# Section Tone Shift

> The page turns from paper to ink as a marked section takes the middle of the screen, the colour following the scroll. The text changes side halfway, and an event tells your header.

Scroll · scroll, background, color, dark section, theme, header, landing, scrub · HTML, CSS, vanilla JS · no dependencies · updated 2026-11-06
Demo: https://kodza.dev/components/section-tone-shift/
Source on GitHub: https://github.com/kodza-dev/kodza/tree/main/components/section-tone-shift

Takes the whole screen (or reacts to the page scroll): give it a page, not a small box.

## Files

The code below, served as files: byte for byte what the Kodza site copies (the CSS includes its theme guard).

- [`kodza-section-tone-shift.css`](https://kodza.dev/registry/section-tone-shift/kodza-section-tone-shift.css) · 22.1 KB
- [`kodza-section-tone-shift.js`](https://kodza.dev/registry/section-tone-shift/kodza-section-tone-shift.js) · 10.8 KB
- [`kodza-section-tone-shift.html`](https://kodza.dev/registry/section-tone-shift/kodza-section-tone-shift.html) · 2.7 KB · the markup, to adapt and paste into your page

**Can you run shell commands? Download the CSS and the JS, don't retype them.** Retyping costs thousands of tokens and can drop or change lines of the CSS. Put the files where your stack expects them (Use it says where: change the `-o` paths):

```bash
curl -fsSL --create-dirs -o kodza/kodza-section-tone-shift.css https://kodza.dev/registry/section-tone-shift/kodza-section-tone-shift.css
curl -fsSL --create-dirs -o kodza/kodza-section-tone-shift.js https://kodza.dev/registry/section-tone-shift/kodza-section-tone-shift.js
```

Then load the files from your page as Use it shows, instead of pasting the content. The HTML is the part you adapt (text, links, modifiers): paste it from the Code section. Copy the CSS and the JS from the Code section only if you can't run commands, exactly as they are. (Windows PowerShell: `curl.exe`.)

## API

- Root: `[data-kodza-section-tone-shift]`
- Variables (set them on the root element itself: it declares its own defaults):
  - `--kz-section-tone-shift-from: var(--kz-color-page, #f2f2f0)`
  - `--kz-section-tone-shift-from-ink: var(--kz-color-ink, #0a0a0a)`
  - `--kz-section-tone-shift-from-muted: color-mix(in srgb, var(--kz-section-tone-shift-from-ink) 66%, transparent)`
  - `--kz-section-tone-shift-from-line: color-mix(in srgb, var(--kz-section-tone-shift-from-ink) 14%, transparent)`
  - `--kz-section-tone-shift-to: var(--kz-color-ink, #0a0a0a)`
  - `--kz-section-tone-shift-to-ink: var(--kz-color-page, #f2f2f0)`
  - `--kz-section-tone-shift-to-muted: color-mix(in srgb, var(--kz-section-tone-shift-to-ink) 66%, transparent)`
  - `--kz-section-tone-shift-to-line: color-mix(in srgb, var(--kz-section-tone-shift-to-ink) 16%, transparent)`
  - `--kz-section-tone-shift-duration: 0.3s`
  - `--kz-section-tone-shift-ease: cubic-bezier(0.65, 0, 0.35, 1)`
  - `--kz-section-tone-shift-mono: var(--kz-font-mono, "Geist Mono", ui-monospace, SFMono-Regular, Menlo, monospace)`
  - `--kz-section-tone-shift-bg: var(--kz-section-tone-shift-from)`
  - `--kz-section-tone-shift-ink: var(--kz-section-tone-shift-from-ink)`
  - `--kz-section-tone-shift-muted: var(--kz-section-tone-shift-from-muted)`
  - `--kz-section-tone-shift-line: var(--kz-section-tone-shift-from-line)`
- Attributes:
  - `data-kodza-section-tone-shift`
  - `data-tone-shift`
- Events: `kodza:tone` (bubbling, from the root)
- Lifecycle: `kodza:init` / `kodza:destroy` on `document`, with `{ detail: { root } }` to target a container.

## Dark mode

The values Kodza uses on a dark background (`#0a0a0a`). For a page that follows the system theme, add them after the component's CSS:

```css
@media (prefers-color-scheme: dark) {
  .kodza-section-tone-shift {
    --kz-section-tone-shift-from: #0a0a0a;
    --kz-section-tone-shift-from-ink: #f2f2f0;
    --kz-section-tone-shift-from-muted: rgba(242, 242, 240, 0.66);
    --kz-section-tone-shift-from-line: rgba(242, 242, 240, 0.16);
    --kz-section-tone-shift-to: #f2f2f0;
    --kz-section-tone-shift-to-ink: #0a0a0a;
    --kz-section-tone-shift-to-muted: rgba(10, 10, 10, 0.66);
    --kz-section-tone-shift-to-line: rgba(10, 10, 10, 0.14);
  }
}
```

A site with its own theme switch puts the same rules under its dark selector instead (`[data-theme="dark"] .kodza-section-tone-shift { … }`); a single dark section, under that section's class.

## Use it

### Plain HTML page

- CSS: `kodza/kodza-section-tone-shift.css` next to the page (the Files commands as they are), linked in `<head>`: `<link rel="stylesheet" href="kodza/kodza-section-tone-shift.css">`. Without a shell, paste it in a `<style>` in `<head>` instead. It only touches `kodza-` classes.
- HTML: where the component goes. Paste it as many times as you need: instances never interfere.
- JS: `kodza/kodza-section-tone-shift.js`, loaded with `<script src="kodza/kodza-section-tone-shift.js" defer></script>` in `<head>`. Without a shell, paste it in a `<script>` before `</body>` (or in `<head>`: it waits for the page). One copy per page, whatever the number of instances.
- Restyle with the `--kz-…` variables, set on the component's root element itself (the root declares its own defaults, so a value on an ancestor is ignored), and with the modifiers / attributes listed under API.
- Font: it takes the page's own. A site with its own type sets it once for every Kodza component, on `:root`, never by editing the CSS (unset, nothing changes): `--kz-font-display`, the display face (headings, big numbers, wordmarks); `--kz-font-display-weight`, its weight; `--kz-font-display-scale`, a multiplier on its sizes (1 by default); `--kz-font-display-tracking`, its letter-spacing; `--kz-font-display-case`, its case (`uppercase`…); `--kz-font-label`, the face of the small labels (meta, captions, counters, hints, footer links, button labels); `--kz-font-label-size`, their size, one for all of them (`11px`…); `--kz-font-label-weight`, their weight; `--kz-font-label-tracking`, their letter-spacing; `--kz-font-label-case`, their case (`uppercase`…; code and units keep theirs); `--kz-font-label-leading`, their line-height (`1.45`…; buttons, pills and keys keep their box); `--kz-font-mono`, the monospace face (code, labels, counters). The Kodza look is Geist: `<link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Geist:wght@400;500;600;700&family=Geist+Mono:wght@400;500&display=swap">`.
- Corners: a site with its own shapes sets them once for every Kodza component, on `:root`, never by editing the CSS (unset, nothing changes): `--kz-radius-pill` sets the pills (`0` squares them).
- Motion: a site sets its pace once for every Kodza component, on `:root`, never by editing the CSS or the JS: `--kz-motion-scale` multiplies every duration (`0.5` twice as fast, `2` twice as slow, `0` no motion at all, loops stopped, like reduced motion). Unset, nothing changes.
- Content added later (AJAX navigation, a SPA route, a builder preview): start it with `document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root: container } }))`; before removing it, the same call with `'kodza:destroy'` stops it and puts the original markup back.

### Claude artifact (claude.ai)

- Paste the CSS in a `<style>` and the JS in a `<script>` at the end, in the artifact itself: it loads stylesheets only from Google Fonts and scripts only from a few CDNs, so no `<link>` or `<script src>` to Kodza.
- Writing the artifact file with a shell? Insert the downloaded files (Files) with a command instead of retyping them: a line `KODZA-CSS` alone inside the `<style>`, `KODZA-JS` inside the `<script>`, then `sed -e '/^KODZA-CSS$/{r kodza/kodza-section-tone-shift.css' -e 'd' -e '}' -e '/^KODZA-JS$/{r kodza/kodza-section-tone-shift.js' -e 'd' -e '}' page.html > artifact.html`.
- Font: load Geist from Google Fonts (allowed): `<link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Geist:wght@400;500;600;700&family=Geist+Mono:wght@400;500&display=swap">`. A site with its own type sets it once for every Kodza component, on `:root`, never by editing the CSS (unset, nothing changes): `--kz-font-display`, the display face (headings, big numbers, wordmarks); `--kz-font-display-weight`, its weight; `--kz-font-display-scale`, a multiplier on its sizes (1 by default); `--kz-font-display-tracking`, its letter-spacing; `--kz-font-display-case`, its case (`uppercase`…); `--kz-font-label`, the face of the small labels (meta, captions, counters, hints, footer links, button labels); `--kz-font-label-size`, their size, one for all of them (`11px`…); `--kz-font-label-weight`, their weight; `--kz-font-label-tracking`, their letter-spacing; `--kz-font-label-case`, their case (`uppercase`…; code and units keep theirs); `--kz-font-label-leading`, their line-height (`1.45`…; buttons, pills and keys keep their box); `--kz-font-mono`, the monospace face (code, labels, counters).
- Corners: a site with its own shapes sets them once for every Kodza component, on `:root`, never by editing the CSS (unset, nothing changes): `--kz-radius-pill` sets the pills (`0` squares them).
- Motion: a site sets its pace once for every Kodza component, on `:root`, never by editing the CSS or the JS: `--kz-motion-scale` multiplies every duration (`0.5` twice as fast, `2` twice as slow, `0` no motion at all, loops stopped, like reduced motion). Unset, nothing changes.
- Dark mode: the viewer sets `data-theme="dark"` or `"light"` on `<html>`, or nothing when it follows the system. Write the Dark mode rules twice: inside `@media (prefers-color-scheme: dark)` with `:root:not([data-theme="light"])` in front of each selector, and with `:root[data-theme="dark"]` in front of each selector.

### WordPress

- HTML: a **Custom HTML** block (or a pattern / template part). WordPress keeps this markup as it is only for users allowed to post unfiltered HTML (Administrators; Super Admins on multisite): for anyone else it strips tags such as `<svg>`, `<input>` or `<dialog>`, so add it from the theme (a pattern or template part) instead.
- This one spans the page: a block theme keeps a Custom HTML block to the width of the text column, so put it inside a **Group** block set to **Full width**, with **Inner blocks use content width** turned off.
- CSS and JS: the downloaded files go in the theme, under `wp-content/themes/<your-theme>/kodza/` (the child theme if there is one), enqueued from its functions.php (or a code-snippets plugin):
  ```php
  add_action('wp_enqueue_scripts', function () {
    $dir = get_stylesheet_directory() . '/kodza/';
    $uri = get_stylesheet_directory_uri() . '/kodza/';
    wp_enqueue_style('kodza-section-tone-shift', $uri . 'kodza-section-tone-shift.css', [], filemtime($dir . 'kodza-section-tone-shift.css'));
    wp_enqueue_script('kodza-section-tone-shift', $uri . 'kodza-section-tone-shift.js', [], filemtime($dir . 'kodza-section-tone-shift.js'), true);
  });
  ```
  Scoped to `kodza-` classes, the CSS never touches the theme. One copy of the JS, whatever the number of blocks.
- No access to the theme files? The CSS can also go, as it is, in **Appearance → Customize → Additional CSS** (classic theme) or **Styles → Additional CSS** in the Site Editor (block theme).
- Theme with AJAX page transitions: fire `kodza:init` on the new content after each swap (and `kodza:destroy` on the old one).
- Performance plugin (WP Rocket, LiteSpeed Cache, Perfmatters…) with **Delay JavaScript execution** turned on: add `kodza` to the scripts it must not delay. Otherwise the component waits for the visitor's first scroll, tap or mouse move, and that first click can be lost.
- Colours: it takes the colour of the text around it (or keeps its own monochrome): nothing to point at the theme.
- WordPress turns straight quotes and `--` into typographic ones in the text of a Custom HTML block (not inside `<code>` or `<pre>`).

#### With Elementor

- HTML: an **HTML** widget (Elementor shows it to administrators only). It keeps the code exactly as pasted, straight quotes included.
- This one spans the page: give the widget its own container, **Content Width: Full Width**, padding 0.
- CSS and JS: as above. Elementor's Site Settings → Theme Style styles every button, field, link and image of the page, components included; the theme guard at the end of the CSS keeps the component's buttons, fields and link colours as they are.
- The Elementor editor redraws each widget after the page has loaded: without the script below, the component stays still in the editor preview (the published page works). Add it once per site, in the footer like the component's script (`kodza/elementor-editor.js`, or a code-snippets plugin):

```js
// Kodza in the Elementor editor: the editor redraws each HTML widget after the page has loaded.
// Start Kodza in what it draws, stop it in what it replaces or removes. Once per site.
window.addEventListener('elementor/frontend/init', () => {
  if (!elementorFrontend.isEditMode()) return;
  class KodzaWidget extends elementorModules.frontend.handlers.Base {
    onInit() {
      super.onInit();
      this.kodza = [...this.$element[0].children];
      document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root: this.$element[0] } }));
    }
    onDestroy() {
      super.onDestroy();
      this.kodza.forEach((root) => document.dispatchEvent(new CustomEvent('kodza:destroy', { detail: { root } })));
    }
  }
  elementorFrontend.elementsHandler.attachHandler('html', KodzaWidget);
});
```

- No child theme: everything can go in the HTML widget instead, `<style>` with the CSS, the HTML, then `<script>` with the JS. It works on the page and in the editor without the script above.

### Shopify

- Files: `assets/kodza-section-tone-shift.css` and `assets/kodza-section-tone-shift.js` (the Files commands with `-o assets/…`).
- In the section: `{{ 'kodza-section-tone-shift.css' | asset_url | stylesheet_tag }}` and `<script src="{{ 'kodza-section-tone-shift.js' | asset_url }}" defer></script>`, then the HTML.
- The theme editor re-renders sections: restart them with
  `document.addEventListener('shopify:section:load', (e) => document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root: e.target } })));`
  and the same with `shopify:section:unload` → `kodza:destroy`.

### React / Next.js

- Files, side by side (e.g. in `components/kodza/`): `SectionToneShift.tsx` (below), the CSS block under Code saved as `section-tone-shift.css` and the JS block as `section-tone-shift.js`, both as they are. The HTML block is already inside the component: skip it.
- Use it: `import { SectionToneShift } from '@/components/kodza/SectionToneShift';` then `<SectionToneShift />`. Props: `vars` (the `--kz-…` variables listed under API, e.g. `vars={{ '--kz-section-tone-shift-from': … }}`), `onTone` (the `kodza:tone` event), `className`, `style` and the other props of its `<div>` (`onClick`, `aria-…`).
- Next.js App Router: it is a Client Component already (`'use client'`). Pages Router: Next.js takes global CSS only in `pages/_app`, so move the `import './section-tone-shift.css'` line there.
- Safe under StrictMode, client-side navigation and prop changes: when a prop changes, the `key` gives React a fresh element, `kodza:destroy` stops the script on the old one and `kodza:init` starts it on the new one.
- Built from your data (tabs, rows, options)? Add what the markup is made of to the `key`, as plain values (ids, text, numbers). What the visitor changes (the open tab, the sort, what they type) is the script's: follow it with `onClick` or `onInput` on the root, and change it from your code as a visitor would (click the tab; set the field's value, then dispatch a bubbling `input` event). Fields stay uncontrolled (`defaultValue`, `name`).

```tsx
'use client';
// Kodza — Section Tone Shift, for React. From https://kodza.dev/components/section-tone-shift/
// Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license
// Next to this file: section-tone-shift.css and section-tone-shift.js, the component's CSS and JS from Kodza, as they are.
// Yours to edit: the markup is plain JSX below.
// The script changes this markup once React has rendered it (it adds layers, splits text, moves
// nodes), so React must not patch it afterwards. When a prop changes, the key gives React a fresh
// element: kodza:destroy stops the script on the old one, kodza:init starts it on the new one.
// data-kodza-manual keeps the script from starting it on its own: the effect below does, once
// React has hydrated the markup (on a page that streams in, the script can load first).
// Built from your data (tabs, rows, options)? Put what the markup is made of in the key, as plain
// values (ids, text, numbers): a change starts the script again on fresh markup. What the visitor
// changes (the open tab, the sort, what they type) is the script's: keep it out of the key, follow
// it with onClick or onInput on the root, and change it from your code as a visitor would (click
// the tab; set the field's value, then dispatch a bubbling input event).
import { useRef, useEffect, type ComponentPropsWithoutRef, type ComponentRef, type CSSProperties } from 'react';
import './section-tone-shift.css';

export type SectionToneShiftProps = Omit<ComponentPropsWithoutRef<'div'>, "children" | "vars" | "onTone"> & {
  /** Settings, as CSS variables on the root */
  vars?: {
    /** default: var(--kz-color-page, #f2f2f0) */
    "--kz-section-tone-shift-from"?: string | number;
    /** default: var(--kz-color-ink, #0a0a0a) */
    "--kz-section-tone-shift-from-ink"?: string | number;
    /** default: color-mix(in srgb, var(--kz-section-tone-shift-from-ink) 66%, transparent) */
    "--kz-section-tone-shift-from-muted"?: string | number;
    /** default: color-mix(in srgb, var(--kz-section-tone-shift-from-ink) 14%, transparent) */
    "--kz-section-tone-shift-from-line"?: string | number;
    /** default: var(--kz-color-ink, #0a0a0a) */
    "--kz-section-tone-shift-to"?: string | number;
    /** default: var(--kz-color-page, #f2f2f0) */
    "--kz-section-tone-shift-to-ink"?: string | number;
    /** default: color-mix(in srgb, var(--kz-section-tone-shift-to-ink) 66%, transparent) */
    "--kz-section-tone-shift-to-muted"?: string | number;
    /** default: color-mix(in srgb, var(--kz-section-tone-shift-to-ink) 16%, transparent) */
    "--kz-section-tone-shift-to-line"?: string | number;
    /** default: 0.3s */
    "--kz-section-tone-shift-duration"?: string | number;
    /** default: cubic-bezier(0.65, 0, 0.35, 1) */
    "--kz-section-tone-shift-ease"?: string | number;
    /** default: var(--kz-font-mono, "Geist Mono", ui-monospace, SFMono-Regular, Menlo, monospace) */
    "--kz-section-tone-shift-mono"?: string | number;
    /** default: var(--kz-section-tone-shift-from) */
    "--kz-section-tone-shift-bg"?: string | number;
    /** default: var(--kz-section-tone-shift-from-ink) */
    "--kz-section-tone-shift-ink"?: string | number;
    /** default: var(--kz-section-tone-shift-from-muted) */
    "--kz-section-tone-shift-muted"?: string | number;
    /** default: var(--kz-section-tone-shift-from-line) */
    "--kz-section-tone-shift-line"?: string | number;
  };
  /** "kodza:tone", fired by the script (bubbles from the root) */
  onTone?: (event: CustomEvent) => void;
  className?: string;
};

export function SectionToneShift({ vars, onTone, className, style, ...rest }: SectionToneShiftProps) {
  const ref = useRef<ComponentRef<'div'>>(null);
  const classes = ["kodza-section-tone-shift", className].filter(Boolean).join(' ');
  // Everything the markup is made of: when it changes, React gets a fresh element (see the top)
  const key = JSON.stringify([classes, vars, style, rest]);

  // Starts the script on this element once React has rendered it, stops it when it goes
  useEffect(() => {
    const root = ref.current;
    let live = true;
    // @ts-ignore: a plain script, no types to find
    import('./section-tone-shift.js').then(() => {
      if (live) document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root } }));
    });
    return () => {
      live = false;
      document.dispatchEvent(new CustomEvent('kodza:destroy', { detail: { root } }));
    };
  }, [key]);

  useEffect(() => {
    const root = ref.current;
    if (!root || !onTone) return;
    const listener = (event: Event) => onTone(event as CustomEvent);
    root.addEventListener("kodza:tone", listener);
    return () => root.removeEventListener("kodza:tone", listener);
  }, [onTone, key]);

  return (
    <div data-kodza-section-tone-shift="" key={key} {...rest} className={classes} data-kodza-manual style={{ ...vars, ...style } as CSSProperties} ref={ref}>
      <section className="kodza-section-tone-shift__section">
        <div className="kodza-section-tone-shift__head">
          <div className="kodza-section-tone-shift__lead">
            <p className="kodza-section-tone-shift__label">Atelier Nord · Nantes</p>
            <h2 className="kodza-section-tone-shift__title">Websites for people who are tired of websites.</h2>
          </div>
          <p className="kodza-section-tone-shift__text">Four people above a bakery in Nantes. We build fast, quiet sites for architects, a ferry company and one very particular cheese shop.</p>
        </div>
        <dl className="kodza-section-tone-shift__figures">
          <div className="kodza-section-tone-shift__figure">
            <dt className="kodza-section-tone-shift__caption">First paint, on a train</dt>
            <dd className="kodza-section-tone-shift__value">0.6 s</dd>
          </div>
          <div className="kodza-section-tone-shift__figure">
            <dt className="kodza-section-tone-shift__caption">Carousels shipped since 2019</dt>
            <dd className="kodza-section-tone-shift__value">0</dd>
          </div>
          <div className="kodza-section-tone-shift__figure">
            <dt className="kodza-section-tone-shift__caption">Clients who came back</dt>
            <dd className="kodza-section-tone-shift__value">11 of 12</dd>
          </div>
        </dl>
      </section>
      <section className="kodza-section-tone-shift__section" data-tone-shift="">
        <p className="kodza-section-tone-shift__label">What we refuse</p>
        <h2 className="kodza-section-tone-shift__title kodza-section-tone-shift__title--statement">No carousel. No chatbot. No hero video of people laughing at a salad.</h2>
        <ol className="kodza-section-tone-shift__list">
          <li className="kodza-section-tone-shift__item"><span className="kodza-section-tone-shift__num">01</span>Cookie banners that ask twice.</li>
          <li className="kodza-section-tone-shift__item"><span className="kodza-section-tone-shift__num">02</span>Fonts loaded from four different places.</li>
          <li className="kodza-section-tone-shift__item"><span className="kodza-section-tone-shift__num">03</span>Animations you have to wait for.</li>
        </ol>
        <p className="kodza-section-tone-shift__text">Everything on a page has a job. If we cannot say what it does in one sentence, it goes, and the page gets faster without anybody writing a line of code.</p>
      </section>
      <section className="kodza-section-tone-shift__section">
        <p className="kodza-section-tone-shift__label">Next</p>
        <h2 className="kodza-section-tone-shift__title">Tell us what the site has to do. We will tell you what it can live without.</h2>
        <div className="kodza-section-tone-shift__actions">
          <a className="kodza-section-tone-shift__button" href="#">Start a project</a>
          <p className="kodza-section-tone-shift__note">Replies within a day, from a human.</p>
        </div>
      </section>
    </div>
  );
}
```

## Code

```html
<div class="kodza-section-tone-shift" data-kodza-section-tone-shift>
  <section class="kodza-section-tone-shift__section">
    <div class="kodza-section-tone-shift__head">
      <div class="kodza-section-tone-shift__lead">
        <p class="kodza-section-tone-shift__label">Atelier Nord · Nantes</p>
        <h2 class="kodza-section-tone-shift__title">Websites for people who are tired of websites.</h2>
      </div>
      <p class="kodza-section-tone-shift__text">Four people above a bakery in Nantes. We build fast, quiet sites for architects, a ferry company and one very particular cheese shop.</p>
    </div>
    <dl class="kodza-section-tone-shift__figures">
      <div class="kodza-section-tone-shift__figure"><dt class="kodza-section-tone-shift__caption">First paint, on a train</dt><dd class="kodza-section-tone-shift__value">0.6 s</dd></div>
      <div class="kodza-section-tone-shift__figure"><dt class="kodza-section-tone-shift__caption">Carousels shipped since 2019</dt><dd class="kodza-section-tone-shift__value">0</dd></div>
      <div class="kodza-section-tone-shift__figure"><dt class="kodza-section-tone-shift__caption">Clients who came back</dt><dd class="kodza-section-tone-shift__value">11 of 12</dd></div>
    </dl>
  </section>
  <section class="kodza-section-tone-shift__section" data-tone-shift>
    <p class="kodza-section-tone-shift__label">What we refuse</p>
    <h2 class="kodza-section-tone-shift__title kodza-section-tone-shift__title--statement">No carousel. No chatbot. No hero video of people laughing at a salad.</h2>
    <ol class="kodza-section-tone-shift__list">
      <li class="kodza-section-tone-shift__item"><span class="kodza-section-tone-shift__num">01</span>Cookie banners that ask twice.</li>
      <li class="kodza-section-tone-shift__item"><span class="kodza-section-tone-shift__num">02</span>Fonts loaded from four different places.</li>
      <li class="kodza-section-tone-shift__item"><span class="kodza-section-tone-shift__num">03</span>Animations you have to wait for.</li>
    </ol>
    <p class="kodza-section-tone-shift__text">Everything on a page has a job. If we cannot say what it does in one sentence, it goes, and the page gets faster without anybody writing a line of code.</p>
  </section>
  <section class="kodza-section-tone-shift__section">
    <p class="kodza-section-tone-shift__label">Next</p>
    <h2 class="kodza-section-tone-shift__title">Tell us what the site has to do. We will tell you what it can live without.</h2>
    <div class="kodza-section-tone-shift__actions">
      <a class="kodza-section-tone-shift__button" href="#">Start a project</a>
      <p class="kodza-section-tone-shift__note">Replies within a day, from a human.</p>
    </div>
  </section>
</div>
```

```css
/* Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license */
/* Kodza — Section Tone Shift
   Wraps a run of sections. While one marked data-tone-shift holds the middle of the screen, the
   whole page turns from its own tone to the other one, and back as the section leaves: the
   background follows the scroll, the text and the hairlines change side at once, halfway, so they
   never sit grey on grey. Without the script (or with reduced motion), the marked sections simply
   wear the other tone.
   Tuned with the --kz-section-tone-shift-* variables (the two tones first); the band, the
   thresholds and the smoothing are constants at the top of component.js. */
.kodza-section-tone-shift {
  /* The page's own tone: background, text, quiet text and hairlines */
  --kz-section-tone-shift-from: var(--kz-color-page, #f2f2f0);
  --kz-section-tone-shift-from-ink: var(--kz-color-ink, #0a0a0a);
  --kz-section-tone-shift-from-muted: color-mix(in srgb, var(--kz-section-tone-shift-from-ink) 66%, transparent);
  --kz-section-tone-shift-from-line: color-mix(in srgb, var(--kz-section-tone-shift-from-ink) 14%, transparent);
  /* The tone a marked section turns the page to */
  --kz-section-tone-shift-to: var(--kz-color-ink, #0a0a0a);
  --kz-section-tone-shift-to-ink: var(--kz-color-page, #f2f2f0);
  --kz-section-tone-shift-to-muted: color-mix(in srgb, var(--kz-section-tone-shift-to-ink) 66%, transparent);
  --kz-section-tone-shift-to-line: color-mix(in srgb, var(--kz-section-tone-shift-to-ink) 16%, transparent);
  /* How fast the text and the hairlines change side, once the background is halfway: soft at both
     ends, quick through the middle, where the text passes the grey of the background */
  --kz-section-tone-shift-duration: 0.3s;
  --kz-section-tone-shift-ease: cubic-bezier(0.65, 0, 0.35, 1);
  --kz-section-tone-shift-mono: var(--kz-font-mono, "Geist Mono", ui-monospace, SFMono-Regular, Menlo, monospace);

  /* The tone the content is in now, for your own elements too: color: var(--kz-section-tone-shift-ink) */
  --kz-section-tone-shift-bg: var(--kz-section-tone-shift-from);
  --kz-section-tone-shift-ink: var(--kz-section-tone-shift-from-ink);
  --kz-section-tone-shift-muted: var(--kz-section-tone-shift-from-muted);
  --kz-section-tone-shift-line: var(--kz-section-tone-shift-from-line);

  display: block;
  background-color: var(--kz-section-tone-shift-from);
  color: var(--kz-section-tone-shift-ink);
}

/* Without the script, or asked to sit still: each marked section wears the other tone on its own */
.kodza-section-tone-shift:not(.is-shifting) [data-tone-shift],
.kodza-section-tone-shift.is-shifted {
  --kz-section-tone-shift-bg: var(--kz-section-tone-shift-to);
  --kz-section-tone-shift-ink: var(--kz-section-tone-shift-to-ink);
  --kz-section-tone-shift-muted: var(--kz-section-tone-shift-to-muted);
  --kz-section-tone-shift-line: var(--kz-section-tone-shift-to-line);
}

.kodza-section-tone-shift:not(.is-shifting) [data-tone-shift] {
  background-color: var(--kz-section-tone-shift-to);
  color: var(--kz-section-tone-shift-ink);
}

/* Halfway between the tones, on a mid grey: the soft text takes the full ink to stay readable */
.kodza-section-tone-shift.is-crossing {
  --kz-section-tone-shift-muted: var(--kz-section-tone-shift-ink);
}

/* Running: the whole page paints the mix the script writes (0 its own tone, 1 the other one) */
.kodza-section-tone-shift.is-shifting {
  background-color: color-mix(in oklab, var(--kz-section-tone-shift-to) calc(var(--kz-section-tone-shift-mix, 0) * 100%), var(--kz-section-tone-shift-from));
}

/* The example sections */
.kodza-section-tone-shift__section {
  box-sizing: border-box;
  display: grid;
  gap: clamp(28px, 4vw, 48px);
  align-content: start;
  padding: clamp(96px, 13vw, 168px) max(24px, calc((100% - 1080px) / 2));
}

.kodza-section-tone-shift__head {
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr);
  gap: clamp(24px, 5vw, 72px);
  align-items: end;
}

.kodza-section-tone-shift__lead {
  display: grid;
  gap: 22px;
}

.kodza-section-tone-shift__label {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 0;
  color: var(--kz-section-tone-shift-muted);
  font-family: var(--kz-font-label, var(--kz-section-tone-shift-mono));
  font-size: var(--kz-font-label-size, 12.5px);
  font-weight: var(--kz-font-label-weight, 500);
  line-height: var(--kz-font-label-leading, 1.4);
  letter-spacing: var(--kz-font-label-tracking, 0.02em);
  text-transform: var(--kz-font-label-case, inherit);
}

/* A drawn dot before each label */
.kodza-section-tone-shift__label::before {
  content: "";
  flex: none;
  width: 6px;
  height: 6px;
  border-radius: var(--kz-radius-pill, 999px);
  background: currentColor;
}

.kodza-section-tone-shift__title {
  max-width: 18ch;
  margin: 0;
  font-family: var(--kz-font-display, inherit);
  font-size: calc(clamp(34px, 5.4vw, 72px) * var(--kz-font-display-scale, 1));
  font-weight: var(--kz-font-display-weight, 600);
  line-height: 1.02;
  letter-spacing: var(--kz-font-display-tracking, -0.045em);
  text-transform: var(--kz-font-display-case, inherit);
  text-wrap: balance;
}

.kodza-section-tone-shift__title--statement {
  max-width: 15ch;
  font-size: calc(clamp(40px, 7.4vw, 104px) * var(--kz-font-display-scale, 1));
  line-height: 0.98;
  letter-spacing: var(--kz-font-display-tracking, -0.05em);
}

.kodza-section-tone-shift__text {
  max-width: 46ch;
  margin: 0;
  color: var(--kz-section-tone-shift-muted);
  font-size: 17px;
  line-height: 1.6;
  text-wrap: pretty;
}

.kodza-section-tone-shift__figures {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 24px;
  margin: clamp(24px, 4vw, 48px) 0 0;
  padding: 24px 0 0;
  border-top: 1px solid var(--kz-section-tone-shift-line);
}

.kodza-section-tone-shift__figure {
  display: flex;
  flex-direction: column-reverse;
  justify-content: flex-end;
  gap: 8px;
}

.kodza-section-tone-shift__value {
  margin: 0;
  font-family: var(--kz-font-display, inherit);
  font-size: calc(clamp(28px, 3.4vw, 40px) * var(--kz-font-display-scale, 1));
  font-weight: var(--kz-font-display-weight, 600);
  line-height: 1.05;
  letter-spacing: var(--kz-font-display-tracking, -0.04em);
}

.kodza-section-tone-shift__caption,
.kodza-section-tone-shift__num,
.kodza-section-tone-shift__note {
  margin: 0;
  color: var(--kz-section-tone-shift-muted);
  font-family: var(--kz-font-label, var(--kz-section-tone-shift-mono));
  font-size: var(--kz-font-label-size, 12.5px);
  font-weight: var(--kz-font-label-weight, 500);
  line-height: var(--kz-font-label-leading, 1.4);
  letter-spacing: var(--kz-font-label-tracking, 0.02em);
  text-transform: var(--kz-font-label-case, inherit);
}

.kodza-section-tone-shift__list {
  max-width: 720px;
  margin: clamp(8px, 2vw, 24px) 0 0;
  padding: 0;
  list-style: none;
  border-bottom: 1px solid var(--kz-section-tone-shift-line);
}

.kodza-section-tone-shift__item {
  display: grid;
  grid-template-columns: 56px minmax(0, 1fr);
  align-items: baseline;
  margin: 0;
  padding: 20px 0;
  border-top: 1px solid var(--kz-section-tone-shift-line);
  text-wrap: pretty;
  font-size: clamp(18px, 2vw, 22px);
  font-weight: 500;
  line-height: 1.35;
  letter-spacing: -0.02em;
}

.kodza-section-tone-shift__actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 16px 24px;
  margin-top: clamp(4px, 1vw, 12px);
}

.kodza-section-tone-shift__button {
  display: inline-flex;
  align-items: center;
  height: 52px;
  padding: 0 26px;
  border-radius: var(--kz-radius-pill, 999px);
  background: var(--kz-section-tone-shift-ink);
  color: var(--kz-section-tone-shift-bg);
  font-family: var(--kz-font-label, inherit);
  font-size: var(--kz-font-label-size, 15px);
  font-weight: var(--kz-font-label-weight, 500);
  line-height: 1;
  letter-spacing: var(--kz-font-label-tracking, -0.01em);
  text-transform: var(--kz-font-label-case, inherit);
  text-decoration: none;
}

.kodza-section-tone-shift__button:focus-visible {
  outline: 2px solid var(--kz-section-tone-shift-ink);
  outline-offset: 3px;
}

@media (hover: hover) {
  .kodza-section-tone-shift__button:hover {
    opacity: 0.86;
  }
}

/* Moving: the text and the hairlines change side together, in one short crossing */
.kodza-section-tone-shift.is-moving,
.kodza-section-tone-shift.is-moving :is(.kodza-section-tone-shift__label, .kodza-section-tone-shift__text, .kodza-section-tone-shift__caption, .kodza-section-tone-shift__num, .kodza-section-tone-shift__note) {
  transition: color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease);
}

.kodza-section-tone-shift.is-moving :is(.kodza-section-tone-shift__figures, .kodza-section-tone-shift__list, .kodza-section-tone-shift__item) {
  transition: border-color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease);
}

.kodza-section-tone-shift.is-moving .kodza-section-tone-shift__button {
  transition:
    background-color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease),
    color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease),
    opacity calc(0.2s * var(--kz-motion-scale, 1)) ease;
}

@media (max-width: 759.98px) {
  .kodza-section-tone-shift__head {
    grid-template-columns: minmax(0, 1fr);
    align-items: start;
  }
}

@media (max-width: 559.98px) {
  .kodza-section-tone-shift__figures {
    grid-template-columns: minmax(0, 1fr);
    gap: 20px;
  }

  .kodza-section-tone-shift__item {
    grid-template-columns: 44px minmax(0, 1fr);
  }
}

@media (prefers-reduced-motion: reduce) {
  .kodza-section-tone-shift,
  .kodza-section-tone-shift *,
  .kodza-section-tone-shift *::before,
  .kodza-section-tone-shift *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

/* kodza-guard 8ae6750d6885 — generated by Kodza, do not edit.
   Theme guard: keeps a site's own CSS (WordPress themes, Bootstrap, CSS resets…) off this
   component. :not(#_) is always true and weighs as much as an id, so these lines win over
   theme rules made of classes and tags. Customise the component through its --kz-* variables. */

/* What the browser gives, where the component sets it only in some states: at the lowest weight, so its own rules below put it back */

:where(.kodza-section-tone-shift__label):not(#_),
:where(.kodza-section-tone-shift__text):not(#_),
:where(.kodza-section-tone-shift__caption):not(#_),
:where(.kodza-section-tone-shift__note):not(#_) {
  transition: revert;
  background-color: revert;
}

:where(.kodza-section-tone-shift__title):not(#_),
:where(.kodza-section-tone-shift__figures):not(#_),
:where(.kodza-section-tone-shift__value):not(#_),
:where(.kodza-section-tone-shift__list):not(#_),
:where(.kodza-section-tone-shift__item):not(#_) {
  transition: revert;
  background-color: revert;
  color: revert;
}

:where(.kodza-section-tone-shift__button):not(#_) {
  outline: revert;
  transition: revert;
  outline-offset: revert;
}

/* What the browser gives, on everything the component leaves to it */

.kodza-section-tone-shift:not(#_),
.kodza-section-tone-shift__head:not(#_),
.kodza-section-tone-shift__lead:not(#_),
.kodza-section-tone-shift__figure:not(#_),
.kodza-section-tone-shift__num:not(#_),
.kodza-section-tone-shift__actions:not(#_) {
  box-sizing: revert;
}

.kodza-section-tone-shift__label:not(#_),
.kodza-section-tone-shift__caption:not(#_),
.kodza-section-tone-shift__note:not(#_) {
  border: revert;
  padding: revert;
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  font-style: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__title:not(#_) {
  border: revert;
  padding: revert;
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-height: revert;
  font-style: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__text:not(#_) {
  border: revert;
  padding: revert;
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-height: revert;
  font-family: revert;
  font-weight: revert;
  font-style: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__figures:not(#_) {
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  border-right-width: revert;
  border-bottom-width: revert;
  border-left-width: revert;
  border-right-style: revert;
  border-bottom-style: revert;
  border-left-style: revert;
  border-right-color: revert;
  border-bottom-color: revert;
  border-left-color: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  font-family: revert;
  font-size: revert;
  font-weight: revert;
  font-style: revert;
  line-height: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__value:not(#_) {
  border: revert;
  padding: revert;
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  font-style: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__list:not(#_) {
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  border-top-width: revert;
  border-right-width: revert;
  border-left-width: revert;
  border-top-style: revert;
  border-right-style: revert;
  border-left-style: revert;
  border-top-color: revert;
  border-right-color: revert;
  border-left-color: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-height: revert;
  font-family: revert;
  font-size: revert;
  font-weight: revert;
  font-style: revert;
  line-height: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__item:not(#_) {
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  border-right-width: revert;
  border-bottom-width: revert;
  border-left-width: revert;
  border-right-style: revert;
  border-bottom-style: revert;
  border-left-style: revert;
  border-right-color: revert;
  border-bottom-color: revert;
  border-left-color: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  font-family: revert;
  font-style: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__button:not(#_) {
  border: revert;
  margin: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  box-shadow: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  font-style: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-section-tone-shift__title:not(#_):where(:not([hidden])),
.kodza-section-tone-shift__text:not(#_):where(:not([hidden])),
.kodza-section-tone-shift__caption:not(#_):where(:not([hidden])),
.kodza-section-tone-shift__value:not(#_):where(:not([hidden])),
.kodza-section-tone-shift__list:not(#_):where(:not([hidden])),
.kodza-section-tone-shift__note:not(#_):where(:not([hidden])) {
  display: revert;
}

.kodza-section-tone-shift__title:not(#_):where([hidden]),
.kodza-section-tone-shift__text:not(#_):where([hidden]),
.kodza-section-tone-shift__caption:not(#_):where([hidden]),
.kodza-section-tone-shift__value:not(#_):where([hidden]),
.kodza-section-tone-shift__list:not(#_):where([hidden]),
.kodza-section-tone-shift__note:not(#_):where([hidden]) {
  display: none;
}

.kodza-section-tone-shift__label:not(#_)::before {
  box-sizing: revert;
}

/* The component's own rules, one step stronger: real buttons and fields, what it sets on tags themes style (links, lists, headings, images…), and the root width (a theme may narrow it, never widen it) */

.kodza-section-tone-shift:not(.is-shifting) [data-tone-shift]:where(a, p, h2, dl, dt, dd, ol, li):not(#_) {
  background-color: var(--kz-section-tone-shift-to);
  color: var(--kz-section-tone-shift-ink);
}

.kodza-section-tone-shift__label:not(#_) {
  display: flex;
  margin: 0;
  color: var(--kz-section-tone-shift-muted);
  font-family: var(--kz-font-label, var(--kz-section-tone-shift-mono));
  font-size: var(--kz-font-label-size, 12.5px);
  font-weight: var(--kz-font-label-weight, 500);
  line-height: var(--kz-font-label-leading, 1.4);
  letter-spacing: var(--kz-font-label-tracking, 0.02em);
  text-transform: var(--kz-font-label-case, inherit);
}

.kodza-section-tone-shift__title:not(#_) {
  max-width: 18ch;
  margin: 0;
  font-family: var(--kz-font-display, inherit);
  font-size: calc(clamp(34px, 5.4vw, 72px) * var(--kz-font-display-scale, 1));
  font-weight: var(--kz-font-display-weight, 600);
  line-height: 1.02;
  letter-spacing: var(--kz-font-display-tracking, -0.045em);
  text-transform: var(--kz-font-display-case, inherit);
}

.kodza-section-tone-shift__title--statement:not(#_) {
  max-width: 15ch;
  font-size: calc(clamp(40px, 7.4vw, 104px) * var(--kz-font-display-scale, 1));
  line-height: 0.98;
  letter-spacing: var(--kz-font-display-tracking, -0.05em);
}

.kodza-section-tone-shift__text:not(#_) {
  max-width: 46ch;
  margin: 0;
  color: var(--kz-section-tone-shift-muted);
  font-size: 17px;
  line-height: 1.6;
}

.kodza-section-tone-shift__figures:not(#_) {
  display: grid;
  margin: clamp(24px, 4vw, 48px) 0 0;
  padding: 24px 0 0;
  border-top: 1px solid var(--kz-section-tone-shift-line);
}

.kodza-section-tone-shift__value:not(#_) {
  margin: 0;
  font-family: var(--kz-font-display, inherit);
  font-size: calc(clamp(28px, 3.4vw, 40px) * var(--kz-font-display-scale, 1));
  font-weight: var(--kz-font-display-weight, 600);
  line-height: 1.05;
  letter-spacing: var(--kz-font-display-tracking, -0.04em);
}

.kodza-section-tone-shift__caption:not(#_),
.kodza-section-tone-shift__note:not(#_) {
  margin: 0;
  color: var(--kz-section-tone-shift-muted);
  font-family: var(--kz-font-label, var(--kz-section-tone-shift-mono));
  font-size: var(--kz-font-label-size, 12.5px);
  font-weight: var(--kz-font-label-weight, 500);
  line-height: var(--kz-font-label-leading, 1.4);
  letter-spacing: var(--kz-font-label-tracking, 0.02em);
  text-transform: var(--kz-font-label-case, inherit);
}

.kodza-section-tone-shift__list:not(#_) {
  max-width: 720px;
  margin: clamp(8px, 2vw, 24px) 0 0;
  padding: 0;
  list-style: none;
  border-bottom: 1px solid var(--kz-section-tone-shift-line);
}

.kodza-section-tone-shift__item:not(#_) {
  display: grid;
  margin: 0;
  padding: 20px 0;
  border-top: 1px solid var(--kz-section-tone-shift-line);
  font-size: clamp(18px, 2vw, 22px);
  font-weight: 500;
  line-height: 1.35;
  letter-spacing: -0.02em;
}

.kodza-section-tone-shift__button:not(#_) {
  display: inline-flex;
  padding: 0 26px;
  border-radius: var(--kz-radius-pill, 999px);
  background: var(--kz-section-tone-shift-ink);
  color: var(--kz-section-tone-shift-bg);
  font-family: var(--kz-font-label, inherit);
  font-size: var(--kz-font-label-size, 15px);
  font-weight: var(--kz-font-label-weight, 500);
  line-height: 1;
  letter-spacing: var(--kz-font-label-tracking, -0.01em);
  text-transform: var(--kz-font-label-case, inherit);
  text-decoration: none;
}

.kodza-section-tone-shift__button:focus-visible:not(#_) {
  outline: 2px solid var(--kz-section-tone-shift-ink);
  outline-offset: 3px;
}

.kodza-section-tone-shift.is-moving :is(.kodza-section-tone-shift__label, .kodza-section-tone-shift__text, .kodza-section-tone-shift__caption, .kodza-section-tone-shift__num, .kodza-section-tone-shift__note):where(p, h2, dl, dt, dd, ol, li, a):not(#_) {
  transition: color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease);
}

.kodza-section-tone-shift.is-moving :is(.kodza-section-tone-shift__figures, .kodza-section-tone-shift__list, .kodza-section-tone-shift__item):where(p, h2, dl, dt, dd, ol, li, a):not(#_) {
  transition: border-color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease);
}

.kodza-section-tone-shift.is-moving .kodza-section-tone-shift__button:not(#_) {
  transition: background-color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease),
    color calc(var(--kz-section-tone-shift-duration) * var(--kz-motion-scale, 1)) var(--kz-section-tone-shift-ease),
    opacity calc(0.2s * var(--kz-motion-scale, 1)) ease;
}

@media (prefers-reduced-motion: reduce) {
  .kodza-section-tone-shift *:where(p, h2, dl, dt, dd, ol, li, a):not(#_) {
    transition-duration: 0.01ms !important;
  }
}
```

```js
// Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license
// Kodza — Section Tone Shift
// Measures how much of a band around the middle of the screen the marked sections cover, and
// writes it, with a soft follow, as the mix of the two tones (--kz-section-tone-shift-mix): the
// background follows the scroll. Halfway, the text and the hairlines change side (is-shifted), the
// root says which tone the page is in (data-header-tone, read by Scroll Header) and sends
// kodza:tone, for a header of your own. Reduced motion, or a site pace of 0: each marked section
// wears the other tone on its own, and says so in data-header-tone.
(() => {
  const SELECTOR = '[data-kodza-section-tone-shift]';
  // The band around the middle of the screen, as a share of its height: the page shifts while the
  // edge of a marked section crosses it, and holds the other tone while the section covers it
  const BAND = 0.4;
  // The text changes side once the band is this covered, and back below the second: the gap keeps
  // it from flickering when the scroll stops right on the edge
  const SHIFT_IN = 0.55;
  const SHIFT_OUT = 0.45;
  // Between these mixes the page is a mid grey: the soft text (labels, paragraphs) takes the full
  // ink, so it stays readable if the scroll stops there
  const CROSSING_FROM = 0.2;
  const CROSSING_TO = 0.8;
  // How long the background takes to catch up with the scroll, in ms (times the site's pace): a
  // soft follow instead of a colour glued to the wheel. 0 glues it
  const SMOOTHING = 120;
  // The mix left to travel below this ends the loop
  const SETTLE = 0.0005;

  const reduceMotion = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  // The site's pace, --kz-motion-scale (set on :root, read on the instance): every duration of the
  // script times it, and 0 moves nothing, like reduced motion
  const paceOf = (el) => {
    const pace = parseFloat(getComputedStyle(el).getPropertyValue('--kz-motion-scale'));
    return pace >= 0 ? pace : 1;
  };
  const clamp = (value, min, max) => Math.min(max, Math.max(min, value));
  // Slow out of one tone, slow into the other
  const ease = (t) => (t < 0.5 ? 4 * t * t * t : 1 - (-2 * t + 2) ** 3 / 2);

  // 'dark' or 'light', for any CSS colour (hex, rgb, oklch…): painted on a 1px canvas and read back,
  // then dark when white text would contrast more with it than black text
  let pixel = null;
  const toneOf = (color) => {
    pixel ??= Object.assign(document.createElement('canvas'), { width: 1, height: 1 }).getContext('2d', { willReadFrequently: true });
    pixel.clearRect(0, 0, 1, 1);
    pixel.fillStyle = '#fff';
    pixel.fillStyle = color.trim() || '#fff';
    pixel.fillRect(0, 0, 1, 1);
    const [r, g, b] = pixel.getImageData(0, 0, 1, 1).data;
    const linear = (c) => ((c /= 255) <= 0.04045 ? c / 12.92 : ((c + 0.055) / 1.055) ** 2.4);
    return 0.2126 * linear(r) + 0.7152 * linear(g) + 0.0722 * linear(b) < 0.179 ? 'dark' : 'light';
  };

  // One instance, with its own state: two copies on a page never interfere. Everything it
  // starts is tied to `signal` (listeners get { signal }, observers and timers stop on its
  // 'abort' event), so kodza:destroy stops it all.
  function mount(root, signal) {
    const marked = [...root.querySelectorAll('[data-tone-shift]')];
    if (!marked.length) return;
    const styles = getComputedStyle(root);
    const toneAt = (end) => toneOf(styles.getPropertyValue(`--kz-section-tone-shift-${end}`));

    const pace = paceOf(root);
    const still = reduceMotion || !pace; // the still path: no motion asked, by the visitor or the site
    if (still) {
      root.dataset.headerTone = toneAt('from');
      marked.forEach((section) => { section.dataset.headerTone = toneAt('to'); });
      return;
    }
    const smoothing = SMOOTHING * pace;

    let current = null; // the mix written now
    let shifted = null; // which side the text is on
    let raf = 0;
    let last = 0;
    let shown = false;

    // How much of the band the marked sections cover, eased: 0 the page's own tone, 1 the other one
    const goal = () => {
      const top = (innerHeight * (1 - BAND)) / 2;
      const bottom = innerHeight - top;
      let covered = 0;
      marked.forEach((section) => {
        const rect = section.getBoundingClientRect();
        covered += Math.max(0, Math.min(rect.bottom, bottom) - Math.max(rect.top, top));
      });
      return ease(clamp(covered / (bottom - top), 0, 1));
    };
    // Decided on the scroll itself, before the next frame: a header that reads the tone in its own
    // frame (Scroll Header) already finds the new one
    const decide = (value) => {
      const next = shifted ? value > SHIFT_OUT : value >= SHIFT_IN;
      if (next === shifted) return;
      shifted = next;
      root.classList.toggle('is-shifted', next);
      const tone = toneAt(next ? 'to' : 'from');
      root.dataset.headerTone = tone;
      root.dispatchEvent(new CustomEvent('kodza:tone', { bubbles: true, detail: { tone, shifted: next } }));
    };
    const write = () => {
      root.style.setProperty('--kz-section-tone-shift-mix', current.toFixed(4));
      root.classList.toggle('is-crossing', current > CROSSING_FROM && current < CROSSING_TO);
    };
    const tick = (now) => {
      raf = 0;
      const to = goal();
      const step = last ? Math.min(now - last, 64) : 16.7;
      last = now;
      if (current === null || !smoothing) current = to;
      else current += (to - current) * (1 - Math.exp(-step / smoothing));
      if (Math.abs(to - current) < SETTLE) current = to;
      write();
      decide(current);
      if (current !== to) raf = requestAnimationFrame(tick);
      else last = 0;
    };
    const queue = () => {
      if (!shown || raf) return;
      raf = requestAnimationFrame(tick);
    };
    const follow = () => {
      if (!shown) return;
      queue();
    };
    // Placed at once, without the crossing: on load, or back on screen after a jump (an anchor, Home)
    const place = () => {
      current = goal();
      write();
      decide(current);
    };

    root.classList.add('is-shifting');
    place();
    // Next frame, once the first tone is painted: from now on the text crosses instead of jumping
    requestAnimationFrame(() => root.classList.add('is-moving'));

    const io = new IntersectionObserver(([entry]) => {
      shown = entry.isIntersecting;
      if (shown) {
        place();
        queue();
      }
    });
    io.observe(root);
    const resize = new ResizeObserver(follow);
    resize.observe(root);
    window.addEventListener('scroll', follow, { passive: true, signal });
    window.addEventListener('resize', follow, { signal });
    signal.addEventListener('abort', () => {
      io.disconnect();
      resize.disconnect();
      cancelAnimationFrame(raf);
    });
  }
  // Kodza lifecycle, the same in every component: `kodza:init` starts the instances inside
  // event.detail.root (the whole page by default), `kodza:destroy` stops them and puts their
  // markup back. For themes and apps that swap content without a page load. Each running root
  // keeps its markup as written under KODZA, shared by every Kodza script on the page: a Kodza
  // component inside another one is saved as written, not half-started, and stopped with it. Two
  // components on one root (a reveal on a stat card) both start, and stop together.
  const KODZA = Symbol.for('kodza');
  const RUNNING = Symbol.for(`kodza ${SELECTOR}`); // a root this component runs on, for every copy of this script
  const instances = new WeakMap();
  const find = (scope = document) => [scope, ...scope.querySelectorAll(SELECTOR)].filter((el) => el.matches?.(SELECTOR));
  const attrsOf = (el) => [...el.attributes].map((a) => [a.name, a.value]);
  const put = (el, saved) => {
    [...el.attributes].forEach((a) => el.removeAttribute(a.name));
    saved.attrs.forEach(([name, value]) => el.setAttribute(name, value));
    el.innerHTML = saved.html;
  };
  // The markup inside a root as written: Kodza components already running in it give back their own
  const written = (root) => {
    const all = [...root.querySelectorAll('*')];
    if (!all.some((el) => el[KODZA])) return root.innerHTML;
    const copy = root.cloneNode(true);
    const twins = copy.querySelectorAll('*');
    let last = null;
    all.forEach((el, i) => {
      if (!el[KODZA] || last?.contains(el)) return;
      last = el;
      put(twins[i], el[KODZA]);
    });
    return copy.innerHTML;
  };
  const init = (scope) => find(scope).forEach((root) => {
    // Already running, maybe from another copy of this script. Marked is-ready with no Kodza component
    // running on it, a root is a copy of a started one (a cloned slide): it is left as it is
    if (root[RUNNING] || (root.classList.contains('is-ready') && !root[KODZA])) return;
    // Rendered by React (data-kodza-manual): React starts it, with an init aimed at that markup once
    // it has hydrated it. Any earlier start would change markup React has not taken over yet
    const owner = root.closest('[data-kodza-manual]');
    if (owner && !(scope && owner.contains(scope))) return;
    const controller = new AbortController();
    // Another Kodza component already running on this root: its markup as written is kept, and the
    // two stop together
    const before = root[KODZA];
    const saved = { html: before ? before.html : written(root), attrs: before ? before.attrs : attrsOf(root), stop: () => destroy(root) };
    if (before) before.above = saved;
    instances.set(root, { controller, saved, before });
    root[KODZA] = saved;
    root[RUNNING] = true;
    mount(root, controller.signal);
    root.classList.add('is-ready');
  });
  const destroy = (scope) => find(scope).forEach((root) => {
    const instance = instances.get(root);
    if (!instance) return;
    instances.delete(root);
    instance.saved.above?.stop(); // a Kodza component started after it on the same root stops first
    // The Kodza components running inside it stop first: once its markup is put back, their own
    // script could not find them any more
    root.querySelectorAll('*').forEach((el) => el[KODZA]?.stop());
    instance.controller.abort();
    delete root[RUNNING];
    // Started on top of another one: that one stops next, and puts the markup back
    if (instance.before) {
      delete instance.before.above;
      root[KODZA] = instance.before;
      return instance.before.stop();
    }
    delete root[KODZA];
    put(root, instance.saved);
  });
  document.addEventListener('kodza:init', (event) => init(event.detail?.root));
  document.addEventListener('kodza:destroy', (event) => destroy(event.detail?.root));
  init();
  // Loaded in <head>, the script runs before the markup exists: once more when it is parsed
  if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', () => init(), { once: true });
})();
```

Free to use, from Kodza (https://kodza.dev).