# Burger Button

> A menu button: the lines meet, then cross, and Menu rolls to Close at a fixed width. It follows aria-expanded and fires kodza:burger, so it drives the menu you already have.

Navigation · burger, hamburger, menu, toggle, button, morph · HTML, CSS, vanilla JS · no dependencies · updated 2026-10-27
Demo: https://kodza.dev/components/burger-button/
Source on GitHub: https://github.com/kodza-dev/kodza/tree/main/components/burger-button

## Files

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

- [`kodza-burger-button.css`](https://kodza.dev/registry/burger-button/kodza-burger-button.css) · 7.4 KB
- [`kodza-burger-button.js`](https://kodza.dev/registry/burger-button/kodza-burger-button.js) · 6.2 KB
- [`kodza-burger-button.html`](https://kodza.dev/registry/burger-button/kodza-burger-button.html) · 0.8 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-burger-button.css https://kodza.dev/registry/burger-button/kodza-burger-button.css
curl -fsSL --create-dirs -o kodza/kodza-burger-button.js https://kodza.dev/registry/burger-button/kodza-burger-button.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: `.kodza-burger`
- Variables (set them on the root element itself: it declares its own defaults):
  - `--kz-burger-ink: #0a0a0a`
  - `--kz-burger-on-ink: #ffffff`
  - `--kz-burger-height: 40px`
  - `--kz-burger-duration: 0.5s`
  - `--kz-burger-meet: cubic-bezier(0.65, 0, 0.35, 1)`
  - `--kz-burger-ease: cubic-bezier(0.22, 1, 0.36, 1)`
  - `--kz-burger-gap: 6px`
  - `--kz-burger-half: calc(var(--kz-burger-gap) / 2)`
- Modifiers: `.kodza-burger--bare`, `.kodza-burger--round`, `.kodza-burger--three`
- Attributes:
  - `data-target`
- Events: `kodza:burger` (bubbling, from the root)
- Lifecycle: `kodza:init` / `kodza:destroy` on `document`, with `{ detail: { root } }` to target a container.

## Keyboard

What each key does, by where the focus is. Keep it working when you adapt the HTML: same elements, same classes.

- On the button (focus in `.kodza-burger`):
  - `Enter` / `Space`: Opens or closes, the lines cross or part
- While it is open (focus in `.kodza-burger[aria-expanded="true"]`):
  - `Escape`: Closes, and brings the focus back from the menu

## 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-burger {
    --kz-burger-ink: #f2f2f0;
    --kz-burger-on-ink: #0a0a0a;
  }
}
```

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

## Use it

### Plain HTML page

- CSS: `kodza/kodza-burger-button.css` next to the page (the Files commands as they are), linked in `<head>`: `<link rel="stylesheet" href="kodza/kodza-burger-button.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-burger-button.js`, loaded with `<script src="kodza/kodza-burger-button.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. 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">`.
- 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$/{r kodza/kodza-burger-button.css' -e 'd' -e '}' -e '/^KODZA-JS$/{r kodza/kodza-burger-button.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">`.
- 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 is inline (it flows like a word): pasted alone, many themes leave it at the edge of the page (block themes, and classic ones like Twenty Twenty-One or Blocksy), so put the Custom HTML block inside a **Group** block to line it up with the text.
- 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-burger-button', $uri . 'kodza-burger-button.css', [], filemtime($dir . 'kodza-burger-button.css'));
    wp_enqueue_script('kodza-burger-button', $uri . 'kodza-burger-button.js', [], filemtime($dir . 'kodza-burger-button.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: by default, match the theme's palette. After the component's CSS, point these variables at the theme's colours, on the component root, Kodza's value as the fallback:
  `.kodza-burger { --kz-burger-ink: var(ACCENT, #0a0a0a); --kz-burger-on-ink: var(BACKGROUND, #ffffff); }`
  TEXT, BACKGROUND and ACCENT (the colour the theme fills its own buttons with) are the theme's own colour variables — block themes (theme.json, like Twenty Twenty-Five): `--wp--preset--color--contrast`, `--wp--preset--color--base`, `--wp--preset--color--contrast` (they fill their buttons with it; their accent-1… colours are decorative); Astra: `--ast-global-color-2`, `--ast-global-color-4`, `--ast-global-color-0`; Kadence: `--global-palette3`, `--global-palette9`, `--global-palette1`; GeneratePress: `--contrast`, `--base-3`, `--accent`; Blocksy: `--theme-palette-color-4`, `--theme-palette-color-8`, `--theme-palette-color-1`. Use only these names, and only if the site really has them (the theme's CSS, or Styles → Colors): the `--wp--preset--color--black`, `--white`, `--vivid-…` that WordPress adds everywhere are not the theme's palette. Another theme, or one without these variables (Hello Elementor, OceanWP): leave the variables alone, it keeps Kodza's monochrome; same when the developer asks for monochrome or the Kodza look. Leave the translucent greys (`rgba(10, 10, 10, …)`) as they are: they suit any light background. On a dark palette, set the other variables from Dark mode too.
- 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.
- 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. This one reads the page around it, and a script in the widget runs before the rest of the page exists: put its `<script>` in an HTML widget at the bottom of the page instead.

### Shopify

- Files: `assets/kodza-burger-button.css` and `assets/kodza-burger-button.js` (the Files commands with `-o assets/…`).
- In the section: `{{ 'kodza-burger-button.css' | asset_url | stylesheet_tag }}` and `<script src="{{ 'kodza-burger-button.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/`): `BurgerButton.tsx` (below), the CSS block under Code saved as `burger-button.css` and the JS block as `burger-button.js`, both as they are. The HTML block is already inside the component: skip it.
- Use it: `import { BurgerButton } from '@/components/kodza/BurgerButton';` then `<BurgerButton />`. Props: `variant` ("bare", "round", "three", or several in an array), `vars` (the `--kz-…` variables listed under API, e.g. `vars={{ '--kz-burger-ink': … }}`), `onBurger` (the `kodza:burger` event), `className`, `style` and the other props of its `<button>` (`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 './burger-button.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 — Burger Button, for React. From https://kodza.dev/components/burger-button/
// 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: burger-button.css and burger-button.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.
// 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 './burger-button.css';

type Variant = "bare" | "round" | "three";

export type BurgerButtonProps = Omit<ComponentPropsWithoutRef<'button'>, "children" | "variant" | "vars" | "onBurger"> & {
  /** Modifier class(es): .kodza-burger--bare, .kodza-burger--round, .kodza-burger--three */
  variant?: Variant | Variant[];
  /** Settings, as CSS variables on the root */
  vars?: {
    /** default: #0a0a0a */
    "--kz-burger-ink"?: string | number;
    /** default: #ffffff */
    "--kz-burger-on-ink"?: string | number;
    /** default: 40px */
    "--kz-burger-height"?: string | number;
    /** default: 0.5s */
    "--kz-burger-duration"?: string | number;
    /** default: cubic-bezier(0.65, 0, 0.35, 1) */
    "--kz-burger-meet"?: string | number;
    /** default: cubic-bezier(0.22, 1, 0.36, 1) */
    "--kz-burger-ease"?: string | number;
    /** default: 6px */
    "--kz-burger-gap"?: string | number;
    /** default: calc(var(--kz-burger-gap) / 2) */
    "--kz-burger-half"?: string | number;
  };
  /** "kodza:burger", fired by the script (bubbles from the root) */
  onBurger?: (event: CustomEvent) => void;
  className?: string;
};

export function BurgerButton({ variant, vars, onBurger, className, style, ...rest }: BurgerButtonProps) {
  const ref = useRef<ComponentRef<'button'>>(null);
  const classes = ["kodza-burger", ...([] as string[]).concat(variant ?? []).map((v) => `kodza-burger--${v}`), 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('./burger-button.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 || !onBurger) return;
    const listener = (event: Event) => onBurger(event as CustomEvent);
    root.addEventListener("kodza:burger", listener);
    return () => root.removeEventListener("kodza:burger", listener);
  }, [onBurger, key]);

  return (
    <button type="button" aria-expanded="false" key={key} {...rest} className={classes} style={{ ...vars, ...style } as CSSProperties} ref={ref}>
      <span className="kodza-burger__lines" aria-hidden="true" />
      {' '}
      <span className="kodza-burger__label">
        <span className="kodza-burger__word">Menu</span>
        <span className="kodza-burger__word" aria-hidden="true">Close</span>
      </span>
    </button>
  );
}
```

## Code

```html
<button class="kodza-burger" type="button" aria-expanded="false">
  <span class="kodza-burger__lines" aria-hidden="true"></span>
  <span class="kodza-burger__label"><span class="kodza-burger__word">Menu</span><span class="kodza-burger__word" aria-hidden="true">Close</span></span>
</button>

<button class="kodza-burger kodza-burger--round kodza-burger--three" type="button" aria-expanded="false" aria-label="Menu">
  <span class="kodza-burger__lines" aria-hidden="true"></span>
</button>

<button class="kodza-burger kodza-burger--bare" type="button" aria-expanded="false">
  <span class="kodza-burger__label"><span class="kodza-burger__word">Index</span><span class="kodza-burger__word" aria-hidden="true">Close</span></span>
  <span class="kodza-burger__lines" aria-hidden="true"></span>
</button>
```

```css
/* Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license */
/* Kodza — Burger Button
   The lines meet in the middle, then cross; the label rolls from Menu to Close without changing
   the button's width. Closing undoes it in the same two steps: uncross, then part, and Close rolls
   up while Menu comes back from below.
   It follows aria-expanded: the script flips it on click, and so can your theme's own script.
   Everything is tuned with the --kz-burger-* variables. */
.kodza-burger {
  --kz-burger-ink: #0a0a0a;
  --kz-burger-on-ink: #ffffff;
  --kz-burger-height: 40px;
  --kz-burger-duration: 0.5s;
  --kz-burger-meet: cubic-bezier(0.65, 0, 0.35, 1);
  --kz-burger-ease: cubic-bezier(0.22, 1, 0.36, 1);

  /* The lines: how far apart (two lines), and where each one ends up. Whole pixels, so both
     lines sit on the pixel grid the same way and look the same weight */
  --kz-burger-gap: 6px;
  --kz-burger-half: calc(var(--kz-burger-gap) / 2);

  display: inline-flex;
  align-items: center;
  gap: 10px;
  height: var(--kz-burger-height);
  margin: 0;
  padding: 0 18px 0 16px;
  border: 0;
  border-radius: 999px;
  background: var(--kz-burger-ink);
  color: var(--kz-burger-on-ink);
  font: inherit;
  font-size: 15px;
  font-weight: 500;
  line-height: 1;
  letter-spacing: -0.01em;
  white-space: nowrap;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

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

/* Round: the lines alone, in a circle */
.kodza-burger--round {
  justify-content: center;
  width: var(--kz-burger-height);
  padding: 0;
}

/* Bare: no fill, for a header that keeps its links plain */
.kodza-burger--bare {
  padding: 0 4px;
  background: transparent;
  color: var(--kz-burger-ink);
}

.kodza-burger--three {
  --kz-burger-gap: 5px;
  --kz-burger-half: var(--kz-burger-gap);
}

.kodza-burger__lines {
  position: relative;
  flex: none;
  width: 14px;
  height: calc(var(--kz-burger-gap) + 2px);
}

.kodza-burger--three .kodza-burger__lines {
  height: calc(var(--kz-burger-gap) * 2 + 2px);
  /* The middle line: drawn as a background, it shrinks to its centre as the others meet */
  background: linear-gradient(currentColor, currentColor) 50% var(--kz-burger-gap) / 100% 1.5px no-repeat;
  transition: background-size calc(var(--kz-burger-duration) * 0.4) var(--kz-burger-meet) calc(var(--kz-burger-duration) * 0.4);
}

.kodza-burger__lines::before,
.kodza-burger__lines::after {
  content: "";
  position: absolute;
  left: 0;
  width: 100%;
  height: 1.5px;
  border-radius: 1px;
  background: currentColor;
  /* Kept on its own layer: the browser draws it the same way at rest and while it moves, so the
     lines never thicken during the turn and snap thin at the end */
  will-change: transform;
  /* Closing: they uncross first, then part */
  transition:
    rotate calc(var(--kz-burger-duration) * 0.44) var(--kz-burger-meet),
    translate calc(var(--kz-burger-duration) * 0.44) var(--kz-burger-meet) calc(var(--kz-burger-duration) * 0.36),
    clip-path 0.3s var(--kz-burger-ease);
}

.kodza-burger__lines::before {
  top: 0;
}

.kodza-burger__lines::after {
  top: var(--kz-burger-gap);
}

.kodza-burger--three .kodza-burger__lines::after {
  top: calc(var(--kz-burger-gap) * 2);
}

/* Whole at rest, as an inset: the pointer slides it to a shorter one (from none it would jump) */
.kodza-burger__lines::after {
  clip-path: inset(0 0 0 0);
}

/* Pointed at: the bottom line draws back */
.kodza-burger:hover .kodza-burger__lines::after {
  clip-path: inset(0 45% 0 0);
}

/* Open: they meet in the middle, then cross */
.kodza-burger[aria-expanded="true"] .kodza-burger__lines::before,
.kodza-burger[aria-expanded="true"] .kodza-burger__lines::after {
  clip-path: inset(0 0 0 0);
  transition:
    translate calc(var(--kz-burger-duration) * 0.4) var(--kz-burger-meet),
    rotate calc(var(--kz-burger-duration) * 0.6) var(--kz-burger-ease) calc(var(--kz-burger-duration) * 0.34),
    clip-path 0.3s var(--kz-burger-ease);
}

.kodza-burger[aria-expanded="true"] .kodza-burger__lines::before {
  translate: 0 var(--kz-burger-half);
  rotate: 45deg;
}

.kodza-burger[aria-expanded="true"] .kodza-burger__lines::after {
  translate: 0 calc(var(--kz-burger-half) * -1);
  rotate: -45deg;
}

.kodza-burger--three[aria-expanded="true"] .kodza-burger__lines {
  background-size: 0% 1.5px;
  transition-delay: 0s;
}

/* The label: both words in one cell, so the button is as wide as the longer one. The script
   rolls them, both ways: the old word goes up out of its mask while the new one comes up from below */
.kodza-burger__label {
  display: grid;
  margin: -3px 0;
  padding: 3px 0;
  overflow: hidden;
}

.kodza-burger__word {
  grid-area: 1 / 1;
}

.kodza-burger__word + .kodza-burger__word {
  translate: 0 115%;
}

.kodza-burger[aria-expanded="true"] .kodza-burger__word {
  translate: 0 -115%;
}

.kodza-burger[aria-expanded="true"] .kodza-burger__word + .kodza-burger__word {
  translate: 0 0;
}

@media (prefers-reduced-motion: reduce) {
  .kodza-burger *,
  .kodza-burger *::before,
  .kodza-burger *::after {
    transition-duration: 0.01ms !important;
    transition-delay: 0s !important;
  }
}

/* kodza-guard 425fbb1a1717 — 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-burger):not(#_) {
  outline: revert;
  outline-offset: revert;
}

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

.kodza-burger:not(#_) {
  text-decoration: revert;
  transition: revert;
  list-style: revert;
  box-sizing: revert;
  position: revert;
  box-shadow: revert;
  appearance: revert;
  max-height: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
  min-height: revert;
}

.kodza-burger__lines:not(#_),
.kodza-burger__label:not(#_),
.kodza-burger__word:not(#_) {
  box-sizing: revert;
}

.kodza-burger__lines:not(#_)::before,
.kodza-burger__lines:not(#_)::after {
  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-burger:not(#_) {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  height: var(--kz-burger-height);
  margin: 0;
  padding: 0 18px 0 16px;
  border: 0;
  border-radius: 999px;
  background: var(--kz-burger-ink);
  color: var(--kz-burger-on-ink);
  font: inherit;
  font-size: 15px;
  font-weight: 500;
  line-height: 1;
  letter-spacing: -0.01em;
  white-space: nowrap;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

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

.kodza-burger--round:not(#_) {
  justify-content: center;
  width: var(--kz-burger-height);
  padding: 0;
}

.kodza-burger--bare:not(#_) {
  padding: 0 4px;
  background: transparent;
  color: var(--kz-burger-ink);
}
```

```js
// Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license
// Kodza — Burger Button
// Flips aria-expanded on click (the CSS does the rest), says so with a kodza:burger event, and
// puts is-open on the menu named by data-target. Escape closes it again. It also rolls the label,
// both ways: the old word goes up, the new one comes up from below.
(() => {
  const SELECTOR = '.kodza-burger';
  const reduceMotion = window.matchMedia('(prefers-reduced-motion: reduce)');

  // 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 words = [...root.querySelectorAll('.kodza-burger__word')];
    const isOpen = () => root.getAttribute('aria-expanded') === 'true';
    const rolls = new Map();
    let shown = isOpen();
    const target = () => {
      try {
        return root.dataset.target ? document.querySelector(root.dataset.target) : null;
      } catch {
        return null;
      }
    };

    // The word a screen reader hears is the one on screen
    const sync = () => words.forEach((word, i) => {
      if (i === (isOpen() ? 1 : 0)) word.removeAttribute('aria-hidden');
      else word.setAttribute('aria-hidden', 'true');
    });

    // A click during the roll turns it back from where the words are
    const roll = (open) => {
      if (reduceMotion.matches || words.length < 2) return;
      const style = getComputedStyle(root);
      const raw = style.getPropertyValue('--kz-burger-duration').trim();
      const duration = parseFloat(raw) * (raw.endsWith('ms') ? 1 : 1000) || 500;
      const easing = style.getPropertyValue('--kz-burger-ease').trim();
      words.forEach((word, i) => {
        const coming = i === Number(open);
        const from = rolls.has(word) ? getComputedStyle(word).translate : coming ? '0 115%' : '0 0';
        rolls.get(word)?.cancel();
        const frames = { translate: [from, coming ? '0 0' : '0 -115%'] };
        let run;
        try {
          run = word.animate(frames, { duration, easing });
        } catch {
          run = word.animate(frames, { duration, easing: 'cubic-bezier(0.22, 1, 0.36, 1)' });
        }
        rolls.set(word, run);
        run.finished.then(() => rolls.get(word) === run && rolls.delete(word), () => {});
      });
    };

    const set = (open) => {
      root.setAttribute('aria-expanded', String(open));
      target()?.classList.toggle('is-open', open);
      root.dispatchEvent(new CustomEvent('kodza:burger', { bubbles: true, detail: { open } }));
    };

    root.addEventListener('click', () => set(!isOpen()), { signal });
    document.addEventListener('keydown', (event) => {
      if (event.key !== 'Escape' || event.defaultPrevented || !isOpen()) return;
      const menu = target();
      const inside = menu?.contains(document.activeElement);
      set(false);
      if (inside) root.focus();
    }, { signal });

    // Another script flips aria-expanded (a theme closing its own menu): the words follow
    const observer = new MutationObserver(() => {
      if (isOpen() !== shown) roll((shown = isOpen()));
      sync();
    });
    observer.observe(root, { attributes: true, attributeFilter: ['aria-expanded'] });
    sync();
    signal.addEventListener('abort', () => {
      observer.disconnect();
      rolls.forEach((run) => run.cancel());
      target()?.classList.remove('is-open');
    });
  }

  // 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.
  const KODZA = Symbol.for('kodza');
  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) => {
    if (root.classList.contains('is-ready')) return; // already running, maybe from another copy of this script
    const controller = new AbortController();
    const saved = { html: written(root), attrs: attrsOf(root), stop: () => destroy(root) };
    instances.set(root, { controller, saved });
    root[KODZA] = saved;
    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);
    // 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[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).