSX cells and PPTX slides, stored in the file the way Word, Excel and PowerPoint store them
 - **Real-time collaboration**: live edits, avatars, collaborators' cursors, offline edits sync on reconnect
-- **Dark mode**: `theme="dark"` or `"auto"` (follows the OS); documents keep their own colors
+- **Dark mode and theming**: `theme="dark"` or `"auto"` (follows the OS), or a theme object with design tokens for colors, type and shape ([Theming](docs/theming.md)); documents keep their own colors
 - **Embed anywhere**: React component, hook, vanilla `mount()`, `<office-viewer>` web component, single `<script>` file
 
 Full list, format coverage and limitations: [Features](docs/features.md).
diff --git a/docs/api.md b/docs/api.md
index 83858f6..ccae60c 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -46,7 +46,7 @@ PDF goes through the browser print dialog ("Save as PDF"), so text stays selecta
 />
 ```
 
-CSS is auto-injected, no import needed. Container must have a height.
+CSS is auto-injected, no import needed (or import `@p10node/office-engine/styles.css` with `injectStyles={false}`). Container must have a height. Colors, type and shape: [Theming](theming.md).
 
 | Prop               | Type                                           | Default   | Notes                                                                                                                    |
 |--------------------|------------------------------------------------|-----------|--------------------------------------------------------------------------------------------------------------------------|
@@ -60,7 +60,8 @@ CSS is auto-injected, no import needed. Container must have a height.
 | `credentials`      | `RequestCredentials`                           | –         | Cross-origin cookies                                                                                                     |
 | `worker`           | `() => Worker \| false`                        | inline    | Custom worker (CSP), `false` = main thread                                                                               |
 | `styleTarget`      | `Document \| ShadowRoot`                       | document  | Where CSS is injected                                                                                                    |
-| `theme`            | `'light' \| 'dark' \| 'auto'`                  | `'light'` | Color scheme of the chrome; `'auto'` follows `prefers-color-scheme`. Documents keep their own colors                     |
+| `injectStyles`     | `boolean`                                      | `true`    | Inject the stylesheet; false when the page loads `@p10node/office-engine/styles.css` itself                              |
+| `theme`            | `'light' \| 'dark' \| 'auto' \| ThemeOptions`  | `'light'` | Color scheme of the chrome; `'auto'` follows `prefers-color-scheme`; an object adds token overrides ([Theming](theming.md)). Documents keep their own colors |
 | `editable`         | `boolean`                                      | `false`   | Open in edit mode (Pages, Keynote and Numbers files stay view only)                                                      |
 | `allowEdit`        | `boolean`                                      | `true`    | Show Edit/View button                                                                                                    |
 | `allowSave`        | `boolean`                                      | `true`    | Show Save/Download button, enable Ctrl+S                                                                                 |
@@ -126,7 +127,7 @@ const { client, error, progress } = useDocument(src)
 if (client?.kind === 'xlsx') return <div className="de-root"><XlsxView client={client} /></div>
 ```
 
-The views style themselves from CSS variables on `.de-root` (`--de-bg`, `--de-chrome`, `--de-accent`…): override them to match your app. Add `de-dark` to the root element for the dark theme.
+The views style themselves from design tokens on their root: `useThemeRoot(theme)` gives its class name and style (see [Theming](theming.md)).
 
 ## Without a React build
 
diff --git a/docs/features.md b/docs/features.md
index a8cbb6e..505502c 100644
--- a/docs/features.md
+++ b/docs/features.md
@@ -174,7 +174,7 @@ Single row, buttons that don't fit collapse into `⋮`; custom-drawn dropdowns (
 
 ### Dark mode
 
-`theme="dark"`, or `"auto"` to follow the OS / browser setting (`prefers-color-scheme`), darkens the chrome: bars, toolbar, menus, dialogs, sheet headers and tabs, thumbnails, popovers, scrollbars. Pages, slides and cells keep the colors the document gives them, like paper in a dark PDF viewer. Everything is driven by CSS variables on `.de-root`, so a host can also tune the palette.
+`theme="dark"`, or `"auto"` to follow the OS / browser setting (`prefers-color-scheme`), darkens the chrome: bars, toolbar, menus, dialogs, sheet headers and tabs, thumbnails, popovers, scrollbars. Pages, slides and cells keep the colors the document gives them, like paper in a dark PDF viewer. Everything is driven by design tokens (CSS variables on `.de-root`), which a host sets through a theme object or its own CSS: see [Theming](theming.md).
 
 ## Comments
 
diff --git a/docs/theming.md b/docs/theming.md
new file mode 100644
index 0000000..648b0ed
--- /dev/null
+++ b/docs/theming.md
@@ -0,0 +1,90 @@
+# Theming
+
+The viewer's chrome (bars, toolbars, menus, dialogs, panels, sheet headers, tabs) takes every color, font, radius and
+shadow from design tokens: CSS custom properties named `--de-*` on the viewer root (`.de-root`). The document itself
+(pages, slides, cells) keeps its own colors in every theme.
+
+## The `theme` prop
+
+```tsx
+<DocViewer src={file} theme="auto" />                          // light, dark, or following the OS
+
+<DocViewer
+  src={file}
+  theme={{
+    mode: 'auto',
+    tokens: { accent: '#7c3aed', accentHover: '#6d28d9', font: 'Inter, sans-serif', radius: '4px' }, // both modes
+    light: { bg: '#f4f4f5', chrome: '#ffffff' },
+    dark: { bg: '#18181b', chrome: '#27272a', accent: '#a78bfa' },
+  }}
+/>
+```
+
+`tokens` apply in both modes, `light` and `dark` go over them in their mode, and anything left out keeps the built-in
+value of that mode. Names are camelCase (`accentHover` sets `--de-accent-hover`); values are any CSS value, so a token can
+point at the host's own variables: `{ accent: 'var(--brand-500)' }`. `createTheme()` types a theme object written apart
+from the prop, and `THEME_TOKENS` lists every token.
+
+`mount()` takes the same `theme` option; `<office-viewer theme="dark">` takes a mode.
+
+## Plain CSS
+
+The tokens are ordinary custom properties, so a stylesheet can set them as well:
+
+```css
+.my-app .de-root { --de-accent: #7c3aed; --de-font: Inter, sans-serif; }
+.my-app .de-root.de-dark { --de-accent: #a78bfa; }
+```
+
+Class names starting with `de-` are stable and can be styled further; the tokens are the supported way to change
+colors, type and shape.
+
+## Loading the stylesheet yourself
+
+By default the viewer injects its stylesheet once into the document (or the shadow root in `styleTarget`). To load it
+yourself, for a Content Security Policy without inline styles, a bundler that extracts CSS, or a cascade layer of your own,
+turn injection off and import the file:
+
+```tsx
+import '@p10node/office-engine/styles.css'
+<DocViewer src={file} injectStyles={false} />
+```
+
+```css
+/* the viewer's rules below the host's own, whatever their specificity */
+@layer office-engine, app;
+@import '@p10node/office-engine/styles.css' layer(office-engine);
+```
+
+The stylesheet is not put in a layer of its own: rules in a layer lose to every unlayered rule, so a host's element
+reset (`button { … }`) would restyle the viewer's controls. Importing it into a layer is the host's choice.
+
+## Your own root
+
+The views (`DocxView`, `XlsxView`, `PptxView`) can be mounted without `DocViewer` (see [API](api.md)); `useThemeRoot()`
+gives the class name and style their root needs:
+
+```tsx
+const root = useThemeRoot(theme)
+return <div className={root.className} style={root.style}><XlsxView client={client} /></div>
+```
+
+## Tokens
+
+| Group | Tokens |
+|---|---|
+| Surfaces and text | `bg` (around the document), `chrome` (bars), `pop` (menus, dialogs), `ebar` (formatting toolbar), `text`, `muted`, `ink`, `inkStrong`, `inkSoft`, `border`, `sep`, `tbSep` |
+| Accent and states | `accent`, `accentHover`, `accentInk` (text on the accent), `accentSoft`, `on`, `onInk`, `onInkStrong` (pressed buttons), `hover`, `hoverSolid`, `hoverSoft`, `disabled`, `danger`, `dangerBorder`, `ok` |
+| Inputs and tabs | `inputBg`, `inputBorder`, `swatchBorder`, `tabHover`, `tabOn`, `tabInk` |
+| Overlays | `popShadow`, `shadow`, `shadowSm`, `shadowMd`, `shadowLg`, `backdrop`, `toastBg`, `toastInk`, `tipBg`, `tipInk` |
+| Type and shape | `font`, `fontMono`, `fontSize`, `radiusSm`, `radius`, `radiusLg`, `radiusXl` |
+| Sheets | `grid`, `head`, `headInk`, `headBorder`, `cornerBorder`, `freeze` |
+| Comments | `cmBg`, `cmOn`, `cmLine`, `cmLineOn`, `cmCard`, `cmQuote` |
+| Find | `find`, `findOn` (text matches), `findCell`, `findCellOn`, `findCellLine` (cell matches) |
+| Files, people, connection | `kindDocx`, `kindXlsx`, `kindPptx`, `kindInk` (badges), `avatarInk` (text on a person's color), `statusIdle`, `statusLive`, `statusBusy`, `statusError` |
+| Slideshow | `presentBg`, `presentInk` |
+| Paper | `page`, `pageInk`, `sheetInk`, `skeleton` (loading pages), `phBorder`, `phA`, `phB`, `phInk` (placeholders), `phOutline`, `phHint` (empty text boxes) |
+| Source editor | `srcBg`, `srcGutter`, `srcSel`, `srcFont`, `srcComment`, `srcKeyword`, `srcString`, `srcOperator`, `srcNumber`, `srcHeading`, `srcAttr`, `srcTag`, `srcMeta` |
+
+The paper tokens are the same in both modes: a document is drawn on white paper with black ink unless it says
+otherwise. Built-in values: `src/react/styles.css`, the `.de-root` and `.de-root.de-dark` blocks.
diff --git a/e2e/app/main.tsx b/e2e/app/main.tsx
index bb6a98a..79fa95b 100644
--- a/e2e/app/main.tsx
+++ b/e2e/app/main.tsx
@@ -46,6 +46,7 @@ const initial: DocViewerProps = {
   thumbnails: flag('thumbnails'),
   captureSelectAll: flag('captureSelectAll'),
   theme: (q.get('theme') as DocViewerProps['theme']) ?? undefined,
+  injectStyles: flag('injectStyles'),
   onSave: q.has('onSave') ? async (blob, name) => void log({ type: 'save', name, b64: await b64(blob) }) : undefined,
   onDirtyChange: (dirty) => log({ type: 'dirty', dirty }),
   onRename: (name) => log({ type: 'rename', name }),
diff --git a/e2e/viewer.spec.ts b/e2e/viewer.spec.ts
index 97f9c24..96e0c65 100644
--- a/e2e/viewer.spec.ts
+++ b/e2e/viewer.spec.ts
@@ -440,6 +440,35 @@ describe('viewing', () => {
     expect(v.errors).toEqual([])
   })
 
+  test('theme object: tokens for both modes and per mode, pages keep paper colors', async () => {
+    const v = await viewer({ src: 'samples/sample.docx' })
+    const { page } = v
+    const bg = (sel: string) => page.locator(sel).first().evaluate((el) => getComputedStyle(el).backgroundColor)
+    const theme = { tokens: { chrome: 'rgb(1, 2, 3)', font: 'serif' }, light: { bg: 'rgb(10, 20, 30)' }, dark: { bg: 'rgb(40, 50, 60)', chrome: 'rgb(4, 5, 6)' } }
+    await page.evaluate((t) => window.__setProps({ theme: t }), theme)
+    await page.waitForFunction(() => getComputedStyle(document.querySelector('.de-bar')!).backgroundColor === 'rgb(1, 2, 3)')
+    expect(await bg('.de-root')).toBe('rgb(10, 20, 30)')
+    expect(await page.locator('.de-bar').evaluate((el) => getComputedStyle(el).fontFamily)).toBe('serif')
+    expect(await bg('.de-page')).toBe('rgb(255, 255, 255)')
+
+    await page.evaluate((t) => window.__setProps({ theme: { ...t, mode: 'dark' } }), theme)
+    await page.waitForFunction(() => document.querySelector('.de-root')!.classList.contains('de-dark'))
+    expect(await bg('.de-bar')).toBe('rgb(4, 5, 6)')
+    expect(await bg('.de-root')).toBe('rgb(40, 50, 60)')
+    // a token the theme leaves alone keeps the dark default
+    await v.menu()
+    expect(await bg('.de-dd-pop')).toBe('rgb(46, 49, 54)')
+    await page.keyboard.press('Escape')
+    expect(await bg('.de-page')).toBe('rgb(255, 255, 255)')
+    expect(v.errors).toEqual([])
+  })
+
+  test('injectStyles=false: no stylesheet is added', async () => {
+    const v = await viewer({ src: 'samples/sample.docx', injectStyles: false }, { wait: false })
+    await v.page.waitForSelector('.de-root')
+    expect(await v.page.locator('style#office-engine-styles').count()).toBe(0)
+  })
+
   test('links: a script or data link is shown as text, not followed', async () => {
     // the builder refuses script links: write safe placeholders, then put the bad targets in the relationships
     const docx = await parasToDocx([
diff --git a/package.json b/package.json
index 3519541..bd00820 100644
--- a/package.json
+++ b/package.json
@@ -28,7 +28,8 @@
     "./collab": {
       "types": "./dist/types/collab/index.d.ts",
       "import": "./dist/collab.js"
-    }
+    },
+    "./styles.css": "./dist/styles.css"
   },
   "sideEffects": [
     "./src/core/default-worker.ts",
@@ -41,7 +42,8 @@
   ],
   "scripts": {
     "dev": "vite --config vite.playground.config.ts",
-    "build": "bun run clean && bun run build:lib && bun run build:embed && bun run build:worker && bun run build:types",
+    "build": "bun run clean && bun run build:lib && bun run build:embed && bun run build:worker && bun run build:types && bun run build:css",
+    "build:css": "cp src/react/styles.css dist/styles.css",
     "build:lib": "vite build",
     "build:embed": "vite build --config vite.embed.config.ts",
     "build:types": "tsc -p tsconfig.build.json",
diff --git a/playground/main.tsx b/playground/main.tsx
index 7142edc..759427e 100644
--- a/playground/main.tsx
+++ b/playground/main.tsx
@@ -1,6 +1,6 @@
 import { StrictMode, useCallback, useEffect, useMemo, useState } from 'react'
 import { createRoot } from 'react-dom/client'
-import { DocViewer, type DocSource, type Theme } from '../src'
+import { DocViewer, type DocSource, type ThemeMode as Theme } from '../src'
 import type { CollabOptions } from '../src/collab'
 import { OPEN_ACCEPT } from '../src/react/file/importFile'
 
diff --git a/src/index.ts b/src/index.ts
index f1fb2e3..0acc1e9 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -9,7 +9,7 @@ export { SlideView } from './react/pptx/Slide'
 export { useDocument, type DocumentState } from './react/useDocument'
 export { injectStyles, stylesText } from './react/injectStyles'
 export type { Zoom } from './react/common/ZoomControl'
-export type { Theme } from './react/common/hooks'
+export { THEME_TOKENS, createTheme, themeStyle, useThemeRoot, type Theme, type ThemeMode, type ThemeOptions, type ThemeToken, type ThemeTokens } from './react/theme'
 
 export { DocumentClient, setDefaultWorker, type OpenOptions } from './core/worker/client'
 export type { DocSource } from './core/source'
diff --git a/src/react/DocViewer.tsx b/src/react/DocViewer.tsx
index 26063bf..63865be 100644
--- a/src/react/DocViewer.tsx
+++ b/src/react/DocViewer.tsx
@@ -15,7 +15,8 @@ import type { DocKind } from '../core/opc'
 import { extOf, HAS_SOURCE, PLAIN_EXT, PLAIN_FILE, unpackedName, type PlainFormat } from '../core/plain'
 import type { LegacyFormat } from '../core/legacy'
 import { injectStyles } from './injectStyles'
-import { isTextEntry, useDarkTheme, useSize, type Theme } from './common/hooks'
+import { isTextEntry, useSize } from './common/hooks'
+import { useThemeRoot, type Theme } from './theme'
 import { SourceEditor } from './source/SourceEditor'
 import { PictureView } from './picture/PictureView'
 import { PptxView } from './pptx/PptxView'
@@ -52,8 +53,14 @@ export interface DocViewerProps {
   /** Where to inject the stylesheet (document or a shadow root). */
   styleTarget?: Document | ShadowRoot
   /**
-   * Color scheme of the viewer chrome (bars, menus, dialogs): 'light', 'dark' or 'auto' (follows the OS / browser setting).
-   * The document itself keeps its own colors. Default 'light'.
+   * Inject the stylesheet. Default true. Set false when the page loads `@p10node/office-engine/styles.css` itself
+   * (a CSP without inline styles, a cascade layer of its own, a bundler that extracts CSS).
+   */
+  injectStyles?: boolean
+  /**
+   * Color scheme of the viewer chrome (bars, menus, dialogs): 'light', 'dark' or 'auto' (follows the OS / browser setting),
+   * or a theme object with that mode and design token overrides (see docs/theming.md). The document itself keeps its own
+   * colors. Default 'light'.
    */
   theme?: Theme
   onLoad?: (client: DocumentClient) => void
@@ -148,7 +155,7 @@ function fmtBytes(n: number) {
 
 export function DocViewer(props: DocViewerProps) {
   const { src, name, className, style, toolbar = true, toolbarExtra, zoom, thumbnails, headers, credentials, worker, styleTarget, theme, onLoad, onError } = props
-  const dark = useDarkTheme(theme)
+  const root = useThemeRoot(theme, style)
   const { allowEdit = true, allowSave = true, allowDownload = true, fileMenu = true, allowOpen = true, captureSelectAll = true, onSave, onDirtyChange } = props
   const [editing, setEditing] = useState(!!props.editable)
   useEffect(() => {
@@ -157,7 +164,10 @@ export function DocViewer(props: DocViewerProps) {
   const [dirty, setDirtyState] = useState(false)
   const [saving, setSaving] = useState(false)
   const [barEl, setBarEl] = useState<HTMLDivElement | null>(null)
-  useInsertionEffect(() => injectStyles(styleTarget), [styleTarget])
+  const inject = props.injectStyles ?? true
+  useInsertionEffect(() => {
+    if (inject) injectStyles(styleTarget)
+  }, [styleTarget, inject])
   // File → New / Open: a local file shown instead of `src` until the host passes another `src`
   const [opened, setOpened] = useState<Imported | null>(null)
   const [renamed, setRenamed] = useState<string | null>(null)
@@ -531,7 +541,7 @@ export function DocViewer(props: DocViewerProps) {
   else body = <PptxView client={client} initialZoom={zoom} thumbnails={thumbnails} />
 
   return (
-    <div ref={rootRef} className={'de-root' + (dark ? ' de-dark' : '') + (className ? ` ${className}` : '')} style={style} onKeyDown={onKeyDown}>
+    <div ref={rootRef} className={root.className + (className ? ` ${className}` : '')} style={root.style} onKeyDown={onKeyDown}>
       {toolbar && (
         <div className="de-bar">
           {client && <span className={`de-badge de-badge-${client.kind}`}>{client.info?.from ?? client.info?.converted ?? (client.info?.imported ? IMPORTED_BADGE[client.info.imported] : client.kind)}</span>}
diff --git a/src/react/common/hooks.ts b/src/react/common/hooks.ts
index e28af92..5b8bfae 100644
--- a/src/react/common/hooks.ts
+++ b/src/react/common/hooks.ts
@@ -5,13 +5,13 @@ import { isWebImage } from '../../core/opc'
 export const useIsoLayoutEffect = typeof window === 'undefined' ? useEffect : useLayoutEffect
 
 /** Color scheme of the viewer chrome: 'auto' follows the browser / OS setting (prefers-color-scheme). */
-export type Theme = 'light' | 'dark' | 'auto'
+export type ThemeMode = 'light' | 'dark' | 'auto'
 
 const DARK_MQ = '(prefers-color-scheme: dark)'
 const prefersDark = () => typeof matchMedia === 'function' && matchMedia(DARK_MQ).matches
 
 /** Whether the dark theme applies for `theme`; 'auto' tracks prefers-color-scheme live. */
-export function useDarkTheme(theme: Theme = 'light'): boolean {
+export function useDarkTheme(theme: ThemeMode = 'light'): boolean {
   const [dark, setDark] = useState(() => theme === 'auto' && prefersDark())
   useEffect(() => {
     if (theme !== 'auto' || typeof matchMedia !== 'function') return
diff --git a/src/react/pptx/PptxView.tsx b/src/react/pptx/PptxView.tsx
index 9c0d1b7..8eb8118 100644
--- a/src/react/pptx/PptxView.tsx
+++ b/src/react/pptx/PptxView.tsx
@@ -86,7 +86,7 @@ export function useSlide(client: DocumentClient, index: number): SlideModel | {
 export function SlideSlot(props: { client: DocumentClient; index: number; meta: PresentationMeta; scale: number; live: boolean; editing?: SlideEditing; overlay?: ReactNode }) {
   const { client, index, meta, scale, live, editing, overlay } = props
   const model = useSlide(client, index)
-  if (!model) return <div className="de-slide" style={{ width: meta.w * scale, height: meta.h * scale, background: '#fff' }} />
+  if (!model) return <div className="de-slide" style={{ width: meta.w * scale, height: meta.h * scale, background: 'var(--de-page, #fff)' }} />
   if ('error' in model) {
     return (
       <div className="de-slide de-ph" style={{ width: meta.w * scale, height: meta.h * scale, display: 'flex' }}>
diff --git a/src/react/pptx/Slide.tsx b/src/react/pptx/Slide.tsx
index 233e76e..acd39ce 100644
--- a/src/react/pptx/Slide.tsx
+++ b/src/react/pptx/Slide.tsx
@@ -245,7 +245,7 @@ function PicView({ el, client, live }: { el: Extract<SlideEl, { t: 'pic' }>; cli
           {el.target?.split('.').pop()?.toUpperCase()} image
         </div>
       ) : null}
-      {el.video && <div className="de-ph" style={{ position: 'absolute', right: 8, bottom: 8, padding: '2px 6px', border: 0, background: 'rgba(0,0,0,.6)', color: '#fff' }}>▶ media</div>}
+      {el.video && <div className="de-ph" style={{ position: 'absolute', right: 8, bottom: 8, padding: '2px 6px', border: 0, background: 'var(--de-tip-bg, rgba(0,0,0,.6))', color: 'var(--de-tip-ink, #fff)' }}>▶ media</div>}
     </div>
   )
 }
@@ -318,7 +318,7 @@ export const SlideView = memo(function SlideView({ model, client, scale, live =
   const bg = useFillCss(client, model.bg, live)
   return (
     <div className={model.hidden ? 'de-slide de-hidden-slide' : 'de-slide'} style={{ width: model.w * scale, height: model.h * scale }}>
-      <div className="de-slide-inner" style={{ width: model.w, height: model.h, transform: `scale(${scale})`, background: '#fff', ...(bg ?? {}) }}>
+      <div className="de-slide-inner" style={{ width: model.w, height: model.h, transform: `scale(${scale})`, background: 'var(--de-page, #fff)', ...(bg ?? {}) }}>
         {model.els.map((el, i) => (
           <ElView key={i} el={el} client={client} live={live} editing={editing} />
         ))}
diff --git a/src/react/styles.css b/src/react/styles.css
index 0a07b1d..6b49dd5 100644
--- a/src/react/styles.css
+++ b/src/react/styles.css
@@ -48,6 +48,66 @@
   --de-cm-line: #f29900;
   --de-cm-card: #ffffff;
   --de-cm-quote: #f29900;
+  --de-cm-line-on: #c26401;
+  /* type and shape */
+  --de-font: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
+  --de-font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
+  --de-font-size: 13px;
+  --de-radius-sm: 4px;
+  --de-radius: 6px;
+  --de-radius-lg: 8px;
+  --de-radius-xl: 12px;
+  --de-shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.15);
+  --de-shadow-md: 0 2px 8px rgba(0, 0, 0, 0.3);
+  --de-shadow-lg: 0 8px 28px rgba(0, 0, 0, 0.28);
+  /* file kind badges */
+  --de-kind-docx: #2b579a;
+  --de-kind-xlsx: #217346;
+  --de-kind-pptx: #c43e1c;
+  --de-kind-ink: #fff;
+  /* white text on a person's color (avatars, cursors, comment pins) */
+  --de-avatar-ink: #fff;
+  /* find */
+  --de-find: #fde293;
+  --de-find-on: #ff9632;
+  --de-find-cell: rgba(251, 188, 4, 0.28);
+  --de-find-cell-on: rgba(255, 150, 50, 0.45);
+  --de-find-cell-line: #e37400;
+  /* tooltips over the document (picture size), the slideshow */
+  --de-tip-bg: rgba(32, 33, 36, 0.85);
+  --de-tip-ink: #fff;
+  --de-present-bg: #000;
+  --de-present-ink: rgba(255, 255, 255, 0.5);
+  /* connection state (collaboration) */
+  --de-status-idle: #9aa0a6;
+  --de-status-live: #1e8e3e;
+  --de-status-busy: #f9ab00;
+  --de-status-error: #d93025;
+  /* paper: pages, slides and sheets keep these in the dark theme too (documents keep their own colors) */
+  --de-page: #fff;
+  --de-page-ink: #000;
+  --de-sheet-ink: #1d2127;
+  --de-skeleton: #eef0f2;
+  --de-ph-border: #b8bec6;
+  --de-ph-a: #f6f7f9;
+  --de-ph-b: #eff1f4;
+  --de-ph-ink: #6a737d;
+  --de-ph-outline: rgba(60, 64, 67, 0.4);
+  --de-ph-hint: #80868b;
+  /* source editor (Markdown, HTML, diagrams) */
+  --de-src-bg: #ffffff;
+  --de-src-gutter: #f6f7f8;
+  --de-src-sel: color-mix(in srgb, var(--de-accent) 25%, transparent);
+  --de-src-font: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
+  --de-src-comment: #6a737d;
+  --de-src-keyword: #8e3bc7;
+  --de-src-string: #1a7f37;
+  --de-src-operator: #c2410c;
+  --de-src-number: #0b7a8a;
+  --de-src-heading: #0b57d0;
+  --de-src-attr: #0b57d0;
+  --de-src-tag: #b42318;
+  --de-src-meta: #8a5a00;
   color-scheme: light;
   position: relative;
   display: flex;
@@ -58,7 +118,7 @@
   overflow: hidden;
   background: var(--de-bg);
   color: var(--de-text);
-  font: 13px/1.4 system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
+  font: var(--de-font-size)/1.4 var(--de-font);
   text-align: left;
   isolation: isolate;
 }
@@ -116,6 +176,18 @@
   --de-shadow: 0 1px 2px rgba(0, 0, 0, 0.5), 0 2px 10px rgba(0, 0, 0, 0.45);
   --de-cm-card: #2b2e33;
   --de-cm-quote: #fdd663;
+  --de-src-bg: #1b1d20;
+  --de-src-gutter: #202327;
+  --de-src-sel: color-mix(in srgb, var(--de-accent) 35%, transparent);
+  --de-src-comment: #8b949e;
+  --de-src-keyword: #d2a8ff;
+  --de-src-string: #7ee787;
+  --de-src-operator: #ffa657;
+  --de-src-number: #79c0ff;
+  --de-src-heading: #8ab4f8;
+  --de-src-attr: #8ab4f8;
+  --de-src-tag: #ff7b72;
+  --de-src-meta: #e3b341;
   color-scheme: dark;
 }
 
@@ -135,16 +207,16 @@
 }
 .de-badge {
   flex: none;
-  font: 600 10px/1 system-ui, sans-serif;
+  font: 600 10px/1 var(--de-font);
   letter-spacing: 0.06em;
   text-transform: uppercase;
   padding: 4px 6px;
-  border-radius: 4px;
-  color: #fff;
+  border-radius: var(--de-radius-sm);
+  color: var(--de-kind-ink);
 }
-.de-badge-docx { background: #2b579a; }
-.de-badge-xlsx { background: #217346; }
-.de-badge-pptx { background: #c43e1c; }
+.de-badge-docx { background: var(--de-kind-docx); }
+.de-badge-xlsx { background: var(--de-kind-xlsx); }
+.de-badge-pptx { background: var(--de-kind-pptx); }
 .de-title {
   flex: 1;
   min-width: 0;
@@ -206,7 +278,7 @@
   color: var(--de-danger);
   background: var(--de-pop);
   border: 1px solid var(--de-danger-border);
-  border-radius: 8px;
+  border-radius: var(--de-radius-lg);
   padding: 14px 18px;
   box-shadow: var(--de-shadow);
 }
@@ -219,7 +291,7 @@
   align-items: center;
   background: var(--de-chrome);
   border: 1px solid var(--de-border);
-  border-radius: 8px;
+  border-radius: var(--de-radius-lg);
   box-shadow: var(--de-shadow);
   overflow: hidden;
 }
@@ -250,14 +322,14 @@
 }
 .de-btn {
   padding: 4px 8px;
-  border-radius: 6px;
+  border-radius: var(--de-radius);
 }
 
 /* ---------------------------------------------------------------- docx */
 .de-pages { position: relative; }
 .de-page {
   position: absolute;
-  background: #fff;
+  background: var(--de-page, #fff);
   box-shadow: var(--de-shadow);
   overflow: hidden;
 }
@@ -267,7 +339,7 @@
 }
 .de-page-skeleton {
   position: absolute;
-  background: #fff;
+  background: var(--de-page);
   box-shadow: var(--de-shadow);
   opacity: 0.6;
 }
@@ -275,12 +347,12 @@
   content: '';
   position: absolute;
   inset: 12% 12%;
-  background: repeating-linear-gradient(#eef0f2 0 10px, transparent 10px 24px);
+  background: repeating-linear-gradient(var(--de-skeleton) 0 10px, transparent 10px 24px);
   animation: de-pulse 1.4s ease-in-out infinite;
 }
 @keyframes de-pulse { 50% { opacity: 0.45; } }
 .de-doc {
-  color: #000;
+  color: var(--de-page-ink, #000);
   font-kerning: normal;
   text-rendering: optimizeLegibility;
 }
@@ -316,8 +388,8 @@
 .de-tbl-wrap { position: relative; }
 .de-tbl-wrap > .de-tbl { margin: 0 !important; }
 .de-col-resize { position: absolute; top: 0; bottom: 0; width: 6px; cursor: col-resize; z-index: 2; touch-action: none; }
-.de-col-resize:hover { background: rgba(26, 115, 232, 0.35); }
-.de-tbl td.de-cell-sel { box-shadow: inset 0 0 0 9999px rgba(26, 115, 232, 0.16); }
+.de-col-resize:hover { background: color-mix(in srgb, var(--de-accent) 35%, transparent); }
+.de-tbl td.de-cell-sel { box-shadow: inset 0 0 0 9999px color-mix(in srgb, var(--de-accent) 16%, transparent); }
 .de-tbl td {
   vertical-align: top;
   overflow-wrap: break-word;
@@ -329,10 +401,10 @@
   display: inline-flex;
   align-items: center;
   justify-content: center;
-  border: 1px dashed #b8bec6;
-  background: repeating-linear-gradient(45deg, #f6f7f9 0 8px, #eff1f4 8px 16px);
-  color: #6a737d;
-  font: 12px/1.2 system-ui, sans-serif;
+  border: 1px dashed var(--de-ph-border, #b8bec6);
+  background: repeating-linear-gradient(45deg, var(--de-ph-a, #f6f7f9) 0 8px, var(--de-ph-b, #eff1f4) 8px 16px);
+  color: var(--de-ph-ink, #6a737d);
+  font: 12px/1.2 var(--de-font, sans-serif);
   text-indent: 0;
   vertical-align: bottom;
   overflow: hidden;
@@ -359,7 +431,7 @@
   flex: none;
   background: var(--de-chrome);
   border-bottom: 1px solid var(--de-border);
-  font: 12px/30px ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
+  font: 12px/30px var(--de-font-mono);
 }
 .de-fx-ref {
   width: 88px;
@@ -382,8 +454,8 @@
   min-height: 0;
   overflow: auto;
   /* the sheet keeps its own colors in the dark theme */
-  background: #fff;
-  color: #1d2127;
+  background: var(--de-page);
+  color: var(--de-sheet-ink);
   outline: none;
 }
 .de-grid-view {
@@ -423,7 +495,7 @@
   justify-content: center;
   background: var(--de-head);
   color: var(--de-head-ink);
-  font: 11px/1 system-ui, sans-serif;
+  font: 11px/1 var(--de-font);
   font-variant-numeric: tabular-nums;
   border-right: 1px solid var(--de-head-border);
   border-bottom: 1px solid var(--de-head-border);
@@ -509,7 +581,7 @@
 .de-slide {
   position: relative;
   overflow: hidden;
-  background: #fff;
+  background: var(--de-page, #fff);
 }
 .de-slide-frame {
   position: absolute;
@@ -521,7 +593,7 @@
   top: 0;
   transform-origin: 0 0;
   overflow: hidden;
-  color: #000;
+  color: var(--de-page-ink, #000);
 }
 .de-el { position: absolute; }
 .de-txt {
@@ -536,11 +608,11 @@
 }
 .de-txt.de-nowrap > div { white-space: pre; }
 /* empty placeholders while editing (new slides, blank presentations) */
-.de-slide-editable .de-el > .de-txt:empty { outline: 1.5px dashed rgba(60, 64, 67, 0.4); outline-offset: -1px; }
+.de-slide-editable .de-el > .de-txt:empty { outline: 1.5px dashed var(--de-ph-outline); outline-offset: -1px; }
 .de-slide-editable .de-el > .de-txt:empty::after {
   content: 'Click to add text';
-  color: #80868b;
-  font: 28px/1.2 system-ui, -apple-system, 'Segoe UI', Roboto, Arial, sans-serif;
+  color: var(--de-ph-hint);
+  font: 28px/1.2 var(--de-font);
   text-align: center;
   pointer-events: none;
 }
@@ -565,7 +637,7 @@
   height: 28px;
   padding: 0 10px;
   border: 1px solid var(--de-border);
-  border-radius: 6px;
+  border-radius: var(--de-radius);
   background: var(--de-chrome);
   color: inherit;
   font: inherit;
@@ -622,10 +694,10 @@
   height: 28px;
   padding: 0;
   border: 0;
-  border-radius: 4px;
+  border-radius: var(--de-radius-sm);
   background: transparent;
   color: var(--de-ink);
-  font: 600 14px/1 system-ui, sans-serif;
+  font: 600 14px/1 var(--de-font);
   cursor: pointer;
   transition: background-color 0.1s;
 }
@@ -643,7 +715,7 @@
   bottom: 3px;
   height: 3px;
   border-radius: 1px;
-  box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.12);
+  box-shadow: inset 0 0 0 1px var(--de-swatch-border);
 }
 .de-tb-pop {
   position: absolute;
@@ -652,7 +724,7 @@
   z-index: 30;
   padding: 10px;
   background: var(--de-pop);
-  border-radius: 8px;
+  border-radius: var(--de-radius-lg);
   box-shadow: var(--de-pop-shadow);
 }
 .de-tb-none {
@@ -660,7 +732,7 @@
   margin-bottom: 8px;
   padding: 5px;
   border: 1px solid var(--de-border);
-  border-radius: 4px;
+  border-radius: var(--de-radius-sm);
   background: var(--de-pop);
   color: inherit;
   font: inherit;
@@ -677,10 +749,10 @@
   height: 28px;
   padding: 0 2px 0 6px;
   border: 0;
-  border-radius: 4px;
+  border-radius: var(--de-radius-sm);
   background: transparent;
   color: var(--de-ink-strong);
-  font: 13px/1 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  font: 13px/1 var(--de-font);
   cursor: pointer;
   transition: background-color 0.1s;
 }
@@ -699,10 +771,10 @@
   overflow-y: auto;
   padding: 6px 0;
   background: var(--de-pop);
-  border-radius: 8px;
+  border-radius: var(--de-radius-lg);
   box-shadow: var(--de-pop-shadow);
   color: var(--de-ink-strong);
-  font: 13px/1.3 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  font: 13px/1.3 var(--de-font);
 }
 .de-dd-opt {
   display: flex;
@@ -740,10 +812,10 @@
   height: 26px;
   padding: 0;
   border: 1px solid var(--de-input-border);
-  border-radius: 4px;
+  border-radius: var(--de-radius-sm);
   background: transparent;
   color: var(--de-ink-strong);
-  font: 13px/1 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  font: 13px/1 var(--de-font);
   text-align: center;
   outline: none;
 }
@@ -792,7 +864,7 @@
   opacity: 0;
   pointer-events: none;
 }
-.de-editing { outline: none; caret-color: #000; }
+.de-editing { outline: none; caret-color: var(--de-page-ink); }
 .de-editing .de-page-inner { cursor: text; }
 .de-editing [contenteditable='false'] { cursor: default; }
 .de-find {
@@ -806,7 +878,7 @@
   padding: 6px;
   background: var(--de-pop);
   border: 1px solid var(--de-border);
-  border-radius: 8px;
+  border-radius: var(--de-radius-lg);
   box-shadow: var(--de-shadow);
 }
 .de-find-row { display: flex; align-items: center; gap: 2px; }
@@ -815,7 +887,7 @@
   height: 28px;
   padding: 0 8px;
   border: 1px solid var(--de-border);
-  border-radius: 6px;
+  border-radius: var(--de-radius);
   background: var(--de-input-bg);
   color: var(--de-text);
   font: inherit;
@@ -823,13 +895,13 @@
 }
 .de-find input:focus { border-color: var(--de-accent); }
 .de-find-count { min-width: 56px; text-align: center; color: var(--de-muted); font-size: 12px; font-variant-numeric: tabular-nums; }
-::highlight(de-find) { background-color: #fde293; }
-::highlight(de-find-cur) { background-color: #ff9632; }
-::highlight(de-cm-draft) { background-color: rgba(251, 188, 4, 0.6); }
+::highlight(de-find) { background-color: var(--de-find); }
+::highlight(de-find-cur) { background-color: var(--de-find-on); }
+::highlight(de-cm-draft) { background-color: var(--de-cm-on); }
 .de-range {
   position: absolute;
-  background: rgba(26, 115, 232, 0.1);
-  border: 1px solid rgba(26, 115, 232, 0.6);
+  background: color-mix(in srgb, var(--de-accent) 10%, transparent);
+  border: 1px solid color-mix(in srgb, var(--de-accent) 60%, transparent);
   pointer-events: none;
   z-index: 2;
 }
@@ -842,8 +914,8 @@
   outline: none;
   resize: none;
   overflow: hidden;
-  background: #fff;
-  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
+  background: var(--de-page);
+  box-shadow: var(--de-shadow-sm);
   line-height: 1.2;
   white-space: pre-wrap;
 }
@@ -851,18 +923,18 @@
 .de-fx-input:focus { background: var(--de-input-bg); box-shadow: inset 0 -2px 0 var(--de-accent); }
 .de-tb-hint { margin-left: 8px; color: var(--de-muted); font-size: 12px; }
 .de-slide-editable [data-sid] { cursor: text; }
-.de-slide-editable [data-sid]:hover { outline: 1px dashed rgba(26, 115, 232, 0.6); }
-.de-txt-edit { outline: 2px solid var(--de-accent); outline-offset: 0; caret-color: #000; cursor: text; z-index: 2; }
+.de-slide-editable [data-sid]:hover { outline: 1px dashed color-mix(in srgb, var(--de-accent) 60%, transparent); }
+.de-txt-edit { outline: 2px solid var(--de-accent); outline-offset: 0; caret-color: var(--de-page-ink); cursor: text; z-index: 2; }
 .de-gridpick { display: grid; grid-template-columns: repeat(8, 16px); gap: 3px; }
 .de-gridpick button { width: 16px; height: 16px; padding: 0; border: 1px solid var(--de-border); border-radius: 2px; background: var(--de-pop); cursor: pointer; }
 .de-gridpick button.on { background: var(--de-on); border-color: var(--de-accent); }
 .de-gridpick-label { margin-top: 6px; text-align: center; color: var(--de-muted); font-size: 12px; }
 .de-prompt { display: flex; gap: 6px; align-items: center; }
-.de-prompt input { width: 240px; height: 28px; padding: 0 8px; border: 1px solid var(--de-border); border-radius: 6px; background: var(--de-input-bg); color: var(--de-text); font: inherit; outline: none; }
+.de-prompt input { width: 240px; height: 28px; padding: 0 8px; border: 1px solid var(--de-border); border-radius: var(--de-radius); background: var(--de-input-bg); color: var(--de-text); font: inherit; outline: none; }
 .de-prompt input:focus { border-color: var(--de-accent); }
 .de-prompt .de-btn { border: 1px solid var(--de-border); background: var(--de-pop); }
 .de-shape-sel { position: absolute; border: 1.5px solid var(--de-accent); pointer-events: none; z-index: 5; transform-origin: 50% 50%; }
-.de-handle { position: absolute; background: #fff; border: 1px solid var(--de-accent); border-radius: 2px; pointer-events: auto; }
+.de-handle { position: absolute; background: var(--de-page); border: 1px solid var(--de-accent); border-radius: 2px; pointer-events: auto; }
 .de-h-nw, .de-h-se { cursor: nwse-resize; }
 .de-h-ne, .de-h-sw { cursor: nesw-resize; }
 .de-h-n, .de-h-s { cursor: ns-resize; }
@@ -876,12 +948,12 @@
   display: flex;
   align-items: center;
   justify-content: center;
-  background: #000;
+  background: var(--de-present-bg);
   outline: none;
   cursor: none;
 }
 .de-present .de-slide { box-shadow: none; }
-.de-present-n { position: absolute; right: 16px; bottom: 12px; color: rgba(255, 255, 255, 0.5); font: 12px system-ui, sans-serif; }
+.de-present-n { position: absolute; right: 16px; bottom: 12px; color: var(--de-present-ink); font: 12px var(--de-font); }
 .de-present-btn {
   position: absolute;
   right: 16px;
@@ -890,7 +962,7 @@
 }
 .de-grip-c { position: absolute; top: 0; width: 6px; cursor: col-resize; z-index: 3; }
 .de-grip-r { position: absolute; left: 0; height: 6px; cursor: row-resize; z-index: 3; }
-.de-grip-c:hover, .de-grip-r:hover { background: rgba(26, 115, 232, 0.35); }
+.de-grip-c:hover, .de-grip-r:hover { background: color-mix(in srgb, var(--de-accent) 35%, transparent); }
 .de-ctx {
   position: fixed;
   z-index: 50;
@@ -898,9 +970,9 @@
   max-width: 340px;
   padding: 6px 0;
   background: var(--de-pop);
-  border-radius: 8px;
+  border-radius: var(--de-radius-lg);
   box-shadow: var(--de-pop-shadow);
-  font: 13px/1.3 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  font: 13px/1.3 var(--de-font);
   color: var(--de-ink-strong);
   user-select: none;
 }
@@ -930,15 +1002,15 @@
 .de-ctx-sep { height: 1px; margin: 6px 0; background: var(--de-sep); }
 .de-ctx-head { padding: 6px 16px 2px 38px; color: var(--de-muted); font-size: 11px; font-weight: 600; letter-spacing: 0.03em; text-transform: uppercase; }
 .de-tab-add { font-size: 18px; padding: 0 10px; }
-.de-tab-input { width: 120px; margin: 4px 2px; padding: 0 6px; border: 1px solid var(--de-accent); border-radius: 4px; background: var(--de-input-bg); color: var(--de-text); font: inherit; }
+.de-tab-input { width: 120px; margin: 4px 2px; padding: 0 6px; border: 1px solid var(--de-accent); border-radius: var(--de-radius-sm); background: var(--de-input-bg); color: var(--de-text); font: inherit; }
 /* formula editing: reference boxes, colored references, autocomplete */
 .de-fx { position: relative; }
 .de-fref { position: absolute; border: 2px solid; pointer-events: none; z-index: 2; }
 .de-fref-pt { border-style: dashed; }
-.de-cell-hl { z-index: 4; pointer-events: none; color: #202124; overflow: hidden; overflow-wrap: break-word; }
+.de-cell-hl { z-index: 4; pointer-events: none; color: var(--de-sheet-ink); overflow: hidden; overflow-wrap: break-word; }
 .de-cell-edit { overflow-wrap: break-word; }
-.de-cell-edit-fx { background: transparent; color: transparent; caret-color: #202124; box-shadow: none; }
-.de-cell-edit-fx::selection { color: transparent; background: rgba(26, 115, 232, 0.25); }
+.de-cell-edit-fx { background: transparent; color: transparent; caret-color: var(--de-sheet-ink); box-shadow: none; }
+.de-cell-edit-fx::selection { color: transparent; background: color-mix(in srgb, var(--de-accent) 25%, transparent); }
 .de-fassist-at { position: absolute; z-index: 30; }
 .de-fassist {
   min-width: 240px;
@@ -946,9 +1018,9 @@
   padding: 4px 0;
   background: var(--de-pop);
   border: 1px solid var(--de-border);
-  border-radius: 6px;
+  border-radius: var(--de-radius);
   box-shadow: var(--de-pop-shadow);
-  font: 12px/1.45 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  font: 12px/1.45 var(--de-font);
   color: var(--de-text);
   text-align: left;
   white-space: normal;
@@ -958,8 +1030,8 @@
 .de-fsug-name { font-weight: 600; }
 .de-fsug-args { margin-left: 2px; color: var(--de-muted); }
 .de-fsug-desc { margin-top: 2px; color: var(--de-muted); font-size: 11.5px; white-space: normal; }
-.de-fhint { padding: 6px 10px; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
-.de-fhint .de-fsug-desc { font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif; }
+.de-fhint { padding: 6px 10px; font-family: var(--de-font-mono); }
+.de-fhint .de-fsug-desc { font-family: var(--de-font); }
 .de-fhint b { color: var(--de-accent); }
 
 /* docx: picture selection, outline, dialogs */
@@ -969,7 +1041,7 @@
   width: 9px;
   height: 9px;
   margin: -5px 0 0 -5px;
-  background: #fff;
+  background: var(--de-page);
   border: 1.5px solid var(--de-accent);
   border-radius: 2px;
   pointer-events: auto;
@@ -988,10 +1060,10 @@
   bottom: -28px;
   transform: translateX(-50%);
   padding: 2px 6px;
-  border-radius: 4px;
-  background: rgba(32, 33, 36, 0.85);
-  color: #fff;
-  font: 11px/1.4 system-ui, sans-serif;
+  border-radius: var(--de-radius-sm);
+  background: var(--de-tip-bg);
+  color: var(--de-tip-ink);
+  font: 11px/1.4 var(--de-font);
   white-space: nowrap;
 }
 .de-outline {
@@ -1008,7 +1080,7 @@
   background: var(--de-pop);
   border-radius: 10px;
   box-shadow: var(--de-pop-shadow);
-  font: 13px/1.35 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  font: 13px/1.35 var(--de-font);
 }
 .de-outline-head { flex-shrink: 0; display: flex; align-items: center; justify-content: space-between; padding: 4px 4px 6px 10px; font-weight: 600; color: var(--de-ink-strong); }
 .de-outline-item {
@@ -1017,7 +1089,7 @@
   width: 100%;
   padding: 5px 10px;
   border: 0;
-  border-radius: 6px;
+  border-radius: var(--de-radius);
   background: transparent;
   color: var(--de-ink-soft);
   font: inherit;
@@ -1038,7 +1110,7 @@
   width: 34px;
   height: 34px;
   border: 1px solid var(--de-border);
-  border-radius: 8px;
+  border-radius: var(--de-radius-lg);
   background: var(--de-pop);
   color: inherit;
   box-shadow: var(--de-shadow);
@@ -1052,9 +1124,9 @@
   height: 26px;
   padding: 0;
   border: 0;
-  border-radius: 4px;
+  border-radius: var(--de-radius-sm);
   background: transparent;
-  font: 15px/1 system-ui, sans-serif;
+  font: 15px/1 var(--de-font);
   color: var(--de-ink-strong);
   cursor: pointer;
 }
@@ -1076,9 +1148,9 @@
   width: min(420px, calc(100vw - 32px));
   padding: 20px;
   background: var(--de-pop);
-  border-radius: 12px;
-  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.28);
-  font: 14px/1.4 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  border-radius: var(--de-radius-xl);
+  box-shadow: var(--de-shadow-lg);
+  font: 14px/1.4 var(--de-font);
   color: var(--de-ink-strong);
 }
 .de-dialog-title { font-size: 16px; font-weight: 600; }
@@ -1087,7 +1159,7 @@
   width: 100%;
   padding: 8px 10px;
   border: 1px solid var(--de-input-border);
-  border-radius: 6px;
+  border-radius: var(--de-radius);
   background: var(--de-input-bg);
   color: var(--de-text);
   font: inherit;
@@ -1096,29 +1168,29 @@
 }
 .de-dialog input:focus, .de-dialog textarea:focus { border-color: var(--de-accent); box-shadow: inset 0 0 0 1px var(--de-accent); }
 .de-hf-zone { position: absolute; left: 0; right: 0; z-index: 1; cursor: default; }
-.de-hf-zone:hover { background: rgba(26, 115, 232, 0.05); }
+.de-hf-zone:hover { background: color-mix(in srgb, var(--de-accent) 5%, transparent); }
 .de-hfd { width: 460px; }
 .de-hfd textarea { min-height: 70px; }
 .de-hfd-tabs { display: flex; gap: 4px; flex-wrap: wrap; }
 .de-hfd-tabs button { padding: 5px 10px; border: 1px solid var(--de-border); border-radius: 14px; background: var(--de-pop); color: var(--de-text); font: inherit; font-size: 12.5px; cursor: pointer; }
 .de-hfd-tabs button.on { background: var(--de-accent); border-color: var(--de-accent); color: var(--de-accent-ink); }
 .de-ps { width: 380px; max-width: calc(100vw - 32px); gap: 10px; }
-.de-ps-note { font-size: 12px; color: var(--de-muted, #5f6368); margin-top: -4px; }
+.de-ps-note { font-size: 12px; color: var(--de-muted); margin-top: -4px; }
 .de-ps-row { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
 .de-ps-head { font-size: 12px; font-weight: 600; display: flex; align-items: center; gap: 10px; min-width: 72px; }
 .de-ps-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 8px 16px; }
 .de-ps-field { display: flex; align-items: center; gap: 6px; font-size: 13px; }
 .de-ps-field > span { min-width: 48px; }
 .de-ps-field input { width: 64px; }
-.de-ps-field em { font-style: normal; color: var(--de-muted, #5f6368); font-size: 12px; }
+.de-ps-field em { font-style: normal; color: var(--de-muted); font-size: 12px; }
 .de-ps-wide { flex: 1; }
 .de-ps-wide select { flex: 1; }
 .de-ps-radio { display: inline-flex; align-items: center; gap: 4px; font-size: 13px; cursor: pointer; }
 .de-ps-radio input { width: auto; padding: 0; margin: 0; }
 .de-ps-preset { font-weight: 400; font-size: 12px; }
-.de-ps select, .de-hfd select { padding: 6px 8px; border: 1px solid var(--de-input-border); border-radius: 6px; background: var(--de-input-bg); color: var(--de-text); font: inherit; }
+.de-ps select, .de-hfd select { padding: 6px 8px; border: 1px solid var(--de-input-border); border-radius: var(--de-radius); background: var(--de-input-bg); color: var(--de-text); font: inherit; }
 .de-page-cols > * { break-inside: avoid; }
-.de-ps-bad { color: #c5221f; }
+.de-ps-bad { color: var(--de-danger); }
 .de-dialog-btns .de-btn:disabled { opacity: 0.5; cursor: default; }
 .de-dialog-btns { display: flex; justify-content: flex-end; gap: 8px; margin-top: 4px; }
 .de-dialog-btns .de-btn { padding: 7px 14px; border: 1px solid var(--de-border); border-radius: 18px; background: var(--de-pop); }
@@ -1136,11 +1208,11 @@
   z-index: 60;
   transform: translateX(-50%);
   padding: 10px 16px;
-  border-radius: 6px;
+  border-radius: var(--de-radius);
   background: var(--de-toast-bg);
   color: var(--de-toast-ink);
-  font: 13px/1.4 system-ui, sans-serif;
-  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
+  font: 13px/1.4 var(--de-font);
+  box-shadow: var(--de-shadow-md);
 }
 
 /* xlsx: find, borders popover */
@@ -1148,8 +1220,8 @@
 .de-xlsx .de-find { top: 40px; }
 .de-find-opts { gap: 10px; padding: 2px 4px; color: var(--de-ink-soft); font-size: 12px; }
 .de-find-opt { display: inline-flex; align-items: center; gap: 4px; cursor: pointer; user-select: none; }
-.de-findcell { position: absolute; z-index: 1; background: rgba(251, 188, 4, 0.28); pointer-events: none; }
-.de-findcell.on { background: rgba(255, 150, 50, 0.45); box-shadow: inset 0 0 0 1.5px #e37400; }
+.de-findcell { position: absolute; z-index: 1; background: var(--de-find-cell); pointer-events: none; }
+.de-findcell.on { background: var(--de-find-cell-on); box-shadow: inset 0 0 0 1.5px var(--de-find-cell-line); }
 .de-borders-pop { display: flex; gap: 8px; align-items: flex-start; }
 .de-borders-side { display: flex; flex-direction: column; gap: 4px; padding-left: 8px; border-left: 1px solid var(--de-sep); }
 .de-find .de-find-opt input { width: auto; height: auto; margin: 0; padding: 0; accent-color: var(--de-accent); }
@@ -1157,21 +1229,21 @@
 
 /* ---------------------------------------------------------------- collaboration */
 .de-collab { display: inline-flex; align-items: center; gap: 8px; flex: none; }
-.de-collab-status { display: inline-flex; align-items: center; gap: 6px; height: 24px; padding: 0 9px; border-radius: 12px; font-size: 12px; color: var(--de-muted); background: var(--de-head); white-space: nowrap; }
-.de-collab-dot { width: 7px; height: 7px; border-radius: 50%; background: #9aa0a6; flex: none; }
-.de-collab-live .de-collab-dot { background: #1e8e3e; box-shadow: 0 0 0 3px rgba(30, 142, 62, 0.18); }
+.de-collab-status { display: inline-flex; align-items: center; gap: 6px; height: 24px; padding: 0 9px; border-radius: var(--de-radius-xl); font-size: 12px; color: var(--de-muted); background: var(--de-head); white-space: nowrap; }
+.de-collab-dot { width: 7px; height: 7px; border-radius: 50%; background: var(--de-status-idle); flex: none; }
+.de-collab-live .de-collab-dot { background: var(--de-status-live); box-shadow: 0 0 0 3px color-mix(in srgb, var(--de-status-live) 18%, transparent); }
 .de-collab-live { color: var(--de-ok); }
 .de-collab-connecting .de-collab-dot,
-.de-collab-syncing .de-collab-dot { background: #f9ab00; animation: de-collab-pulse 1s ease-in-out infinite alternate; }
-.de-collab-offline .de-collab-dot { background: #9aa0a6; }
+.de-collab-syncing .de-collab-dot { background: var(--de-status-busy); animation: de-collab-pulse 1s ease-in-out infinite alternate; }
+.de-collab-offline .de-collab-dot { background: var(--de-status-idle); }
 .de-collab-error { color: var(--de-danger); }
-.de-collab-error .de-collab-dot { background: #d93025; }
+.de-collab-error .de-collab-dot { background: var(--de-status-error); }
 @keyframes de-collab-pulse { to { opacity: 0.35; } }
 @media (max-width: 640px) { .de-collab-label { display: none; } }
 .de-peers { display: inline-flex; align-items: center; }
 .de-peer {
   display: inline-grid; place-items: center; width: 26px; height: 26px; margin-left: -6px; border-radius: 50%;
-  border: 2px solid var(--de-chrome); color: #fff; font-size: 11px; font-weight: 600; letter-spacing: 0.02em; cursor: default; user-select: none;
+  border: 2px solid var(--de-chrome); color: var(--de-avatar-ink); font-size: 11px; font-weight: 600; letter-spacing: 0.02em; cursor: default; user-select: none;
 }
 .de-peer:first-child { margin-left: 0; }
 .de-peer-more { background: var(--de-muted); }
@@ -1180,15 +1252,15 @@
 .de-peer-caret::before { content: ''; position: absolute; top: -3px; left: -2px; width: 6px; height: 6px; border-radius: 50%; background: var(--peer); }
 .de-peer-flag {
   position: absolute; bottom: 100%; left: -1px; margin-bottom: 2px; padding: 1px 6px; border-radius: 4px 4px 4px 0; background: var(--peer);
-  color: #fff; font: 600 11px/16px system-ui, -apple-system, 'Segoe UI', sans-serif; white-space: nowrap;
+  color: var(--de-avatar-ink); font: 600 11px/16px var(--de-font); white-space: nowrap;
 }
 .de-peer-sel { position: absolute; background: var(--peer); opacity: 0.18; border-radius: 1px; }
 .de-peer-outline { position: absolute; border: 2px solid var(--peer); border-radius: 3px; }
 .de-peer-outline > .de-peer-flag { left: -2px; margin-bottom: 1px; }
 .de-peer-range { position: absolute; border: 2px solid; pointer-events: none; z-index: 2; }
 .de-peer-tag {
-  position: absolute; top: -17px; left: -2px; padding: 0 5px; border-radius: 3px 3px 3px 0; color: #fff;
-  font: 600 10px/15px system-ui, -apple-system, 'Segoe UI', sans-serif; white-space: nowrap;
+  position: absolute; top: -17px; left: -2px; padding: 0 5px; border-radius: 3px 3px 3px 0; color: var(--de-avatar-ink);
+  font: 600 10px/15px var(--de-font); white-space: nowrap;
 }
 
 /* ---------------------------------------------------------------- comments */
@@ -1201,7 +1273,7 @@
   min-height: 0;
   background: var(--de-chrome);
   border-left: 1px solid var(--de-border);
-  font: 13px/1.4 system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  font: 13px/1.4 var(--de-font);
   color: var(--de-text);
   position: relative;
   z-index: 7;
@@ -1211,17 +1283,17 @@
 }
 .de-cm-bar { display: flex; align-items: center; gap: 6px; padding: 8px 8px 8px 14px; border-bottom: 1px solid var(--de-border); }
 .de-cm-title { flex: 1; display: flex; align-items: center; gap: 6px; font-weight: 600; color: var(--de-ink-strong); }
-.de-cm-badge { min-width: 18px; padding: 1px 6px; border-radius: 9px; background: var(--de-accent-soft); color: var(--de-accent); font: 600 11px/16px system-ui, sans-serif; text-align: center; }
+.de-cm-badge { min-width: 18px; padding: 1px 6px; border-radius: 9px; background: var(--de-accent-soft); color: var(--de-accent); font: 600 11px/16px var(--de-font); text-align: center; }
 .de-cm-filter { font-size: 12px; color: var(--de-muted); }
 .de-cm-filter.on { color: var(--de-accent); }
 .de-cm-list { flex: 1; min-height: 0; overflow-y: auto; padding: 10px; display: flex; flex-direction: column; gap: 10px; }
 .de-cm-new {
   display: flex; align-items: center; gap: 8px; width: 100%; padding: 8px 10px;
-  border: 1px dashed var(--de-border); border-radius: 8px; background: transparent; color: var(--de-ink); font: inherit; cursor: pointer; text-align: left;
+  border: 1px dashed var(--de-border); border-radius: var(--de-radius-lg); background: transparent; color: var(--de-ink); font: inherit; cursor: pointer; text-align: left;
 }
 .de-cm-new:hover { background: var(--de-hover); border-color: var(--de-accent); color: var(--de-accent); }
 .de-cm-keys { margin-left: auto; color: var(--de-muted); font-size: 11px; }
-.de-cm-notice { display: flex; align-items: center; gap: 6px; padding: 6px 6px 6px 10px; border-radius: 8px; background: var(--de-hover-soft); color: var(--de-ink-soft); font-size: 12px; }
+.de-cm-notice { display: flex; align-items: center; gap: 6px; padding: 6px 6px 6px 10px; border-radius: var(--de-radius-lg); background: var(--de-hover-soft); color: var(--de-ink-soft); font-size: 12px; }
 .de-cm-notice span { flex: 1; }
 .de-cm-card {
   flex: none;
@@ -1247,7 +1319,7 @@
 .de-cm-head { display: flex; align-items: center; gap: 8px; }
 .de-cm-ava {
   flex: none; display: inline-flex; align-items: center; justify-content: center; width: 28px; height: 28px; border-radius: 50%;
-  color: #fff; font: 600 11px/1 system-ui, sans-serif; text-transform: uppercase;
+  color: var(--de-avatar-ink); font: 600 11px/1 var(--de-font); text-transform: uppercase;
 }
 .de-cm-who { flex: 1; min-width: 0; display: flex; flex-direction: column; }
 .de-cm-name { font-weight: 600; color: var(--de-ink-strong); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
@@ -1262,7 +1334,7 @@
 .de-cm-item .de-cm-compose { margin-left: 36px; }
 .de-cm-compose textarea {
   display: block; width: 100%; min-height: 34px; max-height: 200px; padding: 7px 10px; resize: none;
-  border: 1px solid var(--de-border); border-radius: 8px; background: var(--de-input-bg); color: var(--de-text); font: inherit; line-height: 1.4; outline: none;
+  border: 1px solid var(--de-border); border-radius: var(--de-radius-lg); background: var(--de-input-bg); color: var(--de-text); font: inherit; line-height: 1.4; outline: none;
 }
 .de-cm-compose textarea:focus { border-color: var(--de-accent); box-shadow: 0 0 0 1px var(--de-accent); }
 .de-cm-actions { display: flex; align-items: center; justify-content: flex-end; gap: 6px; margin-top: 6px; }
@@ -1273,21 +1345,21 @@
 .de-cm-actions .de-btn:disabled { opacity: 0.5; cursor: default; }
 .de-cm-pop {
   position: absolute; left: 0; right: 0; top: calc(100% - 32px); z-index: 30; max-height: 220px; overflow-y: auto; padding: 4px;
-  background: var(--de-pop); border-radius: 8px; box-shadow: var(--de-pop-shadow);
+  background: var(--de-pop); border-radius: var(--de-radius-lg); box-shadow: var(--de-pop-shadow);
 }
-.de-cm-pop button { display: flex; align-items: center; gap: 8px; width: 100%; padding: 5px 8px; border: 0; border-radius: 6px; background: transparent; color: inherit; font: inherit; text-align: left; cursor: pointer; }
+.de-cm-pop button { display: flex; align-items: center; gap: 8px; width: 100%; padding: 5px 8px; border: 0; border-radius: var(--de-radius); background: transparent; color: inherit; font: inherit; text-align: left; cursor: pointer; }
 .de-cm-pop button.on, .de-cm-pop button:hover { background: var(--de-hover-soft); }
 .de-cm-pop .de-cm-ava { width: 22px; height: 22px; font-size: 10px; }
 .de-cm-empty { padding: 24px 8px; color: var(--de-muted); text-align: center; }
-.de-cm-toggle .de-cm-n { min-width: 16px; padding: 0 5px; border-radius: 8px; background: var(--de-accent); color: var(--de-accent-ink); font: 600 10px/16px system-ui, sans-serif; }
+.de-cm-toggle .de-cm-n { min-width: 16px; padding: 0 5px; border-radius: var(--de-radius-lg); background: var(--de-accent); color: var(--de-accent-ink); font: 600 10px/16px var(--de-font); }
 /* XLSX: a cell with a comment */
 .de-cm-mark { position: absolute; z-index: 4; width: 0; height: 0; border-style: solid; border-width: 0 8px 8px 0; border-color: transparent var(--de-cm-line) transparent transparent; pointer-events: none; }
-.de-cm-mark.on { border-right-color: #c26401; }
+.de-cm-mark.on { border-right-color: var(--de-cm-line-on); }
 /* PPTX: a comment on a slide */
 .de-cm-pin {
   position: absolute; z-index: 4; display: flex; align-items: center; justify-content: center; width: 26px; height: 26px; margin: -26px 0 0 0; padding: 0;
-  border: 2px solid #fff; border-radius: 13px 13px 13px 2px; background: var(--de-cm-line); color: #fff; font: 600 11px/1 system-ui, sans-serif; cursor: pointer;
-  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.35);
+  border: 2px solid var(--de-avatar-ink); border-radius: 13px 13px 13px 2px; background: var(--de-cm-line); color: var(--de-avatar-ink); font: 600 11px/1 var(--de-font); cursor: pointer;
+  box-shadow: var(--de-shadow-md);
 }
 .de-cm-pin.on { background: var(--de-accent); transform: scale(1.12); }
 
@@ -1303,10 +1375,6 @@
 .de-split-handle:hover, .de-split-handle:focus-visible { background: var(--de-accent); outline: none; }
 .de-body-stacked .de-split-handle { width: auto; height: 6px; cursor: row-resize; }
 .de-src {
-  --de-src-bg: #ffffff;
-  --de-src-gutter: #f6f7f8;
-  --de-src-sel: rgba(26, 115, 232, 0.25);
-  --de-src-font: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
   flex: 1;
   min-width: 0;
   min-height: 0;
@@ -1314,11 +1382,10 @@
   flex-direction: column;
   color: var(--de-text);
 }
-.de-dark .de-src { --de-src-bg: #1b1d20; --de-src-gutter: #202327; --de-src-sel: rgba(102, 157, 246, 0.35); }
 .de-src-head { flex: none; display: flex; align-items: center; gap: 10px; height: 36px; padding: 0 6px 0 12px; border-bottom: 1px solid var(--de-border); font-size: 12px; }
 .de-src-title { display: inline-flex; align-items: center; gap: 6px; font-weight: 600; }
 .de-src-lines { color: var(--de-muted); }
-.de-src-btn { display: inline-grid; place-items: center; width: 28px; height: 28px; border: 0; border-radius: 6px; background: none; color: var(--de-ink); cursor: pointer; }
+.de-src-btn { display: inline-grid; place-items: center; width: 28px; height: 28px; border: 0; border-radius: var(--de-radius); background: none; color: var(--de-ink); cursor: pointer; }
 .de-dark .de-src-btn { color: var(--de-text); }
 .de-src-btn:hover { background: var(--de-hover); }
 .de-src-notice { flex: none; padding: 6px 12px; font-size: 12px; line-height: 1.4; color: var(--de-muted); background: var(--de-head); border-bottom: 1px solid var(--de-border); }
@@ -1356,22 +1423,14 @@
   caret-color: var(--de-text);
 }
 .de-src-input::selection { background: var(--de-src-sel); }
-.de-tk-c { color: #6a737d; font-style: italic; }
-.de-tk-k { color: #8e3bc7; }
-.de-tk-s { color: #1a7f37; }
-.de-tk-o { color: #c2410c; }
-.de-tk-n { color: #0b7a8a; }
-.de-tk-h { color: #0b57d0; font-weight: 600; }
-.de-tk-a { color: #0b57d0; }
-.de-tk-t { color: #b42318; }
-.de-tk-m { color: #8a5a00; }
+.de-tk-c { color: var(--de-src-comment); font-style: italic; }
+.de-tk-k { color: var(--de-src-keyword); }
+.de-tk-s { color: var(--de-src-string); }
+.de-tk-o { color: var(--de-src-operator); }
+.de-tk-n { color: var(--de-src-number); }
+.de-tk-h { color: var(--de-src-heading); font-weight: 600; }
+.de-tk-a { color: var(--de-src-attr); }
+.de-tk-t { color: var(--de-src-tag); }
+.de-tk-m { color: var(--de-src-meta); }
 .de-tk-b { font-weight: 700; }
 .de-tk-i { font-style: italic; }
-.de-dark .de-tk-c { color: #8b949e; }
-.de-dark .de-tk-k { color: #d2a8ff; }
-.de-dark .de-tk-s { color: #7ee787; }
-.de-dark .de-tk-o { color: #ffa657; }
-.de-dark .de-tk-n { color: #79c0ff; }
-.de-dark .de-tk-h, .de-dark .de-tk-a { color: #8ab4f8; }
-.de-dark .de-tk-t { color: #ff7b72; }
-.de-dark .de-tk-m { color: #e3b341; }
diff --git a/src/react/theme.ts b/src/react/theme.ts
new file mode 100644
index 0000000..edf07ff
--- /dev/null
+++ b/src/react/theme.ts
@@ -0,0 +1,81 @@
+import type { CSSProperties } from 'react'
+import { useDarkTheme, type ThemeMode } from './common/hooks'
+
+export type { ThemeMode }
+
+/**
+ * Every design token of the viewer, as named in the stylesheet without its `--de-` prefix. The stylesheet defines each
+ * on `.de-root` (light) and the colors again on `.de-root.de-dark`; `test/theme.test.ts` keeps this list and the
+ * stylesheet in step.
+ */
+export const THEME_TOKENS = [
+  // chrome
+  'bg', 'chrome', 'border', 'text', 'muted', 'accent', 'accent-hover', 'accent-ink', 'accent-soft',
+  'on', 'on-ink', 'on-ink-strong', 'ink', 'ink-strong', 'ink-soft', 'hover', 'hover-solid', 'hover-soft',
+  'ebar', 'tb-sep', 'pop', 'pop-shadow', 'sep', 'input-bg', 'input-border', 'swatch-border', 'disabled',
+  'danger', 'danger-border', 'ok', 'tab-hover', 'tab-on', 'tab-ink', 'toast-bg', 'toast-ink', 'backdrop', 'shadow',
+  // sheet headers and grid
+  'grid', 'head', 'head-ink', 'head-border', 'corner-border', 'freeze',
+  // comments
+  'cm-bg', 'cm-on', 'cm-line', 'cm-line-on', 'cm-card', 'cm-quote',
+  // type and shape
+  'font', 'font-mono', 'font-size', 'radius-sm', 'radius', 'radius-lg', 'radius-xl', 'shadow-sm', 'shadow-md', 'shadow-lg',
+  // file kind badges, people's colors, find, tooltips, slideshow, connection state
+  'kind-docx', 'kind-xlsx', 'kind-pptx', 'kind-ink', 'avatar-ink',
+  'find', 'find-on', 'find-cell', 'find-cell-on', 'find-cell-line',
+  'tip-bg', 'tip-ink', 'present-bg', 'present-ink',
+  'status-idle', 'status-live', 'status-busy', 'status-error',
+  // paper: pages, slides and sheets (the same in both modes, as documents keep their own colors)
+  'page', 'page-ink', 'sheet-ink', 'skeleton', 'ph-border', 'ph-a', 'ph-b', 'ph-ink', 'ph-outline', 'ph-hint',
+  // source editor (Markdown, HTML, diagrams)
+  'src-bg', 'src-gutter', 'src-sel', 'src-font', 'src-comment', 'src-keyword', 'src-string', 'src-operator',
+  'src-number', 'src-heading', 'src-attr', 'src-tag', 'src-meta',
+] as const
+
+export type ThemeToken = (typeof THEME_TOKENS)[number]
+
+type Camel<S extends string> = S extends `${infer H}-${infer T}` ? `${H}${Capitalize<Camel<T>>}` : S
+
+/** Token values by camelCase name (`accentHover` for `--de-accent-hover`); any CSS value, `var()` included. */
+export type ThemeTokens = { [K in ThemeToken as Camel<K>]?: string }
+
+export interface ThemeOptions {
+  /** Light, dark, or following the OS. Default 'light'. */
+  mode?: ThemeMode
+  /** Tokens for both modes: type, shape, a brand accent that works on both. */
+  tokens?: ThemeTokens
+  /** Tokens for the light mode only, over `tokens`. */
+  light?: ThemeTokens
+  /** Tokens for the dark mode only, over `tokens`. */
+  dark?: ThemeTokens
+}
+
+/** The `theme` prop: a mode, or a mode with token overrides. */
+export type Theme = ThemeMode | ThemeOptions
+
+/** Types a theme object (no runtime work: for editor completion where the object is written apart from the prop). */
+export const createTheme = (theme: ThemeOptions): ThemeOptions => theme
+
+const kebab = (name: string) => name.replace(/[A-Z]/g, (c) => '-' + c.toLowerCase())
+
+export const themeMode = (theme: Theme | undefined): ThemeMode => (typeof theme === 'object' ? (theme.mode ?? 'light') : (theme ?? 'light'))
+
+/** The custom properties a theme sets on the viewer root in the given mode. */
+export function themeStyle(theme: Theme | undefined, dark: boolean): CSSProperties {
+  if (!theme || typeof theme !== 'object') return {}
+  const out: Record<string, string> = {}
+  for (const set of [theme.tokens, dark ? theme.dark : theme.light]) {
+    if (!set) continue
+    for (const [k, v] of Object.entries(set)) if (v != null && v !== '') out['--de-' + kebab(k)] = v
+  }
+  return out as CSSProperties
+}
+
+/**
+ * The class name and style of a viewer root for `theme`: what `DocViewer` puts on its root element, for hosts that
+ * mount the views (`DocxView`, `XlsxView`, `PptxView`) in a root of their own.
+ */
+export function useThemeRoot(theme?: Theme, style?: CSSProperties): { className: string; style: CSSProperties; dark: boolean } {
+  const dark = useDarkTheme(themeMode(theme))
+  return { className: dark ? 'de-root de-dark' : 'de-root', style: { ...themeStyle(theme, dark), ...style }, dark }
+}
diff --git a/test/theme.test.ts b/test/theme.test.ts
new file mode 100644
index 0000000..86482ad
--- /dev/null
+++ b/test/theme.test.ts
@@ -0,0 +1,62 @@
+import { describe, expect, test } from 'bun:test'
+import { readFileSync } from 'node:fs'
+import { THEME_TOKENS, themeMode, themeStyle } from '../src/react/theme'
+
+const css = readFileSync(`${import.meta.dir}/../src/react/styles.css`, 'utf8')
+const block = (selector: string) => {
+  const at = css.indexOf(`${selector} {\n`)
+  return css.slice(at, css.indexOf('\n}', at))
+}
+const defined = (text: string) => [...text.matchAll(/^\s*--de-([a-z0-9-]+):/gm)].map((m) => m[1])
+const COLOR = /#[0-9a-f]{3,8}\b|rgba?\(|hsla?\(/i
+
+describe('theme tokens', () => {
+  test('THEME_TOKENS lists exactly the tokens the stylesheet defines on .de-root', () => {
+    expect([...defined(block('.de-root'))].sort()).toEqual([...THEME_TOKENS].sort())
+  })
+
+  test('the dark theme redefines only known tokens', () => {
+    const dark = defined(block('.de-root.de-dark'))
+    expect(dark.length).toBeGreaterThan(40)
+    for (const t of dark) expect(THEME_TOKENS as readonly string[]).toContain(t)
+  })
+
+  test('every token the stylesheet uses is defined', () => {
+    const used = new Set([...css.matchAll(/var\(--de-([a-z0-9-]+)/g)].map((m) => m[1]))
+    const known = new Set<string>(THEME_TOKENS)
+    expect([...used].filter((t) => !known.has(t))).toEqual([])
+  })
+
+  test('no literal color outside the token definitions and var() fallbacks', () => {
+    const stray = css
+      .split('\n')
+      .map((line, i) => ({ line: line.replace(/var\(--de-[a-z0-9-]+,[^)]*\)?\)/g, ''), n: i + 1 }))
+      .filter(({ line }) => COLOR.test(line) && !/^\s*--de-[a-z0-9-]+:/.test(line))
+    expect(stray).toEqual([])
+  })
+})
+
+describe('themeStyle', () => {
+  const theme = {
+    mode: 'auto' as const,
+    tokens: { accent: '#7c3aed', font: 'Inter, sans-serif', radiusLg: '4px' },
+    light: { bg: '#fafafa' },
+    dark: { bg: '#111', accent: '#a78bfa' },
+  }
+
+  test('maps camelCase names to the custom properties', () => {
+    expect(themeStyle(theme, false)).toEqual({ '--de-accent': '#7c3aed', '--de-font': 'Inter, sans-serif', '--de-radius-lg': '4px', '--de-bg': '#fafafa' } as never)
+  })
+
+  test('the mode set goes over the shared tokens', () => {
+    expect(themeStyle(theme, true)).toEqual({ '--de-accent': '#a78bfa', '--de-font': 'Inter, sans-serif', '--de-radius-lg': '4px', '--de-bg': '#111' } as never)
+  })
+
+  test('a plain mode sets no properties', () => {
+    expect(themeStyle('dark', true)).toEqual({})
+    expect(themeMode('dark')).toBe('dark')
+    expect(themeMode(theme)).toBe('auto')
+    expect(themeMode({ tokens: {} })).toBe('light')
+    expect(themeMode(undefined)).toBe('light')
+  })
+})